I love this community, your suggestions and comments are invaluable! Let’s work together to get this Jag back to health!

From experience, I definitely don't think you have a head gasket issue. That slight mayo on the oil cap is just condensation, very very common this time of year. Same with the exhaust. These older cars have a better flow of gases than modern ones so they do have a bit more condensation coming out of the rear in winter. I would go for a couple hour drive, check the coolant and keep an eye on the temperature just to double check but I think you'll be fine

Worked at Jaguar for 31 years on Research and development and the S-type was one of the cars i worked on, owned a few and loved them. Great cars but did have a few underlying faults, the eletrics was a big one as it was pretty advanced for its time. one tip to you would be if you have eletric gemlins and faults coming up like gearbox fault or ABS fault check the battery 1st as soon as battery starts to go it throws up loads of untrue errors, good luck great seeing you working on it brings back loads of memorys of all the work I have done on them

White smoke (steam?) out the back is nothing to worry about this time of year- go outside and breath out - you will see it - same theory with the car - your breath and exhaust is warmer than the air so will be visible. The small amount of mayonnaise on oil filler cap is probably just condensation , pretty normal if you have used car on a lot of short runs - never gets warm enough to burn it off, wipe it off and take it for a long run and check again, as long as the oil itself doesn’t look creamy you are probably ok.

Interestingly Chris Fix did a head gasket sealer group test on a V6 Jag. He did a before and after tear down of the engine to show how the sealer works and it was still holding after 2 years.

Normal combustion process produces something like 10% water, so the white "smoke" you are seeing is normal, especially in this cold weather. The fact that your sniffer test stayed blue may indicate that there was a slight head gasket leak which you may have now fixed. Just keep an eye on the coolant level as you drive the car and check that it doesn't move. Don't forget to add the correct antifreeze/corrosion inhibitor for your engine!

I used steel seal on my 1993 Subaru. It lasted a year and definitley did work. My advice is just drive the car easy. Eventually I saved up enough to have my head gaskets changed but that £40 bottle allowed me to keep driving another year without issues 👍

I used steel seal and it worked on my 2000 polo. Spoke to my mechanic and he said you'll still see water coming out as the exhaust needs to dry out. Done a few thousand miles it in and touch wood it's still running great. Picked the car up for £550, previous owner wasn't aware of the head gasket issue as an unscrupulous garage just took the thermostat out and charged him £180!. I've had the cambelt replaced and serviced it myself. Plenty of life still left in it.

I had very same issue with my volvo xc90...put vehicle into my local Volvo Dealer they diagnosed "Head Gasket" Paid them £2000 to replace head gasket....and the problem continued.Not happy I gave car back to Volvo and they then diagnosed a fault in the bottom block(engine)...and quoted me another £6000 to repair. Obviously I was incensed with their incompetence having already paid them £2000....local garage mechanic I know suggested £24 bottle of Steel Seal which I did and it fixed the coolant problem. By the way I used to own an S type 3.0SE.Great car.never had any problems with it.good luck with Steel Seal.

Steel seal only works if you follow the instructions on the bottle. The car needs to be stone cold, not 3/4 hours cool. Also, you then have to warm up the car once you've put in steel seal. Switch it off after it gets warm, then leave it until the engine is stone cold again. Which takes about 12 hours, not 3/4 hours.

Hi Joel. Take off the plastic engine cover and track down the source of the water "spitting" from under it. It may be connected with the repaired water pipe. See you in the next one. 👍👍

Hi, KZfaq just randomly showed me your video... I was a Jaguar master tech at 4 main dealers from 1995 to 2015. I think I can remember doing ONE head gasket on a V8, it was not common and I dont remember seeing many others being done either. Maybe now that they are another 7 years older, or if the car has been stood for a long time it would be more likely than back then... The tiny bit of `mayo` on the oil cap you show is not a concern, that is so small it could just be from condensation. Water pumps and thermostats caused overheating , over cooling and leaks. The dual control coolant valve and its wiring caused interior temp problems. There is an electric water pump that can fail and cause overheating. Expansion bottles cracked and all hoses swelled, blew off and generally leaked. I def would not have put any `miracle cure` additive in it, especially if you want to keep it... Good luck.

Saved my 2.5 S Type and ran perfect for another 2 years. Good stuff. 👍 took two bottles though

The combustion process produces steam hence the white "smoke", so this is normal. Possibility that head gasket is leaking into one cylinder and externally hence antifreeze staining on block and levels dropping. You normally also get a slight miss fire on start up. Instant fixes only last a short time (enough to sell the car). Get a cylinder compression test done, this might identify a leak but better to pull the spark plugs and check for rust. If it is a leaking head gasket, it will get worse and lead to rapid overheating. Solution is top end overhaul. Heads off, skimmed if required, valves seated and seals/gaskets replaced. Always replace cam belt (or chain tensioner) thermostat and water pump. £800 and upwards unless you get mates rates. Good luck. Carl.

Loving all the jag content on KZfaq at the moment. I’m on an owners club on Facebook. Great amount of knowledge and quick fixes shared on there. Very helpful bunch. Keep at it

That's brilliant stuff it saved a 53 plate Clio 182 , checked oil and removed cap and it was milky as hell and on dipstick , needless to say I did at least another 14000 miles car was spot on.

Perhaps the white smoke out the exhaust is because of the low winter temperature outside these days

Don’t worry about the condensation from the tailpipes , if it’s been wetting the exhaust for ages will take some drying out also it’s a big engine and it’s winter

Hi Joel. Just finished reading all the comments, another 15 minutes of life I won't get back! I don't know much about the jag V8's, but I own a BMW V8 and know lots about those. Here is the honest and real deal. Apart from a couple of small things that may be wrong with your engine (causing minor coolant leaks) anything else will just not be financially viable. This is why all these V8 cars appear cheap, but really aren't. My advice would be this: adding the Steel Seal is not a wise move, I can't imagine any motor engineer worth his overalls advising you to use it. However, the secondary damage it will cause is probably a while away. The cooling system will definitely require bleeding, so talk to someone who knows the procedure for that engine and carry it out immediately. Forget about any super-serious long trips as the car cannot be trusted, make sure you are in the AA or RAC. Run it around as much as you can and monitor the coolant level once the system has been bled. If it is still losing coolant, a pressure test of the cooling system would not be too expensive and may show up some of the cheaper faults. Otherwise, forget about head gasket replacement, sell the car for whatever you can get.

I used to use E&E services, a Jaguar Specialist in Milton Keynes. They always did a good job on my Jaguar S-Type I had.

As always Joel, an amazing video! Glad I recommend Katy to post shorts that she posts as reels, it’s gained nearly 2k views so far! 😃

Hi Joel, the white fumes are often caused by water collecting in the exhaust system and when the weather is properly cold you'll see white condensation fumes. My advice ? Take it for a 20 mins drive to allow the engine and all it's components are fully warmed through, using a reasonable amount of throttle once warmed up. It won't fully warm up on tickover and stationary, irrespective of what the temp gauge says. I'm not seeing any of the classic blown gasket signs : mayonnaise; bubbles in the coolant header tank; loads of white smoke; temp gauge in the red.

I love this type of content, faults, fault finding and repairs.

My Jag XF 3.0 V6 steams a lot. When stopped in traffic i notice it is more than other vehicles. No loss of power. No mayo on oil cap. I usually top up a cupful of coolant a month but i think that is the expansion tank valve that leaks. Nearly 150,000 miles o it now. Still going. So happy motoring.

The white smoke is very likely to be the normal winter condensation. I have lots of problems with AJ26 SC engine cooling system last year. From experience, if you're worrying about the cooling system, I'd say the first step is to do a cooling system pressure test to identify any water hose leak. It's worth noting that some water hose damages might not be found by doing pressure test on a cold system, because some weird rubber pipe leaks only happen when the system is warm. Once you're assure all water pipes are fine, it'd be better to check the radiator as insufficient or blocked radiator can cause coolant to come out from expansion tank simutaneously when turn off the engine. The sniff test results shoud be accurate. If the fluid remains blue, then there is no exhaust gas leak, proving steelseal did cure the minor headgasket issue. If both of your coolant and engine oil doesn't become melt milk chocolate, then you shouldn't have any further headgasket issue. Does the coolant leak, consumed or pumped out from the expansion tank at driving? I would keep an eye on the coolant level but drive it normally.

Steal Seal works very well if used as per instructions. I used it on the notorious K series engine in an MGF and it solved the head issue, I sold the car 4 months later and I still see it at various car events and it still hasn't had a gasket replacement, that was 6+ years ago when used steak seal, a thumbs up from me for the project

I’ve used steel seal on many cars and have had great results with only one fail and that was on an old BM 7 series

I have just done the steel seal on my car and it worked! Fantastic. Went from bad back pressure coolant bubbling and rising and hoses splitting from pressure to working normal

A cold vehicle emits white, gray or black smoke when first started due to condensation, but not after the vehicle is warmed up. When a vehicle is started, water is emitted in the form of a vapor. By the time the vapor hits the exhaust system it condenses, and becomes visible

I highly recommend Tom Lenthall Ltd if the Wokingham area isn't too far for you, Tom and the team are very knowledgeable on both modern and classic Jags. Also used by Harry's Garage on the XJC resto👍

You need properly breed the coolant, as there is air in the system, thus the level goes down. The oil cap can be creamery because of the condensation, you need to check the oil on the dipstick if that’s has sighs of water, not the oil cap.

Joel! Fantastic content as always, between you and a few other KZfaqrs you guys were the main driving force behind my purchase of a 2000 Jaguar XJ 4.0 V8. Exactly the same engine as in your S-type! Now my car, and engine are sorted, hopefully I can now return some useful information. The white exhaust smoke is nothing to worry about, time or year large capacity engines etc. it’s to be expected. My daily XF 5.0 V8 is just as bad!! To note though, a quirk with those engines is the upstream O2 sensors can fail without even throwing an engine warning light. Stupid I know, but could be contributing to your emissions you can see if they have given up the ghost. Mine packed up on both banks without any warning lights! The fluctuating coolant level, especially when the radiator fan cuts in would suggest to me a stuck or sticking thermostat, another weak area on these engines, the plastic thermostat housing can also break. Now ally replacements can be found. Lastly, these engines love to trash cam-cover gaskets, which leak onto the hot exhaust manifold heat shields. When the car is warm and the blowers are on, the burning smell makes its way straight to your nostrils!! Last point, you could do worse than checking out Autoreserve Jaguar, I can’t remember where they are based but they are a great team. All the best, keep going with the great content!!

The white " smoke" You're describing is basically steam due to the cold weather. The smell from the heater could be due to a slight leak from the heater matrix or the pipes attached to the matrix however the " stop leak " you put in the expansion tank may even cure that leak. I would suggest you get the cooling system pressure tested either at a garage or try and buy a pressure tester and do it yourself. Good luck 👍

Always enjoy your videos mate, just a normal guy working on normal cars and the issues older cars more often than not have

A coolant leak will usually produce a solid white smog. All I see is normal cold weather steam. Also, if separate exhausts, highly unlikely you would have blown both head gaskets.

You might have just caught a small breech in the head gasket in time with Steel Seal 👍

Genuinely don’t worry about the white smoke from your exhaust, that’s only condensation & heat mixing. Think of heat coming out of your boiler flue you don’t really see it in the summer same as with your exhaust smoke. In terms of the cream/white on the oil cap that’s minimal only condensation again this time of year I’ve had cars with almost like a lemon yoghurt in the cap. I think you may have another slight coolant leak from a hose again in an awkward spot. Buy a cheap borrescope from Amazon & have a look around the engine. In future don’t rush to put a sealer in a suspected head gasket get a compression test done first

The white smoke is condensation and the rear exhaust boxes with water in them. It needs a good long run.

Enjoying the journey with you Joel. Looks like you got a fix ;)

Sorry you’re having issues but I’m enjoying watching your investigations. Hope you get to the bottom of it soon. 🤞👍

A little water out of the exhaust is fairly normal. Love what you are doing. Good luck with the car.

Great post ,very informative and I hope that you get it sorted

Hello, done this a few times before myself. It does work but not always straight away. You havent done the final step in the instructions either. Youve forgotten to let the engine completely cool again before trying again to see if head gasket leak is cured , this step is important. Once you leave the car over night and use it again next morning , it will be fine. Dont forget to warn people to be very wary of messing with scolding hot water that can blow straight out of the expansion tank at you if your not careful especially with head gasket problems.. Hope this helps. happy motoring.

My Granada V6 blows white smoke this time of year even when hot but gaskets are fine . Don't worry about the smoke if your water level stays up .

Hi Joel, I wouldn't worry about the steam from the exhaust but the loss of coolant should be checked with a pressure test. I wouldn't have put that stuff in the coolant. Good luck 🤞

At the beginning of the vid, it showed your drive with moss between the blocks. To clear, get a hoselock lance sprayer, 4 litres of water, 1 litre of bleach and a good squirt of washing up liquid. It works a treat! Good luck with the S Type!

Test came back negative. Car is ready to go, don't be paranoid. I think you could go to Berlin and back easy 😄

I love that you couldn't be bothered with following the directions...Lol.

In my experience, there's only 1 way to cure a head gasket fault....and it involves removing the head(s) and replacing the gasket(s) Check for head cracks at the same time

That V8 sounds SO nice idling away there.

Looks like you have an air lock Joel. Suggest you drain the system fully, refill and bleed correctly. Take your time and familiarise yourself with the procedure and layout of the various pipes etc. Wait for a good day, take out for a long drive after. Top up as required, and repeat long trip. Good luck, love your vids

It might be worth checking if your car has an EGR-cooler that's leaking internally. EGR-cooler is basically a heat-excanger between exhaust and coolant. If it starts leaking, coolant leaks either directly to the exhaust system, or via intake/combustion. It's even possible that exhaust finds its' way to the cooling system in some cases.

I wouldnt worry about the white smoke from the tail pipe that could just be coz it’s cold outside or the fact it’s a bit older. If your 2nd sniff test came back ok I’d suggest you start to use the car and see how you get on with it, maybe keep a few litres of water in the boot with you incase anything happens. Then you will see if it’s fit for your future plans. Keep up the great work too, I really enjoy your style, taste in cars and love the challenges you do in the videos. 👍🏻👍🏻

Good video Joel and love your choice of car, they were a special beast the old V8 but fun. Stop worrying about the minor issues and let’s get it on a serious journey.

If you can smell coolant in the car it could be the heater matrix.

Love it Joel. Having a classic as well it’s always a job balancing the cost and keeping these wonderful cars on the road. 👍👍. If you do keep it can we have a meet up as I have a CL 500 2002.

If one of the headgaskets had gone you would only have smoke out of one exhaust, unlikely that you have had both fail at same time... I'd also think that the system would be pressurising if a headgasket had failed.

That era of V8 Jag was notorious for faulty thermostat housings causing a leak. Plastic moulding that distorted over time and there was no visible "drip" because the water ran down the engine and evaporated. Good news......cheap easy fix.

Love your videos mate, your commitment and your energy! The second hand car market is a complete bastard. Don't think it's a head gasket issue, cars of that age idle with smoke normally, especially in the cold.

My V8 Jag only gets used occasionally, but when I fire it up, it puffs out steam like a train. But it goes once warmed up.

Back then in the early 2000s, GM produced the Northstar V8 that had major Head Gasket Issues. The later released something called "GM Sealant Tabs". You can try these if it doesnt work on the long run.

No external leaks first, expansion tank caps is another cause coolant loss due to not pressuring the system correctly to achieve a higher boiling point of the coolant. Vauxhall engines "corsa d" run very hot and still produce a bit of condensation in cold weather which is normal.

Well the temperature seems stable even after a long period sitting idling. We have a 3ltr straight six BMW and it pumps out condensation under almost any condition, however, it does stop after a decent run, I mean a 100 mile decent run. .... the car performs really well, it's ultra reliable, the coolant level doesn't change and there's a tiny residue under the oil filler cap. The fans rarely kick in and there's absolutely no signs of overheating. We are at a loss to understand the issue but perhaps there isn't one. Ours has been doing this for the past 10k miles so I can only assume it's water vapour from burning the petrol. We think it's the design of the exhaust which might have something to do with it, i.e, the backend of the pipe isn't getting hot enough so condensation forms. I can't say for certain but I have heard 1 gallon of petrol produces 1 gallon of water. That number might be wrong but at least a fair amount of water is produced whilst burning fuel. Finally, simply because there's a tiny amount of sludge in the oil cap it doesn't mean a head gasket failure. Swarf is produced as a result of vapour in the fuel and oil in the block. From my experience I think your Jag looks perfectly fine.

Just for info, water under pressure boils at a higher temperature than 100° (as designed to do so in a sealed engine coolant system). By running the engine with the expansion tank cap removed, the coolant system sensor will register a higher than normal temperature because it is not running presurised. This is why the water level rose in the expansion tank and the cooling fan came on whilst you performed the "blue test". Also, white smoke (water vapour) is very common in such a large capacity engine exhaust system, especially in the cold. Your engin is drawing in cold air with a high water content, all this is passing through the engine as well as the condensation in the exhaust due to cold air and hot surfaces. Hope that helps, Baz.

Like your style Joel, you're very open and honest in that you don't have a clue, likewise here mate. I'm definitely no mechanic but i do know this with being an old timer literally all cars (and I've owned many over the years) kick out the white smoke especially at this time of year so like a lot of the guys have said on here possibly nothing to be too concerned about. Have subscribed to your channel as i find your content interesting and you come across a very polite young gentleman. I know I've been no help to you whatsoever but i just thought I'd say those few words anyway. Keep the faith Joel. I have my fingers and legs crossed you get to the bottom of the issue, good luck mate!

The white ‘"smoke" is condensation/ steam caused by hot air hitting cold air. The best check to do is a cooling system pressure test. Good luck Joel.

Looks to me like you need to make sure the whole cooling system is properly bled, take a look in the manual, there is usually a specific procedure given as to how. Some can be extremely tricky to get the last few air bubbles out but patience and persistence will win 👍 great channel, very true to the reality of owning an older 'special ' vehicle. Go man go 👍

Really enjoyed this video good luck love the car 🚗

i took my s-type jaaaaaaaggg to northern france and it ran like a dream, not to rub in! the v8 is still silent even at french motorway speeds , 80 mph.............ish. brilliant content as always jeol.

White exhaust is normal at prolonged idle, take it for a blast and the exhaust should clear up.

I think there's a few important things I would mention from experience of owner both the early V8s and later V8s as well as general observations - as a lot of people have mentioned, I the cold weather its hard to determine whether smoke is anything serious or not. I would be concerned about the antifreeze residue on the cam cover gasket and the smell you describe. Burning antifreeze smells quite sweet, if that's what your getting it means coolant is escaping and burning on the engine block. These v8s have a number of flaws - firstly the thermostat housing and water pump are plastic and they crack with age, they sit right under the engine cover towards the front of the car. Secondly, there is a small rubber pipe that exits under the throttle body which is prone to split with heat/age usually resulting in coolant leaking from the back of the engine underneath the car, but only when hot. I would reccomend checking these items first - white in the oil cap again is indicative of condensation rather than head gasket - check the dip stick for white is a better bet of head gasket failure. Lastly, if you do any more major work, you really need to do the timing chain tensioners, they're also plastic and will fail, usually without warning resulting in engine failure

Great video!

I used steel seal on a Citroen C5 mk2 taxi with 550000 miles that boiled every 5 miles. Cured it and I sold it at 740000. Brilliant stuff

I've used Steel seal in the past and had no problems long as you have read the instructions, some times 2 bottles are need depends on the litre capacity of your vehicle, just run as normal after. The white smoke might be just build up of water left behind in the exhaust. take the vehicle for a run. I've had great success using the stuff, then when ready get a gasket fitted in time, I would say it would be on how good or bad the fix is using Steel Seal, giving it this road test will show it, but always a have a back up plan just in case.

I have used this stuff on my son's fiat Punto because there was bubbles appearing in the system. It worked fine in his car .He once brought a Vauxhall Corsa 1200 cc that had mayo on the oil cap but that wasn't a head gasket. To be honest I wouldn't put any shit in my cars as if I'm keeping them , which I do till they are no longer worth spending money on . I would just do the head gasket as it isn't that much work . Just make sure you keep an eye on your timing settings and don't try to do short cuts . It's a pain to clean that stuff out the system if you need to as it coats everything.

Hi Joel, I've used Powerbell Garage near Maidenhead for my XJ many times and have always been pleased with them, so might be worth try. Good luck with it!

Don't worry about that amount of water vapour coming out of the exhaust, perfectly normal on a car of this era in winter! The small amount of 'mayo' on the oil cap, again is not always a concern, especially if you're doing shorter journeys in cold damp weather. What is more a concerm is coolant loss without an obvious visible leak. The steel seal you used is a good temporary fix. I had the 3.0 v6 s-type a 1999 model, had the same satnav as yours, quite a rare option, with I think cist around £1200 originally, most most had a lockable cuby draw type thing there! I used to enjoy using it but was more often driving over grassy fields on the screen as any new roads weren't on there! Mine came with the satnav book and originsl software CD, as far as I remember there is a unit in the boot that reads the CD so I guess you might be able to update the maps? I had a few electrical gremlins in mine that I couldn't pinpoint, the front passenger door would have a mind of it's own, sometimes locking sometimes not, sometimes double locking, so you couldn't even open it from inside, then oddly it would randomly start working again! I was just concerned if that happened in an accident and I couldn't open doors....⚠️😲 So had to part with it very reluctantly, nine was absolutely mint, paid just £600 had a full jaguar service history only had around 95k. Very nice car to drive, just a very thirsty car....😳😁

I used it on my dads car for larger engines you need two bottles of the steel seal. It does work brilliantly.

Hi Joel hope your well I've used steel seal many times and it's excellent you can't really mess it up with regards to the smoke I wouldent worry to much its so cold out you'll find alot of the time it's just the hot air meeting the cold from your exhaust looking like it's smoking when it's actually not. You'll find this more with petrol engines than diesel 👍 wish I lived closer to you I'd more than happy to help you out

Uncle had a major head gasket problem on his Ford ranger used this stuff and fixed it ran it for 2 years no problem!

Looks like condensation Joel. Take the plastic engine covers off to see where that other coolant residue was coming from. That is a big win that it is not the head gasket.

I had this exact same problem with the water leaking out under pressure from the expansion tank on my 01 S-type. . I was lucky to have a very diligent mechanic who replaced all the hoses to the heater and the expansion tank. Please have a pressure test done on the cooling system as overheating the engine will have damaged the head gasket and you don't want that to happen again even if the additive worked. I have never had much luck with additives and just replaced head gaskets as I never felt confident in the engine again.

I ran one of these in mid 2000s with a blown head gasket for 18 months without issue, pain to keep topping up the fluids for sure, but tbh it was bullet proof! It's the electrics that will bite you on the arse mark my words. Top tip.... Get a decat straight thru exhaust for a glorious V8 soundtrack. Good luck fella 👍

Not to be the voice of doom, but I used to have a 1999 e39 540 and had a very similar issue, white smoke and loss of coolant. Just the same as you, replaced the whole cooling system, which actually made the problem worse as there was nowhere for the pressure to escape. In the end I went down the not cheap route of stripping the engine, and it turned out the bores were scored. New engine job!

I've used a bars leak alumna seal on a Ford ranger with the 4.0 v6 pushrod engine. It solved a coolant leak and over heating problem. Bars sealant used to make a sealant that looked like liquids copper that worked for sealing a cracked cylinder head on a straight 6 chevy.

Hi. Nice car. No experience with Jag V8s, but I do run another V8 from the same era in a similar car, and can tell you a couple of things. 1. the white sludge on the bottom of the oil cap could be condensation. These engines are large, and have more oil in them than your average 1.4 Vauxhall. That means that it takes longer for them to fully get up to temp (and I mean oil temperature, not water temperature as indicated by the gauge). If you use the car for short(er) drives, or it's been shuffled around on the lot before you bought it, the oil probably rarely got nice and hot, and thus, will have a bit of moisture in it. Take the car on a good long (1+ hour motorway) drive, get it nice and hot, and recheck. 2. The white smoke out of the exhaust is normal, especially on these cold winter days. The combustion process leaves a bit of water behind, and on a long car with dual exhausts there's plenty of real estate for that to condensate back and turn into steam. If the exhaust itself doesn't smell sweet, and there's no oily residue coming out of the tips, I wouldn't worry too much about it. 3. You may have had a slight head gasket leak, leading to blow-by entering the coolant system. This explains why, as soon as the thermostat opened and the fan kicked on, the coolant rose. It's essentially the system burping out the exhaust gas. I personally don't have a lot of confidence in those products fixing a fully broken head gasket/heavy leak, but if it's a slight crack in the gasket, or perhaps coolant mixing with intake gasses through the crossover, I can see that product improving matters.

I have to agree with Deano, your "white smoke" is probably condensation from the exhaust system. It's a cold day, so you will get that.

I wouldn't worry about the white smoke at this time of year. I would be more worried about seeing if the coolant is still dropping .

Chris forbes, best jaguar specialists in the country, and very fair on cost, Coventry area, not a million miles away

Drive it for longer periods. Steel seal takes time to work. It's definitely nothing to worry about. Mayonnaise again is condensation. Drive it and enjoy it

Ive had great success with sealers once in a head gasket and 3 times to stop major oil leaks . Hope it works .

Chin up mate, it sounds like all is not lost reading through some of the comments here. Fingers crossed!

Joel = Lowest , deepest baritone voice ever. Also Joel = high pitched laugh like a 10 year old school girl when the other Jag flashed the lights. LMAO!

As a point of information, we have an old BMW Z3 that has all the white steam signs of a bad gasket, as well as lots of white goo in the oil around the cap. However, the car does not use any coolant (been like this for over 15 years)... it's plainly due to the car running short trips all the time, it takes hours of driving to get rid of all the steam--it does go away eventually. Looks like you have fixed it (for now). I have over the years had a few cars where the sniff test has gone yellow. Another symptom of the problem is coolant leaks all over the place as the pressure destroys the system. Coolant that rises and then falls as the thermostat opens is another sign as the gas from the engine displaces coolant in the block before the thermostat opens. In my cases, I removed the head and replaced the gasket etc etc etc. If you want to keep a car for a long time then a head gasket failure is a good excuse to address many potential issues at the top end of the motor and valve train. However, on a car like that Jag its going to be days and days of work which will cost way more than the value of the car unless you can do it all yourself.

Water vapour is a normal part of the exhaust gases, so steam from the exhaust when idling is perfectly normal, especially on a cold day. Before you spend any more time and money on it, try driving the Jag around and see if the coolant level stays the same.

Regarding the smoke from exhaust, it might be that there is some water in the exhaust mufflers. If you have minor leaks in the head gasket you want see any avoporation, the leak should be notable and probably you will see smoke.

Definitely get a pressure test kit. Similar price to the bottle of sealant. If it holds 15psi for 10 minutes cold there is unlikely to be a leak. If it drops you have a leak, just a matter of finding it. If the coolant level drops every time after driving it's got a problem that needs fixing. Good luck,no loss of coolant for 3 years on my s type 4.0.

I managed to resolve a head gasket issue on my XJ6 series 3 (4.2 litre inline 6) using a head gasket sealer. Slightly different product, I did use 2 bottles, and I did flush the system first. But it worked.

Straight pipe it, baby!! Make it sound like an Aussie supercar! I wish I'd known about this product when I couldn't resolve overheating issues with my twin turbo 350Z. I'd still have it now, instead of selling it for far less than i invested in it. That's always the case with modifying. But if that product would have worked on it, I'd still own it and still be enjoying it. I even spent £7k on an uprated bottom end and supplied the gasket kit to the garage fitting it. As it is, the guy I sold it to stripped down the engine and informed me the head gasket had gone and that the failed gasket looked very old. The garage didn't fit the new one but were adamant they did (fit the new head gasket). Instead they continuously changed parts such as radiator, thermostat and bleeding the system. So yeah, I really wish I knew about this product. I'd have given it a whirl.

I used a bottle of rad weld on my diesel smart run around after my coolant leaked all over the floor. A bottle down the expansion tank and a few miles later it was sealed. No issues since and maintaining coolant levels