In the early 90s, I needed a cheap driver once and almost bought an older Cadillac with this engine from a flipper (here in south Florida, low mileage cars like this from the elderly are all over). I asked him if the HT4100 was reliable (this was pre Internet, and I had no experience with it) and he thought for a second and said "it is not - this one works fine, but it won't for long, if I'm being honest". I was stunned and grateful.

I remember even in the first few weeks and months after these terrible engines came out in the 1982 model year, coming across numerous 4100 engines and especially bare engine blocks in scrapyards, Not wrecking yards where parts are salvaged, but actual metal recycling SCRAPYARDS.

As a heavy line mechanic for Cadillac in the 1980s, I worked on several of these HT4100 engines. The most common issues with customer cars with this engine were oil leaks, mostly intake manifold. Also, overheating and warped blocks. Worth noting, the crankshaft flange only had 3 Torx screws that secured the flex plate to the crankshaft🤣. Also, this engine had such low vacuum that it wasn't enough to run the vacuum accessories of the car. So GM put a belt driven vacuum pump in with the other accessories in front of the engine (what a joke!). Cadillac should have kept the Olds Rocket 350 for these cars through the 80s!! The best engines Cadillac ever had were the 472 and 500 V8s. Honorable mention is the 425 and 368 derivatives of the 472....

The diagnostic system was amazing....all the code resets and real time data....plus the sequence to clear it all out....is great...once you learn how to do it. A lifesaver

I never was a big fan of GM, but they played a big part in my life. They had a wiring plant in my hometown, and my uncle worked there for 20+ years, from the mid ‘70s on. He passed away recently at 75.

Although I spent the first 13 years of my career as a mechanic at a Ford dealership (1983-1996), I did occasionally work on other makes of cars. Usually something taken in on trade by the used car department. One of those times came when they had taken a Caddy in on trade with a seized 4100 engine. It was a beautiful car owned by a reality company that was used to haul prospective buyers around town to look at property. Somehow, no one ever changed the oil. At 59,000 miles the engine locked up. So they traded it in on a Lincoln Town Car. The used car manager asked me to get it running. We got a replacement engine from a local wrecking yard. It wasn't terribly difficult to swap, but I could never get the damn thing to idle properly. The internet wasn't widely available then, so repair information on that engine was hard to come by. I tried all the tricks I would use on a Ford with poor idle quality. I ended up swapping the TBI off the old engine which seemed to fix it. I guess the ECM didn't play well with strangers.

It's always refreshing to be able to listen to someone with real knowledge on a subject, wax poetic on the character both good and bad on a love-hate platform. I've always wondered about how Cadillac people felt about the HT4100 and now I know! I'll look for a 4.5 or 4.9 Deville.

In the early 90s I worked at a machine shop and we specialized in the “HT” series engines. I liked doing a complete engine rebuild job on the rear wheel drive Caddys but hated the FWD ones, especially the oil cooler lines. It was one trying day that a 4.5 convinced me to go back to school for engineering and get out from under these things:)

The on-board diagnostics was a great feature for the time. My 85 Seville had it, my 94 Eldorado Northstar had it.

Drove my 85 Eldorado 4100 from Erie to Atlanta. Smooth at 85. It's my daily driver. You're right about the smoothness. I pointed it out to my wife. No shake or pull. I also have an 84 Sedan Deville with the 4.1. Yes, it is slow, but I drive like a real luxury car. As you said, the party doesn't begin until it shows up! Balboa Blue, Balboa Blue vinyl top, original paint. She's a head turner.

My dad had an 87 coupe de ville with this engine and we drove it from Los Angeles to Queens NYC back in 2003. The car was misfiring from the start and would struggle going up the Colorado mountains. It also almost left us stranded in the middle of nowhere on route 66. Craziest road trip of my life.

When I graduated from college in 1986, I bought a 1983 Coupe DeVille with this engine. It didn’t have much power but it was so smooth and quiet. I absolutely loved that car. Unfortunately, less than a year after I bought it, I was hit by an F-150 at a high rate of speed. The car was totaled. I replaced it with a new 1988 Chevy Corsica.

You sir....are loved and respected... thank you for you!!

"The party arrives when you do" -- love that! Another very informative overview. Thank you, sir.

I thank GM from the bottom of my heart, these engines provided this old mechanic with probably a million dollars of revenue over the years, there was a period of about 5 years where they are pretty much all I worked on

My uncle was a transmission specialist in the late 80s up to early 2000s for Cadillac, he sold me a 1986 sedan DeVille he had rebuilt the transmission and probably maintenanced at the dealer in late 2000 and the car ran smooth as butter for having the 4.1v8

Honestly, I think this engine and the reputation it earned- for being a grenade and a total slug in terms of performance- was the biggest straw that broke the Cadillac back. The Cimarron was a disaster, sure, but the 4.1 ruined what would've otherwise been great '82-'85 Cadillacs. I think it turned off a lot of buyers who happily left and went to Lincoln... which ironically had a 302 that wasn't much more powerful than the 4100. As shown by the Brougham that ran into '92 (albeit with the Olds 307 in '86 and the Chevy motors in '90), the cars themselves were great and honestly hold up very well even now 30+ years later. In particular, I feel the '80 redesign for the Coupe DeVille produced one of the most handsome cars of the era, but unfortunately any year aside from the 1980 is saddled with poor engines. I can't blame shoppers in the early 80s for shunning these cars, no matter how good they looked or how comfortable they are. The 4100 should have been held off until the downsized cars arrived for 1985- by then the engines had sorted through a lot of problems. I think the Chevy 305 or even Olds 307 would have been a much better option during this time after the V8-6-4 was deemed unacceptable. Even limiting cars to the 4.1 V6 or even the 3.8 probably would've hurt their reputation less. That being said, the 4100 did become what I would consider a good motor in the 4.5 and 4.9, which are nice to drive and have a much better reputation.

Cadillac tech for thirty years ,I named it 4100 hidden troubles. Had to keep up with the TSBs. When I got the vehicle in for 1 engine issue I would pull engine and do all the upgrades and fixes

I love these longer videos, the tranquil setting is wonderful too. Thank you so much.

Your knowledge of these cars is why this channel is exploding. Experts are hard to find. I really enjoy the calm demeanor and well presented material. Thanks.

I had an 83 Fleetwood with that engine, and I beat the hell out of that car. It leaked everything, had a throw-out bearing holding tension for water pump/alternator and other junk. It lived, never overheated, and ran fine. I graduated to a 4.9 93 DeVille, and after 2 transmissions, I happily saw I drive away to get parted out. I still have a 6.0 368 V8-6-4 in an 81 Fleetwood, still running but of course, cylinder deactivation is permanently deleted.

I rememb3r,as a Ford service technician in the late 80s the gm aluminum v8s were stacked to the ceiling in machine shops.. If I recall the cylinder sleeve o-rings were a continuous problem....

Thanks for thos review. I did not realize how slow those engines were. I liked your references to Bose and easy driving.

I cannot tell you how thrilled I am to find this video that you have made! I’m seriously considering purchasing a 1986 Cadillac Sedan Deville Limousine Hess and Eisenhart

The growth in the channel is fantastic - well done Adam! Great “Porch Chat” as always. Another classic engine!

Great job on this video. Your critique was outstanding on this motor

Years ago I worked for a firm on Atlanta's south side, whose fleet colors were Dove Gray. We had a Cadillac hearse from 1986. I do not recall who did the coachwork. Anyway it had a 4100 in it. We just hated it, not so much for lack of dependability, more for the lame power output. That engine combined with the weight of a Fleetwood 75 chassis and specialized coach work was completely overwhelmed. I really enjoy your in-depth reviews and knowledge. Thank you!

The 4100 which I had in an 82 Cadillac Eldorado was underpowered and used to ping when under load or going up a hill. The transmission would over rev and then buck to go from first gear to second. Yes, I do not remember ever going over 85 mph in this car. When I first bought it, all the sensors were clogged and had to be replaced. It wouldn't go over 65 mph and the engine had low miles on it. My favorite of all times was the water hoses that were channeled around the electronic ignition system. Someone didnt' hook them up tightly enough and one fell off its fiting and dumped gallons of coolant right on the electroncs. Killing it instantly .

Thank you so much for this video! This was the most comprehensive summary of the issues plaguing those of us who owned 4.1 Cadillacs. I had an 85 Sedan deVille just like the one you pictured and I absolutely loved the car as a whole. It was smooth, very quiet and extremely pleasant to drive. My 4.1 had been rebuilt before I got it, but I did have issues: 1. I suddenly lost the oil pump while driving. Fortunately I was on a quiet residential space and I shut it off within 5 seconds of the oil light going on. I towed the car back to my house and dropped the pan, what had happened was one of the large steel pins that the pump gears ran on had slowly worked downward, allowing the shaft to disengage from the distributor. I bought a new Cadillac oil pump at the dealer, it was an updated pump from the 4.5. This issue made me lose trust in the car. 2. It was very sensitive to plug wire condition. Once the wires started to go bad it would slam into a lower gear very harshly, at first making me think that the trans had gone south. I drove out to a very dark place at night and watched sparks go all over the wires. I replaced them and the problem went away, only to reappear maybe a year later. New wires again solved the problem. 3. My 4.1 and many others I heard had a dull thumping sound in the engine. Somewhere I read or was told that it was camshaft end play. I don't know, but it sounded bad. 4. My thermostat went bad twice. Not bad enough to overheat and turn the light on, but when I parked and shut it off I could hear coolant boiling. I kept the coolant fresh and used the tabs. This was promptly repaired on both occasions.

The 4.5 was ok, the 4.9 was great! I had a 93 De Ville 4.9. Great gas mileage, a hot rod for performance. a pleasure to drive. Car had a few troubles, no internal engine problems. Trans gave trouble, gas mileage dropped from 28 mpg average to 20. Traded it off at 245K miles in '05 for a new Le Sabre. Another great car!

I enjoy your videos. Your patience and Mr. Roger's way of describing some of these nightmares makes me worry about my mental health since I've had some of these junks and thought they'd be better off in the bottom of a lake.

I am absolutely astounded at your knowledge. Killing time watching a lot of your videos tonight and you are an encyclopedia. Bravo.

I worked at a Cadillac dealer and worked on several of these engines, and the 4.5, and 4.9 caddys and the early northstars. The biggest issues with these were they liked to spit the rods out, as did the 4.5.. the 4.9 was the best of these engines.. the 4.9 had a ton of torque .

This kind of video is exactly what i like on this channel. We all can basically agree that this motor is NOT good at all. But still, some people love these year Cadillacs and want to buy one. So instead of just badmouthing it to death, it's better to help the lovers/owners of these cars know how to preserve them to minimize damage and issues. Please do a video on the onboard diagnostics. It would be well worth your time.

I worked in a Cadillac dealership from 82-87 as a major motor repair technician. First the diesel then the 4100 kept me busy and made me money. It was my understanding that the 4100 was designed for a downsized Corvette ghat they never built.

Great video.

I worked at a Caddy dealer 84-86. Had a front row seat to all the disasters. HT, 4-6-8, and the diesel.

That was a nice summary of the 4100. Brought back some memories, like the Off/Warmer self -diagnostic feature. Thanks for the video.

Thank you for such an enjoyable presentation. Detroit let Cadillac buyers down with the sub-par HT 4100, to say the least. HT=hook & tow.

You are really pumping out lots of wonderful, long, videos. You're now at the top of my list. Thank you for your time and please keep them coming.

I had a trick on the FWD HT4100. I could change the water pump in less than half an hour. That was fun.

Your knowledge is amazing. Are you an automotive engineer/exec or grow up with a parent who was an auto exec? My Aunt Helen and Uncle Mit traded in their 77 Electra Limited for an 84 Coupe Deville. It was to be their retirement treat. Less than a year later they got rid of it and went back to Buick. It was a shame because the Deville was really an attractive car.

Alloy head on a cast block I've heard of,but cast head on alloy block.Never met one,that's why Holden here in Australia had full cast motors until 04 for the V6 and 2000 for the 5000 V8.Then they went LS1

My first car was an 89 coupe deville with the 4.5 and I loved that engine but sadly I was young and hotrodded it. I ended up blowing a hole the size of a softball in the side of the transmission. Really miss that car though, it was so reliable.

I find this content fascinating for some reason

My dad had a 1985 Deville and you are absolutely right. Quiet and slow as a rock, made worse by a shitty 3 speed transmission....both of which died at around 65000 miles.

That water pump if I remember had to come apart with the front engine cover. My thing about these engines were the rocker assemblies.You had to assemble them on the bench and then there were five or six nuts that held them in place. This was one of GMs first Helicoil engines and they meant it. These engines had that gold colored oil pan I forget what they were made of but GM made a big deal out of it. You had to make sure you had an endless supply of red RTV if you pulled one of these engines apart.

For GM's Flagship Line, Cadillac had some pretty crappy engines after 1981

You did hit on something there about rushing to and fro. I don't understand people in Audis/BMWs etc going really fast on the public roads. Indeed the party doesn't start until 'you' get there. Enjoy the ride. Feel the 'Corinthian' leather. Listen to the quality stereo. Oh no ... I arrived perhaps 2 1/2 minutes later ... but had a truly grand time getting there. Gimme a Jag/Cad/Linc from the 'era' and someone else can pound the lateral g 's and wind up to 6000 rpms if they really must.

I worked at a Caddy dealership in the early 80s, they were coming in everyday.

I remember doing spark plugs on one of these. Passenger side back spark plug was horrible to get to.

Found your video on the Aurora and now I am subscribed and eating up your videos. Appreciate your perspectives and that fact that you are cementing this automotive history online, especially the interviews with former designers and such! Bravo!!

My GF bought a 1983 Cadilac Burritz in 1989. We knew, at the time, how crappy the 4100 engine was. You are exactly correct about the different metals used in the build. It leaked everything. I told Peggy before she bought that car to get an extra warranty on the engine and the dealer said sure. I think the car had about 50,000 miles when she bought it. After 9 months of ownership and all sorts of electrical issues the engine finally gave up. The dealer replaced the engine at a cost of $5000 (for them) and I think the salesman was fired for selling the warranty with the car. It was a beautiful car with a stainless steel roof. But, otherwise was a POS. Peg purchased a Jeep after that ordeal. Caddy had problems with other engine arrangements too. The 8-6-4 as another POS but likely due to early crude electronics. I'm retired now and have built several engines in the last 14 months. 454, 428CJ, 283, 350, 351, and a 502 and would love to get a 632 but at $30K I suppose I will wait on that one.

I drove an '85 El Dorado a few times. It belonged to a friend. It had the 4.5 and I think it was fwd. It wasn't super fast but it wasn't a slouch either. I reckon it was about 8 to 9 seconds to 60. Not great but not 16 seconds. It was super smooth and comfy though. A nice car to pile some miles on.

As a 1991 Cadillac Deville owner I love these videos, I agree with you about the 4.9 engine, it's great! I'm planing to change the water pump this summer by myself. Not looking forward to it. :/

I was an engine specialist at Cadillac in 84 and 85. We did bare block overhauls on these things as early as 27000 miles. They were so bad that Cadillac stopped putting HT4100 emblems on the fenders and then made the tuned port injected small block Chevy engine available in the rear wheel drive cars. I went back to a Chevy dealership. The HT4100's were BAD.

I never had a problem with my bi-metal Toyota engines, 300k miles and zero head gasket/oil leak problems.

You have a very pleasant way of conveying an impressive knowledge of these cars. Keep it up, the channel will no doubt do very well.

This car was my Father's pride and joy. Ours too as kids. I was around 10 years old when we bought it used. 1982 Gold Cadillac coupe DeVille. I can remember it like yesterday. We were coming home from a long trip, we were about a half hour away from home. Then bam the engine was knocking and threw a rod. The engine was dead. We were towed all the way home. My Dad kept it in the garage for a year, then sold the body for cheap. I loved that car

My grandparents had an '88 Sedan DeVille.. The car was garage kept and looked show room floor new. It had the 4.5 V8. As a kid, i remember the beautiful red leather interior. It was always serviced by the dealership. I remember the dealership would put some sort of tablets to put in the radiator every 3,000 miles. This was Cadillac's way of fixing the problem with blowing head gaskets. My granddad didn't catch it in time to save the engine. It only had 110,000 miles on it when it was scrapped.

I had a friend back in the 80s that I would race quarter mile with, he had a 79 mustang with a tube frame and fiberglass body we got the idea of building a cad 4100, I worked at a Cadillac dealer so I could get warranty engines for free, we milled the heads to get 13 to 1 compression, ported the heads made custom headers, had custom cams ground, car weighed 1400 pounds and ran 9.0 , the engines did not last long but we would do 3 at a time, they made about 500 horsepower so these will make a lot of power, but only for 10 miles or so LOL

Significant issues now there is an understatement.

The 5.7 liter diesel was right up there as well.

At the time, buyers wanted good mpg cars and Cadillac was attempting to do this, the 4100 was written up in car magazines for a few years as a good engine, then by 86 -87 problems started and the engine was redone into the 4.5 and later 4.9 and those were Cadillacs least warranty issue engine, so once this was redone, it was fine. I knew a few people who owned a 4.1 Cadillac and took care of it and ran them over 100k but also my Mom drove her 81 Riviera diesel for 20 years, and was still running when she got rid of it. Lincoln had a lot of trouble with their V6 continental 89-93, lot's of upset people with those.

I worked at a Cadillac dealer in the 80s, made a lot of money on that engine, seems like the first thing that would happen us the intake bolts would loosen, causing oil burning and coolant leaks, we called them hand tight 4100s lol, if you got it early all you had to do was tighten them but we had so many customers that wanted new engines under warranty, we had to hold the old engine until the factory rep looked at it, then I would take them home, fix them up, they went for over a grand, lots of demand, I was making more money on the free engines than my regular pay, ahh, the good old days!!!

The Iron Duke was a hell of an engine though.

Those injector dropout tests are great. My '88 5.0 Mustang (with an '89 MAF computer) can do that too.

hard to believe that a 1983 mercedes 240D will achieve a similar top speed. while the factory rated top speed is 84 most of these will reach 90 mph

Your videos are at the top of my watch list when I go to you tube. Great information coming to us without fan fare or fluff. Keep up the great work, Adam.

i avoided this video for a long time sence i figured it would be someone who had no idea about the engine just shitting on it. how i was wrong. i have a 1985 deville and this is super usefull info. thanks! also ive binged alot of your videos now and i do prefer the tranquil setting

My 96 Buick Roadmaster sedan has the on board diagnostics in the electronic climate control. My temperature gauge quit working so I use it to make sure the engine coolant is at least 100° before I start driving

In 1995 I inherited my grandfather’s Fire Mist Red 1984 Coupe De Ville when he passed away. It sat a long time before then due to his health. I drove it for about a year and during that time I had manifold issues, cam lobe issues, exhaust leaks, and other stuff. The weird rubber collar between the rear bumper and sheet metal was dry rotted and impossible to fix and I tried everything. I wanted to honor his memory and keep it well maintained and nice but in the end it just wasn’t cost effective. I donated it to a Catholic organization for the tax write off which was more than I could have sold it for.

My favorite car guy! Your hair and skin are wonderful! The best 🚗 LTDs and Mercury ❤️

Adam, you have a great thing with these videos. Such interesting conversations that so many of us can appreciate. Your experience speaks volumes (pun!) and all these videos don’t necessarily need to be road tests.kind of a fireside chat of sorts. Glad these are doing well for you. I find them wonderfully comprehensive. Thanks

I worked in a Cadillac only dealer in the late 1980s. We had fair size room in the parts department full of these engines. Always felt sorry for longtime Cadillac owners stuck with these…probably rarely had to deal with major engine issues in decades past.

This garbage engine is one of my passions. I had a 1985 Deville which was the first year of the transverse mounted 4100. Mine had 150k miles on it when I had it/sold it (I didn't own it for long I maybe put 3k on it). It was somehow the original engine, numbers matching. I didn't have any problems specifically with the engine, it used maybe a quart of oil every 1000 miles or so. I made maybe 19mpg combined out of that car which I thought was really good for such a barge. It was pretty slow for sure, but honestly it kept up with traffic and had no trouble keeping 75 mph. The engine was smooth and quiet, and had a nice sound to it to me. But the engineering story of this engine pisses me off so badly that I really enjoy retelling it with the lens of it being a perfect example of why you give your engineers the time to really do a good job and don't focus on making arbitrary deadlines. Fucking your customers with a shitty product will do you worse than the short bump in cash will net you.

Fun fact: the 88-89 4.5 was way overbuilt. That block continued in the Allante up to 92. The 90 4.5 is by itself. If you got an 88 coupe Deville, it did the quarter in 15 seconds. As fast as an 86 Monte Carlo SS. A 91 Eldo is an absolute rocket ship.

My bustle back caddy, with the HT4100, was my last American made vehicle.

Geeze a top speed of 88! Was on I-10 recently and traffic was moving at 90. A clappped out Camry with body parts literally flapping in the wind blew by me at over 100.

Hey Adam, I have a friend that had a Seville with the 4100 in it & he had nothing but trouble with it. Thanks for another interesting chat!! 👍👍

Thanks Brother, Very informative and well done.. Shalom~

Awesome have. 1985 Biarritz 80k miles please talk about the computer

I had a '84 Sedan DeVille with a HT4100. It had 310,000 miles when I let it go. If you drill out the rocker arm fulcrum bolt holes and add helicoils it is a good engine.

A classic.... something unique or best or worst of it's kind.

I had a 1983 Sedan Deville with this horrible excuse for an engine. NEVER AGAIN!

Huh all our post office mail trucks still use run the 4 tech they run great

........about my comment below on using Evans NPG+ Waterless Coolant. It is recommended to run a 0 or low PSI radiator cap. That should help stop pressure induced head gasket leaks/coolant leaks in a system that runs high pressure.........

Have you covered the Oldsmobile 260-ci/4.3L V-8? That one certainly is worth mention.

Look up the VW Wasserboxer engine for something to really talk about - It was only ever used in the Vanagon - it makes the Subie EJ25 look indestructible.

My dad had a 1985 Sedan DeVille, exactly like the one Adam pictured. The engine suffered the dreaded demise complete with oil and coolant mixing, even though the car had few miles and Dad drove it gingery. He had the engine rebuilt and drove the car uneventfully until about 2004. I had a 1991 Seville. No engine problems but I remember it vibrated significantly, which I thought surprising for a Cadillac. Also remember adding the coolant pellets and the prominently placed engine sticker instructing you to do so.

My 87 Buick Century had a 2.8 V6 that as a total piece of junk. The only good thing about that car was the Bose Stereo

1986, just back to the US from my first overseas tour in the USAF bought a 1984 Eldorado Birritz, Silver with a red leather interior. Car was slow and smooth but held up well here in the LA basen. Thanks!

In the Fall of ‘86 I inherited an ‘85 “G” platform Pontiac Bonneville as a company car. It had a V-8 (I believe either the 267 or 305 and a 4-speed automatic). I almost got into a wreck trying to pass a car when I first drove it. At 60 mph it wouldn’t even downshift into passing gear. Having grown up during the muscle car era, I just couldn’t believe how anemic V-8s had become. Fortunately, I quickly transitioned into a new 1st Gen Mercury Sable with a V-6. It was like night and day in performance, handling, and interior ergonomics.

in the early 80's when these engines came out, i knew they were going to be garbage when you were required to put stop leak tablets in the cooling system to plug up the coolant leaks due to poor design and manufacturing. my dad had one of these in a seville and it was a total nightmare. it went back to the dealer at least 8 times in the first year, he tried to have it lemon-lawed but was refused.

I'm very interested in a gorgeous 85 Seville, pristine, with 45K miles. This video scares the hell outta me, so I guess I'll just have to go with my gut. It would only be a weekend driver. Worries me but I love the car.

I used to go to auto auctions growing up, helping my dad check out cars to potential buy. Lots of HT4100 Caddys at the auctions at the time. We almost always avoided them. We didn't want to deal with upset customers with 4100 problems. We stayed far away from the 4-6-8 cars too. We actually liked the 5.7 diesel Caddys, Olds, Buicks, etc. Had more than a few as the family car, never had issues with any of ours but we were diesel people. I would LOVE to have a diesel Delta 88 today. Such a comfy cruiser of a boat, love the feel & styling.

My buddies dad has PTSD from changing dozens of ht4100s with failed camshafts at 1500 miles. The dealer had pallets stacked 4 high with customers' names on them just waiting for them to come back for when their current engine fails

Really interesting

My uncle had one in an 1985 Cadillac, nothing but trouble.

Please do make the on board diagnostics video. Im working on an 86 and the lack of gauges is messing with me.