Speaking as someone who has been using flammable materials to find vacuum leaks for over 40 years I have seen my share of flash fires.I always thought it a necessary evil but it is not the safest way, I recently found out. The safest way is to generate and inject smoke into the intake under mild pressure and see where it comes out(with the engine off). Just last night I saw a guy confirming bent valves with the same method by setting the cam lobes to fully closed and injecting smoke into the spark plug hole.Genius! You learn something new every day.

The smoke test method is also the safest as you don't have to worry about a running engine!

Finally. Someone who knows what breaks the rubber down when using flammable liquids. I haven't seen anyone else mention that.

Not only excellent tips to find a vacuum leak, but excellent explanations of the pros & cons of each method, as well as safety precautions!

I have been doing research on finding vacuum leaks. Positive smoke pressure seems by far the most effective and SAFEST way to do it.

Extremely informative with much wisdom involved. The quality of instruction I would want for any mechanical staff with caution I would also want in a compliance inspector. You are the man.

Absolutely a fantastic video. Loved the safety tips. A lot of good stuff here. Am 69 years old. Have been working on cars for a long time. Feel this video taught me a lot. Thanks for the great video. Loved it.

Love your idea! Give you another idea. You can do this on a cold engine not running. Get a fog machine. Attach a PVC pipe and hose to the machine. Connect it to the brake booster vacuum line and you will see the smoke coming out. A friend of mine was struggling to find a vacuum leak. He had been working on it for a few hours. We used this method and found it within a minute.

Good video. Yes, the soapy water method is good for finding positive pressure leaks such as pin holes in tires and wheels, not vacuum leaks

I was a small engine mechanic for years and always used starter fluid because of the small amount of oil present in my mind made me think it was less likely to over dry. I really like the propane idea.

I'm 62 and have never heard of this before today where I have seen it twice.

As a precaution with rubber hoses and fittings is use a 1/4 spray bottle of gasket leak sealer mixed with 50% mixed coolant and 50% distilled water. This stuff keeps all your rubber stuff as new and restores old rubber. I even spray it on exposed gasket around the head and underneath the car and around tyre rims and air valves even my wetsuit. A $50 bottle lasts forever and saves a lot of heartache.

I was a carb cleaner user for years, though scared I was going to catch fire and burn to the ground myself. You've convinced me to switched to the propane method bud! Great video. Clear and concise with no BS added. Thank you!

Good video 👍. If you are keeping your car and your hoses are old and cracked. Start replacing Vacuum hoses they are inexpensive sold by the foot. It will save you time and give peace of mind.

My father told me he was going to propane to find the vacuum leak on my car and I got quite nervous. Thanks to your video, I can now breathe again.

Thank you for sharing a safe way to detect a vacuum leak using the propane tank.

For the most commone torch nozzles, be they brass or steel, the sizes for the hoses tend to be either 1/2" inner diameter for the brass tips and 3/8" for the benzomatic tips.

I'm having a idle issue and am going to do this before going to the fuel. Thanks bother. Good info!

Thanks never tried the propane method and have a car with that exact problem .

I'm glad I found this vid. I was thinking about using my old propane rig, which is already set up with a hose, so I came in and checked KZfaq. Here you are, thanks!

It's better to do this outside. Propane is a heavy gas, heavier than air, and can collect in the floor drain/pit of your garage creating an explosion hazzard. I do HVAC/R and we had to have training on flammable refrigerants like R290 (propane). With that said, i agree this is the best method, great video!

I have seen Mechanics make a mess with spraying brake clean to find vacuum leaks. I use propane too and its the best. Nice Vid.

This is the best vacuum leak guide on KZfaq 👌🏻. Just a quick note- vacuum leaks could also come internally from inside the brake booster, EGR valve, or PCV valve, and you can check these by clamping on the hoses that lead to them.

your beard tells me your propane method is safe!

Great video very clear to what works. Fire extinguisher. Yes, that is the next thing i must buy . Cars don't run well when they catch fire!

That beard is a masterpiece. A national treasure.

I used my vape while the engine was off and cold. I simply vaped into my brake booster line and watched where it came from. Found my leak without flammable materials. Great video tho

Done this for years. Very reliable

Older vehicles maybe, but I've found watching for RPM increases with the introduction of propane doesn't work very well with today's Idle Air Control (IAC) which quickly steps in to maintain steady RPM. Perhaps watching for changes in fuel trims on a scanner as propane is introduced but I haven't had much success with that either. But that's just me. I opt for smoke test.

This an excellent, consciousness video; however if you have an older vehicle and are not equipped with a propane torch, I would suggest buying all new vacuum hoses. All hoses are subject to decomposition, and by replacing them you will be rest assured that the problem will not arise in the near future, and you've saved having to by a propane torch you may not frequently have a use for.

Tried Mapp Gas (it was what I had handy at the time) and put it right on where I later identified the leak coming from audibly using a section of pipe to isolate the source and it just didn't seem to react with increased revs in a struggling engine. The leak is huge and you can hear it hissing bigtime. If you can hear the vacuum leak hissing, you can isolate it with a section of pipe put up to your ear. You could probably do the same with a section of hose as well.

As far as I have understood, your 1 should be either: 1) pressurize the system from shop air (regulated of course) and use soapy water, or 2) pur loads of clean water into the engine compartment (nor spray bottle, pour directly from bottle)... The first will bubble on your leaks and works with a shut off engine, the second works at any temperature. As for water in the engine compartment, ask yourself what happens when driving after someone else in the rain. :) Besides these points I only agree with your points for 2 and 3. Thank you for your video!

9:51. Dope deciduous tree silhouette! I’ve been drawing and photographing a couple thousand deciduous tree silhouettes. Ive got a close up looking thru the branches in the foreground w/an abstract nature-scape in the background. They’re nature’s perfect stamp.

Thank you for your time. I know how to do this But my son who was 16 @ the time. Your video was educational and hit all the marks. Thx again🤙🙏 -San Tan Valley, AZ.-

I must say this method has to be one of the best I've seen (I've used the other two and gages) I'm going to try this next time round, thanks indeed!

Appreciated safety tips with fire extinguisher and safety glasses.

I really like the idea of only doing small bursts of propane - that makes it so much safer, as it dissipates quickly. Golden Tip, if you don't have a smoke machine.

Didn't see someone mentioned it in the top 20 or so comments but Propane is heavier than air so this could help putting it where you want in those hard to reach areas.

A home-made smoke machine (including a flow meter & a a small battery powered aquarium pump) can be made on the cheap to provide low positive pressure for visually finding vacuum leaks and if one uses glycerol instead of mineral/baby oil, it becomes both safe, easy to use, and non-toxic to breath the smoke, plus with or without smoke, one can then more effectively use the soapy spray method. As a bonus, you won't need a fire extinguisher with that setup.

Damn excellent idea, I never thought of using propane gas, it makes allot sense.

Not all brake cleaners are good for Plastics and rubbers so keep that in mind. But carb and choke cleaner is safe to go onto plastic and rubber. Edit.. never mind you covered it, awesome!

lol shit. all i needed to do was see a screenshot of a propane torch with a hose on it and i was sold. no need to watch the video. DONE. got it. understood. brilliant.

Excellent video, from smart, common sense instruction....I have learned something...My thanks to the gent that made it.

The best and safest way is the smoke method. You connect a smoke machine (can be rented from most auto parts stores) to the engine through the intake by the air filter. And it's all done while the engine is off. The smoke will come out where the leak or leaks are. No worries about a fire or damage to any components on or in the engine. Plus this is the method auto technicians use. And it is more precise.

Testing for leaks with propane starts at about 7:21 for those who want to learn how to do it instead of" why other ways aren't good". You're using most of the video to tell how not to do it before you get to the testing instructions.

Would have been nice to hear the change in engine idle. Thanks for the tips.

I agree with the reasoning. Propane has and ignition temp of 900° to 1100° that's about 200° hotter than any thing in the engine bay other than a stray spark. On a hand held propane torch, you have a valve to cut the fuel supply to an accidental fire. Or you can remember since you are holding the torch in your hand already, just remove it from the vehicle. Flammable liquids ignite at common engine temperatures, and you can not control or remove the burning fluid if it ignites.

Your video is very clear and easy to understand. Excellent job! Love the tree tattoo on your forearm.

I Sprayed willy nilly once. BAM!!! cracked my rubber!!! Diggin the beard bro.

I have found that using a carbon dioxide fire extinguisher is the ticket. You do not have to worry about cleaning up some yellow flour which is impossible to totally clean up. Where the gas just does things right. Good day and nice video with different points to consider too. VF

hello brother Just want to say that I love the beard And I like The idea of using propane. Keep the videos coming god bless you

Hank Hill approves

I use only propane ,contrary to what some have said it is the safest way. Propane may flash over if it does ignite but it is brief and easy to control. I also use spray lacquer to seal some leaks. Lacquer drys almost instantly and will give a permanant seal to leaks in places like a warped throttle body and Lacquer doesn't damage rubber.It sure beats spending over a half a day taking off all the mess on top of todays engines to fix the leak?

The propane method is pretty good, however if you have vacuum leak from something like a low torque gasket or seal you won’t notice an RPM change. That requires a scan so you can watch fuel trim for change at the same time your testing with the propane. The best thing to use is a smoke machine. Also if you’re using propane method on a carbureted vehicle then the RPM decrease when you hit your leak with the propane.

when I first saw the propane, I thought you would feed it into the system like smoke and check for the odor, lol, your way is much better!

As for the soap and water technique. To make it work you hook the output of a shop vacuum to the TB and open the throttle wide. This will pressurized the intake system. Then spray on the soap and water solution. The outflow of are from a leak will show bubbles like a hole in a pressurized tire. This technique has many advantages: Very safe - no fire extinguishers needed. Shows exactly where the leak is occurring. Done while the engine is cold so parts dont have a chance to heat up and seal the leak. If you are worried about getting water getting on electrical connections, dont worry about it - all the connections are IP67/68 rated for water ingress, and a low pressure spray will not cause *any* issue.

Fill an air tank with 15 psi or so and puff a cigarette or cigar into the break booster till smokes comes out your air filter. Then plug air filter area with grocery bags and release air into break booster. It forces smoke out of even the tiniest leaks. Easiest and most effective way in my 2 days of experience 😂

Fuckin brilliant. Most logical, effective, quickest, and safest method I’ve seen. Thanks brother!

It's easy to remember how to use a fire extinguisher if you can remember the acronym PASS, which stands for Pull, Aim, Squeeze, and Sweep.

what I do is remove the intake from the air filter, jam a plastic cup with a tire valve drilled into it, and just pump some air in with a compressor, without the car running. best solution to date

learned something new. Thanks Ive always used brake fluid, carb cleaner, starting fluid but always afraid to have an arc ignite the puddles that gather at times. I've used it to test fuel pumps as well. I learned to not stomp the gas pedal while injecting starting fluid cause its prone to backfire with a flame. I'm curious if this method would be any different when trying to test for a bad fuel pump. Curious if you tried it and if you pressed the gas pedal while doing it. I'm more then sure it would be the same but with a more explosive reaction due to it being a vapor then a liquid fuel.

I used to use a nonflammable electric contact cleaner on snowmobile crankcases to detect vacuum leaks. While idling the engine rpms would drop off the instant the spray hit the leak. This might be useful here too.

Very clear instruction. Thanks.

So cool I accidentally found this tip. Thank you!

I'd argue that the smoke test method is the best. Cost less than 15 bucks to make and much easier to spot leaks!

Actually, Propane can pool as it is heavier and air and will settle at the lowest point that it cannot escape. This includes under intake manifolds etc. Not a big worry but would be a good idea to run a low flow fan to keep the gas moving down under the engine bay,.

This is a solid video. Great info! I never liked the Ether method...

1. Disconnect a vacuum hose. 2. Take huge hit off a Bob Marley sized doobie and blow the smoke in the vacuum line. 3. Where you see the smoke exit is where you have a leak. 4. Hopefully you find the leak before you pass out.

Thanx sir I especially like the safety reminders great job my good man!

Keep simple and safe, i like the vaporizer method.

Very direct and educated!

Thanks, excellent video and explanation, blessings to you and family.

Never thought of that that's pretty damn smart

grate video I learned a lot and you brought up a lot of good points like for IE spraying starter fluid on rubber hoses that are not leaking but may from it drying out the hoses. so glad i found your video

Good video, thank you. But instead of using dangerous substances use seafoam spray - much, much safer way, non-combustible, no hydraulic shock, and you will hear changes in the engine.

My husband just went out side. Oh geez he will butn the car to the ground. I hope he listens to the safety instruction. I have the fire extinguisher ready!

Best one yet. I'll pass on cigar smoke.

in addition, I would add a piece of tubing on the end of the hose! a smoke machine works well too!

Ive had my gas and propane ticket for years and youve got abilities backwards.Its heavy and seeks lowest anD LNG disperses unless knowhere to go. Just the facts no bad intention

Dude you got me with this one video! I subbed right away! Awesome presentation.

Great teaching skills :) Have a good day!

I like the idea it's easy it's cheap and does work 👍 I have personally used on my Tahoe and seen it's done....... Keep it up

My grandfather used to tell me that they would sell smoke in a can and that's how he always found vacuum leaks in the old days. I can't find that at stores but I can finding on Amazon

Brake clean...all I use for last 46 years...works just fine....light sprays until idle changes...leak found..spray evaporates quickly

Exellent description . Thanks for your help

Thank you man. Super helpful

Good presentation in my opinion and including safety awareness is noted. Thx

Awesome video!😊

Smoke test is the best

Excellent vid , masterful dissertation.

Check and see, but I think Map gas is acetylene gas, burns hotter for silver solder. I used the spray carb cleaner too, I have used soapy water & compressed air on finding AC leaks too. next time ill try propane ,Good video !

Thank you! I’m going propane!

FYI-LPG or Propane is heavier than air. If u use a lot of it the propane “gas” will pool in below grade or pits or crawl spaces etc, as a gas. That could be dangerous. I would only use this method if I was in a lemme know when close area outside away from the house assuming I only needed to test a few specific areas. Therefore not releasing that much propane. Good luck

good video, though I think spraying plain water and watching for any white smoke coming out from the tail pipe is very good test and 100% safe

Nice Flag 👍🏻

A smoke machine is $100 dollars or under. I spent $135 for mine. It has built in compressor and a gauge. Worth every penny. I like it better than a potential bomb in my hand. I used it on a bmw 323i that had a cracked valve cover never could have found it with the bomb method. Play it safe get or make a smoke machine sell it when your done you'll only be out a few bucks.

I use propane instead of starting fluid for diagnosing a potential fuel delivery issue, or to get an engine running when the mechanical fuel pump isn't primed. I've seen 2 vehicles go up in flames when fluid was used. Starting fluid doesn't flash off as quickly in the cold, allowing it to accumulate and become a hazard.

Thank you good looking out

I can only HOPE to grow a beard like that... Since my job doesn't allow me to I have to wait until my retirement in a few years!!!! 💯

Awesome Video!!!