Using propane for vacuum leaks
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Cargo Master
Joined: Apr 2003
Posts: 3,476
Likes: 224
From: Frequently frozen MN
Using propane for vacuum leaks
I've read here and elsewhere about using propane and other flammable stuff to check for intake leaks. I'd appreciate a few details.
I assume that we're talking just a small torch, and maybe just cracking it on a quarter turn or so -- is that right?
I also assume that you have to lay the torch over to reach the various locations. Any problems with that? I've heard that it's best to keep the torch upright.
Also, do you get a lot of sudden flames? Anything to watch out for?
I'm really curious because I know that propane can be some nasty stuff. I realize that it's just a torch, and I do plumbing, etc with mine, but leak checking is a new deal for me
Thanks,
I assume that we're talking just a small torch, and maybe just cracking it on a quarter turn or so -- is that right?
I also assume that you have to lay the torch over to reach the various locations. Any problems with that? I've heard that it's best to keep the torch upright.
Also, do you get a lot of sudden flames? Anything to watch out for?
I'm really curious because I know that propane can be some nasty stuff. I realize that it's just a torch, and I do plumbing, etc with mine, but leak checking is a new deal for me
Thanks,
Elder User
Joined: Jun 2004
Posts: 540
Likes: 0
From: Northern MD
Remove the head from a Bernz-O-Matic torch and connect a length of hose to it. Open the valve and move the hose around where you think the leak might be. If idle speed increases, then you've found your leak. I've used this before, but I didn't have a vacuum leak like I thought. It's supposed to work and be neater than sparying carb cleaner all over the place.
Lead Driver
Joined: Apr 2001
Posts: 6,335
Likes: 6
From: Midwest
[QUOTE=ford2go;6303270]
Also, do you get a lot of sudden flames? Anything to watch out for?
correct me if i am wrong,but you don't actually light the torch,it is the gas from the torch that causes the engine to change idle speed,no flames involved.
Also, do you get a lot of sudden flames? Anything to watch out for?
correct me if i am wrong,but you don't actually light the torch,it is the gas from the torch that causes the engine to change idle speed,no flames involved.
MSEE
Joined: Apr 2004
Posts: 10,386
Likes: 35
From: Austin, TX
That is my understanding cjben. Vacuum leaks are detected by idle speed increasing due to a more flammable chemical being introduced into the combustion chamber. I haven't used propane but I use carb cleaner all the time. It dries so fast that it doesn't really get messy, the only problem is trying not to inhale it.
Hotshot
Joined: Jan 2004
Posts: 19,768
Likes: 1,082
From: St Louis
The computer is so fast that will "fix" the idle speed and you'll never hear any difference.
That used to work for old carbed engines.
I use my scan tool and watch the short-term fuel trims and look for a sudden spike when the enrichment agent hits the intake air stream.
Steve
That used to work for old carbed engines.
I use my scan tool and watch the short-term fuel trims and look for a sudden spike when the enrichment agent hits the intake air stream.
Steve
Lead Driver
Joined: Jul 2007
Posts: 7,868
Likes: 9
From: Rhode Island
If it is not a drive by wire vehicle, you can unplug the air idle valve, and stick a piece of paper as a wedge in the throttle linkage to set the idle speed manually.
My neighbor used WD40 and some Marvels Mystery oil in a spray bottle, and sprayed the intake of my truck down to find the vacuum leak. The engine would start to run rough and put out excessive smoke whenever it sucked in some WD40 or MMO
My neighbor used WD40 and some Marvels Mystery oil in a spray bottle, and sprayed the intake of my truck down to find the vacuum leak. The engine would start to run rough and put out excessive smoke whenever it sucked in some WD40 or MMO
Postmaster
Joined: Nov 2006
Posts: 4,517
Likes: 3
From: SE Wyoming
The computer is so fast that will "fix" the idle speed and you'll never hear any difference.
That used to work for old carbed engines.
I use my scan tool and watch the short-term fuel trims and look for a sudden spike when the enrichment agent hits the intake air stream.
Steve
That used to work for old carbed engines.
I use my scan tool and watch the short-term fuel trims and look for a sudden spike when the enrichment agent hits the intake air stream.
Steve
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Posting Guru
Joined: Feb 2006
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I use starting fluid. Hasn't failed yet. WD 40 and such would be too messy for me to even consider. 
jd
jd
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Lead Driver
Joined: Jul 2007
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From: Rhode Island
Now thinking on it, my dad's GMC Envoy is drive by wire, the throttle valve is controlled electronically, so there is no idle air valve. It responds pretty much instantly to turning the AC on/off rolling windows down or up, etc..
Trucks with idle air valves seem to take a moment before responding to changes.
Trucks with idle air valves seem to take a moment before responding to changes.
Fleet Mechanic
Joined: Jul 2003
Posts: 1,572
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I've used two small cracker tins availible at any thrift store. Get one smaller than the other so one will fit inside the other one with a least a 1/2 inch to spare. Drill vent holes in both about 1/3 of the way up. Loosely pack fibreglass insulation between the two. Put a small amount of bark chips in smaller can and light, put the lid with a hole drilled in it on the smaller can. Now you have a smoke generator. PS you don't need a lot of bark mulch. Vacuum leaks wiil suck the smoke in. HVAC supply houses have smoke candles, but I think they make too much smoke.