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E34 (1989 - 1995)

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  #1  
Old 05-05-2013, 02:45 PM
allenbee allenbee is offline
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Best vacuum leak detector ?

I'm trying to chase down what might be a vacuum leak on my engine. If it is a vacuum leak, its ****ing elusive. M50.

AFAIK, there are two ways to trace this. The first is by spraying carb cleaner at all joints, gasket points, etc, on the engine while the engine is on. That the throttle body, afm towards the throttle body, ccv point, dipstick tube, brake booster connection to the intake manifold, intake gasket areas on the cylinder head, injector ports on the intake manifold, and the valve cover gasket's outline..

If there is a vacuum leak at that spot, the carb cleaner gets sucked it through that once you hit it, and the idle normalises from rough or there is a clear change in the engine's note : it sounds 'stronger'.

The second is by coating each of those joints with soapy foam or shaving foam, also while the engine is running. If there is a vacuum leak, the foam gets sucked in (even if its underneath the ports concerned, the inrushing air pulls the foam towards the spot) by the leak. You can see this visually in a few seconds. No change in engine's behaviour.


Can there be leaks small enough to fail at the carb cleaner detection but be successful with the shaving foam ? Large leaks are never the problem, only the really small ones.


Thanks.
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  #2  
Old 05-05-2013, 03:04 PM
upallnight upallnight is offline
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I like using a Cohiba for vacuum leak detection.

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  #3  
Old 05-05-2013, 03:09 PM
allenbee allenbee is offline
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I don't smoke. LOL Might have to learn though ! Thanks ups forgotten about this test.

I guess my basic question is that would some vacuum leak tests fail while others succeed, when we are dealing with tiny leaks ?

Which is the best test for detecting micro leaks ?

Last edited by allenbee; 05-05-2013 at 03:10 PM.
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  #4  
Old 05-05-2013, 08:10 PM
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Bimmerfan84 Bimmerfan84 is offline
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Personally when I first bought my e34 I replaced all the vacuum gaskets INCLUDING injector seals (people often forget about these) I also replaced the hoses and boots. Almost all these rubber parts are extremely cheap as long as you don't mind doing the labor. However, I was still having a vacuum problem. It was then that I tested my Catalytic converters only To find they were restricted and causing vacuum issues. So don't forget the cats!
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  #5  
Old 05-10-2013, 02:24 PM
imae34driver imae34driver is offline
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Darn, i was gonna say smoke a cig and watch were the smoke goes.. got beat to that..




fck jdm / fck honda
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  #6  
Old 05-13-2013, 12:32 AM
paperplane94 paperplane94 is offline
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That cigar test is nice, but it ain't foolproof at all.
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  #7  
Old 05-14-2013, 08:14 AM
Larrick Larrick is online now
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I saw a great method on youtube. It is less dangerous and more precise than using carb cleaner.
Use a small propane or map gas tank, which plumbers use to solder copper pipe.
Place a section of hose tightly onto the valve nozzle and you can accurately locate the leak.
When the engine rpms go up and engine smoothes out you have located the leak.
It is a safe and clean method.
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  #8  
Old 05-14-2013, 08:59 AM
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CarDriver CarDriver is offline
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Quote:
Originally Posted by upallnight View Post
I like using a Cohiba for vacuum leak detection.

That is how I located the vacuum leak in my MB
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  #9  
Old 05-14-2013, 09:05 AM
PlasmaE34 PlasmaE34 is offline
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Quote:
Originally Posted by Larrick View Post
I saw a great method on youtube. It is less dangerous and more precise than using carb cleaner.
Use a small propane or map gas tank, which plumbers use to solder copper pipe.
Place a section of hose tightly onto the valve nozzle and you can accurately locate the leak.
When the engine rpms go up and engine smoothes out you have located the leak.
It is a safe and clean method.
Isn't propane gas less safe than carb cleaner ? Especially considering that you're probably going to be hosing down many places where there is no leak, before you get to the point where there is a leak. So that's alot of propane being vented around.

Last edited by PlasmaE34; 05-14-2013 at 09:06 AM.
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  #10  
Old 05-14-2013, 06:00 PM
snowsled7 snowsled7 is offline
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Both will burn.

The carb cleaner will leave a residue everywhere you spray it. If it isn't atomized enough it wont show the leak, if it is too much you are probably hitting a huge area. You can't control the stream or pressure very well.

As mentioned, propane is clean, most of it just blows away but you can direct well atomized combustible gases more accurately. You would have to contain and ignite propane gas for it to become much of a hazzard.
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  #11  
Old 05-14-2013, 06:21 PM
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BMR_LVR BMR_LVR is offline
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^ +1
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It's Deja Poo - as in, I've heard this **** before.
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  #12  
Old 05-14-2013, 07:25 PM
PlasmaE34 PlasmaE34 is offline
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Quote:
Originally Posted by snowsled7 View Post
Both will burn.

The carb cleaner will leave a residue everywhere you spray it. If it isn't atomized enough it wont show the leak, if it is too much you are probably hitting a huge area. You can't control the stream or pressure very well.

As mentioned, propane is clean, most of it just blows away but you can direct well atomized combustible gases more accurately. You would have to contain and ignite propane gas for it to become much of a hazzard.

Gotcha. Thaks..
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