how to find intake leak
how to find intake leak
(OP)
I seem to have an intake leak upstream of the throttle, and I'm looking for suggestions at to how I might find it. The vehicle is a 2005 scion xb.
I first suspected that I might have a leak when I started hearing a "squealing" noise that was throttle dependent - no noise at idle, and no noise at ~10% load, but at very slight openings there is a whistle/squeal which has only recently become noticeable (but is annoying). I did a pretty quick visual inspection of the intake system and didn't find anything obvious... I decided that if there was a leak it must be a small one, so no big deal (except that damn squealing).
I've just gotten back the results of an oil analysis, and (surprise, suprise) it shows high silica and various wear-related metals. Seems like my engine is getting dusted. Now I need to find that leak.
When I'm under the hood with the engine running, the leak is not loud enough for me to get a bead on it even if I monkey around with the throttle. It doesn't help any that I've got some halfway-bad alternator bearings joining the chorus (I'll replace that when it stops charging).
I first suspected that I might have a leak when I started hearing a "squealing" noise that was throttle dependent - no noise at idle, and no noise at ~10% load, but at very slight openings there is a whistle/squeal which has only recently become noticeable (but is annoying). I did a pretty quick visual inspection of the intake system and didn't find anything obvious... I decided that if there was a leak it must be a small one, so no big deal (except that damn squealing).
I've just gotten back the results of an oil analysis, and (surprise, suprise) it shows high silica and various wear-related metals. Seems like my engine is getting dusted. Now I need to find that leak.
When I'm under the hood with the engine running, the leak is not loud enough for me to get a bead on it even if I monkey around with the throttle. It doesn't help any that I've got some halfway-bad alternator bearings joining the chorus (I'll replace that when it stops charging).





RE: how to find intake leak
You might even get better gas mileage ! ( OK - it's a joke - just thought I'd start that whole discussion again... )
The classic check is to have the engine running and spray a little carb cleaner around suspect areas. The rpm will go up if you have a leak.
Do it at your own risk - carb cleaner is very flammable.
RE: how to find intake leak
I thought about the ol' spray cleaner trick... while that approach seems to work fine with relatively small areas (gasket interfaces, for example), in this case I'm talking about a few feet of convoluted plastic crap, and I'm a bit worried about both fire and inhalation.
Any other suggestions?
RE: how to find intake leak
Regards
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RE: how to find intake leak
RE: how to find intake leak
Regards
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips Fora.
RE: how to find intake leak
RE: how to find intake leak
RE: how to find intake leak
So, find a smoker and use their talent, or find a smoke machine.
Franz
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RE: how to find intake leak
RE: how to find intake leak
RE: how to find intake leak
Rod
RE: how to find intake leak
RE: how to find intake leak
No good alterate explanation for the dusted oil... will have to have another analysis done in a few k-miles to see if the problem persists.
RE: how to find intake leak
There is a resonance in the manifold at idle or just off-idle that sounds remarkably like a vacuum leak. They all do it.
A "false air" situation (upstream of throttle) never makes a whistling noise.
RE: how to find intake leak
RE: how to find intake leak
Regards
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips Fora.
RE: how to find intake leak
Hope that helps.
RE: how to find intake leak
How many engineers does it take to find a pinhole in 2 feet of tubing.....
RE: how to find intake leak
Oh yeah, that may not fix the problem??? Love engines, just love 'em.
Rod
RE: how to find intake leak
RE: how to find intake leak
Cheers
Greg Locock
SIG:Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips.
RE: how to find intake leak
Just for giggles, Isaac...I once had an odd scratching sound in my '61 Vette...My cat got 'lost'...we found him behind the passenger side kick panel!
Rod