how to find intake leak

[ivymike]

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).

 

[RossABQ]

The fact you hear it in the car may suggest it is an HVAC damper motor under the dash, or the line to the heater control, that is leaking. Many damper operators have controlled bleed-offs (outside air door for example, so it closes when engine is shut off).

 

[GregLocock]

Try spraying the serpentine belt with water or detergent and see if the noise goes away.



Cheers

Greg Locock

SIGlease see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[evelrod]

I don't like that idea, Greg. If you want to double ck the belt, pick up a small can of belt dressing and shoot a couple squirts on the belt. If it's slipping, it'll stop...if it's not slipping, no harm, no foul.

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