finding a vacuum leak

**Spikito** · 08-09-2011, 01:45 PM

OK so Ive got a gremlin Ive been chasing since february, I've posted about this before, but the hunt continues.

Well I've had a breakthrough, and hopefully a good one.

Backstory: Vacuum leak after header install, its a high pitch whistling inside the cab, that increases and decreases in volume in direct relation with RPMs....i hit the gas, whistle goes up, i let off, whistle gets quieter. Ive tried hunting around by ear, doesn't help, ive gone over everything with carb cleaner, no result. The first suspect was the AIR solenoid, but all that checked out.

The whistling also starts and stops at random, sometimes its there on start up, some times not, but very often, it starts and stops when I hit a bump, even very small ones.

So the other day I was at a red light....whistling like hell, I adjusted my A/C fan speed, and the whistling cut off, instantly. So now the last few days, when it starts, i just play with the knobs and it works pretty often, seems like its the two outside knobs that affect it, fan speed, and turning A/C on and off, heat/cold adjustments have no affect.

I forgot those controls run off of vacuum lines.....any suggestions?

**pajeff02** · 08-09-2011, 02:04 PM

Do all the controls function correctly? Any chance it is an electrical whine rather than a vacuum whistle?

**Spikito** · 08-10-2011, 07:05 AM

i dont guess i know what an electrical whine is, unless you mean the sound of an electric motor, but no, its not that.

im pretty sure its a vacuum whistle, but yeah the controls seem to work properly. I do remember a distinct "Pshh" sound when i changed functions, like i mini blow of valve, lol...but it doesnt do that anymore

**Spikito** · 08-10-2011, 07:25 AM

but like i said, its volume also volumes RPMs exactly

***SMWS6TA*** · 08-10-2011, 09:18 AM

check the HVAC line. It could have come off the back of your intake or have a crack in the line. This will effect your A/C and cause a vacuum leak and could make a whistling sound as the pressure increases or decreases.

**Spikito** · 08-10-2011, 09:26 AM

back of the intake....ofcourse....

***SMWS6TA*** · 08-10-2011, 09:34 AM

did you find it? It attaches to the MAP sensor.

**Spikito** · 08-10-2011, 10:29 AM

its 107 outside....my ass is on the couch, lol

***SMWS6TA*** · 08-10-2011, 11:03 AM

baby.....

**Spikito** · 08-10-2011, 11:28 AM

shut it, lol...i sprayed some carb cleaner back there the other day, no rev...but the leak is also intermittent.

can i pull the knob cluster out and check for a leak back there?

**pajeff02** · 08-10-2011, 06:49 PM

On our T/A, there is a vacuum pot for the HVAC that is accessible after removing the panel below the steering column (4 screws) and the panel over the pedals (2 pins). Look above the gas pedal and you will see vacuum lines and such in that area.