Pressure testing questions...

**BITRBO** · 08-10-2008 03:08 PM

Is it normal to hear a "bubbling" sound coming from the engine while pressure testing? It almost sounds like engine oil, if that makes any sense

And yes, I've got the oil filler cap off.

Also, once I've got the system pressurized (~10psi) should it hold that pressure indefinitely, or will air still manage to leak out (even on a "healthy" system)...

edit: Oh, and does it matter if the car is warm or cold? Or if the ignition is turned on or off (ACC)? Not sure if either one of these will affect the results...

**Jibberific** · 08-10-2008 04:44 PM

Mine did the same thing. No hissing, only bubbling. I was told that this is normal.

**BITRBO** · 08-10-2008 04:58 PM

Phhhew. I thought for a minute that I might've had a band ring or two and was getting tremendous blow-by... So just out of curiousity, WTF is that noise if you're only supposed to be charging the intake system?? I guess I thought by disconnecting the PCV line there should be no air going to the crank case...

**Jayco88** · 08-10-2008 05:14 PM

my intake system doesn't hold pressure for shit. I have to constantly run air through it, and i know i don't have a leak because i can get my full 15psi boost... that's a good question though BITRBO, how does the air get into the crankcase?

**BITRBO** · 08-10-2008 09:04 PM

Yeah, not sure but maybe someone (*cough* *cough* Jerbel *cough*) will chime in...

Well for all that trouble, at least I found a couple leaks... one at the main junction of the spider hose and the other where I installed a T-fitting for the boost guage. These didn't appear to be gaping leaks, but we'll see if fixing them helps any of my other issues... But the leak it my spider hose may explain why I have an oily residue/build-up in that general area (and against the firewall). I knew something was leaking back there, but could never pin-point it. Everytime I would change my oil I would get a burning oil smell (when stopped or in traffic) for the first few-hundered miles or so... then it would just go away. So I guess I gotta find a replacement now for that too

On a side note: Is it just mine, or does everyone else's PCV hose clip on loose as hell? I mean, I can wiggle this thing all over the place... I don't think that crappy clip and o-ring do a thing!

**lvevo** · 08-10-2008 09:49 PM

Originally Posted by Jayco88

my intake system doesn't hold pressure for shit. I have to constantly run air through it, and i know i don't have a leak because i can get my full 15psi boost... that's a good question though BITRBO, how does the air get into the crankcase?

Don't go by the boost gauge. If you have a leak, the turbos will work harder to compensate for that leak. Which is why a boost leak is one of the killers of turbochargers.

**Slow4** · 08-10-2008 09:59 PM

Pressure tested mine this weekend, never really heard a "bubbling" noise. All I heard was the hissing going through the engine...

I did however find a leak

**HotSauce** · 08-10-2008 10:06 PM

Pull your dipstick out, that should eliminate some of the bubbling, and yes, it is oil bubbling. Totally normal.

And no, it will not hold pressure indefinitely. You will hear a pretty obvious hissing if you have a leak.

All sounds normal.

**Jayco88** · 08-11-2008 01:54 AM

Originally Posted by lvevo

Don't go by the boost gauge. If you have a leak, the turbos will work harder to compensate for that leak. Which is why a boost leak is one of the killers of turbochargers.

very true. thanks for pointing that out.

**BITRBO** · 08-11-2008 08:21 AM

Originally Posted by HotSauce

Pull your dipstick out, that should eliminate some of the bubbling, and yes, it is oil bubbling. Totally normal.

And no, it will not hold pressure indefinitely. You will hear a pretty obvious hissing if you have a leak.

All sounds normal.

Cool, thanks! Yeah the leakdown wasn't drastic, and I even sprayed soapy water on everything just to be sure I didn't miss anything... I'm actually surprised that my AMS TBB wasn't leaking... I had my doubts that it would last very long.

So any idea how/why that bubbling happens; it's pure curiosity at this point

**HotSauce** · 08-11-2008 08:27 AM

An explanation beyond that of "You're pressurizing your crankcase"?

**BITRBO** · 08-11-2008 08:38 AM

yeah, I mean... I'm just trying to visualize how pressurizing the intake system also presurizes the crank case. The only way I figure is that some of the valves are open (exhaust or intake) and the air is going into the valve journal/sleeves... otherwise, I just don't get it.