Dan Martinic

So.. I'm driving home today on the highway.. lovin' it!!!... put it in fourth.. pedal down... pulling hard!!!... then right at max boost, a faint pop, a little stumble. Still pulling.. .still smiling!! I slow down to do it again; this time, at max boost I hear a loud whoooooosh. Like someone popped open an air line.

Car is still driving fine! It didn't skip a beat. However, now every time I get a bit of boost going--even a bit--it's accompanied by the whooooosh of pressurized air escaping out of.. something. Kinda neat. But clearly no bueno!

Can't see anything on top so tomorrow I'll try and get it up in the air at work and hopefully see an obvious hole somewhere. Which brings me to my Q:

Is it ok to plug the exhaust & apply some small amount (5 psi) to the intake? When checking for vacuum leaks, I always leave the exhaust open and can hear the air going through the motor. If you plug the exhaust, it will be solid psi on all seals

The other thing will be trying to see what's going on under boost while on a hoist (ie. getting the installed wastegate to open)

Now this is the kind of issue I don't mind; no need to park the car for weeks lol

Anyway.. I'll post what I find. Any guesses?

Chapman951

BOV/ diverter valve failed?

divil

I think the only way you could lose air through the exhaust during an intake test is if you happen to have valves overlapping - if you turn the engine over a little I think one or the other of those valves will close.

Dan Martinic

I thought there was always at least one exhaust valve somewhat open among the cylinders? In any case, every time I do the intake test, some air is "flowing through"

Dan Martinic

Will try and find out tomorrow... though it sounds more like psi pushing out throttle down, not on release

I have this feeling the wastegate signal line has popped off

Chapman951

Sounds like it could be a torn hose or weak connection somewhere when pressure builds up.

Are you running cyclic/Venturi system still? So many items underneath the intake manifold that could fail.

pressure test/smoke test might be the way to go.

Dino951

Maybe the boost pipe going into the intercooler? I've had that happen to me...a whoosh sound at boost. Turned out I forgot to fully tighten the clamp holding the pipe to the intercooler. Oops.

Mike Goebel

Me too!

Mike G.

GPA951s

My bet would be on the BOV.. If you are running a stock one there is a rubber disk inside and I have had mine "fold over" Causing a leak.. Take it off and feel up inside and you can push it right back into place.. This is REALLY pronounced when you are running a MAF Sensor hand have that K&N Filter on it.. My 86 Does it, and with a boost enhancer its allot of fun to just "Roll" into the boost... watch that needle climb and "Snap" off the gas ..WWWWWWWhhhhoooooosh! Makes people turn their heads on the sidewalks.. LOL

Humboldtgrin

Dan I think your right with the wastegate signal line popping off or I’ve had one melt due to youth and not knowing any better on what material to use. Way Pre-rennlist days.

Chapman951

While I was trying to find a no boost issue on my car, the hose connecting to the wastegate cracked in 1/2 when I touched it. It was bone dry. There is a lot of heat generated back there.
Your issue could very well be in that location

Dan Martinic

May have found it

Pressure test revealed this; it's the intercooler pipe into the throttle..















I put some of this weld putty I have lying around but wow.. what a strange place for a hole to develop.

Haven't had a chance to drive; company coming over soon. Didn't hear anything much when pressure testing here ...though only using 5 psi

Chapman951

Looks to small to be the culprit in my opinion. Unless the hose is cracked underneath.

hopefully I’m wrong and your all set 😎

Dan Martinic

Correct! Still whoooshing... perhaps slightly less loudly

The search continues! Though I have to admit, I kinda like the sound. Push the throttle a little more and whooooooosh off we go

It's neat. But, it's also a vacuum leak I guess, which isn't too good for many reasons. Strange that I soap-sprayed *everything* and all I could find was that little hole. I certainly didn't hear any psi while pressure testing; with it so loud while driving, even at very small boost level, you'd think I could hear something more obvious when pressure testing

Maybe it's in the exhaust like that small cat pipe after the wastegate? But I'm guessing that wouldn't sound so "clean"

Mike Goebel

Gotta be one of the intake clamps after the compressor!!

Mike G.