Smoke test / Boost leak
 

Would a smoke test always find a boost leak?

The reason I ask, a few weeks back I thought I had a boost leak, had a smoke test done and it found nothing.

Driving the car today, I gave it a boot full in 4th, took it upto about 6500rpm and heard quite a loud squeal, backed off and it went.

Now at around 2500rpm I can hear a faint squeal, over 2500rpm it seems to go.

So, could it still be a boost leak that the smoke test missed or suggestions what else it could be?

Thanks,
Scott

a smoke test will only show a leak or a split thats permanant.

if you have a squeal. scream or other noises under boost a smoke test will not be of any use.

The leak will either be pre turbo or after turbo.

1st few things id check is;

up pipe gasket/bolts
intercooler is on the turbo properly and tightened
vacuum lines arent split etc
nuts on back of turbo are tight
and go from there

You confirmed my thoughts exactly.

Tomorrow I'm going to remove the TMIC, check the Y pipe, TMIC > Throttle body and all associated hoses etc..

If this doesnt solve it then I'll check all post turbo stuff.

Thanks,
Scott

Think it will be after the turbo compressor outlet, any where down to the inlet manifold to cylinder head gasket.

Cheers, will give them a check over too. Don't have a boost leak tester made yet so it'll just be a case of inspection at this stage.

Hope it's not an elusive leak :(

Scott

You may have to consider a rolling road session so the car can be held on boost whilst looking under the bonnet to locate the leak.

But just be methodical, ensure all jubilee clips are located properly and tight, then go for a drive to see if it has disappeared. Are you running a VTA dump valve? As this could be the leak if the spring has weakened.

No, no VTA. Bog standard except for PPP.

Yep thats the plan, inspect the hoses for visible damage, tighten everything up and give it a try.

Rolling road isn't a bad idea if I don't find anything.

I did post up my first log with romraider not too long back and the main reason for the log was to see what was going on as I suspected something wasn't right as the car didnt seem to pull as hard as it did, but being a newb with logging I don't really know if anything is a miss or not.

The log is here: https://docs.google.com/spreadsheet/...XWktGNlE#gid=0

Just incase anyone can see anything going on there.

Cheers,
Scott

So, update.

Took off the TMIC and checked over everything I could post turbo. The IC > TB hose jubilee clips wasn't exactly tight, nor was the prodrive Turbo > IC.

The IC > TB hose had a little oil in it which I noticed seems to have blown out over the Turbo > IC hose, it had a fine misting of oil on it, so I presume that hose had a tiny leak.

Cleaned all hoses with carb cleaner, sprayed a little hair spray in the tubes before refitting and torqued them all back up.

Ran a log with romraider and it appears I'm gaining an extra 1psi now so I guess there was a small leak.

But...why is there always a but?

The noise is still there, it's like the sound a balloon makes if you let air out, but not as high pitched and only very faint.

The noise ONLY appears under load at 2400 - 2600 rpm, any higher/lower it doesn't.

At this rpm I'm not in boost right? So would this point to a vac/uppipe leak?


Cheers,
Scott

DID YOU FIX YOUR PROBLEM?
 

HI SCOTT, I WANNA KNOW IF YOU COULD FIX THE PROBLEM OF THE SQUEAL? IS BECAUSE I HAVE THE SAME PROBLEM IN THIS MOMENT

exhaust gas leak on downpipe on cat joint ?

could also be a leak at the uppipe or the turbo intake. If you can't find it with a smoke test (did you smoke the exhaust as well or just the intake) then a pressure test shoudl find it. Don't put too much pressure in and remember to take off the breather pipes on the intake so you don't blow a seal out.

The turbo intake pipe is fond of ripping underneath where you can't easily see it, same for the uppipe if it's split then the heatshield will be covering it (tho an exhaust smoke test may show you some clues).