Boost or exhaust leak, up-pipe gasket replacement, etc
 

G'day. New guy here. Long time motorcyclist, recent WRX convert. Bought an MY94 six months ago, all original except the plumbed BOV. Only 110,000 kms on this fantastic little car. Runs and drives like new; well it did until recently!

Gave it a bootful a week ago and took it up to redline in 1st gear. Has made a whizzing noise under boost since, the cause of which I'm yet to locate. Seems to be coming from under the bonnet rather than through the exhaust, heard equally from both front seats. Turbo area I guess.

I've sought opinions and advice on another WRX forum but they don't seem too enthusiastic or mechanically interested. I'm sure their cars have nice looking wheels though.

I've been over the inlet tract from MAF to throttle body and all hoses, clamps and pipes seem ok. Save a leak in the intercooler, the inlet manifold or the turbo itself I guess I can rule out a boost leak. Hooked up a (crappy) boost/vac gauge to the manifold which shows boost steadily increasing to 10 or 11 psi at 5500 rpm. Can't remember the vacuum reading at idle. Engine idles and responds crisply.

Suggestion has been made of a leaking exhaust manifold to up-pipe or up-pipe to turbo gasket. Pulled off the heat shields from around the manifold/up-pipe join and from around the turbo but can't see or hear signs of leaks. Also had a shop do a quick test by sending smoke back through the exhaust but again no obvious signs of gasket leaks (though the CAT is probably toast). But given gaskets are cheap I'm considering changing them anyway, to rule them out if nothing else.

Questions:
1. Is it possible to change those 2 gaskets by separating the up-pipe from the manifold and the base of the turbo, without removing the turbo's oil and coolant lines and with only separating the down-pipe from the turbo*(not from the rear of the exhaust)?

2. Any other ideas of what might make a whizzing noise under boost?

3. How might I determine whether or not it's the turbo itself?Is it just a matter of eliminating everything else first, then pulling the turbo off for inspection?

Thanks in advance.
Ballbag.

short of just heading to a workshop and getting them to take a look, i reckon the next best thing would be to get a mate to give it a few revs while you walk around with a mobile/video camera and whack it on youtube so the armchair mechanics can have a guess.

while the car might only be 110k, don't forget its nearly old eniough to vote.

Here's a vid. Hard to drive and film, obviously, but boost is hitting 10 psi at 4500 rpm (boost gauge reads a little under actual). Noise can be heard from about 4000rpm.

[url]http://www.youtube.com/watch?v=cNsq3GOrdfY[/url]

Nice legs.
I'd guess your turbo is poo

hehe, they're due for a wax.

Any comments on the gasket replacement procedure (regardless of if they're the cause of the noise)?

the oil lines are hard lines, i doubt its possible or at least easy to do gaskets without taking them off

Yeah but I figured I'll only need 5mm play to get the exhaust gaskets in and out.

The oil line 'gaskets' (as the service manual calls them) are just copper washers, right?

Will only undoing the down pipe at the top and not at the bottom give me enough play? The less joints disturbed the better.

Have you pulled your turbo off? No offence, but I can make guesses myself. Looking for the advice of someone who's done it.

My MY99 started making a very similar noise after being serviced. A quick look in the engine bay revealed that the BOV wasn't bolted on tight enough. It would start leaking at higher levels of boost and would make a similar noise as the air passed over the gasket. It's worth a look to see that it's bolted on properly and that the gasket is still on good condition.

BOV setup is different for the earlier model, I think. '99 would be connected to the intercooler with a gasket. '94 is plumbed into the turbo-to-intercooler hose.

Have gone over all the BOV plumbing a couple of times and it's all ok.

Hey Ballbag... lol.

Yes. It is easy and straight forward to remove, (drop) the headers down an inch or two, replace gaskets. Undo the headers/up pipe flange, replace gasket there, and for a standard turbo, its moreso the securing bracket that will give you heartache. I can remove the exhaust and up pipe off mine now without removing the turbo.... but mines seen some ahhh... modifications.

(Dremel 400 love). :D

Brent.
:)