Hi guys,

Bear with me, bit of explaining..

I bought a used prodrive backbox and whilst fitting it, I thought I'd change the gaskets. I told the topmount off to get to the turbo, but found that the 5 stud gasket was fine so decided to leave that headache of a job!

I proceeded to replace the other gaskets. One at the bottom of the down pipe with the wider hole, and the normal sized gasket at the end of the new backbox. The dohnut gasket in the middle was fine with no leaks and nice new bolts. I sprayed each gasket with washing up liquid to check for leaks, all good along the whole exhaust.

I then suspected it was the notorious bov gasket. I found that it was in bad shape with most of the rubber worn away so I bought a new Oem one to replace it. Again, this gasket and the central hose were checked for leaks, no bubbles.

Any ideas what this could be?! Maybe the two gaskets underneath the topmount? They are the only ones I can't spray to check whilst running the engine. Perhaps they were disturbed when I removed it..?

Here's a quick video of the noise. It sounds almost like a belt slipping, but it only happened directly after playing with the topmount and exhaust system.

 

I have had this a couple of times before and both times it was the actual prodrive back box making the noise....your going to have to put your old one back on to check.
​​​​​​But obviously if not that it is a leak at one of the gaskets.

 

It has been resolved! After replacing the three lower gaskets for brand new genuine ones, the sound still hadn't gone. I thought I would spray all hoses with washing up liquid solution to see if there was a boost leak, all tight with no bubbles. I must admit, it didn't sound like a boost leak, but best to check. Still there!

I just today managed to get the time to pop off the Prodrive back box to put the stock one back on. Voila, no squealing noise again! I wanted to give the seller the benefit of the doubt as the back box looked to be in great shape from the outside, but clearly it's the baffle inside that has rusted around the edges, allowing air to escape and create an awful high pitched whistle on full boost. This is apparently quite common on the prodrive boxes having read a couple of past posts.

As it's not a daily car I hadn't driven it hard since I installed it, and thus didn't realise there was a fault with it. I have had some disgusting, and downright rude messages from the seller on eBay telling me that I'm immature, foolish and inexperienced etc. I had the fitment verified by the MOT chap just 2 days ago. I'm not quite sure how you CAN install a back box incorrectly. New OEM gasket installed, along with fresh bolts and copper grease, torqued correctly etc.

Am I ok to post his responses and his username to help earn other of his nature? I'm as honest and decent as they come, so I was extremely upset. He is apparently a 'well respected' and knowledgeable Subaru dealer of used parts. Granted it has taken a month or so for me to get back to him, but I would have never jumped to conclusions and insulted someone like that. It has made that terrible noise since the first time I boosted.
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It was indeed. Thanks for the heads up Smithy :-)

Is there any way to repair the baffle, or actually remove it entirely?

 

Who was it?

 

I had this when buying a new Scorpion BB from Roadrunner in Notts(who made the prodrive BB),
I ended up back at Scorpion and they sorted it, and gave it a polish.