Leaky BOV = boost leak symptoms?

[radiod]

Just curious as to whether a leaking (recirculated) blow off valve would cause similar symptoms to a boost leak. I noticed just last week that my blow off valve was making a funny noise when I had it up at full boost over 4,000rpm and shifted. I'm going to take it off and clean it up regardless because of that issue, but today I noticed that it doesn't seem to pull as hard and I hit fuel cut right around 9psi when normally it's around 11.5-12psi. It also seemed to struggle to build boost up that high as well. Turbo is fresh (around 1500 miles on it) and nothing has been giving me any issues up until now. Just trying to figure out if it's something that may be resolved by cleaning up the blow off valve or I need to go pick up supplies to make a boost leak tester.

 

[hvyman]

That would be a boost leak.

 

[RazoE]

correct me if I'm wrong, but a recirculated BOV wouldn't cause a boost leak, as the same amount of air is still present in the system, right?

 

[bioskyline]

yes and no. the volume of air is there, but the pressure isnt there. and as theres alot of suction on the intake side of the turbo, it will suck the air back out of the system post ic to pre ic.

 

[radiod]

correct me if I'm wrong, but a recirculated BOV wouldn't cause a boost leak, as the same amount of air is still present in the system, right?

That's exactly what I was thinking. Well, we'll try messing with the BOV first and then see what happens, it just may need to be pulled off, cleaned, lubricated, and back together happy.

 

[hvyman]

If the bov was vented would you agree that its a boost leak? If so why would recirc be any different.

 

[radiod]

I know that the recirc fitting on the BOV does leak, so it could be just escaping past there if the BOV is leaking. It recircs most of the air, but you can definitely feel some escape if you get it to actuate. On another note, if I'm pulling this apart, you think the gasket between the BOV and the flange will be safe to reuse? I've never had an issue with it, but it's probably getting old. It's a Blitz BOV, so I'd likely have to buy some "make your own gasket" material or use some silicone of some sort to seal it back up. I don't know of anywhere local that sells Blitz and who knows how much they'd charge for that gasket.

 

[jetjock]

If the bov was vented would you agree that its a boost leak? If so why would recirc be any different.

You have to define leak. As already noted it's not quite the same. After all lots of people drove lots of miles with blown out stock valves and didn't know it.

 

[radiod]

Ok, so I took the BOV off, cleaned it out with some brake clean, the put some WD-40 back in there to make sure it was well lubricated. Put it all back together and still the same issues . Hit fuel cut at 9psi (on the dot pretty much) and the BOV makes a bit of a chirp/wine when I let off rather than the typical "pshhhhhhhh" I've always heard in the past. This only happens when I'm above 4k rpm.

I don't know about how it's supposed to be, but I took off my recirc to see what the BOV was doing and at idle is was half open. Is that normal? If I took off the vacuum "signal" line it would snap shut, and if I rev'd the motor, it would shut (from what I could tell all the way) and then open to let pressure out like it should.

Does it sound like my BOV is showing signs of dying?

 

[jetjock]

Sounds like it's working to me. Then again I never felt your symptoms were valve related.

 

[radiod]

I guess the chirping (or whatever) sound could be air escaping. Time to track down any leaks I guess.

Just to clear up a few things...

You eliminate the PCV by capping off the line going in to the accordion hose and the port on the throttle body so you don't blow out your oil seals, correct? Also, isn't there valve overlap that the air could escape through the combustion chamber? The other way I've heard of trying to find it is spraying carb cleaner around connectors etc and listening for a variance in the rpm, is that reasonable or should I just go try and make myself a little tester out of PVC etc and try and find a buddy with an air compressor/regulator?

 

[hvyman]

Just pull off the oil cap off. It will let the most air out of there the fastest.

The tester will be the better way to about it but if you got some carb cleaner or brake cleaner on hand its worth a shot.