BOV not working, lines have vacuum !!

[mitsugst95]

I just threw on a rebuilt head with 264/264 / running a small 16g with an o2 dump. The car builds boost fine, about 18 psi. When I let off the compressor spools down, no bov. Yesterday at about 6500 rpms it shot my hks ssqv right off, mounted with a c clamp, no surprise. Then today I put my stock bov on and it still is not working, the vacuum line is off intake manifold and tees to the boost controller, and when removed there is vacuum. WTF is going on, any suggestions would help, and no it is not leaking anywhere on the system after a few boost leak tests. Actually, this was tested by 3 bovs, my hks and 2 1g bov. this is on a 92 TSI AWD 6/4 bolt

 

[vr6chris]

you do have a vaccum line running to the bov right?

 

[sweet97]

How much vacuum is your gauge reading now with the cams? Try T'ing into the line your boost gauge gets it's signal from. If the BOV is not blowing off you would get a good amount of compressor surge, the infamous turkey gobble. Could be blowing off but slowly. I think the gauge line where you know you have a positive boost signal and then vacuum when you let off will help diagnose this. 3 BOV's are not likely bad. If they were not releasing any positive pressure the compressor would stall or at least screech at you! mark

 

[mitsugst95]

the boost gauge is off of the line with the fpr. i was thinking of trying this but why does the boost controller work as it is on the same line as the bov

 

[ddavisaf]

Use an air compressor to open the BOV manually. Just to ensure that they are in fact operating the way they should. Watch for the arm in the BOV to raise up.
Then run a boost leak test. You might also want to replace the vacuum lines associated with the BOV.

 

[talonkev]

BOV's are opened by vacuum not pressure. You might have Teed into a port on the wrong side of the throttle plate. You need direct manifold pressure as the source, not the pressure inside of the IC pipes.

 

[ddavisaf]

You're right, I had wastegate in my mind mixed up with BOV. Thanks for the correction.

 

[SethA]

I believe ddavisaf had a good idea for diagnosing the problem but use a vacuum pump instead of compressed air. Small hand pumps are available at parts stores. Some stores even let you borrow tools with a refundable deposit (Checker maybe?). Get a pump, connect your BOV and see if it opens (you might need to remove in from the UICP).

Seth

 

[mitsugst95]

BOV's are opened by vacuum not pressure. You might have Teed into a port on the wrong side of the throttle plate. You need direct manifold pressure as the source, not the pressure inside of the IC pipes.

definately no, its teed into the line off the intake manifold after the throttle body, and yes i know vacuum is used to open the bov, damn dsms, one problem after another......

 

[sweet97]

How much vacuum does your gauge read when you shift, ley off the throttle? mark

 

[mitsugst95]

it works now, i found the hole on the 1g bov to the pipe plugged, most likely the problem but the closed throttle switch wire was not hooked up either. oh well issue solved.

 

[sweet97]

Congrats! Mark