Turbo XS MBC Leaking?

[KuZo]

My roommate and I were installing his Turbo XS MBC (Standard Model) last night and once we started the car we could hear the "hiss" of a vacuum leak. So after searching around it we found it to be coming out of the top of the MBC where the 2 o-rings are located. Now I have never used one of these MBC's so know nothing about the build and quality of these units.

I can't imagine these are designed to purge air or anything, has anyone had this type of problem with theirs??

When we took it out for a run, the car would boost to 14, drop to 10 and level off at 13-14psi. I'm lost on this one.

For reference it looks like the unit in this link:
http://www.saabperformanceparts.com/item114.htm

 

[ddavisaf]

It's a bleeder valve. I have one in my car also. They're designed that way. You're fine.

 

[KuZo]

thanks.... do all MBC's have the fluctuations in boost like I'm having?

 

[ddavisaf]

It's more or less your car and it's setup than the MBC. Are you driving an automatic or a manual?

 

[KuZo]

it's an AWD 2G manual, a newly installed Evo III 16G on the stock sidemount.

 

[ddavisaf]

I'm going to let someone else tackle the explanation since I'll probably mess it up (Hasn't been a good day). I can tell you that with manual boost controllers though, you have to tweak it just a little bit in order to get the boost steady. I've done countless 1/8 inch turns on mine to get it to sit just right. You've got the controller set to what sounds to be 10 psi right now. You're spiking at 15, leveling out at 10, and creeping to 13-14. Do a search on boost creep to find ways to try and counteract it and you'll be good to go. If that doesn't help or can't find the info you're looking for pm me and I'll help ya along better.

 

[oldman]

My roommate and I were installing his Turbo XS MBC (Standard Model) last night and once we started the car we could hear the "hiss" of a vacuum leak. So after searching around it we found it to be coming out of the top of the MBC where the 2 o-rings are located. Now I have never used one of these MBC's so know nothing about the build and quality of these units.

I can't imagine these are designed to purge air or anything, has anyone had this type of problem with theirs??

When we took it out for a run, the car would boost to 14, drop to 10 and level off at 13-14psi. I'm lost on this one.

For reference it looks like the unit in this link:
http://www.saabperformanceparts.com/item114.htm

1. Where are you running the pressure source from? BOV/manifold or compressor?

2. Bypass the mbc and run the pressure source directly to the actuator. If you get a steady boost of 10-12, the mbc is the source of your inconsistent boost level.

3. If problem persists with the mbc bypassed, perform a boost leak test and fix all leaks.

 

[KuZo]

Thanks it's running from the BOV, I'll bypass the controller tomorrow and see what happens.