I lost 3psi after boost leak test?

[tbonitz301]

OK.So last night i did a BLT and found 4 leaks. My MBC, BOV line, TB shaft seals and gaskets. Well i fixed the MBC leak and the BOV line. Now my boost holds at 13 when i was running 16Psi. Im just wandering if fixing those two leaks made my TB seals and gaskets worse?Anyone have any suggestions?

 

[Mr Peepers]

If your MBC/MBC line was leaking it would raise your boost past what the MBC was set to. Bleeder style MBC raise boost by leaking air from the wastegate line, making it open later, and raising the boost. Your leak was doing the same thing.

Also, make sure you aren't T'ing into the BOV line for the MBC.

p.s. a bleeder style MBC will always show up as a boost leak. A ball and spring style will as well since it as a bleeder hole, but will depend on what it's set to.

 

[tbonitz301]

well i fixed the leak on the mbc. should i let it leak or what? i noticed the cars spools way better. it just doesnt have the topend pull because of the three psi im missing


also my BOV line runs from the intake manifold.

 

[turbosax2]

What leak on the mbc did you fix?

Mbc's are meant to have a bleeder hole.

The bleeder hole is not large enough to affect the signal to the Waste Gate but it is necessary to gently vent off excess vacuum or pressure in the line which causes a type of signal lock. If the hole wasn't put in, the controller would have difficulty controlling boost above about 15 pounds.

http://www.geocities.com/chmwatson/FAQs/mbc.html

When you do a boost leak test, you need to take the mbc off and cap off the pressure source feeding it.

Fix those other boost leaks.
Throttle Body O-Ring

 

[CrazyM]

As Mr Peepers said. Your MBC leaking would raise the boost. Now that you have fixed the leak, the boost is at where the MBC was 'technically' set to. If you want it back at 16 PSI you will have to adjust it that little bit and get it back there.