MBC leaking air? 710N's backwards?

[alias747]

I really hope that is normal... I just did a pressure test last night and my MCB was making a ton of noise. I figured that would have to be normal since there was a hole in the MBC itself. Some kind of bleeder valve I'm assuming?

Another question, right now I have my 710N's positioned as what people would call backwards, with the nipples up. Does anyone else run it like this? I had read that 710N's run better this way. Any truth to this?

[The_Jerbel]

a) What kind of MBC are you running?

b) No.

[alias747]

a) What kind of MBC are you running?

b) No.

A) Umm... A gold one... haha

B) No to what?

Thanks Jordan

[The_Jerbel]

I really hope that is normal... I just did a pressure test last night and my MCB was making a ton of noise. I figured that would have to be normal since there was a hole in the MBC itself. Some kind of bleeder valve I'm assuming?

No, most MBC's (including the VAST MBC) should not be leaking air with a pressure test.

Another question, right now I have my 710N's positioned as what people would call backwards, with the nipples up. Does anyone else run it like this? I had read that 710N's run better this way. Any truth to this?

No, there is no truth to this. Put them in the correct way.

[BlackS4TT(Josh)]

No, most MBC's (including the VAST MBC) should not be leaking air with a pressure test.

Incorrect. A standalone MBC vents air to the atmosphere to control boost. 100% normal for it to leak during a high pressure test.

[The_Jerbel]

Incorrect. A standalone MBC vents air to the atmosphere to control boost. 100% normal for it to leak during a high pressure test.

Incorrect. It depends on what setting the MBC is on.

[revhards4]

I have my 710N's "backwards" and it's just fine

[The_Jerbel]

Yeah backwards will work ok, but it's definitely not better..

[exorcet]

Incorrect. It depends on what setting the MBC is on.

you mean MBC psi setting vs. pressure test psi, right?

OP: if your MBC has a 'bleed hole' it's made for 'standalone' use (i.e. no N75 control). If you're using an N75 to control boost and MBC just to cap/lower it, then you can plug that hole w/ JB Weld.

If you are running standalone, leave the hole... you can usually even hear air escaping from the hole under full boost, from inside the car.

[The_Jerbel]

The MBC in parallel will still work ok even with the hole in it. Not ideal, but you don't have to turn the MBC into a parallel version permanently by JBwelding it if you don't want to.

No, I'm talking about the MBC pressure setting. If the MBC is close to letting the turbos run at full bore, then the air coming out through the bleed hole will be minimal, probably not even noticeable (I know from experience) during a leak test. If the MBC is turned way down, it will let a fair amount of air pass through the bleed hole, which you'll hear when doing the pressure test.

[alias747]

Ok well my MBC is running stand alone, but I mean I felt a TON of air coming out of it during the pressure test and I think i was only testing at like 15psi or so. I mean MBCs can't brealk can they?

[PSYC0TIC ONE]

Ok well my MBC is running stand alone, but I mean I felt a TON of air coming out of it during the pressure test and I think i was only testing at like 15psi or so. I mean MBCs can't brealk can they?

I'm sure MBC's can fail... what does your car usually boost at? If its low, than what Jerbel said is what you should be looking at...

[The_Jerbel]

Yeah, the spring inside the MBC can break. It's pretty uncommon, but it can happen.

[Sleeeper X]

my ebay cheapo did. I now rock a hallman

[Daft]

my ebay cheapo did. I now rock a hallman

OMG, Marc Hallman is still making those?!? LOL.

I had a Hallman valve in 1997 when he first started making them for DSM cars...hehe.

[alias747]

I'm sure MBC's can fail... what does your car usually boost at? If its low, than what Jerbel said is what you should be looking at...

I usually spike to around 21 and then hold and taper to 18-19 to redline. Now I am lucky to see a 15psi spike and I can hear a loud whistle of air coming out somewhere. I just did a leak test and should have got all the leaking spots in the intercooler hoses.

I'm guessing that the loud whistle I hear could possibly be the MBC leaking. Im gonna try just putting some duct tape over that bleeder hole and see if that makes the noise go away, if it sounds muffled after putting the tape on I know it's the MBC.

I'll post my findings, THANKS ALL!

[The_Jerbel]

Better yet, just remove the MBC, clamp off the bottom line going to the MBC, and then pressure test.

[alias747]

Better yet, just remove the MBC, clamp off the bottom line going to the MBC, and then pressure test.

Well I am pretty certain from my last pressure test that the rest of the piping should be ok. What is the advantage of taking the MBC out when I already know its leaking air, whether its meant to or not? Sorry I'm just a little confused.

[The_Jerbel]

That way you can see if you have any other leaks around that area (the boost reference line from the compressor housing) without being distracted by the MBC. Also, try running the N75 and see how the boost behaves.

[gointoscott]

Isaac,

I have my old n75, I can give that to you to use next time we meet up so if you want to try running that you can try it to see how it works. I could mail it to you too, probably wont cost much to send. I did replace my n75 with a new one, but I'm thinking the old one was fine and I just had my mbc turned up too high as to why it wasnt spiking correctly.

[alias747]

That way you can see if you have any other leaks around that area (the boost reference line from the compressor housing) without being distracted by the MBC. Also, try running the N75 and see how the boost behaves.

Oh duh yeah. Sorry I have my car at work right now so I was saying for the drive home I would put that tape on there to see if it makes the whistling noise that I hear while driving go away. But yeah when I pressure test, taking the MBC out totally would be a good idea.