boost leak test help.

[AKbag]

hey there. so i have searched around on this but couldnt really find my exact ansewr i was looking for. i so i have been in the process of finding boost leaks in my car because it runs rich as hell and i beleave some of that is in the tuning but it did have a few rather large leaks. so i have fixed every leak i could find and as far as i can tell i have no leaks but im not confident saying i have successfully completed a boost leak check, for one i still am not building much pressure on the gauge on the the tester i do have a little blow by filter on my valve cover that i feel like is losing air but its not just pissing air out there. i have a manual boost controler with a little pin hole in it that i just try and block when i do the test is this wrong of me? i also have not potitioned the pistons in anyway just did the test however the car is sitting is this maybe my problem? anyway as im sure you can tell im pretty new to this. so any help would be great.

 

[Marchev]

Air escaping from the valve cover will indicate a leak past the piston rings, some leaking there is normal. Try warming up the engine to operating temperature first to minimise that leak.

You need to bring the pistons up to close up the intake valves so you're not leaking into the combustion chambers. I believe if you bring the engine to 30* BTDC that would do the trick. A quick search can verify that number.

You have a bleeder type boost controller so it is normal for it to leak from the pinhole. However I would disconnect it and attach a vacuum hose in its place to eliminate that leak, for the sake of the test.

Hope this helps

 

[BlackDSMthingy]

Be sure to check your throttle body shaft seals also. I think it's fair to say most of us either had to replace them or have to...

 

[Chuck98TSI]

I would recommend checking the PCV valve. Ensure it is functioning correctly (not allowing pressure into the valve cover) I suspect it is not fully closing.

The MBC is meant to bleed off air. For your test, simply close it all the way (remember to count how many turns / clicks so you can put it back in proper setting after.

Let us know!

 

[AKbag]

Ok yeah I never tried closing the MBC all the way. The pcv should be fine I replaced it with a new one like a week ago. I'm away at work now so trying g grab some ideas to try when I get home. As for the throttle body shaft seals go would I be able to tell if they were bad with out taking the tb off? Sounds dumb now that I say that out loud haha.

 

[EvilGST]

Ok yeah I never tried closing the MBC all the way. The pcv should be fine I replaced it with a new one like a week ago. I'm away at work now so trying g grab some ideas to try when I get home. As for the throttle body shaft seals go would I be able to tell if they were bad with out taking the tb off? Sounds dumb now that I say that out loud haha.

You will hear air leaking from the TB shaft seals, and opening and closing the throttle plate will make it leak more or less, thats how you know if they are leaking.

 

[91ET]

I don't think you need to rotate the Pistons at all. Every time I've ever done a boost leak test I've just connected to the intake pre turbo and put a couple lbs of air in and go around squirting soapy water on all the suspected area of leak. Never had a problem this way.

 

[AKbag]

I don't think you need to rotate the Pistons at all. Every time I've ever done a boost leak test I've just connected to the intake pre turbo and put a couple lbs of air in and go around squirting soapy water on all the suspected area of leak. Never had a problem this way.

Thats basically what I accomplished with my boost leak test. I feel pretty good that I have found the leaks but I do like the idea of testing to over the psi you will run. That I am not confident I have accomplished so I still am gun shy about messing around with ecm link.

 

[JFPryde]

The BISS screw seal in the TB should also be checked of your going to do the TB shaft seals. Just make sure your careful to set it back at the right depth (or have Link to fix it).

 

[steve]

i also have not potitioned the pistons in anyway just did the test however the car is sitting is this maybe my problem?

You need to bring the pistons up to close up the intake valves so you're not leaking into the combustion chambers. I believe if you bring the engine to 30* BTDC that would do the trick. A quick search can verify that number.

I don't think you need to rotate the Pistons at all. Every time I've ever done a boost leak test I've just connected to the intake pre turbo and put a couple lbs of air in and go around squirting soapy water on all the suspected area of leak. Never had a problem this way.

The odds are high that the engine will stop at a place where at least one set of valves per cylinder are closed but sometime people get lucky and hit the jackpot, in this case that being where a cylinder is in overlap that the air just escapes out the exhaust.

I'm the source of the 30* number. I picked it because at 30* ATDC no cylinder is in overlap and it's relatively easy to estimate how far past TDC to advance the crank. People used to run around telling everyone to boost test at TDC and that's the worst place since cylinder 4 is in overlap but it's hard to kill internet BS once it starts. Now no one remembers why we use 30* for boost testing but at least it is safe and works if they get the sign correct.