Boost leak test questions...

[lunarhybrid]

Long story short.. I have 97GST w/ 6bolt swap, 16G, and I was getting fuel cut at around 4k RPM and so I did what it says about a 100 times in these forums to do which is a boost leak test. Well I made up a nice little tester and I put about 25psi and there was very obvious leak from the injectors, so I popped them out and discovered that the o rings(all 3 on each injector) was rock solid, so I ordered new ones from the dealer and put them in and now it is not leaking from the injectors. The only obvious leak is from the idle screw on the trottlebody. and another but can't find it anywhere, I have sprayed soapy water on everything. Now when I put about 25psi it holds presure but you can hear it leaking what appears to be from inside the head...So my questions are as follows....
#1 how much psi should I be putting in?
#2 How long should it hold the presure for?
#3 Any ideas on other places it could be leaking?

Any advice will be greatly appreciated...

 

[SL_]

#3. Try replaceing your pcv valve, it cost like 5 bucks and will eliminate that from your list. Also test at the tb elbow and post results. Get the valve from the dealership, will save you time in the long run as 99.9999999999% of generic ones leak.

Cheers,

SL

 

[lunarhybrid]

I did replace with new from dealer(pcv), I checked all around the tb and egr etc, the intake is tight...

 

[daren_p]

You don't need to use that much pressure, unless thats how much you normally boost. Basically test at the amount of boost you usually run.

 

[fwdeclipse]

Yeah do a test on the tb or the lower icp and if your still getting air in the crankcase you could have rings wearing out or valve seals.

 

[lunarhybrid]

I don't plan on pushing more than 15-16 psi w/out upgrading injectors and having a piggyback...so till then 16psi is the most I plan on boosting... I have been putting 15psi and it is holding... I am concerned about what is too much psi.....

 

[SL_]

I've read many times on this site that your motor should hold 20psi for atless 40 secs. This is what I've done with my motor with no ill effect. Have you hooked the tester up to either the Throttle Body Elbow or LICP and pressurize from there? I can hold 20Psi from LICP for about 40-50 secs. But at the turbo inlet I can't even pressurize pass 16Psi, Which last for <20 secs.

Cheers,

SL

EDIT: "I can hold 20Psi from LICP for about 40-50 secs" LICP should have been TB elbow

 

[L'ville]

I've read many times on this site that your motor should hold 20psi for atless 40 secs. This is what I've done with my motor with no ill effect. Have you hooked the tester up to either the Throttle Body Elbow or LICP and pressurize from there? I can hold 20Psi from LICP for about 40-50 secs. But at the turbo inlet I can't even pressurize pass 16Psi, Which last for <20 secs.

Cheers,

SL

WOOOOOO why is that i don't get it .... shouldn't it hold from the turbo just like from the LICP?

Explain..

 

[FORMONTOYA]

I usually wont even do a test at the turbo inlet as the seals will most likely leak without oil pressure to help them seal properly, even on a brand new turbo. Start your test from the lower IC pipe. You should be able to hold 20psi from there without any problems for 20 plus seconds. If not, you have a problem.

More than likely you have a leak at the EGR valve and that is what you are hearing inside the engine. Carbon builds up on it and it doesn't seal properly. One way to confirm that it is not leaking past the valves is to turn the crank clockwise, NEVER TURN THE CRANK COUNTER CLOCKWISE, to roughly 30 degrees after TDC. If you still hear air leaking inside the engine then it probably is the EGR. Just plug off the PCV valve to be sure you just don't have a new one that leaks as a leaking new PCV valve is not uncommon.

But either way, you should be fixing leaks as you go so you can eliminate them. When you fix one leak it can hold enough pressure to allow you to find other leaks that you didn't know you had because they were too small to show up with the bigger "hole" letting the air escape. I would never just end the test by saying my only leak is "this". Air like most things, will find the path of least resistance to escape from the inside of your pipes.