Its delivering a constant volume of air to maintain that pressure, if you dont block upper i/c pipe off @ the air will escape through open valves etc. If he turned the engine to tdc I doubt he would lose as much if any air, it's just easier to block off the upper i/c pipe @ the tb.

 

/\ I agree that it is easier and more convenient to do it that way...but where is the leak coming from..haha

 

ok tried to block of the t/b, the problem is that with the t/b blocked the tester does not pressurize any of the vacumm lines, so how can do a 100% leak test. also already tried TDC and air still escaped.


** I have done this test 3 or 4 times before and the lines all pressurized w/out blocking the T/B... I am so confused

 

honestly we think the air is escaping past the wastegate flapper due to inproperly seating. just really weird it has worked perfect in the past. the symptom we are having is unstable idle when coming to a stop with a flash of the oil light....then stalling. any ideas.......? weird

 

Well, I would say break it down into sections. Cap at the spot where the lower IC pipe meets the fmic and try it. If THAT leaks then it's in the turbo outlet and connections up to the FMIC. Then cap at the other side of the FMIC or halfway thru the upper IC piping ... break it down into sections. If you're cool from the turbo intake to the TB then you're golden. If not, a hose is not connected somewhere. Your MBC and BOV must be in place, don't forget ...

I'm no pro and have little time at this but these are my thoughts... good luck!

 

What happened when you blocked off the TB? Did it still leak?

 

what was the last thing u loosend around ur intercooler pipes, check them. instead of check all these other things, think of things u have modified and maybe became loose over time. recheck them and go from there.

 

did you try it on a warmed up motor or was it cold ?

 

motor was cold

 

Make sure all the hoses under the intake manifold are connected, especially the one to the egr valve.

 

Try it with a warmed up motor . I hear that a warmed up motor seals up better than a cold motor . When I do a boost leak test my motor is warm , not at TDC and it takes about 15-20 sec to leak through the motor from 20 psi to 5 psi .I found that the TB leaks a little and i can hear the air going through the motor . If that dont work plug the pipe that goes to the TB , but as you found out it dont pressurise the anything after the TB like the vacume hoses .

 

humm , was that at me ?

 

I doubt it.

 

i did my boost leak test when the motor was cold and it wasnt at tdc and everything went fine

 

What do you mean by the air is escaping past the wastegate flapper? Because of the vacuum line that goes to the wastegate, or do you mean the pressurized air goes through the motor, through the exhaust manifold, and then escapes through the wastegate flapper? If it's the latter, that doesn't make sense, the air will easily pass through the turbine wheel and hotside housing such that the wastegate flapper will never have any pressure on it to leak!

Something simple, crank the motor so that the valves find a new position and try again. Maybe the motor just stopped at a convenient place that has a bit of intake/exhaust valve overlap on one of the cylinders allowing all your test pressure to work it's way through the engine. Find a new resting spot and it may take care of itself.

If you think you have a hurt motor, ring blow by would pressurize the crankcase and it wouldn't be coming out of the tailpipe. A bad pcv valve would do the same.

A bent/burnt valve would cause it to come out the tail pipe. An open egr valve would do the same. Does anyone know the "resting state" of the egr valve with no power to it? If it is open, then turning the key on to supply juice to the egr relay may close it while doing the test.