Boost Leak Test Help Needed!

[Jalopy]

I am doing my first BLT and I am having some issues. I hooked up the tester (homemade) and the system will hold no pressure. I have rotated the crank to 6 teeth past TDC to eliminate valve overlap. (I'm thinking EGR, so I figure this is a great time to put in a block off plate). So, I decided to eliminate the IM from the equation, I pulled off the UICP from the TB and plugged it. Now if I add air at the turbo inlet, I can only get a few pumps of the hand pump before I hear a loud hiss from right around the turbo. I used soapy water, I'm not seeing anything. I pulled the J pipe off, held my hand over the outlet, and pumped a few pumps, it immediately starts hissing. I don't hear it bubbling in the oil. I have a compressor, but it's not handy and I wanted to try this before I dragged it out. Am I not putting enough air in? I have to use a tire gage to check PSI and it leaks out before I can get it on the valve. I know that some air will escape into the crankcase during the test, but how much? I have heard about some other turbos leaking at the compressor housing O-ring, I am wondering if that might be the case. I just want to know if I should pull the turbo off or just get the compressor out and keep testing. is there any other potential leak in that area?

Also, I went ahead and put the tester back on the TB, it's not holding any air. I am sure my valves should not be overlapped, and I was doing it with the EGR holes plugged so it's not that. the car runs miserably and backfires in the exhaust, I think I am on the right path to finding out why.

 

[BIGBLAZE79]

Yes the turbo compressor housing o-ring can leak, My 16G had a blown compressor housing o-ring and the car would backfire and pop if I floored it with boost above 10psi. I would hook it up to the TB and plug every vac line comming off the intake manifold and work your way back to the turbo once the leaks were fixed.

 

[LiquidX]

I always start at the TB and you should use your compressor as you won't get enough pressure built up with a hand pump with these kinds of leaks.

Use the spray bottle of soapy water and as your are filling the system spray EVERYTHING all over that sees any air. Chances are your throttle body shaft seals are bad, injector insulator o rings are bad too. Rotate the throttle plate as well while your are testing.

Check to see if your PCV is working properly by blowing into it. If you can blow through it then it's bad and you'll need to get a new OEM unit or you can put a cheap inline check valve before the PCV.
3/8" Kynar® Standard Check Valves | U.S. Plastic Corp.

Thoroughly check for leaks and look for bubbles. Pressurize the system to above what you are going to be running and if it's leaking then you still have a leak somewhere unless it's leaking out of the valves due to them being open.

Once those are fixed, move it to the intercooler and check for holes, lastly to the turbo to pressurize the whole system.


Just to make sure, you do have your BOV recirculated right?

 

[Jalopy]

Yes, I am recirculating. Just to be sure I tested from the LICP to the UICP, no leaks. I am going to go plug all the hoses and retest once i get my egr back together with the blockoff plate (i was just plugging the holes). I'm sure the TB gasket/shaft seals are not optimal, but I am familiar enough with that part of the engine to track down those leaks given enough time. My concern is that a lot of air seems to be passing right through the turbo. with the j-pipe blocked, it doesn't have much volume so I would think I should be able to pressurize just the turbo and hold that pressure for at least a while. It seems like it might be making it into the exhaust... is there a seal or something that could be going allowing intake air into the exhaust? My turbo seams good, no oil in the LICP or shaft play at all. I think I am capable enough to find a "normal" boost leak (hose, gasket etc.) I just don't know enough about the inner workings of turbos to determine whether this is an issue. I have read the writeups, and I know you are supposed to pressurize to say 20 psi and see how long it takes to leak down, but if only the turbo is tested, how fast should the leak be?

 

[talon111]

i have a stock 91 eclipse gst..and on the stock intake pipe box near MAF sensor is a HOSE FITTING i have boost line but cannot figure out where it runs to..anybody know where

 

[LiquidX]

Yes, I am recirculating. Just to be sure I tested from the LICP to the UICP, no leaks. I am going to go plug all the hoses and retest once i get my egr back together with the blockoff plate (i was just plugging the holes). I'm sure the TB gasket/shaft seals are not optimal, but I am familiar enough with that part of the engine to track down those leaks given enough time. My concern is that a lot of air seems to be passing right through the turbo. with the j-pipe blocked, it doesn't have much volume so I would think I should be able to pressurize just the turbo and hold that pressure for at least a while. It seems like it might be making it into the exhaust... is there a seal or something that could be going allowing intake air into the exhaust? My turbo seams good, no oil in the LICP or shaft play at all. I think I am capable enough to find a "normal" boost leak (hose, gasket etc.) I just don't know enough about the inner workings of turbos to determine whether this is an issue. I have read the writeups, and I know you are supposed to pressurize to say 20 psi and see how long it takes to leak down, but if only the turbo is tested, how fast should the leak be?

You have the turbo blocked off properly, where is the air leaking out of? You should be able to figure this out. Justin (jusmx141) if he happens to chime in would be able to give you a better answer about how the turbo seals air insides itself pre outlet.

i have a stock 91 eclipse gst..and on the stock intake pipe box near MAF sensor is a HOSE FITTING i have boost line but cannot figure out where it runs to..anybody know where

First, you should make your own thread if you cannot search and find your answer. Next, which fitting on the intake pipe are you referring to, there are three; charcoal canister, valve cover vent, and BCS nipple. Lastly, a boost leak is pressurized air leaking out which would be post turbo. Pre turbo and post MAF would be a vacuum leak on the intake pipe.