New FMIC install and need the details of Boost Leak test

[Mike G]

I just had my favorite muffler guy assist in a giant FMIC install. This thing looks pretty and the pipes flow like art. But unfortunately the car stumbles at idle and doesn't build any juice now. Of course I figure there's a leak in the system somewhere so I need the specifics on testing. I am quite comfy under the hood, so I figure at least a soapy spray bottle will be my best friend soon. Do I pull the piping from the throttle body and load the system up to the turbo with an amount of air pressure, looking to the leaks? I understand how to build an end to cap and fill the system with air, my problem is where to start and end.

Thanks all, --Mike

 

[TSG59_Steve]

I could be wrong but from my understanding the only thing you would detach would be the intake tube. You put the blt on the compressor side of the turbo and pump the whole system with air. I've also hear of blocking off the mbc because they are known to leak.

 

[DSMunknown]

Completely filling in your profile would be great for starters.


Generally speaking, no more than 25-30 psi should be used when testing the system. You should start at the TB elbow and work your way back to the compressor-side housing. Many people just clamp on their BLTers to the intake pipe mounting spot and test away. Others would not recommend this because it puts stress on the turbo gaskets. You decide. Also, some people manually turn their engine so there is no valve overlap and so that the intake valves are closed.

If you really feel pro-active, you could take off the entire FMIC and piping system and test it by itself. You would just need to find some sort of rubberized cap to put on the end of one of the pipes.

I could be wrong but from my understanding the only thing you would detach would be the intake tube. You put the blt on the compressor side of the turbo and pump the whole system with air. I've also hear of blocking off the mbc because they are known to leak.

You don't test with the MBC installed because many MBCs are bleed-type controllers, and their job is to help bleed off excess boost. Look through the thread here to see what you can install in the place of an MBC.

 

[TSG59_Steve]

And don't try starting your car with the system pressurized.

 

[romeen]

If you are having trouble locating a hard to find leak then starting at the TB and working backwards can make things easier because you are dealing with smaller sections of the intake. Having said that I have always done it from the compressor inlet of the turbo and never had a problem. I do regular leak tests and there is no reason for me to take apart sealed sections of my intake.

 

[DSMunknown]

I am quite comfy under the hood, so I figure at least a soapy spray bottle will be my best friend soon.

Also Mike, another good friend to have around is quiet.

Do I pull the piping from the throttle body and load the system up to the turbo with an amount of air pressure, looking to the leaks?

It doesn't make too much sense to take off the UICP and then attach the BLTer to the compressor-side housing, now does it? Unless you intend to cap off the end of the exposed piping, you have now created a BIG boost leak (because all the compressed air you're pumping in the compressor-side housing is easily going out through the end of the UICP).

 

[Mike G]

It doesn't make too much sense to take off the UICP and then attach the BLTer to the compressor-side housing, now does it? Unless you intend to cap off the end of the exposed piping, you have now created a BIG boost leak (because all the compressed air you're pumping in the compressor-side housing is easily going out through the end of the UICP).

Now that's funny.. My thought was to pull the UICP and cap that with a method to pressureize the system, then capping at the J-pipe so that it isolated the IC system all together. The overall piece I was missing was using the compressor housing as the source spot for injecting the air. I would othewise cap the UICP to avoid the possibility of valve leaking.

I figure it should be nice and quite in the garage around 10 pm tonight, except for the gas escaping my opening beer bottle...

--Mike

 

[romeen]

I hate it when the air compressor motor kicks on right when you are zeroing in on that elusive leak. Now I just shut it off before I do the test. 13 gallons of compressed air is plenty for me to complete the leak test.

 

[DSMunknown]

I hate it when the air compressor motor kicks on right when you are zeroing in on that elusive leak. Now I just shut it off before I do the test. 13 gallons of compressed air is plenty for me to complete the leak test.

Good one! I usually can get two solid tests done before the compressor motor turns on right as I'm about to listen for leaks in the third test. It pisses me off! I have to hurry up and put the hose down (being careful not to f up the body paint job any more than it is), go to the motor and turn it off, and then hussle back over and put my ear to possible leaking areas. Plus, the hose adapter leaks, so I always have to disconnect the dual tire chuck.

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I don't know about anyone else, but I always do at least five tests in a row (you know, just to make sure).

 

[Dream On]

Definitely have somebody with you when you do it. One, to look for leaks together, and two, so someone can watch your boost gauge.

 

[DSMunknown]

Definitely have somebody with you when you do it.... so someone can watch your boost gauge.

Adam, this is in regards to the link I gave in post #3. If he or anyone else has a little extra cash (or better yet, an extra pressure gauge) at his disposal, this is easily a one-man job.

 

[romeen]

Adam, this is in regards to the link I gave in post #3. If he or anyone else has a little extra cash (or better yet, an extra pressure gauge) at his disposal, this is easily a one-man job.

Agreed. I have never had a helper for a boost leak test. IMO, the added guage on the tester for less than $10 more than pays for itself.

 

[Dream On]

I didn't read it, but I'm assuming you're talking about putting a gauge on the leak tester itself. I think it's still better to have the boost gauge check since it is farther up in the system and it may be seeing less pressure than at the inlet. Maybe it's the same, but it's always helpful to have someone else around to help you isolate leaks.

EDIT: Just looked at the pics, seems like you could move it around and check.

 

[Mike G]

Definitely have somebody with you when you do it. One, to look for leaks together, and two, so someone can watch your boost gauge.

I usually have someone handy, but it's to hold my beverage

As luck should have it, the UICP which looked fishy to me to start with wasn't secured correctly (darn muffler guys...) so I did a little re-aligning and think it's good to go. I do have an extra vacuum gauge in my chest of goodies, so I would have placed that in line under the hood instead of relying on the boost guage in the car.

Wish me luck (I didn't get a test run in last night) --Mike