boost leak test/intake valves

[jim97gst]

OK, I made a boost leak tester in preparation for when I install my 16G. I did the test on my fairly stock setup. I am using an air tank. When I get it above 10 psi or so, I can hear a hissing sound. It then goes down to about 5 psi, and then slowly leaks down to 0. The hissing sound seams to be coming from somewhere around the intake manifold. I can't pinpoint it by myself, as I only have about 5-10 seconds after I pressurize it before it hits 5 psi or so and goes away. I tried to have my wife help me out. She confirmed that it was coming from around the intake manifold as well, but couldn't pinpoint it. She simply described it by saying it "sounded deep", like far down into the engine bay.

I've only done a quick inspection of the vacuum lines on the intake manifold, and I know I need to do the soapy water test, and I need to get another car person to help me out, but I've got a question. No matter where the camshaft is rotated, at least one of the intake valves is going to be open, right? Am I possibly just hearing air escape from an open intake valve? Am I doing something wrong with this test?

Thanks

 

[oldman]

The leak could be the injector seals as well as the intake manifold gasket, soapy water will probably pin point it.

On your next test, open the oil cap and listen for leaks in the crankcase then do the same at the tail pipe. Post back results.

 

[eclipsegsx1736]

I had a similiar leak around the same area when I tested it cold, then I read that the engine should be pretty hot when doing a leak test, as sometimes the seals will seal better when the engine is hot. I tried the test again with the engine hot, and that leak around the intake manifold went away, although I found another near the BOV. It would make sense to test the engine hot anyway, as you dont care about leaks that arise when the engine is cold, only when its hot.

 

[jim97gst]

Well, I finally got around to doing this again. I did it with the car hot this time and still had the same results. Soapy water did not help at all. I sprayed it everywhere around the sound and didn't see any bubbles. No hissing at the tailpipe. I opened the oil cap and there a kind of gurgling/draining sound. Like oil got pushed somewhere and was draining back to where it came from.

 

[oldman]

Move the tester to the TB elbow. Observe holding pressure compares to turbo inlet as well as whether gurgling sound disappears.

 

[jim97gst]

Gurgling sound disappeared. Still same boost hold results. It really sounds like it is around the throttle body, but no bubbles with the soapy water. Can the throttle body leak internally and not cause any bubbles?

 

[oldman]

Gurgling sound disappeared. Still same boost hold results. ?

Gurgling was air through the turbo seal to your oil pan, perfectly normal during a static pressure test without oil pressure. Are you sure there no air/hissing out of the oil cap though the gurgling is gone?

It really sounds like it is around the throttle body, but no bubbles with the soapy water. Can the throttle body leak internally and not cause any bubbles

Open and close the throttle plate and see if hissing changes as well as open the BISS crew cap and listen. You might also want to increase the concentration of your soapy water, 10psi at TB without hissing out of the oil cap means your IM gasket, TB related gaskets and injector seals are probably leaking. The leaks are there, you just have to be patient with it, now you know why most people skip or lie about their leak test results.

 

[jim97gst]

OK, I did forget to listen carefully for hissing at the oil cap, I just noticed the gurgling went away. I can now hear a faint hissing coming from the oil filler.

When I open and close the throttle body it seems to not change the current hissing, but just adds a hiss of its own when it's opened up that goes away when it's closed.

I was even more liberal with the soapy water and still no bubbles.

You are one helpful sum' bi*** old man. If you are ever in Tucson look me up. I'd like to buy you a beer.

 

[oldman]

OK, I did forget to listen carefully for hissing at the oil cap, I just noticed the gurgling went away. I can now hear a faint hissing coming from the oil filler

Disconnect the pcv hose from the intake manifold and cap it off, see if hissing stops. Also makesure again there no hissing out of the exhaust, EGR and valve overlap is some of the usual suspects.

I was even more liberal with the soapy water and still no bubbles.

I was talking about the amount of SOAP in your so call soapy water solution.

When I open and close the throttle body it seems to not change the current hissing, but just adds a hiss of its own when it's opened up that goes away when it's closed.

TB shaft seals for sure, what about the BISS screw? Also, if you have not done the vacuum removal, make sure you spray all the tiny little vacuum hoses as they're all connected to either the TB or IM.

What kind of mbc do you have? Is it connected to the BOV line?

You are one helpful sum' bi*** old man. If you are ever in Tucson look me up. I'd like to buy you a beer.

I will hold you up to that.

 

[jim97gst]

Disconnecting the PCV valve didn't seem to change anything.

Do you think it is only the TB shaft seals since it seemed to add an additional hiss rather than changing the existing?

Where is the BISS screw located? You're saying to just remove a cap that goes on the screw?

All the vacuum lines are still in place. I will check them more carefully.

No MBC, I'm running the stock BCS, a must for ESP cars in SCCA Solo II. Although I will soon be in street mod when I install my evo III 16G and a MBC. But not until I get this boost leak taken care of.

I did some research and it looks like these are the seals I need for the throttle body. I need 2 of them, correct?

https://ec.kamandirect.com/projectfiles/part.jhtml?PARTID=20673657

 

[oldman]

Do you think it is only the TB shaft seals since it seemed to add an additional hiss rather than changing the existing?

No I don't think it's only the shaft seals, if there are hissing, there are leaks. Here's another possible leak.

Where is the BISS screw located? You're saying to just remove a cap that goes on the screw?

BISS. The o-ring under the screw could be leaking.

No MBC, I'm running the stock BCS, a must for ESP cars in SCCA Solo II. Although I will soon be in street mod when I install my evo III 16G and a MBC. But not until I get this boost leak taken care of.

Although it's connected to your compressor housing and will not affect the TB test, when you retest at the turbo inlet after the TB test, you will want to block off the bcs as it will leak being a bleeder type valve.

The throttle body shaft seal replacement looks like a PITA. About how much is an OEM throttle body less the core?

Many have done it and I'm sure you won't have a problem doing it. Just like everything else, the hardest part is getting started.