Leakdown test...frustrating results.

[PullinGs]

Tonight I did a quasi-leakdown test on my car just to see where things are leaking due to my recent discovery of the 135psi I was seeing with the compression test. This was on my less than 2000 mile 8.5:1 rebuilt motor.

Okay, the first part is really strange. When I would put compressed air into cylinder #1 I would get lots of air rushing out of cylinder #2. This would make me think that there was a headgasket problem. (Metal Mitsu gasket). But when I put air into cylinder #3 I got some air coming out of cylinder #1.

Also, when putting air into the cylinders I could hear air flowing through my IC piping.

I just don't get it. Why would it leak so much? It would be understandable if my head rebuild job wasn't done correctly, but could my rings just not have seated that badly? I have ARP headstuds torqued to 84. Rgh. Very frustrating.

 

[turboholic]

-Are your timing marks align? Did you crank the piston to TDC on the cylinder you're testing on?

 

[PullinGs]

Yes, I've checked all of my timing marks and they line up. I also made sure that the pistons were at TDC. Some people have mentioned that they needed to be on the compression stroke and I didn't make sure of that, though. I imagine something is way off though since it has 135psi comp.

 

[98TsiAWD]

So when you put pressure in through your spark plug opening, you are gettin air leaking through your head, into your intake manifold and then into your intake pipes?

That would make me think there is something messed up in the head.

As far as puttin air in clylinder 1 and air coming out 2, I would also think head gasket or cracked head. But when you put in 3 and it comes out 1, that is just weird. Well wait a minute, if your head is messed up, or timing is off so the head is opened up wouldnt it leak up through the head and could come out of any cylinder? When you have each cylinder pressurized, go put your ear up to your exhaust pipe and see if you hear any air leaking out, that should be your rings if you do hear it out the tailpipe.

Like he said tho, make sure you are at TDC, its kinda hard to get it perfectly.

 

[turboholic]

-Was the final assm done by you or by a shop, one time I didn't clean the machined block thorough enough, some metal shaving ruin the cylinder wall & bearings.

 

[candela]

If you hear it out the tailpipe isnt it your exhaust valves leaking?? That is what I was taught at aleist...

 

[98TsiAWD]

Originally posted by candela
If you hear it out the tailpipe isnt it your exhaust valves leaking?? That is what I was taught at aleist...

Yeah it might be, I cant quite remember, exhaust valves would make more since. how would a leaking ring make noise out your tail?

 

[PullinGs]

I did the final assembly and I was sure to clean the cylinder walls before putting it together. I think I'll just have to pull the head and see what I find. From what I heard, if you hear sound in your crankcase then it's your rings. Exhaust pipe-exhaust valves. IC piping-intake valves.

I'm hoping that the head isn't cracked because I haven't really done anything that would have cracked/warped it. Also, the metal headgasket should hold. My only concerns are that the head wasn't rebuild properly.

 

[QKGSX]

This sounds exactly like what happened to me a couple of months ago when I did a leakdown test. I was getting air coming out of other plug holes, my intake, exhaust, and slightly from the crankcase.If it's a head gasket I can understand that because the motor was overheated last year (water pump) and uses a small amount of coolant but it still seems weird that it's that bad. The gauge only read 10-15 psi., meaning 90% leakdown. That just sounds rediculuous especialy since I got 160 across the board for compression and the motor seems to run as hard as it ever did, 90,000 mi. I'm as cunfused as you but figured I'd rip the head off this winter and see what I see. Let us know what you come up with.

 

[turboholic]

Originally posted by PullinGs
Okay, the first part is really strange. When I would put compressed air into cylinder #1 I would get lots of air rushing out of cylinder #2. This would make me think that there was a headgasket problem. (Metal Mitsu gasket). But when I put air into cylinder #3 I got some air coming out of cylinder #1.

-This is too wreid, I have reuse the Mitsu metal H/G 3 times without problem, the only other thing I can think off is sticky or bend valves that won't close tight.

 

[PullinGs]

I hope it's the valves, in a way, because I can probably get a warranty on the work I had done. Even if not, it's work that I can have someone else do and not feel guilty about having someone else do it.

 

[turboholic]

Originally posted by PullinGs
I did the final assembly and I was sure to clean the cylinder walls before putting it together.

-I don't mean just the cylinder walls, you have to flush all the tiny oil passages on the block to 1000% sure there aren't any chip in it.

 

[Slowboy]

What cams do you have in the car?

Just curious.

Mike Huml

 

[PullinGs]

Well, the entire block was hottanked but I see what you mean about there being residual filings in the oil passages. The guy that did my block does excellent work and is very keen about things like that so I can't imagine he'd let there be crap everywhere.

Stock cams, BTW.