Leakdown Test results and problems

[mitsu_matt]

Ok, noticed a puff of white smoke coming out the tail pipe when I shift, so I started checking things. First I did a compression test...

cylinder 1 - 175
cylinder 2 - 200
cylinder 3 - 195
cylinder 4 - 186

Then I did a leakdown test, but i can not build any pressure in any of the cylinders! I hear the air leak right out. I see no bubbling in the coolant. One crazy thing is when i pressurize cylinder 3 tons of air comes out cylinder 1. Yes I had the crank at TDC. Why cant I get any pressure? The motor only has 500 or so miles on it. Also it runs dam good. the pistons/rings were new and the cylinder was decked and honed. also the valves, seals and guides were replaced.

Also every time i drive i lose a little bit of coolant. I am not sure where its going but my overflow catch can if full every time.

Please help!!!!

 

[mitsu_matt]

ok, so i am thinking its the HG. so i pulled off the valve cover and checked the head studs, some of them were really loose. i re torqued them to 80lbs (per arp). could this little amount of torque cause the HG to leak? Also do you think i should just replace HG anyway?

I am sitting here with greasy hands....

 

[joe sobo]

ill give you a hand. if the bolts were loose, and it was leaking, most likely it damaged the head gasket, (if it was a stock graphite type) if it was like a cometic or another metal type, i would just try to re-torque them and try it

 

[mitsu_matt]

yes it was a metal cometic.

 

[Rob10_99]

How long did you run it before you figured out the headstuds were loose?
Joe's right on the HG is probably toast from being ran without it tight. How did you get good compression but fail leakdown horribly =P

edit, your coolant overflow being full is the first indication of an issue. Short trip around the block and its full? Engine exhaust is getting past the HG and boiling coolant.

 

[joe sobo]

the best bet would prob. be to replace, but in all honesty, if you are not running 25+ pounds of boost, id just re-torque them and see how it does

 

[mitsu_matt]

I have about 600 miles on it. When i built the motor I rechecked the head studs but I think i only checked them to 65lbs. It seems that maybe the valves are not closing all the way at TDC when i do the leakdaown test. Because if i rotate the crank while i pressurize the cylinder i can get pressure and hear the valves open and close letting the air out. but it seems the exaust valve seals before TDC. But there is always the chance I do not know what I am doing...

 

[joe sobo]

you also could not be on the compression stroke,

 

[mitsu_matt]

is the compression stroke only every so many turns? if so how do you know where the compression stroke is? I thought TDC was TDC no matter.

 

[joe sobo]

yea tdc for compression stroke and exaust stroke. you can spin it one full revelation i beleive. some one correct me if im wrong or not wording properly

 

[mitsu_matt]

Let me ask this: When performing a leakdown test, should it hold air nearly perfectly? I mean you should not hear air escaping and it should build and hold pressure?

 

[Clipseinc]

A leak down test is similar to a compression test, but the point of a leak down test is to see how fast air leaks out of each cylinder. Each cylinder should build pressure and each will leak air, unless each cylinder is perfectly sealed (probably not). The air should not be leaking out fast enough to not build pressure though, as is in your case.

 

[Rob10_99]

As long as you have the valve cover off retorqing those ARP's you can make it easy on yourself.
Just turn the engine manually and line up each cylinder so the cams aren't pushing open the valve for each cylinder.
I know 65ftlbs is LOW for what you should be running, so most of the time ARP's are done to 85ftlbs. They can take up to 100ftlbs some people say.

 

[mitsu_matt]

ok, re-torquing the bolts did it! Yea, coolant remained in the system. Compression test was 200 across the board. And leakdown worked and I got about 2.5% loss across the board! I think she is healthy!!!!

Now last thing, i still get a little smoke out the tail between shifts. Is this normal? I do have some updown play and no inout play on the turbo. oil pressure is perfect at crusing but 0 at warm idle. Should I worry?

 

[Calan]

Let me ask this: When performing a leakdown test, should it hold air nearly perfectly? I mean you should not hear air escaping and it should build and hold pressure?

A bunch of information about leak-down and compression tests can be found here.