Chevyguy358

iTrader: (4)

Troubleshooting a small loss of coolant and found some film under the oil cap indicative of head gasket or warped head ect. So I went ahead and started tearing the motor apart and removed the drivers side head before I decided a leak down test would have been a better course of action. So before removing the passengers side head I went ahead and did this and came up with with 35%-38% in each, this was on a cold engine and the pistons weren't necessarily on TDC. Anyway, with these results being fairly consistent should I even worry about removing this head, though I realize this is on the high side.

Also, I'm using a Harbor Freight leak down tester which is quite different than the summit one I used to use, it only uses about 40psi with the percent gauge zero'd out and calculates the offset from there. Is 40PSI even enough? the summit one used 100psi

After removing the driver's side I didn't seem to find anything out of the ordinary, head and head gasket look fine though of course I'll take it to a shop to verify it isn't warped.

Chopstix

iTrader: (1)

small amounts of film under the cap can also be from condensation.

did you do a pressure test of the cooling system to pinpoint the leak?

did you do a compression test to verify head gasket issue?

SS RRR

iTrader: (2)

^^^ That.
I've had the complete underside of valve covers covered in film before. Not sure what kind of weather you're having, but nation wide the weather has been REAL wonky these last several weeks which can easily cause excessive condensation on the motor innards. This is why it is always good to start an engine and run it to operating temp before shutting it off. If it were me I'd do a coolant pressure test before messing with a leakdown of that is your only indicator.

Chevyguy358

iTrader: (4)

Yup I did a coolant pressure test, I should have mentioned this. It lost a couple psi per half hour, so negligible. Nothing dripped on the garage floor during this. Also the girlfriend noticed a small white cloud of smoke at WOT when following me in her car. So that's why I suspected a head gasket issue, but it could also be my tune as it still isn't dialed in.

1994Z28Lt1

iTrader: (1)

Even cold with forged pistons that is a heck of high percentage of leak down assuming the gauge is accurate? The key is where was the air escaping? if you heard anything from the radiator cap you'd know instantly what the deal is but im assuming you didn't?

35% is pretty incredible to say the least so im betting on it not being accurate. Are you using head studs?

SS RRR

iTrader: (2)

I dunno, if it were me, I'd pull the plugs and do another pressure test. Let the pressure bleed down to zero and rotate the engine to see if coolant starts coming out of one of the plug holes. You haven't changed the coolant recently?

guppymech

iTrader: (7)

Does the inside of the oil cap smell like antifreeze? I had the typical Vortec intake leak on my pickup and while it had no film in the cap it had orange residue and it smelled like antifreeze. Do you smell antifreeze underhood after a drive, if yes, would be a external leak.
I don't think a tester that uses 40 psi is enough for a leakdown test, 100 psi is the norm. The test is most accurate on a warm engine. Does the engine run well all around? Those leakage rates are high but with a cold engine and the low psi Harbor Freight tester I don't give the results much validity.
Do any of the pistons on the drivers side look alot cleaner than the others? That would indicate that cylinder was burning coolant. If you end up not difinitively finding the cause of the small coolant leak and you have no external leaks it could still be the head gaskets.

great421

iTrader: (1)

Yep - Put compressed air in each spark plug hole via an adaptor (with the engine rotated so that the tested cylinder is at TDC on the compression stroke), then look for bubbles under the radiator cap. When you find the bubbles (and you will!), that is the cylinder with the issue.

NOTE: After you find one cylinder with issues, do not assume you've found the only cylinder - I had one go on each side; so, I had to replace both head gaskets.

Good Luck!