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Old 10-31-2008, 07:01 PM
coppcar coppcar is offline
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2003 Pathfinder Maxima
2003 Pathfinder
 
Join Date: Oct 2008
Location: N. MN
Posts: 2
Default Leak Down Test Failed On #3 - Read All About It

2003 Pathfinder SE, VQ35, 87,000 miles, purchased 1 month ago.

When I inspected the truck prior to purchase it was in nice shape and clean. My inspection did not include a compression test. All other aspects of a typical on-site inspection and test drive were acceptable. No smoke, no deposits in exhaust, engine ran well. I got 23 mpg when I drove it 300 miles back home.

As I began to do all the routine maintenance and started reading the forums, I found instances where some folks were having oil consumption problems. I decided to check the right valve cover, which I've documented here. I also decided to do a leak down test and that's where I'm at now.

Engine is cold, **all plugs removed**. Pistons are cranked into TDC position by hand. Supply pressure to test device is 100 psi. Leak down tester is a dual gauge unit I made. If you're interested in how, let me know. If there's enough interest, I'll do a web page on it.

Cylinder 1 - 10%
Cylinder 2 - 10%
Cylinder 3 - 65% - Air is heard in the spark plug hole of cylinder 1. Head gasket?? Strange considering #1 does not leak into #3. You'd think if the head gasket had failed that air would move between both cylinders. Besides, failed head gaskets don't behave this way, right? No oil in coolant, no coolant in oil.
Cylinder 4 - 10%
Cylinder 5 - 7%
Cylinder 6 - 12%

I installed the spark plug into cylinder 1. Air is heard coming out of the exhaust pipe. Aha! An exhaust valve issue!

I'm trying to think of something that might help. I've read about some folks rapping the valve stem with a plastic mallet in an attempt to seat the valve. I looked at the valve train when the rocker cover was off, I don't think there's anything I could rap on. So, I'm thinking to myself, how can I introduce some sort of shock to the cylinder? I remove my gauge set and hooked up my 100 psi air supply direct to the plug adapter hose. I proceed to pressurize/depressurize several times in succession. I rotate the crank a bit, pressurize/depressurize some more. After a few dozen of these pressurize/depressurize cycles, the leakage has improved to 24%, which is wonderful, but it is still high. I'll cycle the pressure until I see no improvement and then I'll just button everything up and check again later. At least I have a baseline to start from and I have a new tool that I made myself, a leak down tester. How cool is that!

I'll check into GM top engine cleaner.

If you have any comments or suggestions, I'd love to hear them!!

Coppcar
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