Paul Riccioli Jr

iTrader: (1)

Ok well first of all I could only test 4 of the cylinders because my headers were in the way and I didn't want to remove them. I pulled all of the plugs and the number 3 plug looked like it had oil on the threads, but not the electrode. All the rest looked fine. 3 of the cylinders I tested came up around 15-20% which my gauge says is low so they should be ok. The #3 cylinder that had the oil on the plug was different though!
When I started regulating air into it it was very high on the leakdown gauge. Once the pressure got up around 90psi though I would see the needle start to creep up and then shoot to the low range quickly. As it would move to the low range I could feel a large amount of air coming out of the throttle body also. If I let the pressure out and then filled it again it would go right to low again. If I moved the crank a few degrees it would once again start with a very high reading, give a large puff out of the throttle body, and shoot down to a low reading.

What does this mean? Please tell me it's not the rings in that cylinder. Maybe something wrong with the intake valve?? Not seating correctly or something??

1991tealRSt-topGuy

if your sure the piston was at TDC and the valves were closed, i would suspect a bad intake valve (or valve seat)

ede

sort of hard to follow, but i think it means you didn't do the test correctly. if you're saying you have 20% leakage it's way too much.

Paul Riccioli Jr

iTrader: (1)

That's what the gauge said. Although it's listed as low on there. I've never done a leakdown before but I thought you would just put a certain amount of pressure into the cylinder and see how much leaked out over a certain period of time. This one had a constant supply going into the cylinder and then the other gauge told you the percentage.

As for the piston being at top dead center, here's what happened. I'd put it at top dead center and a few of the times the pressure from the tester would force the piston down. Even when the piston didn't move, the same results occured. Plus with a constant source of pressure into the cylinder, would the piston being at TDC even matter?

Would a bad valve seat cause me to burn oil also? Maybe the valve is bad and it caused the valve seal to burn up??
Also how much of a power loss could something like that cause?

yanfoo

I have never manage to do a leak down test alone,
you need to turn your engine for each cylinder so they are in compression step, use a long 1/2 ratchet on the crank nut, take all your spark plug out(made easier to turn) , put your finger in the sparkplug hole you want to test, turn it until you feel the air coming out (it will do it twice ,1for compress and 1 for exaust, so you have to choose the **stronger** push so you know the valves are close)

ok then the harder part, put the test gauge in, and your air ready (i hope you have a valve so the air start coming slowly ) so have a buddy, get a strong one, when you put air, that will - could, push the piston down, and you dont want that, you want it to stay up there, that why you need someone to hold it there.

then you get good result, last time i have done this, the car was a toyota tercel and we found out it was leaky rings.

Air_Adam

I dunno.. my 305 ran with only 65psi compression... ran badly, but it did run.

Paul Riccioli Jr

iTrader: (1)

Ok well I talked to a good friend of mine who's a great mechanic and this is what he told me. The oil on the threads if from an external oil leak since there was none on the electrode. This is possible because I had oil splatter all over the place on me a few weeks ago.

He told me to try readjusting the intake valve on the number 3 cylinder and redoing the leakdown test on that one. If it still is not good then I'll probably have to pull the head. If it gets better then the intake valve is too tight.

I'll have to try it tomorrow maybe.

He also told me that moly rings take forever to seat and that a quarter quart every 500 miles with only 6,000 on the engine is ok. This is the only thing I'm still wary about.

ede

do a compression test, faster and easier. moly rings tend to seat very fast, plasma moly doesn't.

Paul Riccioli Jr

iTrader: (1)

I don't know if I can get a compression tester in on all of the cylinders either. It also took me almost an hour to get all the plugs out today so it will probably take less time to reset that valve and redo the leakdown test on just that one cylinder.