Leakdown test to confirm compression test...

1105 · Dec 18, 2004

Did a leakdown test on the number 5 cylinder today and air was just flowing out of the intake I had the valve cover off so I backed off the nut all the way to where I could flop the rocker around and still a steady flow of air out of my intake gauge was reading 0. Did the test to the number 6 cylinder, air leaked out but not as much, and I'm afraid to do it to the rest of them.

I'm 99.99% certain I need all new intake valves. Should I go ahead and test the other 6 cylinders, or do a few on the pass side and call it a day. Will I need to get a valve job done to my heads? If so how much should that cost? If my car felt this good on 50-60psi of compression and only running on 7 cylinders, I cant wait to see what it feels like with 130+ compression and all 8 cylinders.

xYoung347x · Dec 18, 2004

I suggest to do all of them. When you did the test was the one you were testing on at TDC?

1105 · Dec 18, 2004

yes it was

Joes95GT · Dec 18, 2004

Why do you think you need new valves?

My thinking is this...

For air to get past the valve, it must also be getting past the valve seal and guide. The only way for air to get past the valve is if it's not seating. Of course, this is assuming that the valve isn't broken, and you'd know it if it was. I'd think you either cracked the head or mangled the seat, somehow....

Joe

1105 · Dec 18, 2004

I dont think the guide is damaged since I can only hear the air coming up through the intake. The only way I can know for sure if I have something else other than a bent valve is to pull the head.

5.0_GT_kid · Dec 18, 2004

Subscribing for info.

blksn955.o · Dec 18, 2004

It could be a headgasket leak around the area were there are no water passages close to the intake, like the top of the cyl on the inside by the lifter area. A bud blew a HG in this area and the comp. and oil/gas was going into his intake and gas/oil was running down into his air filter. We think it got into the intake threw the PCV system.

You will need to pull the head for a valve job or any other work so pay attent. to the HG when you pull the head.

urban96 · Dec 19, 2004

i would pull the heads and take them to a machine shop, or even just take your car there and have them run the tests and see what they say

fivepointNO · Dec 19, 2004

You know it leaks on both heads, so you'll have to remove them at some point. I'd just do that next, cheack for other visible damage and get them to a good machine shop. A complete valve job shouldn't be very expensive. If you take the heads to them and there's no cracks or major damage, you'll be out for well under $200(last I had done).

Leakdown test to confirm compression test...

1105

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Leakdown test to confirm compression test...

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