Vavle Job?

J

Joe Murray

New member
Hello,
I have a problem. I have 25% leak in the number 3 cylinder and 20% in number 4.
Could it be just valves or someother problem?
The car does have weak valve springs. The car is 1987 gti 16v.

Thanks for any help (from a newbie)

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ahondafor?
 
Could be the valves, or it could be the rings. If the springs are weak, and it hasn't had a valve job in a while, it might be the valves.

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MARRS #25 ITB Rabbit GTI
SCCA 279608
 
What you need to do is to determine where the leak is occuring. After you've filled the cylinder with air listen to where the air ia escaping from. If you hear or feel it coming out of the oil dipstick tube.. bad news, it's the rings. If you hear it getting past the throttle body, then it's an intake valve, and so on for the exhaust. If you see a puff of smoke when you down shift, it could be as simple as valve guide seals. This is a commonly needed repair on an older engine, as the seals shink over time. JOE
 
Thanks for the help,
There is no smoke, at all, from the exhaust. I will check to see (hear) where the leak is coming from, I think it might be from a bad valve job from the previous owner (maybe). I hope that it does not have to have the head replaced!
If the head was cracked (warped) or bad gasket could that be one of the causes of the leakage?

Forgive the lame comments!?

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ahondafor?
 
If the head gasket was bad, you wouldn't be able to keep water in the head. If the water temp's are "normal" then it's just a valve problem on 1 cyl.

You should be able to get a local machine shop to check the vavles, seats, seals, springs or look on eBay for rebuilt 16v heads, but do your homework on that.

Tim

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Tim Linerud
San Francisco Region SCCA
#95 LP GP Wabbit
http://linerud.myvnc.com/racing/index.html

[This message has been edited by racer_tim (edited March 21, 2003).]
 
Was the motor hot or cold when you did the leakdown ? Try a hot leakdown.

I've had "spec" race motors that had 15-20% static leakage (cold or hot !), that still ran fine and made good power, compared to the other "spec" motors on track with it at the same time (would run midpack at Nat'ls).

Do JoeSellsVW's diagnostic step, and you'll have a better idea of the problem.

You could fix it (pull head, valve job, maybe hone & re-ring the cylinders), or you could just ignore it. Ignoring it is cheaper, and probably won't make the problem any worse. If it's just in the top end, you're looking at $200-500 labor + parts to freshen the head. If it's the bottom end, you can re-ring a motor without pulling the block out of the car.

I hate leakdown gauges. They only give you bad news. I wish I'd never bought one.
 
I agree with you John, those leak down gauges give me the creeps.

Even though I own one, the way I judge motor "wear-down" is the amount of oil in the dump tank after a session. Given similar ambient temperatures, the overflow is telling me blow-by. As it increases, I know the bore-ring relationship is getting old. When excessive, it is time for a rebuild.
 
The leak is coming from the exhaust valves on one cylinder and the intake on another.
All four cylinder have between 20%-25% leakage. This seems to be excessive. If I was to ignore the problem would'nt I be down on power? My engine guy thinks he can reseat the valves and freshen the head, my biggest concern is money (of course).

Thanks for the great input!

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ahondafor?
 
Joe,

Your guy might be able to 'fix' the problem by just re-lapping the valves. Check on www.vwvortex.com and you might find a good deal on a used 16v head. Good luck.

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MARRS #25 ITB Rabbit GTI
SCCA 279608
 
The first year I ran ITC I had the same concerns on my engine. I asked around, and several knowledgable VW guy's gave me this advice.
Run it till it blows!!
If it's running good, don't worry about compression or leakdown numbers, just drive it. Especially if your new,(Welcome!) concentrate on improving as a driver, don't worry about the engine for a few years. When you can keep up with everybody through the corners but they pull away twords the end of the straight, then you need more power and it's time to work the engine!
Mark
 
Gosh.."run it till it blows". That's horrible advice. Besides endangering people on the track you can make a relatively inexpensive rebuild an unmitigated and expensive disaster.

The better expression is "drive it until I know it is down on power".
 
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