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taterbug
 Post subject: low compression on #3
PostPosted: Mon Dec 10, 2012 10:21 am 
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I did a compression check on my buggy and found only 60psi on cylinder #3. Im guessing its the rings. Can i replace just the rings and hone the jugs out and get a jug and piston kit later on down the road

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Red Barron
PostPosted: Mon Dec 10, 2012 10:46 am 
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It could be a valve seat or a cracked head as well, both are easy to check. You can pull the head set it on the bench fill the #3 combustion chamber in the head with gas or water and see if it seeps past the valve. Before trying that make sure your valves are adjusted correctly at .004 intake, .006 exhaust. If the vale is to tight then the valve will not seat an cause the same low compression.

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2800passat
PostPosted: Mon Dec 10, 2012 12:36 pm 
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New trick someone taught me a while back.Put your compression gauge back in and set the piston on top dead center and rotor pointing toward #3 plug wire on your dist. cap.Dicconnect the gauge part of your comp. tester and connect an air compressor hose to it at about 100 psi. With everything silent put your ear over your carb, then exaust tip and then listen down your oil cap and you will know exactly where your comp leak is.A piece of fuel hose in your ear is even better.This is how I knew I had a jumped timing chain on the Passat. aka DirtyGirl.


Last edited by 2800passat on Mon Dec 10, 2012 3:29 pm, edited 2 times in total.

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taterbug
PostPosted: Mon Dec 10, 2012 2:16 pm 
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Ok ill try both ill try the gas on the bench top test with a spair set ive got. do the heads need tobe on the motor to set the valves? ill try the air compressor trick with the head that is on the motor. if the one on the motor checks out could it be the rings?

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Red Barron
PostPosted: Mon Dec 10, 2012 2:55 pm 
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Valves can only be adjusted on an assembled engine. I would suggest you buy a Haynes service manual or a keeping your vw alive hand book, it makes great bathroom reading and when your not using it to work on your bug or rail you can use it as a coffee table book the wife or girl friend will just love a greasy book on the coffee table.

The manual is a good idea the rest is just my poor attempt at Monday humor. :mrgreen: :mrgreen:

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taterbug
PostPosted: Mon Dec 10, 2012 4:41 pm 
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Ive got a haynes manual or whats left rats decided to eat the exploded view of the cabs section. ill double checkthe valve adjustments and do the tests when i get off work

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Red Barron
PostPosted: Mon Dec 10, 2012 4:50 pm 
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No problem dude just trying to save you from tarring down an engine that doesn't need it. Cash is hard to come by so double checking can save lots of cash. I bought a VW some years ago for $250 because the owner said it had a blown engine. After getting it home I pulled the valve covers to find the head bolts loose, tightened them up and ran the engine in a buggy for six more years. :D

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taterbug
PostPosted: Mon Dec 10, 2012 5:31 pm 
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Ill let you guys know what i find out thanks for the advice.

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Red Barron
PostPosted: Tue Dec 11, 2012 8:49 pm 
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Did you sort this out? just checking

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taterbug
PostPosted: Thu Dec 13, 2012 9:47 am 
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I hooked the compressor to the cylinder in question and used a piece of rubber hose to listen and i heard air coming from the oil filler. so im guessing its the rings. sorry for the delay been busy on other projects

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2800passat
PostPosted: Thu Dec 13, 2012 11:25 am 
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2800passat wrote:
New trick someone taught me a while back.Put your compression gauge back in and set the piston on top dead center and rotor pointing toward #3 plug wire on your dist. cap.Disconnect the gauge part of your compression tester and connect an air compressor hose to it at about 100 psi. With everything silent put your ear over your carb, then exaust tip and then listen down your oil cap and you will know exactly where your comp leak is.A piece of fuel hose in your ear is even better.This is how I knew I had a jumped timing chain on the Passat. aka DirtyGirl.

I just want everyone to learn this. awesome!
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taterbug
PostPosted: Thu Dec 13, 2012 1:29 pm 
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I never would have thought about it. but im gonna pull the head off and do the other test and check the rings while im there but its gonna be a few days ive got the put a pilot bearing and throw out bearing in my v8 ranger first.

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hpfreak
PostPosted: Thu Dec 13, 2012 10:12 pm 
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i know guys that can hook up a vacumm gauge to a motor and tell you anything you wanna know. lean/rich, hot/cold, timing, valves, rings, ignition, compression the list goes on.

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tw9294
PostPosted: Thu Dec 13, 2012 10:34 pm 
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2800passat wrote:
2800passat wrote:
New trick someone taught me a while back.Put your compression gauge back in and set the piston on top dead center and rotor pointing toward #3 plug wire on your dist. cap.Disconnect the gauge part of your compression tester and connect an air compressor hose to it at about 100 psi. With everything silent put your ear over your carb, then exaust tip and then listen down your oil cap and you will know exactly where your comp leak is.A piece of fuel hose in your ear is even better.This is how I knew I had a jumped timing chain on the Passat. aka DirtyGirl.

I just want everyone to learn this. awesome!


This is a leakdown test. They make a tool specificaly for this that lets you regulate the pressure and monitor rate of leakdown. 20% is max alowable on any cylider. If you take rockers off or loose theres no question the valves should be closed. Also under certain circumstances you want to check at lower pressures. High pressures can sometimes seat a poorly seating valve and therefore make it look like its ok.

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taterbug
PostPosted: Sat Dec 15, 2012 8:57 pm 
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Well guys i just bought a set of slip in 87mm jugs and pistons rings and wrist pins set. it didnt come with the gaskets that go between the case and jug or jug and head. do i absolutely need them or what

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reno2165
PostPosted: Sat Dec 15, 2012 11:17 pm 
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clean the jug and the block real good where they seal together and use ultra grey..done several and no leaks yet

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ridenrace6
PostPosted: Sun Dec 16, 2012 6:12 am 
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reno2165 wrote:
clean the jug and the block real good where they seal together and use ultra grey..done several and no leaks yet


x2, DO NOT use any kind of paper gasket in this location

you may get several opinions (honda bond, curil t, hylomar, yama bond, several different colors of permatex, etc.....) and most will work fine as long as they can stand the temp, personally i tend to use the red high temp permatex and have never had any issues that im aware of

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taterbug
PostPosted: Mon Dec 17, 2012 9:12 am 
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Havent been able to make any progress its been raining the past few days and i have no shop

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taterbug
PostPosted: Wed Dec 19, 2012 1:42 pm 
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I have a brand new tube of stuff made by the same paople as the red permatex but i was told its good for ball and socket manifold connections. its some kind of copper gasket maker stuff not sure of what its exactly called roght off. could i use this?

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