Rebuild Necessary???
 

The intake valve on my third cylendar got too tight before I noticed. Soon the car got to the point where number 3 was not firing at all. In fact the compression was zero. All my other cylendars had 120 compression.

I loosened the intake valve to the proper adjustment and number three now had compression of about 60. curriously the cylendar in front of 3 now had a compression of 90 instead of 120.

I started the car and it ran again. firing on all four. I only drove it about a half mile and then back down my street as the car had no plates on it or insurrance. When I got back and checked the compression again the cylendar that was at 90 was now back up to about 120 and 3 was up to about 75.

I have called around to some various people who suggest different things. A couple places suggested that I go out and putt 100 miles on the car and see if it get better. Another so called "expert" said that it could be a head gasket leak. it is interesting to note that I did not use head gaskets as I was told by another "expert" that many people do not use them including himself. Was this bad advice?

Further, I know the noise that a sucked valve makes as it was a sucked valve in 3 that caused me to replace the right side head in the first place... the car is not making those awful noises now.. infact it sounds pretty much o.k.

Lastly the top end rebuild I mentioned was my first. I should mention that we also changed the rings for good measure. When I got it finished and the car started I jumped for joy and took and drive. I never bothered to check the compression... I drove it all summer and fall before number three went to zero then back to 70. I now wonder with the fact that I've got 3 firing again if it is the same as it's always been since the rebuild. I further wonder if perhaps I put one of the rings upside down in the third cylendar.

Any ideas what I should do? Should I put 100 miles on the car and see what happens or should I go ahead and start taking the motor out?

P.S. It is only a hunch or guess that I may have put a ring in upside down in number 3. I'm really not sure what is wrong if anything at all. Perhaps a nice long drive will clean it all up and bring up the compression????

Please send replies to my e-mail address as well as posting here. 4321@homepageinc.com

Thank you in advance.

When you did the comp. test did you try a tsp. of oil in the spark plug hole? If compression went up it is a problem with the rings. If the valve is stuck open from carbon a mist of oil may spray out the intake or exhaust ports. I have a similar problem with a 1.7 120, 115, 115, and 70 on a cold engine. I sprayed in some PB Blaster Catalyst and comp came up to 90 but a mist came from the intake port. I have a buddy who is a machinist at NAPA and he has seen a couple of heads come in for valve jobs due to no comp only to find a small amount of corbon holding the valve open. If you don't have tags then how old is the gas? Old gas short trips equal carbon. Try a chemical treatment first before taking off the head. Also if both problem cylinders are on the same side it may be a pulled head stud. If you over torque the head when cold they pull out as the alum block expands.

You bring up an excellent point and also my hopes that perhaps nothing is wrong. About midway through the summer (3 months or so since the top end rebuild) I noticed that if I put my hand over the exhaust pipe a mist was coming out. It almost felt like water on my hand but perhaps this mist was oil and/or gas. This would last for maybe 10 or twenty minutes )i'm not exactely sure. If I kept driving and kept checking it when I made stops (running errands, etc., and leaving the car running) the mist would stop, and the car would seem to be running really good. Do you think that my "problem" could simply be that I am trying to check compression on an engine that is too cold? Should I drive it for an hour and then check the compression?

Was this mist simply too much carbon on the valve, and this in fact burns off or goes more normal once the engine has run for a while?

Thanks again in advance.
Brian

I belive ALL internal cumbustion engines expel water as part of the combustion process. It should be fairly easy to tell if the vapor is oil or water. If it drys off your hand without feeling slick then... I would check your compression when the engine is warm definatly. Read the instructions that came with your tester, it should confirm this. Also when I mentioned that a mist was coming out of my engine I forgot to mention that the motor had not run in 8+/- years and the intake tubes and heat exchanges were off. The engine dosen't have to be boiling to check compression, but it needs to be warm enough that the rings AND pistons AND cylinders are expanded to what they will be during normal opperation. The other test you can perform is a cylinder balance test.
Run the engine to normal opperating temp.
Now check the R.P.M. with an accurate gauge. I don't know if the stock will work or not.
Next carefully remove the high tension lead from the cap to the no. 1 cylinder.
Notice how many RPM the engine drops.
Reattach the lead and remove no.2 and so on with 3 and 4.
If you remove the HT lead from any one cylinder and the RPM dosen't drop then it is dead. Go out and bury it.
Be careful if you try this test as there is a possibility of being shocked so wear insulated gloves and don't ground yourself by touching metal.

I just thought, but mabye that mist was water because the car sat and water got in the tank.

Thanks again for your reply.

Yes it seems that it wasn't too slick (the mist that comes out of the tail pipe on warm up) and so I don't think it was oil. It did seem to evaporate off my hand rather quickly and didn't seem to leave me feeling like I had to go wash my hand. So maybe it was gas and/or water. I can't quite remember since I haven't done this in a few months.

It seems that the weather up here in NY near Lake Ontario is finally getting warmer. It's supposed to be 75 tommorro though I wouldn't be too suprised if we got another snow this year. I will however put the car back on the road soon. I hoping that it is a valve with too much carbon on it or something that is making it stick open, and that once the engine heats up it closes. Perhaps this is why the mist was coming out the back, like if it was the exhaust valve sticking open then it pushing out the unburned gas when the piston comes up. Could this explain the compression of 70? And do you think that perhaps it will go up when the exhaust valve is closed as the piston comes up to the head?

On warm up perhaps the gas is leaking out of the exhaust port as the piston comes up.???

Brian

Here it is again, my CORRECT e-mail.
JPNOONAN@WORLDNET.ATT.NET
Or use the mail icon above.

First off is a warning about the power balance test I suggested. Do not do it on a car with electronic ignitions! The procedure comes from Tom Wilsons book "How to Rebuild a VW Air Cooled engine". The R.P.M. drop may vary between cylinders by as much as 20-40 RPM. A good, working cylinder should drop idle by about 200 RPM.
The other thing I just remembered is if as you say the #3 valve all of a sudden got "tight" and the compression readings seem to bounce around quite a bit. It could be a badly worn lifter. Think of it like this, the lifter base is not flat, it is convex (dished outward). If the cam or lifters wears unevenly then the lifter does not rotate (the reason for it being convex). When this happens the lifter wears VERY fast changing the valve lash to be loose. If you adjust this "loose" valve to spec then the lifter may turn onto a non-worn down part of the lifter now the valve is too tight. So you readjust and "bam" it's too loose again. The only way to check for this that I know of is to remove the pushrod tubes and pushrods, then pull out the lifter (DO NOT MIX THEM UP!!!! they mate to the cam lobe they ride on)place the base of two lifter against each other and they should be touching only at the center of the lifter. Even if they are flat you can reuse them for a little while but if they are badly concave or scored, then good bye. If they are messed up look in the lifter bores at the cam, I can't really explain what the pattern should look like but ask an engine builder that has experience with VW cams what he/she thinks. You may get off lucky and just need new lifters.