Compression Loss Source!!

Scooter311 · 09-10-2004, 04:46 AM

I found it! Yay for me, I just kept taking things apart until I found out out that it was....drumroll...... the seal between the head and cylinder (#3)!!
That explains everything now - as soon as I removed the tin, I could see the evidence in the seam, and when I pulled the head (which I did after lowering the motor slightly, woohoo

) I saw, as plain as Aunt Betty's biscuits, a black sooty mess where gases were getting blown out. The rings are dandy, piston is fine, valves and seats are just lovely, and there are no visible cracks in the head surfaces.
SOOOO, what do I do now

? Should I clean it back up, re-lap the cyl into the head, and use a high-temp sealer of some flavor? Use (ugh) head gaskets - if so, I need to do the other side too, and I left them out purposely for more compression, was that a bad idea? Or should I have the sealing area re-surfaced (I'd have to do both heads in that case, with the benefit of a scooch more compression?)
Look at all those question marks, holy cow...
Anywayz, what are your ideas, concerns, comments?
I'd like to work on it this weekend so I can take my new girly on a ride with the top off. The car, that is. Simmer down people.

jamcleod · jamcleod's Garage

opinons are like *********s, everybodies got one... so mine is (opinion, that is...) remove engine and disturb it as little as you can (ie, don't remove pistons, break seal between piston and case...) reinstall heads that have been checked by a machinist and build it up from there. i estimate that 80% of readers of this board would say to nix the gaskets as there was even an official factory bulletin saying to delete the gaskets. still, i asked a vw mechanic about the gaskets and he said put them in. when i did the top end of my engine, i put new ones in. your engine, your decision.... (PS, do both sides so they are the same)

also my opinion that engine work is MUCH easier with engine out of the car, easier enough that it is worth the time and effort to remove it (engine and trans removed as a unit is... "easy")

silver2.0 · silver2.0's Garage

You may have to fly cut the heads, just have them checked. Also, when you go to lap them in, if you choose to do so, you will have to pull the cylinder, in turn you will have to re-seal the bottom side. I don't see how you can get away without pulling the cylinders if you have a problem with the sealing surfaces. Good luck, it could be worse!

Scooter311 · 09-13-2004, 05:03 AM

A little UPDATE
I brought the heads to a shop (a good friend) and watched him check them out - it seems #3 showed a .003 thou "dip", right where the leak was, and was equally lower than #4 (which was good, and so was the other head).
He's gonna flycut #3 level, and bring #4 down to match it. After seeing all this, we guessed that because #3 was a little lower than #4 to begin with, it must not have sat perfectly square over both cyls, and that's what may have caused it.
?

Does that make sense to you? Also, would this tiny bit of machining affect overall compression?

Ugh, I know, I already pulled the #3 cyl, and #4 is loose, so I have to reseal them both. Surprisingly, I was ExtraSuper careful removing the other head, and the cyls are still sealed. Man, I'm not looking forward to those rings - any tips out there for when the pistons are still attatched??
I also checked my lifters (I was worried about how they broke in) and guess what? Poifect! I couldnt' see any wear, so I stuck those puppies back in. Everything else looked OK, so I'm just going to clean it all up and reassemble carefully. I think I can do it in my sleep now, sheesh.

Oh yeah, I ordered a new front trans seal, and degreased the trans too - I couldn't believe there was a nice metal part under all that goo and undercoating!

Jason Porter · 09-13-2004, 06:28 AM

No gaskets. And after a week or so, get back in there and retorque those cylinder head nuts. Don't back them off and retorque, just put the wrench on them at 25 ft-lbs and turn to click.

Jared at Pelican Parts · 09-13-2004, 06:37 AM

I have to chime in and say to NOT use the head gaskets as well.....

Scooter311 · 09-13-2004, 06:52 AM

Hey doods
Yeah, I'm running sans-gaskets - but what about using that copper-seal-spray stuff as protection? A friend's cousin's fathers' neighbor who drag races said he used to use the spray goo instead of head gaskets and it worked great?? Could it hurt to use a thin coat of it, the product claims it's for use on cylinder heads?
Is it possible for the head nuts to loosen up?

Jason Porter · 09-13-2004, 07:03 AM

Not really loosen up, but things can settleand I've had them back off a ft-lb or two.

karlp · 09-13-2004, 09:45 AM

Scooter-
You'd asked for tips on installing cylinders with the pistons still attached; I've never done it any other way!
(Maybe you are supposed to put the piston in the cylinder and then get the wrist pin through and the clips in but I couldnt see it working)
I made a ring compressor out of a strip of spring steel from this coil spring I had laying around and a pair of vice grips. The strip was about 1 1/4" wide and a bit thicker than, say, measuring tape material. The vice grips were the kind with flat jaws for bending sheet metal. I cut the strip to length, bent a leg at both ends and drilled a hole in each leg and in the vice grip jaws. Once you compress the rings and slid the cylinder over the piston, you have to unbolt one end of the strip to get it out of there.
There is a description of this process in my Haynes book. I'm not known for original ideas.

Karl

silver2.0 · silver2.0's Garage

Make sure the rings are aligned properly. They shouldn't be installed "any old way". Tell me what type oil seal you have and I can tell you the right way. I purchased a ring compressor, they are super cheap, or you can make one like Karl said, just make sure it's the type with pliers, and a curved piece of spring steel. What your friend said makes sense to me. If you make your piece like Karl did, take extra care to debur the metal, as the pistons will scratch easily. Sounds like you are on the right track!