pressure in water tank

[okumaguru]

I just bought a 1981 Diesel Rabbit.  I was told that it was just rebuilt, then it overheated.  I put a battery on it and it had extreme pressure in the radiator fill tank.  Could this be a head gasket or does it sound like something more severe,,,ie a cracked /warped head or does a head gaseket commonly blow that severe.
Thanks in advance
Tim

[fspGTD]

If these motors overheat, the head can lift off the block and wham-o, cause a head gasket leak (commonly this is combustion chamber gasses leaking out and into the cooling system.)  If you managed to promptly cool the engine off after the first overheat and repair the cooling system problem(s), you might get lucky and get the head gasket to reseal.  But often once they leak it seems they don't reseal.  When you take the head off to replace the gasket, check it's flatness.  They can warp sometimes and then even a fresh head gasket won't seal it.  You need a machinist's straight-edge and feeler gauges to check this.  I think .004" measured across the long way or diagonally is the warp limit (check bentley.)  If it's more than this the head will need to be replaced and/or rebuilt.  Throw in some raceware head studs if you don't like your head warping - they seem to help prevent cylinder head warping from happening during overheating.  And be sure to diagnose and fix whatever cooling system problem caused the overheating condition in the first place!

And oh by the way, don't forget to replace all the coolant if there has been a combustion gas leak.  The combustion gasses from a head gasket leak into the coolant make the coolant turn acidic and degrade the coolant quickly.

[okumaguru]

Thank you very much.  I will be pulling the head one day this week and go from there.  If it did crack, can it normally be seen by eye or does the head have to be checked by some other method?
  I am a machinist by trade.  Can I measure something to make certain they used the correct head gasket during the rebuild?
Thanks again.
Tim

[fspGTD]

The warped head condition I'm talking about is not a crack, so it can't be seen by the naked eye.

If you do get looking for cracks though, the only ones that are "normal" are ones through the thin aluminum section of the head between the intake and exhaust valve seats in each cylinder.  These cracks are OK if they aren't so deep that they go through to the water jacket.  Cracks in any other location are red flags.

You measure piston projection to determine head gasket thickness.  Check as per instructions in your Bentley manual (which you have, or are going to buy right away otherwise... right?  :wink: )

[okumaguru]

I don't have one yet but I have a slew of other VW manuals,,,ie Chiltons, Haynes etc.  I have been watching ebay a little but don't have a lot of time right now.
Thanks for the information
Tim

[Centurion]

Haynes will get you through this!

once the engine overheats - as has been said - it will not stick down correctly.

I cannot say anything about Raceware bolts - but I will be getting them shipped at some point this fall.

Cheers - Centurion

[okumaguru]

Where are you going to get your bolts from?  I think when I get it apart I am going to get some just for good measure if I can afford them.
  I just bought another Haynes shop manual on ebay for $10.00.  I kind-of like to make certain I have plenty of paper work on everything.
Thanks
Tim

[okumaguru]

I just pulled the head off and upon looking couldn't see any major defects on the head, block or the head gasket.  It had a 2 notch gasket installed on it which still looks brand new.  When I put a depth indicator on it( I am a machinist so I have one lying around), where the pistons come up to the head(you can still see the circles) is raised about .010" from the area in between.  Is this a problem?  According to the .004" allowable warpage this sounds bad to me.
  I also used the depth indicator to find TDC and the pistons protrude about .028" above the face of the head.
  The people I bought it from just rebuilt it and I was expecting they might have used the wrong head gasket.  There are shiny places on the top of the pistons where it appears the valves have come in contact with the pistons.  I turned the cam over to make certain all of the valves appear to be opening and closing all the way and they appear to be alright.  I can't see any problems with the pistons either except the shiny places.
  According to the information given here by me, does it sound like I can install a new head gasket and be alright?
  Any advice or suggestions would be GREATLY appreciated.
Thanks in advance.
Tim

[okumaguru]

Just to follow up.
  I installed the head after having .016" milled off. I am having a little trouble getting it to run correctly, but, I think my problem is a mixture between the fact that it has been sitting for a number of years and I think I have fuel issues. It did start and run, but smoked like a "pine knot fire". I don't expect this could have anything to do with me putting wheel bearing grease in the cylinders to prevent rust. I finally ran the battery down and called it a day. All it wants to do right now is to start then die. When it did run for a few minutes earlier today, it didn't have enough power to pull itself. Upon closer examination, it had a loose injector.
Also, I tried the trick with the muffler clamp to expand the clamps for the exhaust. I couldn't believe how easy it worked. The things a thinker will come up with in a pinch that work so well.
I'll add more when I get a chance to work on it some more.
Thanks for all the help.
Tim

[okumaguru]

I messed with it until I got it to start and run.  It was smoking so bad that when the wind blew the smoke into the cab of the car with both front windows down I could not see the dash.  The smoke is not a dark black, or blue but kind-of a gray smoke and burns your eyes badly.  I wonder if it could be old fuel. I thought I drained the fuel but obviously that must have been the other Rabbit.
  It also sounds like it is missing.  If it were a gasoline engine I would be looking for which plugs are fouled out.  Being a diesel, I looked for leaks and didn't see any.  I used the boat bulb method for priming from the tank and it worked great.  I also poured some "Power Service" into the tank but the fuel may be so old that not even that can help it.
Tim

[okumaguru]

Just another follow up.  I had an extra set of injectors, I believe to be out of a 1.5L Diesel.  I disassembled them, cleaned, inspected and made sure all moving parts worked easily.  I reassembled them, then installed them.  The car is still smoking just like it was before.
  I intend to try to change the injector pump timing tomorrow if I have the time to see if that helps.  
  I am quite confused about this.  The smoke burns your eyes badly so I am almost certain it is fuel related, but I am running out of ideas as to what to do next.  Keep in mind that I had an excessive amount milled off the head.  I can't figure out how that could play into this situation.  I also never adjusted the valves.  Could one or more of the valves not be closing to something to that effect to cause this.  I am about to give up on the engine so any thoughts would DEFINITELY be appreciated.
Thanks in advance.
Tim

[moosiah]

Hi    I've been here too .... when I got my rabbits the one that "ran" missed on 2 cyls untill it was reved up, then the other 2 lit up.... and it smoked a whitish/ gray smoke too.... if you've got fresh valve marks on the piston heads ,,,,,,,, the valves bin whacken da pistons and might be bent OR not sealing well enough to light the diesel ........... I put in 8 guides and 4 ex valves.......... check the valve lash ....compression.... these engines are muy simple and durable,,,,, Don't give up on it !!!!
ps gray smoke indicates unburned fuel to me.........

[okumaguru]

I feel like such a dummy!  Someone suggested checking the timing again and so I did.  I checked the crank and cam timing.  When I reinstalled the timing belt, I simply put the pin thru the pulley and thought that was good enough.  I didn't reallize that the pulley had a timing mark on it as well.  Upon further investigation, the line wasn't lined up.  When I lined it up, the problem was solved.  I now runs like it should.
  Thanks to everyone for all the suggestions and help.
Tim