over heating

[albsure]

thank you all, i' going to check these things out now and i will report back as soonas i'm finished.

[chrissev]

welcome back i havn't seen you for a couple of days. i took the top hose off of the engine and filled through the rad. then took off the other end  from the rad. and filled to the block. also is the reservoir vented should it be spitting hot water from the res. should i plug the hole?? what are the chances of getting a bad thermal switch and thermostat. should i leave the parts stores alone and just go to the VW dealer and pay the price for oem parts??

ah, that might be your problem.  If you filled through the rad first you would have forced air down into the water pump, where it could not escape because the thermostat is closed.  Try filling it by pouring through the top hose into the engine until the coolant pours out of the hose, then reconnecting the hose to the rad.  

Re:  chances of getting a bad thermostat:  pretty good.  Happened to me.  Almost warped my cylinder head.  

Re:  should it be spitting hot water from the reservoir:  in my opinion no.  My vw diesels have never done that.  When they overheated, the coolant came out of the cap.  But maybe if the cap is not working then the tank will have another relief valve to prevent it from exploding.  Probably does.  

You said you replaced the water pump right?  Because that can cause very quick overheating if it is not functioning properly.  The other cause could be a blown head gasket leaking compression into the cooling system.  That sometimes happens on these turbo diesels because of the amount of pressure in the cylinders.  It is already a very high compression engine, and then you add a turbo....very very high compression...sometimes I wonder about VW engineers.  Anyway, good luck with it.

Chris

ps, in very rare cases, and usually only on the old rabbit 1.5 NA diesels, the engine blocks developed cracked water jackets allowing the coolant and the oil to mix.  This could sometimes result in the cooling system becoming pressurized since diesel engines operate at positive crankcase pressure (ie, no engine vacuum).  But if this was the case with your car, you would see oil in the coolant.  Since you don't, the worst it could be would be the head gasket, unless the cylinder head is cracked and compression is leaking in that way, but you will see that when you take the head off (if you end up having to do that)

[albsure]

thankyou guys, for all of your input and information. at first light i will start going through everything that has been suggested, first of all draining and refilling properly. then the cold start pressure test at the reservoir. then if necessary i'll run the fans by shorting the thermal switch connection and see what happens, before just running out and buying a new one. maybe its not getting hot enough at the switch to kick the fans on. even if it is a head gasket, the motor runs good, for 181000 miles so i think its worth it.

QUESTION: do i need any special tools to do a head gasket? i am fully equipt to work on gassers but this is my first diesel. hopefully it wont come to that. i will report back.thank you again for all of your help.

al b sure

[Hammy]

I didn't notice if anyone mentioned this, so if I'm repeating something, I appologize. Did you happen to see if the ring on the coolant cap is sitting in it's appropriate groove. I once chased what sounds to be the same problem, and it was just the 'o'ring not situated properly in it's groove on the cap. At a quick glance it looked fine, so check it carefully. If the cap is not sealed properly, it will blow the coolant out of it in no tome.

[chrissev]

special tools for headgasket:  You'll need the star shaped tool to take the head bolts out.  Also will need some sort of puller to take the cam pulley off and something to lock the injection pump and camshaft.  You can manufacture tools to do the locking.  And pretty much any sturdy puller will take the cam pulley off (so you can reset the timing belt when you put it back on).  But you'll really need to get the star headed tool to take out the head bolts.  Can't use anything other than the real thing for that

[vanagondiesel]

Quick way to determine blow head gasket or cracked head.  COLD ENGINE.
Open up the resivour.  Crank the motor up. If you have bubbles, you have a leak into the combustion chamber.

No bubbles, chances are the head gasket is intact