cooling system problem

[w0nderpr0]

I bought a 94 golf diesel (1.9l aaz motor) and it had the head blown. i picked up a head that had 100 hours on it for 250 CAD, and got all new gaskets and such. Put the head and everything back together the way the service manual said and double checking on here. Now the car ran fine for 300 km and then it started to overheat with the temp gauge going up to 110 when i would then pull off and let it cool down to about 70. did this twice more and finally got it towed home (never once went over 110). So i replaced the thermotsat and made sure the rad was flushed and water pump infact was pumping. all checks out fine but it back together and burped the coolant system and the car will not blow hot air out the vents with the cap on the coolant bottle. tryed 2 older caps and a new one no luck.....when the cap on the coolant system presurrizes itself up where the rad hoses are rock solid and cant be pinched with your fingers. when you release the coolant bottle cap (after its done pissing all over the place and shooting out water) you get heat out the vents. So i let it run like that watch little bubbles come up for an hour. temp never went over 85. put cap back on and same problem.,......i figure either the head gasket is screwed and i need to put another new one on...or there is one hell of an air lock.....what do you guys think. i even tryed without the thermostat to see if it was pumping water and the same problem of the system pressurizing itself....take off the presure and it seems fine.

[jtanguay]

unfortunately it sounds like a HG issue...

i too was very cautious of my temps, but never let the engine go above 100C (and i was just guessing as to where 100C was on the gauge... i knew at which point the expansion tank registered 87C and used the reference point on the gauge to judge when i should ease off the pedal)

i had a faulty t-stat... it was only opening very little... so it could not cope with the amount of heat generated from highway driving... very very annoying! but my coolant system was pressurizing normally... at 100 deg C you must realize that you are basically creating a mini steam engine, and 20 psi could easily be reached at that point.  

i would flush the entire cooling system... it sounds to me like your heater core is plugged up, or has an air lock in it...

one good check is to run the engine with the cap on from cold, and take the cap off at 1 min of idling... it should not have built up much pressure at all... if it has, then you are heading into hg territory

[w0nderpr0]

i will try it tongiht when i get home. i dont no why everyone fears the head gasket as i do not find it hard to change at all. is there a way to try and flush the heater core out?

[jtanguay]

there's kits out there.. where you splice into the heater core hose, and hook up a hose... let the water run until it comes out clean etc.

just remember that if you get the HG done, you should get the heat checked and planed if necessary.

make sure the shop is reputable too!  because if the head is a bit warped, so will the cam bearing's be once machined!