1.6 - pressure in coolant system - I need help.

[unclejunk]

I have a 1.6 na from an 84 rabbit that has excessive pressure in the cooling system.

I got the motor from a local guy who swapped it for a turbo diesel.  He bought the car with no motor issues aside from a weeping IP, drove it for about 8k miles until the IP weeping turned into an actual leak, and then replaced it with a 1.6TD..  Never had any known issues with the motor aside from the IP leak.

I put on a new IP I had, swapped the motor into my rabbit.. and now I have very high pressure in the cooling system that builds on start-up.  Within 5 seconds of running, the car has over 20psi of pressure in the cooling system and blew the block heater out of the rear of the motor (was held in by RTV .. previous owner).

I did a compression check and got the following results - 29, 26, 30, 26 (bar).  I think the Bently manual calls for 28 bar minimum, but the engine does run pretty decent if I leave the coolant cap off.  The compression gauge didn't seem to drop at all once I stopped cranking, so it looks like all of the cylinders were holding pressure.

Do I have a bad headgasket?  Any suggestions on what else I could do to confirm that it is/isn't the gasket?

[maxfax]

Sorry to say it, but you have a head gasket problem...   That much pressure that fast is most definitely compression leaking into the cooling system..

http://www.vwdiesel.net/forum/index.php?topic=16699.0


Had the engine been overheated that you know of before this problem arose?  Chances are good that you probably just have an old gasket that has deteriorated, but I would most definitely check that head over well...

[burn_your_money]

Also, the rad cap should open around 18 psi or so I think. That might be defective. You should test it if you can.

On a stone cold engine if you are getting pressure within 5 seconds then headgasket is extremely likely. It could be a cracked head or block too, but that`s less common.

With the engine cold can you see bubbles in the coolant tank with the cap off?

[unclejunk]

The radiator cap is new, and I read somewhere that it opens at 25psi.. but it still could be defective.  I'll have to order a new one when I order a gasket just to be sure.

I can see lots of disturbance in the coolant tank with the cap off.. not exactly bubbles.. but the coolant in the tank isn't just sitting still.

I guess I'll pull off the head and take it somewhere to get checked.

[burn_your_money]

I pulled out my mk3 bentley and it specs 19-22psi for the rad cap. I'm not sure if it's the same for the mk1

[maxfax]

The MK1 Bentley says the cap should open at 17 - 19 psi