overheating

[alexgingles]

'91 ecodiesel with a MF motor.  I replaced the water pump and thermostat this week and installed a block heater.  My car now overheats.  My radiator is cold, my hoses and engine are hot and the needle is almost pegged.   I thought it was the thermostat so I removed it.  I boiled some water and it opened up at 160F.  I then buttoned everything up MINUS the thermostat.  Without the thermostat, I am still overheating in the same manor.

I installed a Graf brand waterpump.  Has anyone had problems with these?  Seemed like a solid part when I installed it.  I'm going to pull the hoses off tomorrow and back flush the radiator to see if there is maybe a clog.  I didn't have an overheating problem before I installed these. 

Am I missing anything?  Thanks for your help! 

[Baron VonZeppelin]

What a kick in the arse !

Would either have to be a huge air pocket in the system (but refilling it without a t'stat "should" have eliminated that possibility).

Or the impeller on the new pump is defect / made wrong / wrong impeller installed during manufacture / or slipping spinning on shaft.

Or the radiator is suddenly clogged.

Do you have the belt on the pump pulley - and tensioned (don't cuss me just covering the bases)

Have you run it with the expansion cap off just to see if it would purge any air - and is there a good flow going to the expansion tank ?

They used a restrictor/anti-backflow valve in the hose going to the expansion tank on a lot of mk2's. If its clogged - it could cause some probs - like not letting trapped air purge into the expansion tank.

I'm not familiar with Graf brand.

 

[vanbcguy]

You definitely need a thermostat installed with these engines... when the thermostat opens it also blocks off the radiator bypass, so no 'stat, wide open bypass.

[alexgingles]

Zeppelin, I think the radiator was suddenly clogged.  I removed the upper radiator and started the car.  Coolant flowed out so the pump was definitely pumping.  I shut the engine off and took a garden hose and black flushed the cooling system for about 10 minutes.  I then buttoned it back together and topped it off with water.  Doesn't get past halfway now. 

Tomorrow I will drain the water, reinstall the thermostat and put in coolant and hopefully the problem doesn't resurface. 

Good to know there is a check valve in the small hose to the coolant reservoir.

Thanks for everyone's help!