Overheating - 1981 1.6D in eastern Ukraine

[drgeometry]

1981 1.6D. Engine overheated after a long drive from Kyiv to Dnipro. I discovered that the crank case breather hose had ruptured at its junction and I'd lost coolant. I made a road-side repair using an aluminum can, some wire, duct tape, pipe clamps, etc. Got home, engine temp was fine. Drove that way for three days and temp was fine, engine was happy with the wire and duct tape. Went to the VW service center in Dnipro City and they replaced all engine case coolant hoses (but not the rad hoses or hoses going to the rad). They maybe did not bleed the system correctly. Drove about 100km and the engine overheated. This time one of the new hoses they installed had ruptured.

My friend Vova, a diesel mechanic, pulled the engine apart, replaced head gasket, sanded block, plained cylinder head. System bleed was proper this time. But have the same issue: engine is still overheating. 

Radiator stays cold, but pressurized coolant will spray from relief valve on upper left hand side of radiator. Removed the thermostat at the base of the coolant pump so that water will be sure to flow to the radiator. Removed thermostat on upper right hand side of radiator so that radiator fan is always on, for the purpose of this testing. 

Vova (mechanic friend) has not removed the coolant pump yet to examine it because it’s a bit of a job to do and he’s helping me for free. He’ll get to it this weekend.

In the interim can you suggest anything we may have missed?

[Aidan]

darlek cap ? if it doesn't hold pressure then coolant will boil, needs to hold 1 bar so coolant won't boil below 115'
quack test is not definitive so replace every time, or if in doubt and you don't have a pressure tester that fits the cap, Gates were the best I think

[ZsZ]

I think the thermostat stuck closed. Try to put it in boiling water to see if opens. 
068121113H is the original with 87°C opening temp
you can use instead 056121113A with 80°C opening temp.

The stuck header thank cap Aidan mentioned can also be a problem. I have Japanparts branded two spring one working fine after the OE style Blau failed

[drgeometry]

Can’t get that brand of cap here but ordered five of the brand that is available and will try them all (they apparently have a 50% failure rate). Thank you both for the insight. In the meantime, I’m buying a smart, 1986, Lada 1500 today to get me around until the bus is fixed.

[drgeometry]

Also- we have too much pressure in the hoses at the motor but very low pressure at the radiator.

[ajsimmo]

Another possibility -cracked cylinder head.

Sent from my moto g(30) using Tapatalk

[davidoft1]

Sounds like an air lock and poor flow

[mioba]

How did you get on OP.

Removing the stat is the first thing to do as clearly the pressure is in the head as rad stays cool.

Run it and bleed it.

The water pumps are very strong on these - they are purely mechanical with metal impeller. Only the bearings can fail and that you will hear.

Pressure is because air is in the system, a cracked head - between valve and water jacket can push exhaust gasses into coolant - bit this should still flow leading to a coolant being pushed into expansion bottle. Rears itself when hot at the cracks open up then.

[drgeometry]

What's OP?
Removed the thermostat.
Bled it six ways to Sunday.
No strange noises from the water pump but that is a good insight and thank you!
My friend thinks there's a crack in the block somewhere. 
I may just put in a new engine.
What's the newest, best motor I can find that will fit in my bus? If I'm going to do it, I want to do it right. I use this thing on the front line and vehicles here are hard to come by.
 

[R0B]

OP means Original Poster meaning you.

[drgeometry]

I just posted my problem. What's the point of your question? I'm sorry, I don't understand.

[drgeometry]

Those are nice dogs, aren't they.

[drgeometry]

And the grey of Cheshire warms my heart. I've spent time there. It's like home to me.

[drgeometry]

Back to the VW, I'm gonna replace the engine cause I'm using this bus on then front lines. It's difficult to get a good machine here right now. What's the most robust engine I can put in this thing?

[ZsZ]

It could be a crack in the block or in the head - but that would not cause cold radiator and overheating.
Did you try to clean the long coolant pipes under the chassis?

The newest engines you can fit without any hassle are transverse 1.9 diesels from Mk3 Golfs
IDI (1Y, AAZ) fit without any thinkering with the 1.6 exhaust manifold.
DI (AEY, 1Z, AHU, AFN) needs some sorting with the electric injection pump. Either custom standalone harness, or custom mechanical pump.

You can also fit longitudinal engines from Passats or transverse Skoda engines but those need custom engine mounts and modified water pump brackets.