86 WV golf diesel help

[Aaron T]

I recently acquired a 86 golf diesel. The car does run, I've driven it a couple of time but it definitely has some issues. My concern has to do with the temp gauge. As soon as I start the car the temp gauge goes up to max and the little red light comes on. The thing is that the car does not seem to be over heating and it seems to be circulating the coolant but I'm not 100% sure. The engine fan also doesn't turn on but maybe I just haven't driven the car enough for it to get hot enough to need it. The speedometer doesn't work either. I would really appreciate and tips you guys could give me. Also, I know very little about engines. Thanks

Aaron T

[cleanspeed1]

Does the gauge go back to cold or normal after the engine starts or does it stay there? Given the age of the vehicle, there is going to be considerable corrosion and even sender units and other electrical components ( wiring, switches, etc. ) are going to need looking after. Grounds need to be cleaned up or repaired.

The speedometer not working may come down to a cable that needs to be replaced.

Go test all the components in the circuit and verify operation of the cooling fan, that the wiring is OK and routed properly, that the coolant temp sensor is fine, and any protections like fuses and relays are ok and replace as necessary.

These diesel engines are called "interference" style engines, so in the event of a timing belt failure, the valves will hit the pistons and damage will result ( read very expensive ), so you must do a timing belt service as soon as possible.

Diesels need clean fuel and clean oil, so change the oil and filter, along with the fuel filter. You cannot let water mix with the fuel, so when you fill up, go to a truck stop that has a lot of traffic. The fuel will be fresher. Use a quality treatment in each fillup like Service Power Diesel Kleen with Cetane Boost.

There are plenty of books about engines and VWs, so you need to study. They are not complicated. Just do what is recommended, and they will go a very long time before needing an overhaul.

[JethroBodine]

Looks like it's time to start learning. Three things come to mind; sending unit, wiring, and the guage itself. My suggestion would be to find the sending unit, unplug the wiring from it and see if the condition changes( gauge drops from full to zero). If nothing changes you can either trace the wiring back to the guage or test the guage itself inside the cluster. Not sure about the diesels specifically, but the gas VW's do loose the temperature sending units occasionally.