Volvo 480 Club Europe

The water in my engine is often getting too hot (over 100°C) when standing in a traffic jam and the radiator fan starts too late. When driving, everything is OK, water at 80-82°C.

The first guess is that there is a problem with the thermostat, that controls the fan. However, I cannot find anything about it in the documentation. Can someone give me a hint as for where the thermostat is located and possibly what else may be causing this problem?

I had a similar problem, mine turned out to be a tiny pinhole in one of my radiator pipes. When driving the airflow kept the engine cool enough, but when stopped at traffic lights the water would heat up and start to piss out of the tiny little hole. Look for white coolant leaks on all your pipework?

The thermostat is on the transmission end of the cylinder head, just below the dissy cap though

Thanks. I will check the engine, but I have not observed any changes in water level since the engine started to behave this way, so I think thermo sensor is more likely to be the problem.

The thermostatic switch is in the radiator, on the gearbox end, about 1/2 way down from the top. Access is a little tricky with the radiator in the car, but is possible. You may need to pull the radiator forward to get a spanner to the nut, unless you have a deep socket.

Depending on the year of the car it will either have two or three wires. Later cars have 2 speed fans fitted (three wires), so be sure to get the right type if you need to replace the switch.

To test the fan, jump the pins on the connector to the termal switch. The two wire version is easy, just jump the contacts. The three pin version you need to jump all combinations of pins, one is feed +12V the others go to the fan. Jump the 12V pin to one of the other pins, one pin should give low fan speed, the other pin high fan speed.

To test the switch, heat it up in water, at 95 degrees the fan should switch on (low speed if a two speed fan) high speed is at or just above boiling (add salt to the water to raise the boiling point if needed).

Richard

Thanks for the tip. Will check it out and replace it if needed. I still hope it is just some dirt or something like that.

What is the critical temperature anyway? My other car is aircooled, oil temperatures between 120°C and 130°C are rather common and the fan only starts after temperature of the heads has exceeded 150°C. What is the boiling point of water under pressure in the cooling system?

JJ wrote:Thanks for the tip. Will check it out and replace it if needed. I still hope it is just some dirt or something like that.

It could be a dirty contact, but the switches are a known weak point.

JJ wrote: What is the critical temperature anyway? My other car is aircooled, oil temperatures between 120°C and 130°C are rather common and the fan only starts after temperature of the heads has exceeded 150°C. What is the boiling point of water under pressure in the cooling system?

The infocenter will tel you to stop if anything gets out of wack too far. I think the water will get to 105 or so before anything starts to happen in the boiling department. Normaly the water would stay below 100.

The oil temperature is healthy if it stays below 120 or so with normal driving. Though it can get up to 140 given long runs at maximum power. Again the infocenter will flash stop if it gets too hot.

Richard