V70: Engine Overheating

[ferg55]

Bringing the post back on-topic after my last reply...I'm surprised your car overheated in this scenario as Volvo would have rated the cooling system to be able to cope with all normal driving conditions, and this scenario would certainly fall into that bracket. The Volvo tests would likely have had the rad partially covered, to represent leaves etc. It does suggest you have an underlying fault - maybe a faulty fan thermostatic switch, resulting in it not coming on early enough?

[ferg55]

Originally Posted by ShadeTek

If your engine is overheating or approaching it, you can help matters buy turning your cabin heat up to max, open all the vents, turn the ventilator fan to full and wind down windows to let the heat out. This will dump a lot of heat out of the engine.

And turn the air con off.

[ShadeTek]

Originally Posted by ferg55

And turn the air con off.

Well, the thing is, the air con will load the engine BUT it also switches on the radiator fan to draw air in and cool the refrigerant for when you are in slow moving traffic or stationary. It might be useful to switch it on if a lack of forced air is not available at the front of the car. This would then help to cool it down but the fan should be on anyhow if the engine is getting too hot.

The other spanner in the works is that the gauge is supposed to be displaying coolant temperature and not engine temperature. At what point with a leaking coolant system does it become empty enough so that the coolant is not in contact with the sensor? What then is the sensor actually measuring? Direct engine metal body temperature?

[Tannaton]

Originally Posted by ShadeTek

Well, the thing is, the air con will load the engine BUT it also switches on the radiator fan to draw air in and cool the refrigerant for when you are in slow moving traffic or stationary. It might be useful to switch it on if a lack of forced air is not available at the front of the car. This would then help to cool it down but the fan should be on anyhow if the engine is getting too hot.

The other spanner in the works is that the gauge is supposed to be displaying coolant temperature and not engine temperature. At what point with a leaking coolant system does it become empty enough so that the coolant is not in contact with the sensor? What then is the sensor actually measuring? Direct engine metal body temperature?

...but if the aircon is on then you have the condenser which is directly in front of the engine radiator heating the air up that's going in to the rad. If the water leaving the top of the rad is above a certain temperature then the fan will be turned on anyway.

On some older cars the temperature sensor was screwed directly into the cylinder head but on modern cars (incl Volvo) it's part of the thermostat housing. On very modern cars there are several, and the coolant is routed differently to facilitate a faster warm up.

[apersson850]

Originally Posted by Clan

The current electronic digital instruments can be made to do anything volvo want them to do of course.

It's those I referred to, of course. Not the termo-mechanical temperature gauge of the Volvo PV 544, which showed the temperature even after the engine stopped.

My condenser had over the years developed so many bent fins, that it was blocking a large part of the airflow through itself, the intercooler and the radiator. Now it started to leak, so I had to replace it anyway. But check that. I had the fan starting when towing my caravan even when it was only 10°C outdoors.
By the way, you pump the hot water into the top of the radiator, then get the cold water from the bottom, where it's coolest anyway.