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Hi,

My car has recently begun to overheat.

Initially the first instance presented as very high oil temperature reaching 110 degrees.

a couple of minutes later, after passing 110 mark I noticed the water temperature begin to rise above half way.

Once I reached home I noticed the overflow full of coolant. Mind you it was old coolant.

So after changing the thermostat, coolant, and radiator cap I tested its stability under load.

and sure enough the oil temperature does still reach 110 eventually.

Originally I thought this might just be due to thrashing around abit.

So I decided to go for a run on the freeway. 100 kmh for 30 minutes.

Sure enough the temperature reach 110 again, but water steady.

My questions are, and I apologise for my ignorance.

1) Is the oil heating the water? or is the water heating the oil?

2) if the oil is heating the water, why is it reaching such a high temperature?

3) if the water is heating the oil, what could be causing this?

Thanks

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Hi, My car has recently begun to overheat. Initially the first instance presented as very high oil temperature reaching 110 degrees. a couple of minutes later, after passing 110 mark I noticed the water temperature begin to rise above half way. Once I reached home I noticed the overflow full of coolant. Mind you it was old coolant. So after changing the thermostat, coolant, and radiator cap I tested its stability under load. and sure enough the oil temperature does still reach 110 eventually. Originally I thought this might just be due to thrashing around abit. So I decided to go for a run on the freeway. 100 kmh for 30 minutes. Sure enough the temperature reach 110 again, but water steady. My questions are, and I apologise for my ignorance. 1) Is the oil heating the water? or is the water heating the oil? 2) if the oil is heating the water, why is it reaching such a high temperature? 3) if the water is heating the oil, what could be causing this? Thanks

there's a factory heat exchanger which keeps the water and oil temp inline.. benefits of this.. cools down the oil when it gets too hot and also brings oil temperature to operating temps

Draw backs, if the oil temp exceeds the water temp, it will bring the water temp up. A way around this is to increase your cooling capacity by installing a decent radiator which should theoretically keep the water temps in check and also keep the oil temps a little lower.. but real world says you need to also install an oil cooler to bring the overall temperature of both oil and water down.

People often look for highly technical reasons for overheating..

My first thought always is to take the radiator (or the whole car if you are so inclined) to a radiator repair shop. They will take the top tank off and clean out the core, replace the top tank if necessary (many are plastic) and tell you if a recore is indicated. They can flush the block and replace the thermostat.

If you haven't done this in recent history it is worth doing anyway and will very often fix your problem.

The oil heat exchanger serves 2 purposes.

Firstly it helps get the oil up to temp quicker by pulling heat of of the water and transferring it into the oil and secondly it works the other way around by transfering heat from the oil back into the water once the oils too hot.

Ideally the oil and water temps should be at the same temp as the factory thermostat.

Now if your water temp is good but your oil is getting too hot, there's something wrong if your just cruzing.

Start by checking the oil temp sender and wiring (and possibly gauge).

A bad connection may be causing too much resistance which may explain the high temp readings.

  • Like 1

Due to the water/oil heat exchanger I'd say you are just seeing your water temp reflected on the oil temp gauge.

On my R33 with a blocked radiator the factory water temperature gauge sat at half way from 70C all the way up to 105C - it never budged. Only when you head up north towards 110C the water temp gauge starts to show it getting "a bit warm" - IMO 105C is already way too warm!! (was checking actual WT values using Consult tool).

Blocked radiator, blocked/faulty thermostat, or bad water pump.

As a point of reference my R34 GTT handled continuous abuse on the track and the highest I think I saw was 103C on the water. You should not be reaching that sort of temperature on the street.

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