Normal oil and coolant temperatures

[steve2003rs6]

Just for info. Been out today for a steady run in the car. Mainly A road driving 60 mph and occasional duel carriageway 70 mph driving.
Oil temperature did not exceed 80-85 degrees C.
That was with continuous driving for about 4 hours.

Why do you get a sudden increase in oil temperature when standing in traffic.
Are your fans kicking in ?

[Swan]

Hi Steve,

Yes it will go up when standing in traffic. If I can keep the car travelling at a steady 50/60 it seems to keep the temps below 120.

The fans seems to be running when the engine is on. I would say they certainly ramp up when I turn off the ignition however. Is this normal?

Cheers

[Swan]

Just for some extra info, when the thermostat/oil cooler does kick in and I get the sudden oil cooling, it will drop from 120+ to approx 80C on the dial.

After the cars been running at the cooler temperature for a while, the thermostat closes again and the oil temp will then start to warm up and get hot (120 again).

[Swan]

Another observation - when I have given it full beans and the cooling kicks in. If I turn off the ignition and wait a couple of minutes then turn the engine back on. The temperature will remain under 90C. So I’m thinking this discounts any sensor issue?

It’s got to be thermostat related hasn’t it? But I’ve changed the both the oil thermostat and water thermostat in the last couple of months.

If it was your car, what would be your next point of call?

[Swan]

This is where the needle is sitting right now - post spirited drive when the oil cooler / thermostat seems to be doing its job.

[Swan]

If I was now to go in a leisurely drive out of town at around 50pmh minimum revs it would cool even further and drop to around 70C at which point the thermostat closes and the oil temperature climbs all the way up to 120 again. Like a yoyo.

[Swan]

When then oil temp is below the 90 mark and I turn the ignition off I don’t even get the after run fans.

[Shoppinit]

I would log the oil, coolant and ATF temps on a long drive getting a passenger to use the "mark" feature of VCDS logging to note any interesting events or conditions.

THen I would put it all in an excel sheet and make a graph of it. That might give some clues as to what is happening.

I'd also pull the oil cooler thermostat and see at what temp it opens by putting it in a pan of boiling water. If it doesn't open at 100 degrees, put it in a pan of saturated brine to see if it opens at a temp higher than 100 degrees.

While I was at it, I'd test the old thermostat at the same time for a comparison.

[Shoppinit]

They noted that one of the lines to the cooler had been replaced by a braided hose.

I wonder if the internal diameter is too small (smaller than OE) which is restricting the flow and slowing the cooling effect when the thermostat opens. Might explain the yoyo-ing. That the thinner oil improved things would tend to back up this theory somewhat.

[Swan]

Thanks. All good shouts.

I can test the old thermostat v easily.

I will have to get my head around VCDS. Got the cable but have yet to explore it.

Could be the diameter of the braided line I suppose. Surely a couple of millimetres wouldn’t make that much difference though. It’s like it either cooling or it’s not cooling rather than an intermediate issue.

[AWT]

Hey,did you get to the bottom of this?

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