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-   -   I'm surprised our diesels do not over heat (https://www.the75andztclub.co.uk/forum/showthread.php?t=298468)

macafee2 18th August 2019 07:49

I'm surprised our diesels do not over heat
 
looking at how much coolant radiator is exposed to the air I am surprised our diesels do not over heat. The condenser radiator all but covers the coolant rad. Not sure the under tray helps with cooling, just blocks off the underside

After towing the caravan I always lift the bonnet to let the heat out and it is always very hot.. as expected I guess.

macafee2

trikey 18th August 2019 18:29

Put the OBD temperature readout on, you will be surprised how cool the diesels run.

ZedTeeT 18th August 2019 20:00

The diesels are by nature more thermally efficient so run considerably cooler, so it pays to have a working thermostat or it'll just stay cool.

Mike Trident 18th August 2019 20:24

Mine is usually around 84 to 86 which is cool compared to the petrols.

rovertone 19th August 2019 21:32

Quote:

Originally Posted by macafee2 (Post 2755787)
looking at how much coolant radiator is exposed to the air I am surprised our diesels do not over heat. The condenser radiator all but covers the coolant rad. Not sure the under tray helps with cooling, just blocks off the underside

After towing the caravan I always lift the bonnet to let the heat out and it is always very hot.. as expected I guess.

macafee2

I share your reasoning on this. From my experiences I wouldn't trust my car not to overheat when pulling a van up steep hills.
Mine used to run cool until I replaced the original stat and now running solo the temperature holds a steady 89/91deg. Notably in the winter it would take up to 5 miles to reach this normal running temperature. But using the winter as an example if I have the van on the back normal temperature will be reached in less than half this distance.
My initial experience was when overseas the engine overheated and went into limp mode and I found that the high speed fan wasn't switching in eventually traced due to a faulty fan PCB. Long story short I changed the fan and fitted one of Jules' Revotec fans with this and a working PCB temperature when towing on hills is much better but I have still had a couple of 'near miss' overheats when the top of the hill arrived before 'limp mode' was triggered (approx. 116/118deg) As soon as the engine load eases the temperature drops rapidly.

I have two theories, one, I thought that on the 1990's+ BMW's for towing, you were advised to fit an upgraded fan and radiator but I have been unable to find anything on this and secondly if this wasn't the case then maybe the engine being fitted transversely severely restricts natural airflow passing by the actual engine block, as you say it gets very hot under the lid.

Without the caravan the temperature behaves perfectly normally in all road conditions and ambient temperatures. I am confident that the cooling system is A1 so as said before I wouldn't trust it. The van weighs in at 1420kg max so within permissible limit.

trikey 20th August 2019 07:19

I towed a 1400kg caravan from Cornwall to Lincolnshire using a diesel saloon, on steep hills I noticed the temp rising, turned out the bottom pulley had completely detached itself! The crank was turning but the pulley remained stationary, it lasted the journey home, the temperature was normal unless load was applied.


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