High coolant temp when towing.

[DuncanW]

Information, experience, a solution or any of the above sought.

When towing a light caravan at say 60 mph on the flat collant temp normal or slightly raised. Ascend a motorway "hill" of any real lenghth and temp rises and heads towards 120C, as soon as load decreases temp drifts back down again. Car is 300D 1991, with aircon and standard viscous fan drive.

Any clues??

 

[NormanB]

The first thing I would do is to change the thermostat for a new one. They are cheap and easy and quick to fit (15mins max).

Other than that you might like to check air side is clear and the wet side of the radiator is flushed through. At 60mph the fan would be adding little to the situation even if it was duff.

 

[mike65]

First suggestion - burn your caravan (I'm with Clarkson)

Second - invest in an additonal cooling fan the sort that caravaners have sworn by for years a Kenlow.

Example here -

Mike.

 

[Geoff_Slade]

I've got a 93 300D but its got the viscous fan and two electric fans is this an after market fitment? I assumed it was standard fit. Hhappy to give you more info about my set up (I've only owned the car for a few weeks but I'm happy to have a look see and see what sort they are and how they are fitted)

 

[NormanB]

First suggestion - burn your caravan (I'm with Clarkson)

Second - invest in an additonal cooling fan the sort that caravaners have sworn by for years a Kenlow.

Example here -

Mike.

But why would any additional fans help at 60mph?!!

There is something more fundamental that needs to be addressed methinks!

 

[JimmyTD]

As already said, first thing to replace would be the thermostat, it could be faulty or just slow to react.

Secondly I would check the Viscous fan coupling, I have had to replace 3 recently on BMW 5 series. Run the car stationary until it get hot, switch off engine and feel the resistance on the fan it should be harder to turn when warm. The two electric fans are for the A/C but obviously will have an effect on the engine temp when they are running.

Also check the radiator is clean, feel all over to make sure the whole radiator is getting warm, it could be blocked inside.

 

[DuncanW]

Many thanks for the responses to my problem. I changed the viscous fan coupling last May, it spun freely! I blew some muck out of the air side of the rad. but most seemed to be in the air con cooler matrix which has very close fins. There is a single electric fan for the air con located centrally, though the whole of the front face of the coolant rad looks very "congested". I will progress through your suggestions.

It's very frustration to be able to run solo at any speed, in any ambient temp and up any hill without the temp moving more than a few degrees, hook up the van and the system is over loaded. If I find the problem or solution I will post it.

Many thanks to all.

 

[Geoff2]

Unless the temperature is getting very close to the red zone, there is not a problem. I have an E300 turbo diesel estate, and the suggestion is to install additional cooling fans if towing in hot weather with the air con on. I fortunately bought my car with the additional fans installed. However, towing a 1250kg van it has never come on. Pulling it up Telegraph Hill on the A38 near Exeter, very long and steep if you don't know the area, the temperature raises from half to threequarters, then cools down on descent the other side. Diesel engines will do that, beacause unlike petrol engines, which rely on a spark to ignite the mixture, they work pruley by compression. With the additional fuel mixture going in, they run a little hotter.

 

[Arnie]

If you have an aluminium radiator, you might want to check that it heats up quickly and evenly after running the engine from cold. A few minutes after the thermotstat opens and the top hose is hot, switch the egine off and check the surface of the radiator with you hand to see if there are any cold spots. The aluminium radiators have narrow tubes that are prone to corrosion and blockage, especially if the coolant is not changed every two years.

 

[lookskyward1]

As previously mentioned your radiator may be starting to deteriorate / become blocked.

When you remove the thermostat to replace it and before you fit a new one, put the cover back on and try 'back-flushing' the cooling system with a powerfull hose. (heater control(s) set to hot. This should help clear out some of the built up silt etc. Be generous with the hose and be prepared to get wet :lol: This may solve your temperature problems.

I have towed caravans for quite a few years and found that auto boxes can build up a lot of excess heat. I once had a Vauxhall Calton spitting transmission oil all over the exhaust when I was towing (nice James Bond type smoke screen). A transmission oil cooler from Kenlowe fixed it.

I've only towed once with the MB and although the engine temp appeared to be acceptable, I was aware of the gearbox being hot.( This didn't smoke though). Hopefully the coolant flush will help you, good luck. 8)

 

[lookskyward1]

As previously mentioned your radiator may be starting to deteriorate / become blocked.

When you remove the thermostat to replace it and before you fit a new one, put the cover back on and try 'back-flushing' the cooling system with a powerfull hose. (heater control(s) set to hot. This should help clear out some of the built up silt etc. Be generous with the hose and be prepared to get wet :lol: This may solve your temperature problems.

I have towed caravans for quite a few years and found that auto boxes can build up a lot of excess heat. I once had a Vauxhall Calton spitting transmission oil all over the exhaust when I was towing (nice James Bond type smoke screen). A transmission oil cooler from Kenlowe fixed it.

I've only towed once with the MB and although the engine temp appeared to be acceptable, I was aware of the gearbox being hot.( This didn't smoke though). Hopefully the coolant flush will help you, good luck. 8)

 

[jaymanek]

Hi this is a common problem. Does yours have the extra oil cooler radiator? if not, a good investment if towing.
Otherwise its an extra fan as suggested.

Jay