overheat

diver · May 20, 2020

We've got a 2007 110 2.4tdci. Runs perfectly well until we start towing with it. After a while it starts to overheat. First did it with about a 2 ton boat on the back. Got hot enough to go into safe mode and had been towing for about an hour up to that point. Only cooked up when faced with a moderately steep hill. Flushed out the cooling system (looked clean) and replaced the stat.
All looked Ok until we tried towing a 16' speedboat and it did the same thing. This happened on the M4 and the funny thing was, as soon as the driver changed down, the temp on the gauge dropped.
Anyone got any ideas, everything else looks OK. Coolant and oil are clean, fan working etc.

jamesmartin · May 20, 2020

does rad get hot all across its surface

diver · May 20, 2020

jamesmartin said:
does rad get hot all across its surface

I'll check that but I have to say, having run rad flush through it, what came out was completely clear.

Wimblowdriver · May 20, 2020

Cylinder head temperature sensor might be faulty.

Wimblowdriver · May 20, 2020

Item 13 on the diagram in attachment 5 is the CHT sensor.

diver · May 20, 2020

Thats really helpful. Thanks.

lynall · May 20, 2020

Viscous fan okay?

Offhandlandy · May 20, 2020

diver said:
We've got a 2007 110 2.4tdci. Runs perfectly well until we start towing with it. After a while it starts to overheat. First did it with about a 2 ton boat on the back. Got hot enough to go into safe mode and had been towing for about an hour up to that point. Only cooked up when faced with a moderately steep hill. Flushed out the cooling system (looked clean) and replaced the stat.
All looked Ok until we tried towing a 16' speedboat and it did the same thing. This happened on the M4 and the funny thing was, as soon as the driver changed down, the temp on the gauge dropped.
Anyone got any ideas, everything else looks OK. Coolant and oil are clean, fan working etc.

Can you get different expansion tank caps for this engine?? If it has the wrong cap then it won't relieve the coolant system at the right pressure which might cause the overheating under load??

diver · May 20, 2020

jamesmartin said:
does rad get hot all across its surface

Given it a run for about 20 minutes at idle and the hoses are all hot, gauge showing up to temp, heater working but radiator is uniformly stone cold. Think it needs a longer run under load.

diver · May 20, 2020

lynall said:
Viscous fan okay?

Seems to be fine.

Scooby22 · May 20, 2020

As Lynall suspects I too suspect that the viscous fan may not be locking up and giving effective cooling when temperature is high.

jamesmartin · May 20, 2020

diver said:
Given it a run for about 20 minutes at idle and the hoses are all hot, gauge showing up to temp, heater working but radiator is uniformly stone cold. Think it needs a longer run under load.

thermostat?

Wimblowdriver · May 20, 2020

diver said:
heater working but radiator is uniformly stone cold.

Are you sure? The intercooler sits directly behind the front grill and in front of the radiator. To check the radiator you will need to remove the cowl in front of the engine.

Wimblowdriver · May 20, 2020

A bit more light reading ----

Wimblowdriver · May 20, 2020

Just remembered - if you have aircon, the condenser and electric fan sits directly behind the front grill, then the intercooler, then the engine cooling radiator closest to the engine.

diver · May 21, 2020

Offhandlandy said:
Can you get different expansion tank caps for this engine?? If it has the wrong cap then it won't relieve the coolant system at the right pressure which might cause the overheating under load??

We've never changed the cap and its worked fine in the past.

Wimblowdriver said:
Just remembered - if you have aircon, the condenser and electric fan sits directly behind the front grill, then the intercooler, then the engine cooling radiator closest to the engine.

No aircon so just the viscous fan. Once you take the fan cowling off the radiator is easy to get at so easy to feel it. Already changed the stat. Difficult to tell if the viscous fan is locking up. I think I need to give it a really good run.

Wimblowdriver · May 21, 2020

diver said:
Once you take the fan cowling off the radiator is easy to get at so easy to feel it.

Yes. Just 4 (I think) screws to take out of the top cowl, 5 minute job including a tea break. Just don't stick your hand in there with the engine running otherwise you will soon know if the viscous fan is working ------. While u r in there check the condition of the auxiliary drive belt and that it is not slipping on the water pump. And check the rad and intercooler fins are not blocked up with dead flies and stuff.

Wimblowdriver · May 21, 2020

Wimblowdriver said:
Just 4 (I think) screws to take out of the top cowl,

6 screws

discool · May 21, 2020

diver said:
We've never changed the cap and its worked fine in the past.

No aircon so just the viscous fan. Once you take the fan cowling off the radiator is easy to get at so easy to feel it. Already changed the stat. Difficult to tell if the viscous fan is locking up. I think I need to give it a really good run.

Not that difficult, the fan sounds different... so a roar when u start up from cold then after a 30 seconds/minute or so it goes quiet only to roar again when locked, which with my disco its only in traffic on a hot summer day, but with u it's towing a boat.

When cold the fan won't spin more than the distance of one fan blade so what's that three inches or less, if it's easy to spin then replace the viscous coupling.

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