Xc70 over heating when towing

[brianhall]

We have a 54 plate XC70 D5 auto at which in almost every respect we are delighted with except that when towing our Bailey Senator Indiana caravan with a total MTPML of 1500kg up reasonably long hills the engine starts to overheat. If we turn on the heater inside the car we can get the engine temp to come down but when towing all the way across Spain which we do every year it is an annoying problem. It only happens if the outside temperature is in excess of about 20 degrees. We are well within the cars supposed towing capabilities and are experienced towers and never exceed 60mph on our long runs on the motorway. The garage say is should not happen but cannot find anything wrong. Does anyone have the same problem or any suggestions?

[Clan]

The car radiator could be marginal , due to being furred up ? volvos always have large reserves of cooling capacity in the radiator . Perhaps the thermostat is not fully opening causing a restriction?
When did you last change the auto gearbox oil? What colour is it? The fluid will boil if dirty or contaminated .
As you dont exceed 60 mph remember there will be less air flowing through the radiator , AND the torque converter clutch doesnt lock up until you get to 56 mph so try doing 70 mph if you are allowed that is . When the torque converter locks up the gearbox wont generate any heat .. assuming yours is auto that is ..

If all is in order fit an external oil radiator in the air flow at the front connected to the gearbox cooling pipe going to the car radiator ...

[JimDay]

It could be a faulty fan switch on the rad not cutting in soon enough try running the car up stationary & see when the fan cuts in if it cuts in just over halfway up the temp guage it should be fine if it's any higher try a new switch or fit a by-pass switch so you can over ride the the rad fan switch when you are towing

[Clan]

Originally Posted by JimDay

It could be a faulty fan switch on the rad not cutting in soon enough try running the car up stationary & see when the fan cuts in if it cuts in just over halfway up the temp guage it should be fine if it's any higher try a new switch or fit a by-pass switch so you can over ride the the rad fan switch when you are towing

The radiator fan switch went out with the 400 series luckily , They have been controlled by the engine ECU since .. but if you are doing 60 mph you wont need a radiator fan .
Good point though is the radiator fan running when the temperature is high? Has the system ever boiled over? Is the temperature sensor faulty?

[JimDay]

Oops sorry but there again I am new to Volvo's. But I did come up with something constructive "Clan"

[60041]

We tow with exactly the same outfit without problems, even in temperatures in the mid 30's in Italy.
Are you sure that the engine is overheating, a small rise in temperature is acceptable, as long as it does not rise into the red.
If it is overheating, then the problem is simply that the engine is producing more heat than the radiator and cooling system can disperse.
The first check should be to see if there are any cool spots on the radiator, which would indicate if there is any blockage, if so then the system should be flushed out (actually, it might be worth doing anyway).
The next check should be to see if any external factors are making the engine work harder than it should, these can include dragging brakes, underinflated tyres (don't forget the caravan) and overloading.
Finally, as mentioned above, dirty transmission oil can cause the auto box to run hot and this uses the same radiator to cool itself.
The point raised about running faster than 60 is a good one, the torque converter does not lock up until the high 50's, so speed less than this generates heat in the transmission, I have always found that the most economical towing speed, and the one that the outfit feels happiest at, is about 65 mph, and this also would have the effect of increasing the airflow through the radiator thus helping to keep things cool.
Some car specialists such as Frosts sell additives that are supposed to make cooling systems more effective by reducing the surface tension of the cooling water, but I don't have any direct experience of using them so can't comment on their effectiveness, however Frosts are reputable and their products are usually good, so it may be worth trying it.

[5imon]

I thought that is was reccomended to fix and oil cooler on thses cars is they are used for towing? or is that specific to the S60 D5?

[Clan]

All auto volvos have had an auto gearbox oil heat exchanger since the 1970's you only need an addidional air-oil cooler under extreme conditions , such as the Alps or Tropics .. ..

[Mike B]

Originally Posted by Clan

All auto volvos have had an auto gearbox oil heat exchanger since the 1970's you only need an addidional air-oil cooler under extreme conditions , such as the Alps or Tropics .. ..

As above , but a separate cooler does help !!
keeps g/box fluid last longer.
Regards
Mike B

[Clan]

There are two software upgrades available for this very problem now on the
S60 S80 V70 and XC70 with the D5244T with auto gearbox:
An engine software upgrade 30771346
and for an altered temperature gauge response curve, a DIM upgrade 30677020

must be worth a try ...