960 getting hot (still)

[rogerthechorister]

Any bright ideas?

[rogerthechorister]

My thoughts are turning to the rad. Aberdeen Radiators do a 34mm deep one whereas a Nissen is 32mm. Thoughts?

[Backhill1]

Normally in the uk we should not need to redesign cooling systems as they are designed for a global / tropical climate. many people forget that in all but extreme load engine cooling systems sit in a state of by-pass hence why we no longer refer to thermostats as such and call them regulators.
I would do a string test and verify the fully open temp and compare that to what your getting at full load. This is effectively the fully open temp of your engine.
Complete this test before any mods.
Once you know the fully open temp we need to try and capture the delta T across your rad somehow if you have an issue.
Btw auto boxes don't throw much heat out unless under stall (foot on brake and revving engine in first) the conditions you are describing is the box not in lockup at this point very little heat is generated by the box.

[bluebrickrick]

Roger,

Does the 960 have the same sort of coolant expansion tank as the 940 ?

If so check the spigot where the small balance pipe from the rad goes into it, mine was overheating and stayed pressurised even when cooled and I finally found that the steel pipe core to the moulded spigot had rusted shut, can't recall xakly but I ran something like a 3.5 or 4mm drill through it and back to normal......

Also known the waterpump impellers to either cake up or dissolve away leaving a disc or less - if your kettle scales with hard scale then you may have the 'wrong' water to top up with.......

HTH

Rick

[rogerthechorister]

What is a string test? I have had a new thermostat. I have also had a new water pump. I have also had a new rad.

The reason I think a modified rad may be the answer is that Volvo themselves suggest not towing at over 50 mph, and slowing down and turning off the aircon on steep hills. It's in the handbook.

I am thinking about inserting a threaded boss in the radiator top hose so that I can add a jury-rigged extra temperature gauge because I think that the 960 has a "stabilised" temperature gauge which is rigged to read in the middle until it is getting close to overheating when it suddenly goes whoosh - rather like the notorious Rover 75 diesel which was a nightmare for blowing up engines!

[rogerthechorister]

A thought came to me. My 960 is auto, but I have already bypassed the internal atf cooler in favour of a HUGE Mishimoto atf cooler - so do teh manual 960s ahve perhaps no internal atf or gearbox oil cooler, but retain the oil cooler?

[Rversteeg]

Long shot, but is the fan rotating the right way?

[rogerthechorister]

I did not know that was possible: everything plugs to gether with asymmetric plugs. I think.Also why would the problem only manifest when towing hard?

[Rversteeg]

I agree it should not be possible, but now you have more or less ruled out the obvious, I would say it is worth a check.
During normal driving the fan will not engage, only when driving slowly or standing still for a long time. If the fan is pushing out the air through the front, against the direction of the normal air flow, it will be no problem as long as you are in slow moving or stationary traffic.
If the natural air flow is not sufficient (eg when heavy towing at relatively low speed) the fan will engage as well. But at these higher driving speeds the fan will not be able to work against the natural airflow anymore.
Just a theory...

[rogerthechorister]

Towed over the weekend. Still got two problems when towing and only when towing a caravan.

First, on A and B roads that twist, climb, drop, etc the gearbox becomes reluctant to change down and sometimes changes down two gears in stead of one. This is despite the MASSIVE Mishimoto atf cooler that has been fitted. Mecco is suspecting a problem similar to one he had on a van - something to do with the torque converter and a switch related to it - and alleges it is cheap to fix.

Second, even if selecting third and turning the aircon off, and using "sport" mode in the gearbox, point her at a long motorway climb with the cruise set at 60 and the temperature gauge starts to climb too much for comfort. I am picking up a new fan relay later today and can when fitting check fan rotation - but I bet I am going to have to go the route of a custom radiator! Bear in mind Volvo specifies not to tow at over 50.