RV8 coolant temps

AdamR · Post by **AdamR** » Sun Jan 16, 2011 12:46 pm

What sort of coolant temperature typically constitutes overheating for Rover V8 engines?

My interim 3.9 will happy sit at 95 deg C all day long when at rest and idling, but if I rev the engine this can rise to just over 100. This is all based on running in the garage, as I've not got the car on the road yet. I see this as a worst case scenario as there is no airflow over the radiator other than provided by the electric fan, which is switched on at 95 degrees. Temperatures when moving should be the same or lower.

Are these sorts of temperatures acceptable? How hot does the engine need to get for me to worry about damage? System is pressurised so will not boil until something greater than 100 degrees, though I've not yet worked out exactly what that temperature is.

kiwicar · Post by **kiwicar** » Sun Jan 16, 2011 1:09 pm

Not sure how you are measuring the temperatures, dash gauges are only very aproximate (+- 10 degrees). Having said that a presurised system should run in the range you have described, some on here try and run lower temperatures but the engine is intended to run in the range 90 to 100c.
If you are intending to run the engine at a lower temperature you need to re calculate piston clearances, this is not straight forward as you need to know temperatures down the lengths of the bores and the pistons to work out the clearances for the piston skirts whilst running.
Best regards
Mike

AdamR · Post by **AdamR** » Sun Jan 16, 2011 1:25 pm

kiwicar wrote:Not sure how you are measuring the temperatures, dash gauges are only very aproximate (+- 10 degrees). Having said that a presurised system should run in the range you have described, some on here try and run lower temperatures but the engine is intended to run in the range 90 to 100c.

Temp is measured via a mechanical/capillery gauge plumbed in to the thermostat housing. I've double checked with an infared thermometer, and it seems pretty accurate.

From memory the termostat in my engine is 87 degrees - so shouldn't this be considered the "normal" running temp the engine is designed for?

Post by **katanaman** » Sun Jan 16, 2011 5:07 pm

around 87 will be the normal when its moving and cooling properly but sitting still not to mention revving will depend on how good you radiator and in particular your fan is. I would say your fine and fairly typical temp wise. I would be getting concerned if it was hitting 105 but it doesnt seem to be.

kiwicar · Post by **kiwicar** » Sun Jan 16, 2011 7:45 pm

Hi
A thermostat that is rated at 87 deg C is not intended to hold the temperature of the coolent AT 87 it can't there are too many variables, have a read of this thread for a discussion on the subject http://www.v8forum.co.uk/forum/viewtopic.php?t=8387
sorry I am not going to retype the control theory bit but sufice to say the temperature when under design conditions will settle to a temperature higher than that of the theromostat rated temp.
Best regards
Mike

Denis247 · Post by **Denis247** » Sun Jan 16, 2011 9:44 pm

Using a good oil additive (ZX) to reduce friction in a bedded-in engine has the added benefit of reducing heat.

AdamR · Post by **AdamR** » Mon Jan 17, 2011 3:37 pm

OK, thanks all.

I've now fixed a separate problem with oil pressure, and this seems to have helped a little with cooling, as I haven't since seen the temperature rise about 95, even when revving.

Kiwicar - That's an interesting point about the coolant temp. I don't quite follow the physics, but it's certainly consistent with what I'm seeing.

kiwicar · Post by **kiwicar** » Mon Jan 17, 2011 4:02 pm

As you have just found out the oil in your engine also does a fair bit of the cooling, logically it really is the only cooling for the rotating assembly. There were some very good articles by David Vizard on engine cooling in the early '80s based, from what I remember, on tuning work he did on a pinto engine, if you can find them they are well worth a read.
Best regards
Mike

MendipWursel · Post by **MendipWursel** » Sat Jan 22, 2011 11:14 am

I run my 3.5L with a 76 deg thermostat and the fan cuts in at 82 deg. I'm not so keen on the warmer engine principle because of the cracked block problems, especially with the 3.9L.

I have always been told the best performance is with the engine running below 80deg (65 to 75 deg optimum).

sidecar · Post by **sidecar** » Sat Jan 22, 2011 12:08 pm

MendipWursel wrote:I run my 3.5L with a 76 deg thermostat and the fan cuts in at 82 deg. I'm not so keen on the warmer engine principle because of the cracked block problems, especially with the 3.9L.

I have always been told the best performance is with the engine running below 80deg (65 to 75 deg optimum).

I run my 4.6 around 75-80 for the same reasons, some people reckon that the bore wear does increase at lower temperatures, this maybe true but then again I would consider a dropped liner to be fairly 'worn out'

I used to run my Yamaha R1 sidecar lump at 65 degrees, it would lose BHP if it ran hotter.

The problem with running the coolant at a low temperature is keeping the oil hot enough. My cooler is 85% blocked off AND I run a thermostatic take off plate! (Really I don't need an oil cooler at all but it looks good!)

Robrover · Post by **Robrover** » Tue Jan 25, 2011 12:30 am

Yes I always thought cooler the better too. However I read recently that unleaded fuel really requires an engine to run hotter for optimum performance.

The OEM thermo in my Land Rover is 88 degrees - which seems fairly high, but the enrichment on the ECU doesn't cut out until 82. I thought the high temp was for reducing emissions, but maybe it's for the unleaded fuel.

v8man · Post by **v8man** » Tue Jan 25, 2011 8:41 pm

for performance cooler the better not above 80 on ecu cars delete
fuel enrichment ,
and hotter for low emissions like 95 100 not good on a rover v8

TomLS · Post by **TomLS** » Tue Feb 08, 2011 9:35 pm

Hmmm. I'm worried now!
I've set a digital thermometer probe in silicone inside a steel tube just behind the thermostat in the inlet manifold - so it's pretty accurate!
Whilst driving above 30mph, the temperature never goes above 67C, and when idling my 3 electric fans keep it between 80-85C

It had a brand new 88C thermostat when I rebuilt the engine <3k miles ago.

kiwicar · Post by **kiwicar** » Wed Feb 09, 2011 6:58 am

Not sure what your worry is, that seems about right to me, stick a heavy trailer on it and drive on a the M25 on a hot day and you will see a higher temp, say 85 to 95.
Best regards
Mike

DEVONMAN · Post by **DEVONMAN** » Wed Feb 09, 2011 10:08 am

TomLS wrote:Hmmm. I'm worried now!
I've set a digital thermometer probe in silicone inside a steel tube just behind the thermostat in the inlet manifold - so it's pretty accurate!
Whilst driving above 30mph, the temperature never goes above 67C, and when idling my 3 electric fans keep it between 80-85C

It had a brand new 88C thermostat when I rebuilt the engine <3k miles ago.

Hi, 67C seems a bit low for normal driving given that you have a 88C thermostat. When you say the probe is set in silicone, do you mean silicone heat transfer grease or just silicone mastic? If you have used mastic the probe will read low.

Regards Denis

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