Thread: Normal operating temps for p38s.

Thanks hoges I am not overly technical nor was I wanting to open a debate with synth/min....just wondering if brand quality and thickness made a marginal difference.

Hi

During my recent trip my engine watchdog, which was set to 100, went off twice.

Once in the middle of Wagga in a traffic jam and once on St Kilda boulevard in very slow traffic.

I have since set the alarm to 105 and intend to idle the car when the weather gets hot again.

Generally the engine runs around 94 on the freeway.

Sounds like it is also worth testing the fans to make sure they come on

Steve

According to RAVE there are 2 scenarios that can activate the condenser fans

1. A/C Dual Pressure Switch
2. When engine temperature gets too high

What is the default temperature that the fans get switched on at? And secondly can this be changed?

Gary

So after trawling through RAVE, I haven't been able to find the temperature at which the engine ecu should turn the fans on - but it would seem that the ecu will switch the fans on regardless of whether the aircon pressure switches are working or not.

What ever it is, to me it seems too hot. A simple thermistor switch on the top hose will sort that one out.

It does seem that a lot of people regularly see temperatures over 96, at which the thermostat is completely open. So above that it's a case of the ability for the radiator / oil cooler to cool the fluids - to which the classic rangies did seem to have the edge over the p38's system. So to that a lower temperature thermostat wouldn't do anything whilst sitting in traffic on a hot day, or when asking it to work hard (towing) on a hot day. It comes back to air flow, and radiator capacity.

Another two things i've been trying to read up on, is the variance in wetting ability (thus heat transfer) between a 50:50 mix, and a 70:30 mix. Water is a lot better at transfering heat than coolant, so a 70:30 mix would cool better, but boil at a lower temperature.
And also the differences between thermostats. Some aftermarket ones only have one spring, whereas the genuine ones seem to have two springs....which may make them slower to react? I know the britpart one I bought sits the engine at 89 on a 42c day on the hwy, where as the double spring genuine one sits it at 94.

Sorry for the long post - the mind has been a wondering....

p.s. a classic rangie radiator won't fit... and i've often wondered at what temp the engine would stabilize at idling on a hot day - before I had the nanocom I've had it at 3/4 on the gauge whilst idling for 15 minutes on a 38 degree day, I know the classic didn't do that on a 52c day.

Originally Posted by benji

So after trawling through RAVE, I haven't been able to find the temperature at which the engine ecu should turn the fans on - but it would seem that the ecu will switch the fans on regardless of whether the aircon pressure switches are working or not.

According to the ETM, the fans are controlled by the HEVAC ECU, not the engine ECU.
There's no direct engine temperature reading given directly to the HEVAC ECU but it does get some info from the engine ECU so maybe it's hidden in there somewhere.
I know the diesel condenser fans are only activated by A/C pressure.

My "understanding" is that with the later engine management systems...both GEMS and Bosch, the operating temp was designed to be hotter. with the Thor, it needs to get into the low 90s to go "closed loop". Happy to be enlightened and corrected if this is wrong

Originally Posted by benji

the classic rangies did seem to have the edge over the p38's system.

RRC condenser fans came on whenever the AC was switched on - no jiggery pokery with ECUs.

Originally Posted by Hoges

My "understanding" is that with the later engine management systems...both GEMS and Bosch, the operating temp was designed to be hotter. with the Thor, it needs to get into the low 90s to go "closed loop". Happy to be enlightened and corrected if this is wrong

Hoges

I remember seeing this somewhere as well

Steve