Normal operating temps for p38s.

[benji]

Having driven around in the 40 degree heat for the past few days, I've seen engine temps from 91 to 106.
Around town on a 40 degree day it'll sit on 98 - 102, 100 in the bush (106 on a step hill climb), and 94 on the hwy.

Id mainly like to establish what is 'normal' and safe in hot weather, as the father in law invited up to the high country, but we decided not to go due to the heat and fire risk. But would the car have been alright up those long high country hills in 40c heat?

Personally I'd like to not see temps above 96, and a running temp of 89-91 on the hwy on a 40c day. But I feel the limiting factor in the size of the radiator and the temperature rating of the thermostate.

One thing maybe worth doing is to switch the condensor fans on high at a certain temp, as the temperature rises very quickly when stopped, and only needs 10kph or 1500rpm to lower the temps by 4 or 5 degrees.



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[davidsonsm]

The highest I saw in slow traffic on a 40deg day was 102degs. On the highway it quickly dropped to 90ish. I don't believe that's any reason for concern. I've replaced the pump when the engine was done and have a new thermostat waiting to go in. The expansion tank cap was also recently replaced. All in the name of preventative maintenance. Would like to put in an aussie desert cooler, before the ONE rad craps itself. Car is on 163k.

[daf11e]

benji, my electric fans come on with a high temperature, I can hear them in slow hot traffic, so much so that if it's around 40deg the fans will stay on when the engine is off for a couple of minutes....I thought this was normal...isn't it?
My wife's peugeot does the same on an extremely hot day..

[p38arover]

benji, my electric fans come on with a high temperature, I can hear them in slow hot traffic, so much so that if it's around 40deg the fans will stay on when the engine is off for a couple of minutes....I thought this was normal...isn't it?

Yes it is. I've had the fans switch on when the car is parked (when they used to work). My electric fans used to come on when the engine was hot but I suspect one of the pressure switches in the AC system has failed and the fans no longer come on. I'm think of adding a manual switch for the fans.

I have a Scan Gauge in mine and I monitored the temps a week back on 35+ deg day as I climbed out of a valley on the Wollondilly River and then along Wombeyan Caves Rd.

On the low speed climb, the car's temp gauge rose a needle width above N and the Scan Gauge read 104 deg.

Once I got moving along Wombeyan Caves Rd (at 40km/h - it's a narrow and winding dirt road), the temp dropped back to N and the Scan Gauge read 94 deg.

As speed rose on the straighter and wider sections of the road, the temp dropped to 89 deg and the needle was in its usual position of just below N.

[Hoges]

The key issue is whether or not the coolant boils. A 50/50 anti freeze mix together with a properly functioning radiator (expansion tank) cap (14.6 psi) will sustain temperatures up to about 130 deg C. before boiling.

An engine operating in the 92-96 deg C range is normal ...the warmer the engine runs, the more efficient it becomes. The design specs allow for coolant temps to reach above 100 deg C especially when the engine is under heavy load in high ambient temperatures and relatively low air flow. The other major influence on engine operating temperature often overlooked is the heat transfer efficiency of the oil! An improved oil cooler can be more effective than upgrading a radiator which may well be operating quite satisfactorily!

[mtb_gary]

Driving around town in light traffic my temp is 86-87?C, this climbed up to 94?C the other day when the outside temp was sitting just over 44! I have seen up to 102?C after sustained soft sand driving through the dunes. My temperature reading is taken from an additional sensor (third party) near the factory temperature sensor. The Torque Pro app also indicates the same temperature.

Gary

[glenhendry]

My temps are much like yours Benji, I have seen 109 wheeling in the bush on a very hot day. This is fine. However, you will rarely see below 90 in a warm country, as the thermostat is closed at this point and fully open at 96 deg. Rave says thermostat opens:

->99MY 88 deg C (190F)
99MY-> 85 +/- 5 deg C (185 +/- 9 F)

80 deg C for diesel.

[mtb_gary]

Glen

That sounds like my thermostat is opening too soon. Given I have 2 independent sources providing the same result, I'm confident the temperature reading is correct. I don't think I'll change anything at the moment as I am pleased to be erring on the cooler side of the temperature range.

Gary

[p38arover]

I forgot to say, I don't run the usual P38A thermostat sputnik - min has the item pictured. My thermostat is in the inlet manifold like the RRC and is, I think, an 82 or 88 deg unit.

http://www.aulro.com/afvb/p38a-range-rover/201743-thermostats-2.html#post2187351

[daf11e]

The other major influence on engine operating temperature often overlooked is the heat transfer efficiency of the oil! An improved oil cooler can be more effective than upgrading a radiator which may well be operating quite satisfactorily!

Would this mean that certain oil types may be more beneficial than others for keeping the engine slightly cooler?

[Hoges]

Sorry, I don't have any info re. the heat transfer efficiency of automotive oil types -presume you are referring to mineral vs "synthetic"? I've got no doubt that those well versed in the black arts of oil blending could point to differences detected in lab trials under set conditions... Then you get into the market place with a multitude of different engine designs, flow rates etc etc and I suspect the differences tend to be marginal at best... irrespective of which oil is used which conforms to various international standards, a decent oil cooler is probably the best investment if one is not already fitted!:D

[daf11e]

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.

[TheTree]

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 :o 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

[mtb_gary]

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

[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.

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.

[Scouse]

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.

[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:angel::wasntme:

[p38arover]

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.

[TheTree]

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:angel::wasntme:

Hoges

I remember seeing this somewhere as well :angel:

Steve

[Hammer H]

What does the closed loop mean? Is that adding more fuel like a choke.

With a desert cooler radiator mines running at 81-84c hwy fully loaded and trailer, at 110kms, km2s 33s, getting 18litres per hundred, wondering if I'm using too much fuel.

Also on sustained heavy beach sand, tyres at 15psi temp still 82-85c

Max I've been able to get is 90c where as before I'd be at 105c and having to back off.

Only been cool weather here though at 25c

[TheTree]

What does the closed loop mean? Is that adding more fuel like a choke.

Closed loop means that the O2 sensors are up to heat and working so the system uses them to adjust the amount of fuel.

Open loop operation uses the default values.

Steve

[TheTree]

Just wondering where everyone is getting their temperature readings.

I assume from something plugged into the ODB port?

Steve

[glenhendry]

Just wondering where everyone is getting their temperature readings.
I assume from something plugged into the ODB port?
Steve
Yes, I get mine through the Torque app over ODBII using a PLX Kiwi adapter. Also from a generic ODBII scanner that plugs in.


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:angel::wasntme:
I watched my live data on the way into work this morning, and it changed from Open Loop into Closed Loop at 74 deg C. Interestingly, my MAF is disconnected at the moment, and it is still going into closed loop. I thought that closed loop required O2 sensors and MAF, but obviously not.

[mtb_gary]

X2 here with the Torque Pro App, but with one of the el cheapo Bluetooth OBD11 devices. I also have a permanent engine temperature alarm fitted. Like the one below on eBay

http://pages.ebay.com/link/?nav=item.view&alt=web&id=161549043240

Gary

[Hammer H]

Mines a watchdog temp sensor

[benji]

Mines on the nanocom. I've double checked with the thermocouple on the multimeter and the sensor is spot on.

That aussie desert radiator site sounds like it makes a difference. Basically the thermostate is almost closed.

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[TheTree]

Mines on the nanocom. I've double checked with the thermocouple on the multimeter and the sensor is spot on.

That aussie desert radiator site sounds like it makes a difference. Basically the thermostate is almost closed.

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I have both the nanocom and a watchdog and have noticed the watchdog temperature is usually a few degrees below the coolant temperature reported by the nanocom.

I will have a closer look on the weekend

Steve

[Hammer H]

Mines on the nanocom. I've double checked with the thermocouple on the multimeter and the sensor is spot on.

That aussie desert radiator site sounds like it makes a difference. Basically the thermostate is almost closed.

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So far I'm very impressed with the desert cooler, I've been working it hard on 4-5kms of soft sand but can't get it to break a sweat. It's running at 85 where as before it would of been over 100 and I'd be concerned and had to back off. I would like have a hot day to test it but the south coast of WA is cool at the moment.

[benji]

Thanks heaps for that Hammer, I'd be very interested to hear how it goes on a hot day. Last time I was over your way it was 51 in the shade at Hyden the Fremantle doctor was nice that day!

Steve did you have yours in any hot weather?

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[p38arover]

I got my condenser fans running today!

I worked out the circuit configuration then checked the relays and the fuses and found that whoever replaced the fusebox some years ago (ahem :angel: ) had put F31's 30A fuse into one of the unused spots. You can't trust some cheap mechanics. :D

I still might fit a manual switch.

[TheTree]

I checked the temperature difference and have noticed that the watchdog is almost always running 5 degrees cooler than the nanocom temperature.

So HammerH would see his coolant running around 91 degrees I imagine.

Steve

[Pedro_The_Swift]

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:angel::wasntme:

My Thor info is different,, engine is considered hot after 55-60 deg,, the only reason for a design hotter than 88 is cleaner combustion, but the engine build is so lousy it just wont last at 96---

LR V8's have run far more successfully for many years at much lower operating temps than Thors.

[Eevo]

My Thor info is different,, engine is considered hot after 55-60 deg,, the only reason for a design hotter than 88 is cleaner combustion, but the engine build is so lousy it just wont last at 96---

LR V8's have run far more successfully for many years at much lower operating temps than Thors.

i recall reading somewhere that the LR v8's of the 60's ran about the 60degree mark