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95 RRC LWB 04 Discovery SE7
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Discussion Starter · #1 ·
Hi Everyone, newbs here...

Been online searching threads and asking a number of people about the normal operating temperature for a 2002 4.6 P38. I’ve got a ultragauge hooked to my OBDII port and have been getting readings in the range of 199 to 212. Usually 199 cruising on an open freeway, and 210-12 sitting in traffic or climbing up the mountains. Reading online, most say 200 to 205. But talking to people, it’s as low as 185 on the freeways.

What is the normal operating temperature for a 2002 4.6 Range Rover P38? If mines normal, cool! If not, it might be time to get my hands dirty...again.

Y’all on the forums have been helpful for a long time, thanks again!
 

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1995-2002 Range Rover Classic
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1,414 Posts
I must admit, I have never taken readings. a few yrs ago before my ownership the front end was severely damaged by a deer, thus along with new body work my 00 p38 received radiator, oil coolers, all hoses water pump thermostat, fan a clutch, a/c condenser and fans etc.

I have never seen the gauge any higher than just below the 1/2 way mark even in northern virginia summer traffic with a/c on.
If I do recall correctly according to rave the 03/04 discovery 2, 4.6 with SAI which matches the p38, had an acceptable normal temp range of up to 220 degrees F.
I would say in california heat possible with a/c on, you're running with in the specs of normal temp.
thermostat specs at 190 deg F opening, thus you will have difficulty seeing anything below 190 deg running.
 

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Premium Member
1970-1995 Range Rover Classic
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455 Posts
The temperature gauge is rather vague after 96.
It stays in the middle between 85°c and 107°C.

Normal imho is between 90 and 98 in a moderate to subtropical climate. In a truly tropical climate like here up to 50m of altitude expect it to go up to 102 when climbing.

We always go up the same 12 km climb from 35m to 800m after doing head gaskets, radiators or similar jobs to test the cooling system.
Hence these values are based on many test drives with different p38s and Discoveries with 4.0 or 4.6 e engines.

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95 RRC LWB 04 Discovery SE7
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15 Posts
Discussion Starter · #4 ·
Sorry for the late response. Thanks for the advise. If it ain't broke why fix it? I won't do anything for now, i'll continue to track its temperatures.
 

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I hav a 98 RR 4.0 and I have checked my temp through the OBDII port several times. Since I had to replace the radiator, two water pumps and three thermostats in the last 2 years.

But 2 years ago when everything was going great my temp was reading 172F degrees. I got the tool to check the codes when I had to replace both oxygen sensors three years ago.

But 172 was the normal temp then.

Not sure for th 4.6
 

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1995-2002 Range Rover P38A
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99 Posts
A standard thermostat opens at around 180f or 82c, so I'd say 172f is on the low side.

My guess would be slightly over the thermostat opening temp. I've just replaced the thermostat on mine and seem to be operating 90-95c or 194-203f.

That said, I would think a reasonable range would be 95c +/- 10c or 185-221f. That's just a rough estimate based on the numbers above and the boiling point of coolant under pressure.

To answer your question, 199-212 sounds perfectly normal
 

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How's that Ultragauge on the P38 is it pretty thorough and able to read everything? I was debating a iLand v2 but if you were able to read operating temps on the Ultragauge that sounds cool... and far less expensive.
 

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2000 P38a RR 4.6 HSE
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33 Posts
I have noticed since my rebuild that it stays just at or just below the middle of the gauge unless I'm coasting downhill, downhill mountain roads, the gauge will drop to nearly the low hashmark on the "normal" range. Kinda weird do you think the new thermostat is faulty? It doesn't over heat, it just gets really close to the cold side.
 

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1995-2002 Range Rover P38A
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385 Posts
Mine runs around 83C on the open road, 86 - 88C around town, and on a 30+ degree day, stuck in traffic etc, it might get to 94.

Seems that your is doing as it should, as when coasting there is maximum cooling and little heat generation. Mine on a long downhill run, mountain hwy or similar will drop to around 75C, but bumps up again once you start applying power.

The dash temp gauge is a very course instrument and of course, if you lose your coolant, will read cold as there is no coolant to give a reading. I use one of these and find it excellent. You bolt the sensor to the head on the LHS at the rear (there is an unused threaded hole there if you look/feel). The advantage of these is it is measuring the temperature of the head, regardless of coolant, so if you lose your coolant and start to overheat, this is going to go into alarm and you will know pretty much straight away.
 

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Not sure if a prior owner changed thermostats (meticulously dealer-serviced prior to me, I don’t think they would) but even my 5.0 will both idle and cruise at 180-183 F on an 85 F degree day.


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Same as Dtoyne, mine runs at 83-86 C no matter what the ambient temperature. No idea what that is in Fahrenheit though......
 

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1995-2002 Range Rover P38A
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I installed an adaptor in my lower radiator hose and then an Autometer temperature gauge and sender.
My 4.6 NAS runs at 180F with the dash gauge needle just a little left of straight up. Climbing hills I have only seen it go up to 190 except for the two times I had water leaks and temperature went past 200 before I stopped.
 

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1998 P38 HSE White Gold - Lightstone
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How's that Ultragauge on the P38 is it pretty thorough and able to read everything? I was debating a iLand v2 but if you were able to read operating temps on the Ultragauge that sounds cool... and far less expensive.
I've been running a ScanGauge II on mine since I bought it two years ago. Very convenient, small package that mounts well right on the steering column cover. I have it set up to read temp, mpg, vlt, adjusted mph for larger tires. It's nice to check any engine codes or clear them if needed as well.
 
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