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1995-2002 Range Rover P38A
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Discussion Starter #1
Hi. Bin a while since I came on asking for help. Mainly cos everything has been OK BUT.....
Before everyone shouts at me regarding diagnosing the problem and its already been covered I know and have already been through that.
The oil level is fine and oil in good condition, no blockages in pipes or in radiator. wiring is fine tested on both circuits with multimeter. The issue there is that I think the sensor is faulty - the message shows overheating but according to external temperature sensor the temp is only 45-51 degrees C. according to Rave it should flag at 95 degrees. Double checking the readings tomorrow.

What puzzles me is during the research it shows that some diesels have a an electric fan and some on offer on fleebay but I can't see any reference to a fan on RAVE or the LRCAT. ( Mine has the small radiator behind where the front fogs would be. There's nothing on the car not even a connector. Can one be fitted ???
Cheers, Mike
 

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As far as I know they do have a fan normally and a sensor in the radiator but you are absolutely correct, there is no mention of it in RAVE, the ETM or Microcat (I looked for it a couple of weeks ago when someone had a problem with the sensor). I'd be inclined to check the actual temperature with an infra red thermometer but I will admit I had Transfer Case Overheat come up on my dash one day, only to go away and all I could find was the connections to the sensor weren't particularly tight. Never come back since, not even when towing a 3 tonne trailer when the temperature outside was over 40 degrees.
 

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It is the later model diesels that have a fan fitted to the gearbox oil cooler, while the earlier models did not. I think the change over year was 1997.
The gearbox does run hot when towing in hot weather. Landrover were aware of the problem so they fitted a fan. Solo it shouldn't be any problem at all.
It can't be retrospectively fitted as the early wiring harness won't have the connectors, unless you rig up a DIY system with a manual switch maybe?
If you take the front bumper off you can get at the cooler. The temp sensors (there are two on mine with a fan) clip on the side.
More than likely it is a bad connection.
If you are into mods, a better idea is to fit a small aftermarket cooler behind the front grill and do away with the existing one under the wheel arch. You can then fit fog lights as well.
 

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Indeed, only the later diesels had the fan. I thought it was 1998, might be market specific.
As for the overheat message, does it come on straight away, or only when running for a while? If it comes on straight away, it must be either a faulty switch or a bad connection because the oil takes time to heat up. The switch is closed to ground when temperature is OK and goes open when temperatures rises. So a bad connection will give a faulty overheat signal.

Filip
 

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Discussion Starter #5
It would appear the the fan was fitted to the P38 from 2000 with a new wiring harness so if I fit one in will have to be adapted. The strange thing is that it looks like the cooling radiator has all the tabs so the original may have been replaced. Talking to a local gearbox refurbishment specialist ( who has also owned several P38's) he agrees with me that the sensor is probable faulty giving a false reading. Have ordered a new one which should be here by weekend when I will be able to fit fit IF IT STOPS BL**** DY RAINING.
Many thanks to all that have responded, it is most appreciated. Cheers, Mike
 

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My diesel fitted with fogs started giving that message whenever I'm stuck in traffic or on a long hilly route. I guess, for the same reason my HP22 box gave up about a year ago. Now I have fitted a Chinese made 12V 10" cooling fan with a manual switch . No more gearbox overheat message.
May be this occasion it's a false alarm but it's better you get a fan installed there in case the need arises. A 12V fan is cheaper than a 4HP22/24.
 

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Discussion Starter #7
Thanks Kapilmuni.
Fitting a fan is the next stage down the line. Now received the new sensor and hopefully will fit this weekend and the test it out. As we use the land rover for pulling a a good size caravan - the fan may be necessary. Thanks again to all who have replied, it is most apprciated. Cheers, mike
 

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My diesel fitted with fogs started giving that message whenever I'm stuck in traffic or on a long hilly route. I guess, for the same reason my HP22 box gave up about a year ago. Now I have fitted a Chinese made 12V 10" cooling fan with a manual switch . No more gearbox overheat message.
May be this occasion it's a false alarm but it's better you get a fan installed there in case the need arises. A 12V fan is cheaper than a 4HP22/24.
Sorry, but this is hard to grasp. You got the overheat message, but still decided to keep the fogs even though you know the left one greatly restricts airflow? :unsure:
 

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Discussion Starter #9
I understand your confusion Escape. I am even more confused as I have never mentioned fogs, mainly because I don't have any. Cheers Mike
 

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The gearbox does run hot when towing. I fitted a 4HP24 gearbox to my diesel and at the same time I fitted a thermocouple to the gearbox sump to monitor the transmission temperature.
I have towed a 2 tonne caravan + 0.5 tonne of gear in 40 deg C in the South of France. On an open road the gearbox was ok but stop/start in town at traffic lights the gearbox soon overheated, reaching 120 deg C. on occasion. On the open road the gearbox locks up in top so does not slip or generate heat. Solo there would not be any problem at all.
You can't fit fogs to the diesel as the cooler is in the way. The fogs are quite deep at the back.
 

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Escape - when I bought the car fogs were already fitted using original harness. But at that time I was not using it daily. Afterwards, when it became my daily transport, it started to give the message when I was in slow traffic. Once started moving it vanished and I was not worried. Eventually, the 4HP22 gave up and I changed the box to 4HP24 and installed the fan too. No more over heat message.
 

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I understand your confusion Escape. I am even more confused as I have never mentioned fogs, mainly because I don't have any. Cheers Mike
Mike, that's because my reply was directed at Kapilamuni, hence the quoted text. ;)

Dave, I've seen several diesel automatics with fogs, never checked to see how close of a fit it was or if the cooler had been moved/bent out of the way or something. I just told the owners it was a bad idea.

Kapilamuni, at the first sign of gearbox overheating, I would have taken out the fogs, instead of adding a fan that has a hard time trying to find air to pull through the cooler. I can't remember the last time I used (or wanted to use) front fogs, so I wouldn't miss them either. Maybe you do have a reason to keep them?

Filip
 

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Filip, I saw a write up on here a number of years ago when a guy fitted an aftermarket cooler on the front and did away with the one under the wing. It allowed him to fit fogs.
I would like to do it and the wiring plugs are still there on mine.
However, my car is a bit more complicated. I have a removeable winch and the receiver frame for the winch is behind the number plate. I can't therefore fit a cooler.
Solo there wouldn't be a problem. I don't think the BMW car had a gearbox cooler.
 

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No reason to keep them. Car just looks better & I didn't want to remove something (only thing?) that works perfectly. Also, it is assumed to help to meet the pathetic performance of LOW beam headlight.

I really didn't know how serious that message was. It was like 'bonnet open' message which kept coming whenever it wanted.
The 4HP22 had to face both , the heat as well as the extra power from chipped engine. It gave up after about 2 years of chipping.
When I searched for replacement (thanks to Dave for his 4HP24 installation, that was a real encouragement), I found that overheating is a main reason for auto boxes to go south.
 

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I in turn took advice from Dave Ashcroft who is a Landrover transmission specialist here in the UK.
He recommended I fit a temperature gauge on the gearbox. He said it is the main cause of gearbox failures. The fluid degrades rapidly and if you don't change it, the gearbox won't last long.
I think the top limit is around 130 deg C.
 

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Dave, can I have a fan thermostat fitted to 'line pressure' testing port ? Then I can forget the manual switch for the ATF cooler fan. You have any idea about the thread pattern of that ?

How do you measure the ATF temp in your rig?
 

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Dave, can I have a fan thermostat fitted to 'line pressure' testing port ? Then I can forget the manual switch for the ATF cooler fan. You have any idea about the thread pattern of that ?

Not sure what you mean by that.

I had a boss welded in to the gearbox sump in the sloping part at the back. the sump is just sheet steel. I fitted a thermocouple in it with a readout in the dash.
It failed a while back and is a lockdown job to get working again.
 

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I mean , the outputs from the ATF pump where two ATF oil cooler pipes join. There are extra access points & one is for testing trans oil out put pressure. May be using that port we can insert a thermo switch to run the fan. Only thing is to know the thread size.
ZF4HP24  pump .png
 
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