I have a 98 Land Rover Discovery with the 4.0 V8. I have been having this problem for a little while now. You can run it all day and not have a problem but you let it idle for more than 5 minutes engine overheats. Not sure if it is actually overheating or if it is the gauge. I have replaced thermostat and the radiator cap. Engine has been reuilt about 10k miles ago. I do not loose any fluid and it doesn't boil or boil over. I have replaced the coolant sensor. Both electic fans are working and as far as I can tell fan clutch is working. I pop the hood when engine starts to overheat and fan is going. If yoiu put it in drive and drive it down the road the gauge goes back down very fast. Water pump has been replaced with OEM Land Rover water pump when engine was being rebuilt. I have no idea what is going on. Truck runs GREAT with plenty of power, does not smoke, leak any fluids, and gets 18mpg highway! Not to bad for a tank. HELP!!!

 

It is one of two things, either your new fan belt is routed wrong, which is very easy to do on a DI, or you need a new fan clutch.
Just because the fan is spinning does not mean it is moving enough air to cool the engine.
Here is a diagram of the correct belt routing, even LR tech's have gotten this wrong so dont feel bad.

http://www.roverparts.com/TechTips/s...g_defender.cfm

If the belt is routed wrong not only will your water pump spin to slow but so will your atlernator and eventually your battery will go dead.

 

I checked and my belt routing is correct. I have driven it this way for 10K miles on it and now that it has 140k miles on it I guess a fan clutch is past due. I have replaced them before so it won't be a big deal. I deal with motorcars-ltd.com. So far they have been the cheapest for OEM Land ROver Parts. OEM fan clutch from them is $92. I called Napa and Oreilly and they both quoted me $160 and $190 and they are aftermarket! I thought the whole reason of having aftermarket parts is so they would be cheaper than the OEM part! I hope it is the clutch but then again there isn't a whole lot that could be wrong since I have replaced so much crap already!

 

What about your electronic fans, are they both working?

 

WHen it is hot I have the A/c on and I have checked and both fans do come on and both are on when engine starts to get hot. I just don't get it. It can be 110 degrees outside and I gan drive all day and it never even make it half way up the temp gauge but let it set for 5 minutes and watch the gauge climb. I am going to change the clutch and semp sender again and this time I will use an OEM temp sender.

 

Start with the clutch, pressure wash out the radiator to make sure you have air flowing.
With the a/c off, how long does it take for the electric fans to come on?

 

Do not pressure wash the radiator, if it is old adn close to the end of its life the pressure washer will cause it to leak.
Just use a garden hose.
It overheats at idle becasue there is not enough air moving past the radiator to keep it cool, drive down the road and the "ram air" coming though the grill keeps it cool.
Stop moving and all that heat builds back up.

 

I will wash out my radiator. I just paid $110 shipped priority from motorcars-ltd.com for a brand new OEM fan clutch, temp switch, and switch seal. Not to bad at all! Now I get to fiddle with my ford tools to try and remove my fan clutch. It was real nice and fun when I removed the water pump and I am not looking foward to it but will not pay a rip off mechanic. Thanks for the help and I will keep you posted.

 

I would think Spike is correct.... I had a overheating issue a little more elaborate but i change today my fan clutch and thermostat and my problem is about 98% solved. After i shut down after teat drive and sitting ideling...and im in florida and it 95 degrees today, i heard a very faint his for about 20 secounds comming from the expansion cap. i really had to put my ear next to it but thats wher it seems to be comming from. Thats my 2% fix tomorrow with getting a new cap. I thought my fan clutch was good also as it was spinning but when i took it off and spun it a few revolutions, it spun like crazy and made a very bad bearing noise. it was shot. Whn i put the one i got today it roared. You can tell the difference...

my 2 cents, Chris

 

You can do it in less than 30 minutes. Take a hammer and a big screw driver and place it on the edge of the nut that holds the fan and clutch on. Pointing to your right, counter clockwise. Give it a couple of wraps until you see it move a bit . Dont be afraid to give it a good wack. Once it moves. just spin the fan and it will come right off. Put the fan on your bech or floor and you will need a i think metric allen key. i can remember what size and there are 4 bolts that hold the clutch to the fan. i had to use a hammer to tap the allen key to get them loose. Then take out and switch them. repeate process in reverse and your good to go.

Have fun, Chris