Okay, here it goes.
I have a 98 disco with a overheating problem I can't figure out.
I have replaced the thermostat, I found a leak in the expansion tank and replaced that. Then I found that only one AC condenser fans were working.
I thought for sure that I found the problem. Replaced the fan and it ran with AC on at idle in my driveway for 20 min and never made it to the halfway point.
Drove it for about 15 min and it started to overheat. Turned heat on and temp came back down to normal. I also replaced the serpentine belt that was worn.
Not sure where to go from here. I was thinking about replacing the radiator next. What do you guys think? Thanks in advance for your help!

 

What temp thermostat did you put in it?
How many miles on your truck?
What about water pump?
What color was the coolant when it came out? Coppertone?
Radiators are about $800 new from dealer.
BP Utah sells them but they are cheesy and it took them 4 of them to ship to me before they finally got one that wasn't broke. But guess what, it cracked 4 months later! I ended up going to the dealer. It was easier. 10k later, it still works!
What about the fan clutch? If I were you, I would check to see if you have a bad head gasket first. Then I would check the fan clutch. The last thing I would do is replace the radiator. People say that they can get these radiators recored for $250 but all the places I took it wanted over $500.

 

I have 253000 miles on it.
Water pump is not seeping and looked fine when I replaced belt.
Coolant didn't come out. I can check the color.
Fan does not free wheel so I assume clutch is good. I was thinking about replacing it anyhow.

 

I had the same exact problem on my BMW. The brand new water pump I bought failed and wouldn't circulate properly. The problem was fixed when I bought another water pump with a brass impeller. You may as well have the rad flushed as well, it could be partially clogged with that many miles.

 

What are the signs of a bad head gasket?

 

Any number of things, some times it's hard to tell. The most obvious are white smoke at start up may smell sweet, lots of pressure in your cooling system when engine is running, oil in your coolant, and/or coolant in your oil. A leak down test at a shop is the best for diagnosis. You can also purchase a DIY type tester from a store like Advanced Auto etc. Good luck, I know the feeling.

 

It's your radiator if it will idle in your drive way and not overheat. If headgaskets were leaking it would still happen at idle because it would still over pressurize cooling system at idle. When you drive you put added strain on the system and thats when it over heats. If turning on the heat brings it down that shows you your radiator is likely partially clogged and isnt dissapating the heat like it should be.

Take your truck to a radiator shop and they can high pressure flush it. Usually this is enough to get you back to normal temp ranges for years to come. If that doesnt work they will likely want to recore it. Another member on here recently posted a good deal on an ebay aluminum radiator he seemed happy with it was only around $250 I believe opposed to the $500 new you normally see.

My check list for overheating trucks..
Check for head gasket issue signs. Pressurized rock hard hoses, exhaust gas test, exhaust smoke/steam with sweet smell. etc.
Flush system
t-stat (should be changed at each flush anyway, and they are cheap)
Fan clutch - do the free wheel test. If you've never replaced it you might as well at this point. I do GM standard duty swap - search it.
Radiator flow test - done by local shop to tell you condition of radiator
Water pump - When these fail usually it's the bearings and they will leap from the weap hole. The fins hardly ever wear out although it's not impossible.

 

Thanks, Ill get it flushed next and see if that does it.

 

Read thru this if you have a moment. https://landroverforums.com/forum/ge...verview-51034/

 

With that sort of mileage odds are very good the viscous clutch is shot and the radiator is very clogged, either the fins or internal tubes. More than likely both.
I'd install a new clutch and take the radiator to a shop and have them do what it needs. You may get away with having it rodded, but the likelihood is high you'll need a recore. Go with a heavy duty recore.