1999 discovery is overheating, cooling fans are not coming

Hi welcome main problems are the abs valves causing the 3 dash lights (search 3 amigos online) a really badly sited compressor can cause air suspension models to fail giving the bags a slow leak the V8 is a solid engine but can have radiator expansion tank and cap failures
the other issue is electrics windows and door looms are problematic

Water pump? Did you jump fan cooling switch (on thermostat housing) to see if fans come on?

check fluid level in radiator are you leaking fluid on ground does cooling fans come on if they dont check fuse for fans if fuse is good inspect wires going to fans are fan motors bad is water flowing thru engine anfter thermostat opens if notcould be bad water pump is there water on your oil dip stick if so blown head gasket dont keep driveing hot

the cooling fan that comes on when the AC is turned on isnt working

I would recommend that you bleed all air out of the cooling system. The bleeder valve is located on top of the engine. Once engine starts to overheat or when you can hear bubbling back into the overflow bottle, turn car off and open bleeder valve. If you see bubbling you have air in your system. Bleed the system a couple of times and see if this helps.A heat sensor sending unit which controls activation of the electric fan could also have failed.But is the heat sensor is properly working then check the radiator cap is it properly fitted or got loose.If its loose it will release the pressure and car will overheat.But if the radiator cap is properly closed.Then its time to check the HEAD GASKET.As you have mostly replaced all the possible faults for overheating and if other mentioned possibilities are checked OK.Then its time to check and replace head gasket. Thanks. you can rate this solution and show your appreciation.

From practical experiences of heavy trucks, this problem is created by poor coolant flow thro' the Radiator Core. Flush cleaning the Rad. or decontaminating the exterior air flowways will not cure the problem. My recommendation is a Recore or after market replacement.
Regards.DT

Can your head gasket be blown? Only the combustion can have such high pressure.

YOU NEED TO BLEED THE SYSTEM AFTER FLUSH.

Hi

One simple piece of advice. If you are thinking of buying this particular Discovery - don't.

The reason for this is that although potentially this is an easy fix and is likely to be a thermostat that needs replacing (jammed shut) - there is a risk that the jeep has been running for some time with this overheating problem. At least you don't know how long it has been driven like this.

The risk of driving an overheating engine is that the cylinder head could be warped and even if you resolve the overheating issue - other serious engine damage may already have occurred.

This could easily turn into a very expensive mess. If I was to view a car with an overheating issue like this I would simply walk away. Even if the head is not warped there is a higher risk of a head gasket blowing at some point and this again involves considerable expense in labor terms.

There are plenty of good Discoverys out there. My advice? Keep your money in your pocket until you find one.

Hope this helps. Please do rate this answer. Thanks.

Start with the cheapest part and that would be the thermostat. They are easy to replace and that appears to be the issue. They do wear out or stick.