How to tell if it's my thermostat or fan clutch?
 

My water pump went out on my 1997 RR SE, so I replaced it. Now it keeps overheating. Thinking maybe the thermostat or fan clutch. How can I tell which it may be. The fan turns when the engine runs, but I can't tell if it accelerates with the engine or not. But don't know how to test thermostat since its inside the housing. Any help would be great. Thanks.


Hello, Thanks for all the help. Got a couple more questions for all the Land Rover Gurus. #1. Is there a way to tell if it is the HG vs. a cracked block besides a block test, like any tell-tell signs that could only be one or the other. #2. if it is in fact the HG, do the heads always need to be resurfaced?

Keep in mind that there is no water in the oil, or oil in the water. The hoses get rock hard when in heats up. Besides that it runs like a Champ, no skipping, hesitating, or rough runs. Thanks.

With the engine hot and turned off, it should take a fair bit of effort to turn the fan blade by hand. With the engine cold or just slightly warm is should turn fairly freely.
You can test your thermostat by immersing it in a pan of water with a thermometer and seeing at what temp it opens. It should be fully open at about 88c.

X2, the fan should not turn more than 1 revolution when you give it a spin and release. If it freewheels, time for a new clutch.

Replace the thermostat with a 180F version.

You put the belt on wrong and the water pump is turning backwards or not fast enough, happens all the time.
Tech section, follow link to belt routing.

Ok, changed the clutch fan with a Chevy one the appears to work and still over heating, bypassed the heater coil and still over heating, tested the thermostat it works but still over heats. It runs within normal range for about 10 minutes or so then it over heats. No water in the oil, or white smoke after warm up, so don't think it the head gasket. Does anyone have any other ideas? Thanks.

I'm a bit surprised no one's mentioned the possibility of a clogged radiator.

Yep, other tests.

1. Recheck belt route

2. once engine warmed up, shut off. Measure, by IR thermostat, or by palm, the temp on the fins of the rad from top to bottom. Not the tanks. More than 10F cooler on bottom is a strong indicator of clogged radiator.

3. water pump - if truck overheats at idle or dead slow (traffic), but ok at high way speed, find a long hill. Shift to N and coast. If you are going more than 15-20 mph you have more air flow thru radiator from forward motion than the fan at idle. If it stays cool water pump must be working. If overheats quickly, water pump is not moving water like it should.

Hello again, I can attach a water hose to the top of the radiator, and turn it on and the water sprays out the bottom opening. Is there another way to test it or could there still be a blockage if the water flows through it. Thanks.

When one speaks of the radiator being "blocked," what is really meant is that it's partially blocked. (99.9% of the time, it's the bottom portion that's clogged, where gunk and stop leak will settle.) Water from a garden hose will still come out the other end, bit it's not flowing through all of the cooling tubes, thus greatly reducing its efficiency.
The only ways to tell are by measuring temps, as previously described, or having a radiator shop remove the side tanks and visually inspect the core.

Radiators for Discos pour water in to all tubes horizontally in parallel. So water in one side will flow out other side if just one or two tubes are left open.