I pumped the cooling system up to 20psi this morning and tightened up a couple clamps that were hissing. When I got home from work this evening, it was at 19.5psi, so I believe the head gaskets are good. Not great, possibly, but at least good. I believe that the several small leaks in the cooling system allowed my coolant level to get low enough to create bubbles in the system, and this coincided with a weak water pump. When I started this thread, revving the engine would bring the temperature down, but this is no longer the case. So I think the water pump has failed, and I've ordered a new one. Hopefully that will solve my problem.

 

Water pumps do not fail on a spectrum, their only failure mode is the seal fails and then shortly thereafter the bearing fails. If you are not getting drops out of the weep hole your waterpump is fine. Your pressure test proves the HG is fine. If you are getting hot at idle then you have a stuck or bad thermostat, try removing the thermostat element completely. If you are getting hot on the highway you have a plugged radiator.

 

I tested the thermostat on the stove and it opened completely at 190. The radiator was evidently replaced by the previous owner. It's a Nissens unit with a manufacturing date of 2018, so it's not very old. Before I pull the old water pump, I'll drain the coolant and inspect the impeller. Is there any way to test the flow of coolant?

 

At this point, it sounds like either your water pump, or your radiator is giving you the problems. Sounds like you have a new water pump ordered. As much as I hate just replacing things to, replace things, that would at least rule out issues as you go. It's been a while since I've wrenched on a D2, but water pumps are not that hard to change out - other than having to redo all the coolant.

Would it be worth it to add electronic fans to the radiator, instead of using the clutch fan? Might save you .25 HP on the motor.

 

You can remove the top radiator hose and shove a garden hose in the radiator. Where does it get hot, highway, in town, or idle. Have you removed the thermostat element completely and tested it yet?

 

this is what I would do. Pull the hoses and see what the flow through is like. It shouldn’t have a ton of resistance. Another hope and pray option is to try a coolant flush and see if anything interesting comes out.

 

It's only ever gotten hot sitting still, but I haven't driven it anywhere for a while to avoid killing it. Yes, I've taken the thermostat out of the housing and tested it on the stove. It opens fully at 190. A coolant flush seems like a sensible idea. I took the fan off and inspected the water pump. There's no evidence of weeping or leakage. It got dark before I could take the belt off to test the bearing. My neighbor who's a retired mechanic thinks my fan clutch could be bad because we were able to stop it with a rolled up newspaper when the engine was at temperature. At this point, I'm leaning toward just replacing the pump and the clutch as part of a 20 year renewal.

 

The point of removing the thermostat element is not to test it on the stove, the point was to run the engine without it installed. If it gets how without it installed at idle but not on the highway then you know your clutch fan is bad. However your mechanic friends test is also valid. Either way you found your problem.

 

Ok, I understand. Yes, it still gets hot without the thermostat. I'll replace the clutch and post the results in the next few days.

 

Just an fyi but you can save some money and get a Chevy fan clutch / fan.

https://landroverforums.com/forum/di...n-33724/page2/