Hate to do it, but started yet another thread on this topic. I've been reading almost every post on every forum, and followed every piece of advice I could find, but nothing seems to have worked yet.

So, I'm hoping someone can give me new ideas on what to try. Here's the info on my truck:

2003 Disco II, HSE7
Just turned 90k miles
Has Motorad 180 degree thermostat, only a few months old.
Just replaced water pump due to leaky gasket
No coolant leaks since the water pump replacement
AC not blowing cold (not sure if it's relevant, but could be)
Ran 5w-40 synthetic oil over the winter, haven't changed it yet.

Truck runs pretty well, temps are around 197 on flat highway, 190-194 coasting downhill, 201 under light acceleration

At idle, not moving, temp will slowly climb up to 205-206. Will drop quickly down to 195-197 if I turn on the heater.

Under load (passing, up a steep hill, etc), temps will go up to 205-207 pretty quickly, then level off and drop back down once I back off the gas pedal.

So far I've tried:
Flush/Bleed coolant system - Used Prestone flush, ran it in the motor for 3 days, drained, rinsed, repeat. Inspected the radiator with a scope, it's squeaky clean on the inside.

Swapped out the VC fan & clutch for a known good unit.

New-ish 180 degree Motorad thermostat. (Problem started a few months after the thermostat, so I wouldn't rule out a bad thermostat. Just seems unlikely)

I'm running 5w-40 synthetic in it. The problem seemed to appear shortly after the oil change, though not exactly sure when since my wife had the oil change done and was driving it for a few weeks while I was deployed.

I thought it might be the AC Condenser fan not kicking on (since the AC was never really cold), but fan checks out. All fuses and relays are good. I actually hot-wired the fan today to run continuously and see if that would help. Not really. Changed by a degree or two, but still running hotter than it used to.


I appreciate any/all input. Thanks guys.

-Tim

 

Possibilities
- crud blocking your flow of coolant in the core
- crud blocking the flow of air ( like leaves and dirt wedged behind condenser)
- stat not opening properly
- air in system

You can test the stat with a thermometer and pot of water
You can blow/spray out the radiator fins
You can bleed the system
You can replace the radiator

 

I would not call it overheating under 212F+, even with a 180F thermostat.
Check you are not misleading yourself comparing summerish ambient temperatures with previous winterish ambient. Would explain "running hotter than it used to" if the 'used to' was winter when parts were replaced.
A 180F thermostat does not mean it will not go above 180F. 180F is the temperature when it will send coolant to the radiator.

 

Yeah, when I removed the radiator, I made sure all of the fins were clean. Used the hose and sprayed through both sides to get all of the junk out.

This is my 3rd rover over the past few years, currently have 2 of them. This one runs the hottest out of all of them. I know 207-ish is not horrible, but it's not great either. Today the temp outside was in the 50's and raining, relatively cool day. Hot weather hasn't even hit us yet. Last year, even in 80+ degrees, it wasn't running this warm. Just want to head off any issues before they become major problems.

I will probably pull the t-stat and check it, just to be safe. If it's sticking, a $30 part is better than having to do head gaskets down the road.

Guess I'm just a little paranoid. The 2nd Disco is currently down because of that, can't afford to have two down at the same time.

Thanks again for the input.

-Tim

 

i would replace the MOTORAD 180 with land rover t-stat,
i have new one that will not open even at 210

 

^^ +2

Swap the Motorad out for the genuine LR grey 180° stat... you should see a 10 degree drop in your temps.

 

x3 on the LR 180 t/stat

 

Sorry if I missed it in any of the posts above, but have you checked out your fan clutch? Just a thought.

 

Sounds like replacing the Tstat is a good place to start. I know there was a modification of adding a hole to the thermostat to help with getting rid of the air bubble that is a good idea. did that to mine and no problems.

I replaced my thermostat just as a precaution when I started reading about the effects of overheating my D1. I keep an eye on the temp gauge, and have a list of options, one being scangaugeII which wold give me a temp readout as one of the multiple options for it. Have a ScangaugeII on my other car and I love it!

 

unless you have replaced the thermostat with an in-line style; there is no need to drill a hole. spend the money and buy a genuine LR TD5 t-stat