I was going to get some gas for my tractor in th 98 RR and noticed the temp gauge was on hot and the red light was on, never saw that before.

I slowly drove home, about 8 miles, and the gauge quickly came down and the light went off.

I just changed the Thernostat in a 98 F150 about 30 days ago, so no problem I thought.

I went online to find a thermostat and only found a plastic looking devive with several ports and a bracket to mount the device to a wall.

Does the 98 RR not have a normal looking thermostat like most vehicles have?

 

No it doesn't and many have been caught out by this oversight and put a regular thermostat in where none should be!

Remember that external thermostat you can see at the bottom of the radiator opens on the return line like many newer cars these days. So when you change it you will drop the coolant from both the radiator and the block.

If you refill it from the expansion tank cap ONLY you will NOT fill the block and upon start up severely distress the engine as it won't cool. Of course!

There is a vent plug for air purge on top of the manifold near the top hose outlet, but I prefer to remove the top hose at the radiator and use it like a funnel to pour coolant into the block until its full. Then pour coolant into the expansion tank and it will fill the radiator albeit a bit slowly, due to the fact that the overflow pipe is connected to a port on the top tank. Now re-connect and fire the truck up.
With the cap off let the system normalize itself, the level will drop a bit; then top off and fit the cap. Let the engine run until it attains a normal temperature and check for leaks.
You might also want to consider cleaning the outside of the radiator with soap and water then a gentle purge with a garden hose, summer driving is coming. Range rovers love to run cool and with a well serviced cooling system.
T/V

 

I found the thermostat late last night with a flashlight.

I did notice when I pulled over yesterday as soon as I saw the temp gauge hot, I stopped and opened the hood.

The overflow was boiling inside but the uper radiator hose was not hard or under pressure. I expected the hose to be pressurized but I could squeeze it shut.

Is the fact that the upper hose was not under pressure, but boiling in the overflow a sign of a certain problem problem? There is NO water leaking out from any place, but I was able to add some water at startup after the engine cooled off.

 

Bishop
Sounds to me like typical Landroveritis the precursor to eventual head gasket failure or worse!
You are low on internal block jacket coolant.
Remember the temp gauge sender unit cannot" see" reached gas temp; only bathed hot coolant will make it react and so your gauge shot up when it got a "geyser like" gulp flood of hot coolant.

For the thermostat to open it must have hot coolant flow over the thermostat within the by pass porting which means it must flow out of the head coolant port get cooled in the radiator and then gradually rise & once the whole lot has attained threshold opening temperature open the t/stat internals. This is not happening.
You might have a plugged up radiator core restricting flow, your heater is leaking at the tube O rings, the water pump is leaking slowly, or in fact the cooling fan viscous clutch isn't working. Or in fact the t/stat needs changing which should go with a full flush at about 60,000 miles. Has it had any of this service as to forgo this type of maintenance invites cooling system issues and gasket failures .
My suggestion would be to allow it to cool. Fill it as I prescribed and do a careful road test observing the cooling system activities.
All might be well with a system service in spite of claims this engine is very sturdy--after all it was a Buick in its earlier life.
T/V

 

Last night I ordered a new thermostat and UPS should be by Friday.

That's all I can do at this point for the time being.

I flushed out and replaced the fluids yesterday and with all the levels right I slowly it the road. This time I got about 2 miles and the temp gauge quickly started rising.
As soon as it reached halfway I turned around and headed home very slowly.

Two minutes later as I reached home the gauge was in the red.
I sprayed water thru the grill and the gauge came down a bit.

If the problem is deeper than the thermostat I'll have to change my options. I can fix small things now, sinced I retired.

40 years ago I could stay up all night without sleep and take down a 400ci chevy engine and change all the moving parts, and by morning hit the starter and fire up the engine.
I can't do that any longer. I replaced the piston rings one night 35 years ago under a carport with 10 inches of snow on three sides of the truck. I had a quartz heater blowing a little heat under the truck, but I got it done.

There are a few things I can't do any more, rebuild under the hood is one one them

After the new thermostat in in I'll post the results asap...

 

Bishop
Well I hear you at 70 years old I still do in frames, but I prefer to let the young blades in my shop do the donkey work.
My Hispanic staff are the most willing to tear into the heavy stuff and do a good job!
The young white guys are "candy asses" who just want to cruise and tap keys, at my age I can run rings around them.

These days though I prefer to use the scanner and the knowledge & direct the work required, electrical and module repair is my bag but its hard on the knees/back twisting yourself into tight areas of the car/truck.

I suppose I have to take note/inspiration of an old guy I saw outside Kandahar in the 1970's. Riding a Tiger 100 out of Tehran where I lived at the time up into Ghan, my destination was Samarkand.
On the way back I stopped for some tea at a road side chai stand and watched the tea vendor's 85 year old grandfather digging a huge field to plant crops with just a spade. I was amazed at his strength and endurance cutting furrows and his young great granddaughters planting spuds and opium seedlings.

Keep on trucking and let me know how you get on.
Cheers T/V

 

The thermostat came in late today which is Monday, UPS said there was a train derailment in Ohio is the reason it didn't arrive on Friday. It's kind of like the dog ate my homework.

the RR is not much better at startup. The temp still goes up fast and the radiator is making sounds like boom, boom boom, so I shut it down.

I also picked up a new serpentine belt and I will install it tomorrow before anything else.

I filled the engine with water in the upper hose and filled the radiator at the same point.

I really don't know if it has enough water in the engine so I ran the engine added more water, restarted and added more water.

Tomorrow I'll start it cold and feel the upper hose and the lower hose until hot. I also found the two condensor fans in front do not run when it gets hot AC or not.

Do the two condensor fans reall play a dual roll, helping the AC and helping to cool the radiator?

 

Do the two condenser fans really play a dual roll, helping the AC and helping to cool the radiator? they really do, they are set to come on when the engine starts to gets hot, on a dII its 110F, dont know RR temp off hand.

 

New thernostat and new sep belt installed. I started it up and waited until the temp gauge got about halfway runing at 1800-2000 rpm, about 10 minutes.

I felt the upper radiator hose and it was hot, I felt the lower radiator hose and it was still cold to the touch.

Does that mean stopped up radiator or bad water pump?

 

Also which relay in the engine fuse box can I safely swap to check the condensor fan relay to see if it's bad.

Several relays look alike?