I have a 98 disco. At idle for 5 mins or so the temp gauge starts to climb. to the top of the coolant symbol. I tested the coolant temp in the reservoir and it was around 220 degrees. When I rev the engine or start driving it comes back down to around 205 degrees. I have replaced the t-stat, hoses, fan clutch, and purged air from the cooling system. What could be the issue and what temp should the coolant be at idle in 100 degree weather?

 

Perhaps a clogged radiator or a bad wather pump. I have seen some pumps not turn at idle but when you rev the engine it starts moving. This is mostly the case with plastic impellors. A clogged radiator would not send enough coolant through until it was forced via pressure on the pump and temperature of the coolant to start flowing.
Could also be a massive air pocket in the heater core. I think I saw a post about someone having this problem.

 

Is your fan shroud intact?

My guess would be the waterpump's not pushing enough coolant, not likely airbound tho'

The DI system is more forgiving than the DII.

I believe if the rad was clogged internally, you'd get higher temps when driving.

If clogged with debris, bugs, dirt,etc you may get conditions which you describe as air is not flowing thru' fins well

It's 90 in chicago today & I'm hitting 220 in traffic w/o a/c on

luck,greg

 

Man my temp gauge does not start to move until I hit 230*F.
make sure the belt is routed correctly, then I would look into the water pump.

http://www.roverparts.com/TechTips/s...g_defender.cfm

 

Thanks for the replies. The belt is routed on the truck properly (thanks Spike for the routing). I too thought a clogged radiator would cause higher temps while driving, but this is not the case as it cools while driving.. Hate to spend another 500 on a radiator when this problem could be normal or possibly a bad water pump. No leaking on the water pump, and it spins freely with no slop with the belt off. What are normal temps for this engine when it is 100 outside (MS heat is hot) and been idling for 5-10 mins? Greg says he hits 220, so this may be the gauge? I did take the reading out of the coolant overflow with a meat thermometer but thought it should be pretty accurate one the coolant starts flowing through it. I see in the sticky that opening the coolant tank with the engine off will result in air in the radiator. How would this happen if the radiator screw is left in?

 

Let me expound on the "220" at idle,

I'm running (2) 12" electric fans, the alum shroud I fabbed blocks alot of rad if only (1) fan is running - not to mention bypass air.

Not unlike the AIRSIDE of your rad being dirty. (that's what I meant)

Your temps would go down while driving, as mine do. (I'm retired, I don't do traffic that often, tho' it only takes once, LOL)

If I did it over again, I'd make it stock, with good parts.

luck,greg

 

Do you think it is not the radiator then? I do not see any debris on the air side on the front. Tired of throwing parts at it and not fixing the problem. I hear a VERY faint sound in the heater core barely noticeable. There may be a little bit of air in the system but I have bled according to the sticky 4 times. I do not know what else to do with it.

 

Take your garden hose and rise the radiator off, both sides.
The only way to know for sure what the actual engine temp is is with a OBDII scanner that reads live engine data.
You plug it into your OBD port and drive with the scanner on and it will tell you the engine temp.
As for the meat thermometer trick, remove the plug from the top of the radiator with the engine cold, stick it in, start the truck and let it idle and watch the temp.
Do not drive it, when done checking the temp replace the plug.

Have you done a radiator flush with a cleaner?

 

The fan clutch I put in is an imperial. I can hear it roar when I accelerate but not at idle. It is spinning while running all the time even with a cold engine. I tried to spin it when hot and it feels the same tension as cold. I wonder if I need the HD fan clutch or if it is bad?

 

The fan will spin all the time no matter what, even when cold because of the friction of the spinning shaft it is on.

I would say it is bad or your radiator fins are clogged with dirt and debris and air cant flow to the clutch to heat it up and make it lock.

Take your garden hose and rinse off both the front and back of your radiator.