RPMs up...temp down??

[twojeeps]

water pump??

 

MJ started running hot today..... was stopped at a light, temp was creeping up, but when I upped the RPMs, the temp dropped to normal.......

 

Thanks in advance

[Geonovast]

Does it do it all the time, or just that once?

 

Is your coolant full?

 

I'm thinking either you're running low on coolant or your water pump fins are bent.

[Pete M]

Is the fan shroud intact?

[twojeeps]

First time it has run hot in MONTHS.

 

Today, I let it sit for about 5 minutes running....get back in and temp gauge reads 210. Shut it down for a little while and I notice that the tank (88 MJ) looks like it wants to burst and coolant is seaping out.

 

Start it back up, temp is normal, stop at a light and temp goes back to 210. Start to go and temp drops. Next light same thing, but at the light I upped the RPMs and temp dropped to normal.

 

It does have a new radiator with-in 8 months. When I got home I alsp replaced the bottle and cap..... I bought a new one a few months ago and did not replace yet b/c I had no issue since new radiator.

 

Cannot remember if there is a fan shroud.....

 

Thought it was weird that temp was normal at higher RPMs?????

[Pete M]

higher rpms will pull more air across the radiator.

 

210* is the normal operating temp for the 4.0L

 

Coolant should NOT be leaking out of a closed system. I would address that first. :thumbsup:

[twojeeps]

higher rpms will pull more air across the radiator.

 

210* is the normal operating temp for the 4.0L

 

Coolant should NOT be leaking out of a closed system. I would address that first. :thumbsup:

 

210, really! cool then..... mine has always been at 180.

 

I put new tank/bottle on and new cap, how much coolant should I ad? half full ? full?

 

Thanks fo all the help!!

[Eagle]

water pump??

 

MJ started running hot today..... was stopped at a light, temp was creeping up, but when I upped the RPMs, the temp dropped to normal.......

 

Thanks in advance

Fan clutch. Classic symptoms.

 

I put new tank/bottle on and new cap, how much coolant should I ad? half full ? full?

Half full when cold. It's a surge tank. The coolant expands when it gets hot. You NEED that air space for the expansion. If you fill it full when cold, you'll blow up the new tank.

[twojeeps]

Thought of fan clutch, but when I tried to turn the fan by hand there was some resisitance which made me think it was ok, but I will replace it.....

 

 

Thanks for info on coolant fill

[mvusse]

Might also have been a coincidence with the thermostat opening, allowing cooler coolant from the radiator into the engine. I can see the thermostat open and close just by watching the temp gauge go up and down. It will steadily climb to almost 210, then steadily drop to almost a full line below 210 before going back up.

 

I run a 195 degree thermostat, which I believe is the correct temperature for this engine.