Is 250 too hot?

[Cheaper Jeeper]

I just got back from a 600 mile round trip towing my Jeep over the mountains between here and Spokane Washington. Going over the mountians the engine temp got up to 230 degrees several times and even as high as 245-250 for short periods a couple of times according to the mechanical guage installed by the PO.

The cooling system seemed to handle it OK. Didn't develop enough pressure to blow any water from under the radiator cap or anything. Still seems pretty high to me though. Is this likely to do damage? Any suggestions?

 

[SKimballC]

Ooh, man, I hit 250 in my old truck when subzero temps in Colorado froze the coolant, and coolant boiled over and the engine developed some bad problems not very long after. I don't know how relevant that is but I do know 250 is TOO high period.

 

[Cheaper Jeeper]

Yeah, that's what I was thinking, but I'm wondering if the guage might be wrong too....

 

[RLDSL]

What pressure cap do you have on the radiator? If it's a 15 pounder, you should be OK ( boiling point around 255 ) a 13 pounder and you were probably boiling and getting hot spots ( lead to blowing head gaskets, warping etc ) a 7 pounder and 250 deg would have you in a bad place

If you were running Evans waterless coolant, 250 would be nothing to worry about, even with a zero pressure cap.

------Robert

 

[BigRigTech]

250 is kinda high, puts an awful strain on the headgaskets and etc....I would go through your cooling system and especially check your engine fan - might be a good time to pin the fan for constant airflow.

 

[Mr_Roboto]

I'm all for a hot running diesel, but even then I think 250* is too hot.

 

[Agnem]

Isn't the overtemp light supposed to come on at 242 degrees?

 

[Jim73]

Isn't the overtemp light supposed to come on at 242 degrees?

My thought also!

Possibly a.) The gauge is reading high (hope so!), or,

b.) the overtemp switch or light is dead.

Guess knowing how accurate the gauge is would be nice for your peace of mind.

I'v struggled with cooling issues as well - in sort of a stand down now, but exploring options. Best of luck. You're in the right place for good advice!

 

[Cheaper Jeeper]

What pressure cap do you have on the radiator? If it's a 15 pounder, you should be OK ( boiling point around 255 ) a 13 pounder and you were probably boiling and getting hot spots ( lead to blowing head gaskets, warping etc ) a 7 pounder and 250 deg would have you in a bad place

If you were running Evans waterless coolant, 250 would be nothing to worry about, even with a zero pressure cap.

------Robert

Not sure I'll have to check. Suppose it is 13 pounds. Does the fact that it wasn't blowing any water out from under the cap (or even into the overflow for that matter) mean anything in terms of the problems you described? In other words, will the coolant actually boil and allow hot spots develop, without it pushing any water out of the radiator?

 

[Cheaper Jeeper]

Isn't the overtemp light supposed to come on at 242 degrees?

Yeah, the light came on once. It got scary hot twice - once the guage said 250-255 and that's when the light came on. The second time it was only about 245-250 and the light didn't even come on....

 

[RLDSL]

Not sure I'll have to check. Suppose it is 13 pounds. Does the fact that it wasn't blowing any water out from under the cap (or even into the overflow for that matter) mean anything in terms of the problems you described? In other words, will the coolant actually boil and allow hot spots develop, without it pushing any water out of the radiator?

If it were boiling it should have been pushing it out into the bottle, unless the level is down a couple of inches below the top of the radiator, then it might not. Also, if you're coolant was mixed closer to 70/30, you may not have boiled.

Of course, if you blow the head gasket, the pressure may have gone there

---------Robert

 

[Diesel JD]

Gauge might be reading a couple degrees too high...you could check its accuracy by pulling out the sender and putting the probe in a pot of boiling or near boiling water of a temperature measured by and infrared thermometer or good kitchen thermometer and check the two readings in the dash and on thermometer against each other...just an off the wall thought.

 

[Cheaper Jeeper]

If it were boiling it should have been pushing it out into the bottle, unless the level is down a couple of inches below the top of the radiator, then it might not. Also, if you're coolant was mixed closer to 70/30, you may not have boiled.

Of course, if you blow the head gasket, the pressure may have gone there

---------Robert

Well, it probably is closer to 70/30 than 50/50 - based on the looks of the coolant. All this talk about radiator caps and boiling point made me curious so I went and checked it. It says it is rated at 13 psi. From what I've read 1 psi pressure will raise the boiling point between 2.5 and 3 degrees. So a 13 psi pressure cap should raise the boiling point to between 245 and 251 based on those figures.

Given the fact that the temp light is supposed to come on at 242 degrees, and the temp guage was showing above 250 the only time the light came on, PLUS the fact that it didn't push any water out from under the cap, I'm thinking the temp guage must be reading about 10 degrees higher than the actual temp - at least when its at the upper end of the scale.

I'm still gonna' swap fan clutches and see what that gets me though....

 

[jauguston]

Do you hear the fan clutch engage? There is no doubt when it kicks in, the fan is quite loud. You couldn't miss it.

Jim

 

[Cheaper Jeeper]

Quick update on this. I swapped fan clutches and VIOLA' no more overheating isues. Towed with it on Sunday and never got above 210 on the guage...