Jeepforum couldn't help.. temp spikes?!

[DrMoab]

By definition, steam is hotter than coolant and it will spike your temp gauge.

That isn't the issue here. I've tested mine with a scan gauge and an IR heat gun. It's a fail safe built into the computer. There are 10-20 threads on it here at least.

 

[scot4free]

http://naxja.org/forum/showthread.php?t=1103864

Just solved my temp spike/gauge issues moments ago.

 

[DrMoab]

http://naxja.org/forum/showthread.php?t=1103864

Just solved my temp spike/gauge issues moments ago.

Apples and oranges. The new jeeps and old jeeps get their temp readings in a totally different way.

 

[XJ_Goat]

http://naxja.org/forum/showthread.php?t=1103864

Just solved my temp spike/gauge issues moments ago.

Thanks man, but I dont think that is the same that I am experiencing.

 

[XJ_Goat]

--UPDATE--
I just got done changing out the water pump, and temp sensor. While I was at it I took the thermostat out put it in boiling water to make sure it was operating as it should (it is), I made sure there was a spring in the lower hose and I did a one h3ll of a flush (have you ever cleaned out the inside of your overflow bottle, mine was nasty).
That combined with the previous work of a new radiator, new hoses and a radiator cap I have replaced just about every part of my coolant system. So I just took it for a test drive and....


It didnt fix it, same damn thing is happening.

It is a little warm outside today ~85*F and at idle the jeep runs at 210*, on flat steady drives or around town it stays at 220* but once its up to temp and I go up a longer hill the temp rapidly jumps to 240-250* I pull over and after ~2-3 minutes the temp rapidly drops back down to ~215. WTF. :flamemad:


The only idea I have left is the head is cracked but I dont have any symptoms that are consistent with this. Other ideas?

Thanks.

 

[DrMoab]

Head gasket or head are two very likely possibilities

 

[HUSKYnXJnWI]

My 91' did that in 2002 in the winter. The temp guage was certainly acting weired- once to op-temp it would all of a sudden climb to 240~. WHen it began to rise it would take 2-3 seconds to go from 200-240. It was Winter, 0-30' F, going 70mph. So it didn't make sense. It was the Head/gasket. I initailly was going to swap in a rebuilt head I bought- but once I saw the cylinder walls with wear grooves- I then got a rebuilt block- long way to buying a whole rebuilt motor.

 

[HUSKYnXJnWI]

oh, 10 years later and the same jeep would "spike" (rapid movement) temps on the gauge. It would drop to 100 then pop to 200 then to 100 then to 0 then to 200- (see the range is within 'normal' range) That was the sending unit near the back of the head being dirty and oily= cleaned that up and it was good. But the gauge never would have or shouldn't have shown higher than normal temps-

 

[altrocker1]

I know you replaced the radiator cap but are you sure it was a 16lb cap. Tim is 100% right and a radiator cap that is not the right one will cause this. Its only happened to me once, but it did happen

 

[XJ_Goat]

My 91' did that in 2002 in the winter. The temp guage was certainly acting weired- once to op-temp it would all of a sudden climb to 240~. WHen it began to rise it would take 2-3 seconds to go from 200-240. It was Winter, 0-30' F, going 70mph. So it didn't make sense. It was the Head/gasket. I initailly was going to swap in a rebuilt head I bought- but once I saw the cylinder walls with wear grooves- I then got a rebuilt block- long way to buying a whole rebuilt motor.

I'm afraid that is what looking at (the head/gasket).. I really hope it stops there.

oh, 10 years later and the same jeep would "spike" (rapid movement) temps on the gauge. It would drop to 100 then pop to 200 then to 100 then to 0 then to 200- (see the range is within 'normal' range) That was the sending unit near the back of the head being dirty and oily= cleaned that up and it was good. But the gauge never would have or shouldn't have shown higher than normal temps-

That makes sense with your symptoms but mine is pretty consistent in how the temp spikes so I am doubtful of the sending unit

I know you replaced the radiator cap but are you sure it was a 16lb cap. Tim is 100% right and a radiator cap that is not the right one will cause this. Its only happened to me once, but it did happen

yes, It has a "16" stamping on it.