New Twist to Overheating

**RowJ** · 07-05-2010, 05:33 PM

Search for quite a while and found nothing similar....and I'm stumped!

98 TJ new to me and split the bottom radiator hose. Coolant was loaded with rusty debris and appeared to be factory fill .
130,000 miles , so I decided on new T-Stat.... new H2O pump....new temp sensor.... new radiator... new cap
Also new AP985 Autolite plugs.

TJ runs great and I've driven it for two days. but two strange things occur:
1- When I shut it off, the overflow bottle is full to the top and bubbling (or boiling). After it cools down, fluid sucks back to radiator and the level in overflow is norma1??

2 - Operation temps level off at 215*, but occasionally spike to 245*+/-..... stay there for a while... than return quickly to 215*?? Higher rpm's (over 3000) seem to hold temps at normal level of 215*??

Any seen this before (especially #1) or have any ideas?

RJ

Mousejockey · 07-05-2010, 05:39 PM

Sounds like air in the system. Did you flush out the heater core?

**RowJ** · 07-05-2010, 05:44 PM

Yes, May be some air still in system but very little, if any. Nothing like the bubbling I'm getting in the overflow??
Worried about an air leak, maybe?

RJ

**Sundowner** · 07-05-2010, 05:50 PM

Did you flush the system thoroughly after finding all of that debris?

chainbrain2002 · 07-05-2010, 05:51 PM

there shouldnt be any type of debris in the lower hose. if you have rust built up in the rad then replace the radiator. its obvously clogged up with corrosion. replace the radiator and perform a thourough flush of the coolant system including the heater core with something like bg coolant system cleaner. it works great and reduces hard water and rust buildup after a very short time. best of luck dude.

P.S. if you replace the radiator you might as well perform the flush while it is removed from the vehicle if possible that way none of the old debris makes its way into the new rad.

**RowJ** · 07-05-2010, 06:35 PM

Quote:

Originally Posted by Sundowner

Did you flush the system thoroughly after finding all of that debris?

Yup....before installing new Radiator.

Quote:

Originally Posted by chainbrain2002

.....P.S. if you replace the radiator you might as well perform the flush while it is removed from the vehicle if possible that way none of the old debris makes its way into the new rad.

.
Done and done

RJ

**pdangerp** · 07-05-2010, 06:39 PM

How is your fan clutch? If you're having trouble maintaining temp, it may also contribute.

**RowJ** · 07-05-2010, 06:43 PM

Quote:

Originally Posted by pdangerp

How is your fan clutch? If you're having trouble maintaining temp, it may also contribute.

Never has kicked in so not sure. Not sure I'm really overheating. It's not a steady climb to 245*. Jumps up on about 5 sec shich makes ne suspecy air in system....right?

RJ

**Sundowner** · 07-05-2010, 06:46 PM

Standard OEM thermostat?

jenkins_1120 · 07-05-2010, 06:49 PM

i had a similar problem i replaced everything and flushed still over heated problem was a faulty new thermostat

**wushaw** · 07-05-2010, 06:52 PM

Pressure ck the new cap just to make sure it's holding what it's suppose to hold. Change the thermostat & ck the fan clutch.

**Knuckelhead** · 07-05-2010, 06:55 PM

Quote:

Originally Posted by pdangerp

How is your fan clutch?

Quote:

Originally Posted by RowJ

Never has kicked in so not sure.

Huh???...

Cavitation · 07-05-2010, 07:05 PM

I think you may have just figured it out. Is the fan not turning? Or is it an electric fan? If you have done everything you said and the fan is working it sounds to me like exhaust in the cooling system. Bad head gasket. It sounds very similiar to a problem I had just before the gasket totally blew. The dirty coolant might be clogging the gasket up then it cools then the exhaust blows by and heats up again.

**Sundowner** · 07-05-2010, 07:13 PM

Just caught that thing about the fan clutch...that shouldn't be happening. Also, air passing the temp sensor will cause the spike, if I'm not mistaken.

**RowJ** · 07-05-2010, 08:32 PM

Quote:

Originally Posted by Sundowner

Standard OEM thermostat?

No.... NAPA! I do know better from my Dodge/Cummins P/U. Just figured on a gasser it was not as critical!

Quote:

Originally Posted by Cavitation

I think you may have just figured it out. Is the fan not turning? Or is it an electric fan? If you have done everything you said and the fan is working it sounds to me like exhaust in the cooling system. Bad head gasket.

Yes Fan turns. Just does not turn on in high speed cooling mode. Hope I'm being clear?

Exhaust in coolant would explain the high volume of bubbles in over flow bottle after shut down, but no gas smell? Will check into that scenario.
Anyone else get the quantity of bubbles?

RJ