Jeep Mystery Diagnosis

[Mudderoy]

Since redoing the cooling system on my 1998 Jeep Cherokee I never have running hot issues in the mornings.

This morning I glanced down at the instrument cluster and noticed I was over 210, about 1/2 way to the next line! That's 230 degrees on my rig Bubba!

78 degree air temps and 230?!?!? No way I'm making it home today. I proceeded to work, but started up the Torque app so I could monitor the coolant temp closely and precisely.

It would go down when I was moving and go up when I wasn't. At 235 and sitting still I turned the A/C off. I expected it to drop, it didn't. It went to 237, 238, 240, 242!

It held at 242 and the light was about to change.

After I got moving again it dropped to 235, 230, 222.8. After about 3 miles some stops but mostly moving I was down to 215.

Now on a nice mile long (at least) straight away with green lights I watch it drop to 206.

I have figured out what the problem is now it's your turn. What caused my Jeep to get up to 242 this morning in 78 degree air temps?

Be fair, answer without reading everyone else's post first. :P

[gary63]

I would say it was a bad clutch fan but if I remember you are running elec. fans so if that is true the fans may not be running and if they are not running blone fuse loose wire.

[Mudderoy]

I would say it was a bad clutch fan but if I remember you are running elec. fans so if that is true the fans may not be running and if they are not running blone fuse loose wire.

No I had to take the electric fans out. Matt tried them in his rig, couldn't keep it as cool. I'm running the mech/electric just like it came from the factory.

The fan clutch is new, as in less than 2 months old.

[nickyg]

Since you replaced evreything on the coolong system, It should still be new and shiny. I'm gonna go with leaking Radiator cap or maybe driving too close to the sun.

[4.3LXJ]

Electric fan coming on?

[Mudderoy]

Electric fan coming on?

After I wiggled the connection, yes! :smiley-taunt002:

[4.3LXJ]

That might have something to do with it

[xj4life2]

Thermostat stuck open would be my guess if the fan clutch is new. Stuck open it would not be holding the water in rad for cooling so it would only cool while driving. Now for the last W.A.G. would be a rad hose collapsing when not moving (pressure changes) but I have only seen that once in 37yrs.

[gary63]

something in front of the grill? if the fans and clutch an are ok. or it is you drove to close to the sun.

[Mudderoy]

something in front of the grill? if the fans and clutch an are ok. or it is you drove to close to the sun.

Grill was clear (if you don't count the 4 6" KC lights and SuperWinch)

[Carves]

I have figured out what the problem is now it's your turn. What caused my Jeep to get up to 242 this morning in 78 degree air temps?


Ohhh ... you are such a tease ... just tell us what was wrong with the damned thing .. :poke: .. :D:D


I reached into a bucketful of possible causes ... and pulled out,

... Loose fanbelt ...


Driving too close to the sun ... sounds plausible for an XJ tho .. :smiley-laughing021:

[cpttuna]

How about your temp gage is not reading correctly?

[Mudderoy]

I already answered it way up the line. I figured you guys were playing along and not reading the replies since you wanted to play.

The electric fan wasn't coming on. :P

Wiggled the wires and it came on. I moved it so it was as close to the radiator thinking the heat may have caused the issue.

[dagod16]

Maybe a blocked heater core?

[4.3LXJ]

Hehehe

[Mudderoy]

Maybe a blocked heater core?

It's new. 100% new coolant system.