JackJare9455

hey fellas...

after i bought my xj and drove it home... the temp would never get over like.. 180... we are talking a 100 mile drive..

i figured the wrong thermostat was installed because the PO said they did a thermostat and i could see fresh rtv around the housing..

so i pulled it off.. bought a new thermostat and housing.. oem temperature

when i pulled it off.. i noticed a sloppy job with the rtv.. but it wasn't the worst i have seen..

i installed the new thermostat and paper gasket.. burped the system.. driven it daily for a few weeks now... and the temperature is surging..

so i figured hell.. ill try a coolant flush.. cant hurt anything and it needed to be done regardless because its a new to me vehicle.. didn't fix anything

it slowly creeps up to 210.. but right at 205ish.. and just as the heater starts to get normal (hot) she will slowly (3 seconds?) drop back down to around 180... about another 15 to 20 seconds she will creep back up again... then drop down to 180.. it does this repeatedly over and over and over again... no change in duration

i know its not a faulty gauge because i can feel the difference in the heater temperature that corresponds to the gauge.. i have a laser thermometer that I'm going to shoot the housing with just to makes sure.. but im almost positive the gauge is functioning fine..

so I am leaning towards faulty new thermostat... its a motorad premium t-stat...

I am going to try a new thermostat and see if that fixes it.. because other than that... im kind of stumped..
100,000 miles i doubt the water pump fins took a dump... and its strange the conditions changed right after a t-stat swap

Radi

That's a crappy thermostat in action. I agree with changing it. Get one from the Dealership if you can.

JackJare9455

im gonna go up there tommarro... warranty out my motorad if the stant (mopar) fixes it

Roler

Agree with Radi and stongly recommend getting an OEM one, the one with the hole in the flange. My Stant 195F thermostat tested in warming up water showed it only opened up 1-2 mm, in boiling water that was....the one I got from the dealer opened 4-5 mm at that temp.

Make sure you burp system really well. Air pockets can do strange things with your temp.
Since you are dropping the coolant again anyway, might as well back flush the heater core...to make sure thats not an additional issue....and you guys can use all the heat there atm, as I understand

djb383

When the motor is cold, have u removed the rad cap and is coolant full up in the rad neck? Is the bottle about half full motor cold? Does coolant level in the bottle rise/fall with the motor heat/cool cycles?

It is so easy to test a stat in a pot of water on the stove using a cooking thermometer and u never ever test a stat in boiling water.....it's not exposed to boiling water inside the motor.

Roler

I know this, thats why I stated 'warming (up) water'.
Since the Stant thermostat had not even started to open up at what would be operation temp (90+C), I decided to see if it would open up as temp would further increase. Even at boiling point (and yes, it would usually not be exposed to this) is had not opened up beyond 1-2 mm. Thats all. Not meant to leave the impression to chuck it in boiling water, although it won't do any harm.

djb383

The Stant stat we installed in our XJ opened a good 1/4" (about 6mm) when tested to 210.

I should have said "taking a stat at room temp and tossing it into boiling water is a no, no.......my bad. There have been numerous posts saying "I tested the stat by tossing it into boiling water"......and that rapid of a temp change will likely damage the stat's internals.

Testing like u said (warm-up) will reveal the stat's open temp along with revealing how smoothly the stat opens/closes in it's infinite number of open positions. I call it "hovering" between closed and full open.

JackJare9455

a backflush of the heatercore.. and replacing the thermostat.. seemed to have solved the problem for the most part... it still surges slightly.. but not near as bad as it did... i didnt have a chance to goto the dealer... so i just used a failsafe thermostat from motorad because we sell them at work.. ill let it go for a while and see if it improves.. might even order an oem off ebay soon..

Radi

I have a feeling you won't be happy with that, user experience here with the fail-safe's hasn't been positive. May as well get the OEM unit ordered so you have it on hand.

JackJare9455

just wanted to have something to try and see if it was a faulty thermostat to narrow down my issue... great part about working at a parts store... is i can warranty my own stuff out lol

im going to order it tonight.. im new to the 4.0... does seem to be a pattern that most people want to stick to oem stuff... no problems with that!

Kalali

That's specially important when replacing sensors and electrical components. Looks like the aftermarket crap from overseas is hit and miss.

Radi

That seems pretty true with the Thermostat, the CPS and the TPS. Those things OEM seems to work best.

rand4x4

Go to team Cherokee, They have OEM up the yeng yang. If you replace and it still does stay that hot check out your fan that was the problem with mine.