1999 Grand Cherokee Laredo- Heat declines when i Drive

113,000 Miles
My Grand Cherokee Laredo will warm up in the garage.
As soon as I drive it, the tem. guage will show that my engine temp goes down to around 100 degree ( likes it is when you 1st start up the car).
The only time the temp rises is when im sitting in traffic, but the moment i start to drive, the engine temp drops and i have little to no heat inthe cabin.
When im in traffic and going slow, the temp will rise and air and heat will come out fine ( i do not think its one of those actuator/panel issues)

On a routine maintenance, I took the jeep to get it looked at since my jeep was overheating. They recommended a new Thermostat ( problem ended up being that modulator that controlled the fan, not the therm.).

I took the jeep back and the Jeep dealer stated that they looked at the Therm. and it wasnt stuck. I have a feeling that it is, but please provide some feedback folks...

A) Is there an easy way to check to see if my therm. is stuck open w/ out taking it out?
B )is it hard to remove the therm and boil it to see if it opens and closes ( will i have to drain all the coolant?)
C) can it be another problem that im overlooking?

Just did a Coolant Flush so its new coolant in there and nothing was reported as clogged.

Im so pissed at my Jeep dealer and I dont know if i want to go back there ever. My warentee ran out already on the service and obviously the car and im willing to give some fixes myself.
thanks so much for your feedback!

sounds like a thermostat, possibly stuck open or leaks

Thanks for your feedback.
Any recommendations on how to check and remove the thermostat on my 99 laredo?
I don't have a repair manual...
Thanks

Follow the upper hose on the radiator to where it enters the engine block. There, where the hose is attached, you should find a housing that is bolted to the block. Under this housing is the thermostat. Easy to remove, make sure to note how the old one is attached.

Sounds like yours is stuck open, so you might see that when you take it out.

To test: put it in a pot of water, and boil it, then cool it off in cold water. It should open at about 190* or so, and close below that.

However since it [probably] has failed, just get a new one, some sealer for when you put the housing back on, and replace it.

Thanks for your feedback and I'll be checking it over the nextfew days where my in laws have a heated garage since its rediculously cold in chicago- brrrr.
As a noob question, I'm assuming I'll have the drain all of the coolant right?
There should be a drain plug under the radiator somewhere yah?
I don't want to open the housing of the therm and have coolant all over the inlaws garage- they already don't like me as it is- ha ha ha
To refill- do I just recycle the new coolant into the reserve/overflow container and let it flow from there?
Sorry for the noob question

Hey no sweat on the questions - we've all asked them at one point or another.

If you have an oil drain pan or similar, that should catch what comes out when you pull the upper hose -- there will be some, but not a whole lot that comes out.....where you would get a lot is if you took off the lower hose.

The drain should be located on the engine side of the radiator, near the bottom. On my '04 it's on the passenger side - but again you shouldn't have to drain the system.

Hi guys
Wanted to let you know that you were all right.
Them was stuck wide open.
Seems that a piece of the therm bracket somehow broke, lodging itself in the mechanism that helps close the therm.
I could immediatly tell that the therm was broke and. $15 for a new therm and gasket and the mrs. And I were enjoying heat, plug my gas milage jumped back to the low 20s mpg again.
Thanks for the support and instructions guys.
If possible, avoid that jeep stealership in shorewood IL as they said they took the housing off and everything was fine......bolts were seized on there and no clamps were obviously removed- damn stealership conned me out of some cash and put me on the wild disgnotic rollercoaster. Because they didn't do the job they were paid to do.
Thanks folks. Happy holidays

I hate it when dealers don't do the work they say they'll do.....which is why I do as much as I can myself!

Enjoy the heat....keep on Jeepin'.