I've got a weird overheating problem with my daughters jeep. I've replaced the thermostat, flushed, and burped the car (it's a 4.0). It only overheats in the winter, and this year she lost the heater. It still blows just not hot. So the question is, is this the core? or is it something else?

 

Now is the time where things start to get verified but jumping to any conclusions, or straight to the core. THere are many threads about this very topic. Start with the simple stuff. You have already replaced the T-stat and flushed the system. When you flushed it, were you on hand to witness the clarity of what came out of the cooling system? Was it mucky w/clumps or was it clear? Are you sure you are getting hot coolant to the heater core when the vehicle is in operation? Grab the heater core hoses before the car gets to full operating temp, just as the temp gauge needle begins to move is a good time.

When it's overheating, do you notice the overflow tank bubbling? If the gauge says its over heating but no bubbling then i would check the temp sender in the T-stat housing. Is the electric fan working?

This is a very common thread topic, if you do a search you will surely find that others have this same problem. Search and see what their resolutions were.

Good Luck

 

When you did the coolant flush did you take the hoses off the heater core and flush it out. You can also check to see if your heater core is clogged, get the engine warm and turn the heat to high, touch one of the hoses going into the heater core and feel if its warm then touch the other one, it should be about the same temp. If one is hot and the other cold then you have a clogged heater core. Warning heater hoses can be hot so be careful when you grab them

 

Well said, GI!

 

My heater also failed this winter.

I removed the heater hoses and back flushed the core with a garden hose. Brown gook came out and my heater began to work again.

GI nailed it with his post.

Make certain that your sending unit hasn't failed. Compared to other problems, this is probably the cheapest and easiest "fix" considering the other things that you have done at this point.

 

when i flushed the system it was tan but no chunks of rust. I replaced the fan last year but i guess it could be bad again. Yes it bubbles up, and i have to add water/antifreeze mix (i mix my own) to top it off. I'll look at the sending unit * wonders where he put his multimeter*. and thanks for the help

 

Whoa!!! You said you have to top off the Coolant Overflow Tank? How often do you have to top it off? You shouldn't have to refill this more than once, maybe twice tops after a flush and a refill. Otherwise you have a leak, maybe a cracked head or blown head gasket to where the coolant is leaking internally.

I would also try to do a coolant system pressure test.

 

thanks for the help guys! Maybe i should be clearer here, it bubbles over when it overheats, and i have to add coolant. Sorry about the delay in this reply, it's our Christmas so we've been very busy and scattered. Because of snow i won't be able to get to the jeep till tomorrow or the day after and then i will check the heater hose.