I just took my Jeep on about a 3 hours trip temp was fine for for most of it even in traffic
but when I turned off the hwy the Jeep started overheating. It went from 210 to 240 then to 260. I shut it off and looked under the hood the previously empty overflow bottle was soo full colorant was coming out of the vent on the top and the top radiator hose seemed puffed up. It seemed to cool off quite quick for as hot as it got when it was off. I rushed it home and it just got hot agin like the Tstat wasn’t opening. I waited for it to cool down and replaced radiator cap and Tstat then put about a gallon of coolant back in the radiator. When I went for a test drive it overheated just like last time and I noticed the lower radiator hose collapse as it cooled down. I checked the oil and it wasn’t cloudy Like coolant was in it. What could it be bad water pump, clogged coolant passages in the engine, clogged radiator, blown head gasket?

 

First thought was a bad cap, but you replaced it. Next guess would be the radiator needs a good flushing. Flush it all and see if it improves any. And how old is everything, aside from what you replaced already?

 

Could be a number of things:

1) Could be clogged radiator, but not likely to clog all at once.
2) Could be a flacid lower radiator hose (maybe the spring just rusted out or moved) and it's sucking in while ya drive (seen it happen)
3) Fan not cooling -- still not that likely
4) Water pump impeller gets warm ...expands and free-wheels on the shaft (seen that happen too)

When you run it, and sniff in the coolant bottle, can you smell combustion gasses? Or see bubbles when ya give some throttle?
Look under the oil cap for a milky substance
Water/air sound in the heater core for a while
High pressure on the upper radiator hose once it warms up
Those are all signs of combustion gasses getting into the coolant, probably by a bad head gasket.

Remove the spark plugs out and look at them. See if you have one that looks like it was steam-cleaned.

 

To add on to what JeepWalker said, on #4, I've HAD a fairly new water pump with a plastic impeller just shear the damn impeller clean off. So the shaft spun fine, but the impeller was stagnant. No bearing noise, no weep-hole leaking, but because the coolant wasn't being pumped, it overheated REAL fast. (I actually replaced it on the side of the highway 1000 miles from home. Not fun.)

 

Did you notice the impeller was plastic when you installed it? I think I would of sent it back and bought one that was not plastic unless of course was in dire need then you got to do what you got to do..

 

I did notice at the time but didn't think anything of it since I trusted that the engineers who designed it knew what they were doing.
Of course, I would never have expected it to shear clean off like that - it was only moving fluid. It also wasn't all that old.
Now I won't use a plastic impeller WP if I can avoid it, but I'm also a bit older and a lot more knowledgeable about DIY auto repair than I was back then.

 

What year of Jeep?

 

If you can't determine what the cause is you might check this out. You never know.

 

The Jeep is a 2000 i have aluminum radiator at home As far as I know everything on the cooling system is original except for the parts I replaced. If it was a head gasket wouldn’t the oil look cloudy I just changed it a little over a month ago and it still looked like new if it was a bad water pump would the water still be in the top radiator hose ? Would the hose suck close when it was cooling off I know the spring was their when I last changed the coolant could it have sucked in to the engine and caused the problem. I have a new radiator at home so I might just change that with the hoses and give everything a good flush. Would it be worth doing the water pump too while I have it out? If it is the head or head gasket the jeeps probably totaled as it was also flooded this spring.

 

2000 and 2001 models have the 331 head that is know for cracking, and causing the problems your having, that might be your issue.

 

Have you been hearing a 'whooshing' sound in your heater core in the mornings? Like air and water running through it?

Look under your oil fill cap. It tells a story. Remove it and flip it over ...does it look milky under there? A bad head gasket can live 'bad' for 2 years before they finally 'go'. Then one day Pufff ...white smoke. Sometimes the oil gets milky not always.

Plastic expands more than steel when it gets warm. If it's just pressed on, even if you removed it it might feel tight and normal, but when it gets hot it could slip on the shaft. My brother had just that happening once ..but his was a metal impeller. It's a hard one to de-bug when it happens. Take off the EGR and see if it's all clogged up back there. Clean the carbon out. That doesn't help either (although not likely to be your sole problem if it is clogged up)

 

theres nothing on the oil cap ,the oil isn’t cloudy and I don’t see any white smoke out of the exhaust. I don’t hear anything thing in the heater core either. I stuck the overflow tube into a jug of water and it didn’t bubble right away but started to when it got warmer but I think it was some water flowing out of the overflow tube as it was spitting water out when I puled the tube out. The top radiator hose looked balloned up but I think it might just be because the hose got hot and it’s old and degrading. Also it doesn’t seam like it overheats when it’s idling i

 

when you talk about pulling the egr do you mean pulling the cat would a clogged cat cause an overheating problem? The water pump dose make some noise when it’s running and the pully Looks very shiny to.