Overheating AFTER engine stops...

[wkumale]

I have a 1999 Cherokee Sport 4x4 with the 4.0 with 180,000 miles on it.

I bought this off of a guy that said he parked it one day then went toward his house to ope his door and then heard water pouring out of this jeep. He parked it for a month and did nothing and then sold it to me. I towed it home, Put water in it and saw the upper rad hose had a small needle size hole in it and so i changed it out. I drove it all day long watching the temp guage and everything was fine. I pulled into auto zone to get an O2 sensor for it and when i came out there was water everywhere. Oh yeah, When i pulled into Auto Zone I saw the temp guage was just under the 210 mark. Anyways, the auto zone guy gave me some water and i ran it to see if i could see where it was coming from. Neither one of us could see anything leaking. When we opened the radiator cap we did notice that the radiator had a some dirty looking gunk in it. Rust I believe???????? The auto zone guy said i did need a need a new radiator cap and i bought it and went home thinking maybe it was fixed????? Then when I pulled home and turned it off I noticed it was leaking. After inspecting it, I noticed the LOWER rad hose had the same type of needle size hole and water was coming out of it. It was not pouring out but it did have a lot of pressure behind it. Soooo, thats where i am at now... In the morning I am going to flush and back flush and repeat the flushing process until its clean. I bought a flush kit and some type of flush liquid that suppose to help... Also i will obviously be putting on a new lower rad hose.

NOW here are a few questions I have and please forgive me if they are totally stupid.

1. Am i starting at the right place by flushing it first? I know it needs it but i mean for figuring this problem out....

2. Could a clogged radiator cause this alone? Or am i looking at something else?

3. I read a few posts about a open and closed system? What is this and do i need to convert?

4. Why does it do this AFTER the engine shuts off. I had it running all day long showing off my new jeep to friends and then when its shut off it starts leaking?

5. Is it possible that the old radiator cap could of caused or at least contributed to this happening?

6. Any possibility this is related to the water pump or thermostat?

Thanks in advance.
TJ

[2000izusu]

water pumps can leak when off but not when running, and they are cheap to replace! i just replaced one on a 97 xj for 25 dollars and 2 hours of my time.

i would replace the thermostat just because you are already in that area working.

but in reality my next step would be a pressure test. you can rent the pressure tester at autozone or other big box part stores! pump it up to 16 pounds and see if it looses any pressure, and when it does then go find the leak! most likely it will be your water pump.

also i would consider a full flush and maybe even a new radiator!

also the closed system does not apply to you. you have the better open system which means your radiator cap is on the radiator and not on a plastic bottle on the passenger side fire wall! mike

[denisond3]

I have never found that flushing a system made much of a difference, but it wont hurt anything. If your system didnt have enough antifreeze in it, there would be more boiling after you had shut it down; compared with the amount of boiling if the coolant was a 50% mixture of water and antifreeze. Lots of time with a leak, only water is added, and the percentage of ethylene glycol decreases as only water is added. That would be more likely if the prior owner had plans to sell the vehicle anyway.
If the radiator is original, or hasnt been changed in ten years or so - then a new radiator wont be a waste of money.
I agree with doing a pressure test on the system too.

[wkumale]

Thansk guys I will post results after i do each suggestion... I am finishing do a flush right now... It says i have to run the motor for 6 hours then flush it out.. I should have this done by monday... Then i am changing the thermostat just to know that i have a good one installed. I will keep you informed of the progress... Thanks again for all help.
TJ