af908

Already replaced the thermostat, I guess this is pretty straight forward to assume but it must be the water pump right? If it is the water pump the blades or bearing must have completely broke off all of the sudden thought because the temp gauge rises quick!! Hence why i thought it was the thermostat.

Is there anyway to test to make sure its the water pump before i pull it apart.

Once it gets to 210 its up to 265 in a matter of 30 seconds.


its a 2001 jeep grand cherokee larado

dave1123

Take the thermostat out, start it with the radiator cap off, and check the flow. Could be a lower hose collapsed internally or a plugged radiator. Water pumps don't shed impellers without a lot of noise. You didn't say what engine you've got. On the 4.0 you can get an air blockage on a refill. Take the guage sender out and fill it up till it runs out, then reinstall and top it off.

af908

Thanks, Yes i have the 4.0

Its strange because i didnt refill the coolant for this to happen, I refilled the coolant AFTER it overheated. Could you explain what you mean by taking the guage sender out?

Also, is there any easier way to test the water pump besides removing the thermostat again? I was thinking of taking the smaller hose from the top of the thermostat housing off from the HEATER core side and letting it drain into a bucket. I would assume she would pump plenty of water outta there to at least give me an idea even though the thermostat would be closed

dave1123

Yes, your idea about the heater hose is good. Why didn't I think of that? Duh! The guage sender is on the thermostat housing. By taking it out, you allow air to exit the engine that won't because the thermostat is closed.

Just thinking. There is no backing on the water pump on the 4.0. There is a big hole in the block and you can see the first cylinder barrel inside. My last water pump from NAPA was assembled incorrectly and jammed against the cylinder and wouldn't turn. The replacement I got only had a difference of 1/16 inch. That's how much clearance there is between the impeller and the cylinder barrel! It's possible a plastic impeller could shatter if it came loose.

Check out your flow and get back to me.

Old retired gearhead.

dave1123

Also, if you wind up replacing the water pump, be sure you get the right one! The one with V-belts drives in the opposite direction than the one with a surpentine.

Sickzj

Could also be your coolant temp sensor thats what happend on my 5.2l

af908

Thanks guys,

For all that were curious it WAS the water pump. WHen i took it off there was absolutely nothing left of the plastic impeller. Scares me a bit because i wonder where all the rest of the plastic that broke off ended up.
Thanks for the help

dave1123

The bits and pieces are probably in the bottom of the block, which shouldn't be a problem unless small pieces plug up passages into the head.

Good luck with that.

freegdr

this applys to closed cooling systems only

freegdr

either in block or radiator i would run garden hose in ever hole possible try flush it out plastic dont just go away heater core hoses also

dave1123

My waterpump had a metal impeller. The replacement I bought at NAPA was also metal. The reason I replaced it was the bearings were shot. I could move the fan blade about 1/2 inch and it still wasn't leaking, if you can imagine that! It was rattling though, and the cylinder barrel had a shiny mark on it. It still wasn't overheating.