Hello everybody,

Going home from a BIG servicing project that included an engine replacement, the car ran ok for a while, then the temperature starting climbing up after about 5 min. Within a min, tithe red light came on and I pulled over. Let the car cool down to normal temp, started ok, but then did the same within a min. All pipes are nice and pressurized, and the cooling fans were working hard. Tried to rotate the water pump under the belt and there was minimal slipping between the belt and pump pulley. Before installing the new engine (used), I checked the water pump and it rotated smoothly and freely. I guess there's a blockage somewhere? What's going on??

 

I should add that after the replacement I drove around for a couple of days trying to sort out various electrical issues, no overheating..

 

If your coolant reservoir is not low there are two common possibilities. The thermostat may be stuck closed, or the water pump vanes have failed.

You are at serious risk of losing that engine by allowing it to overheat. The temp. gauge is really more of a idiot light, in that it registers mid scale until the temp. reaches about 235 F and the suddenly climbs. Do not drive the car until you have resolved the problem.

 

Thank you RJ273, I'm parked roadside and happen to have some equipment with me. I'll remove the thermostat and see how I get along

 

The thermostat must be replaced. Unlike many other vehicles, the coolant will not be diverted to the correct passages properly if the thermostat is not present.

 

Darn... The thermostat is literally 3 days old, and overheating has just started. Ahead of reading your post WhiteXKR I took out the thermostat, reassembled the housing and tried again, overheated again within 3 min. How do we check the water pump?

 

Removed the small hose that returns coolant from the side of the thermostat assembly back to the water reservoir, nothing coming out at all. Is that an indicator that water is simply not moving? Any other way to tell?

 

I think the flow through that pipe is minimal.

These cars also have water pumps with plastic vanes that can wear or break. If the thermostat does not solve the problem, removal and inspection of the water pump would be well advised.

 

Thanks again WhiteXKR, will do and report back later today

 

So it was the pump... Loosened the thee bolts, removed the belt, moved the pulley with my hand and noted a sharp contrast to what it was like just three days earlier. The once smooth effortless spinning pulley is now rough and clunky.

Removed the pulley and undid the 5 retaining bolts, and bits of black plastic started to fall out! I happen to have an updated pump (don't ask) with the white plastic spinning bit and a single black metal gasket. Is that it for gaskets or did I lose anything in storage? Am I missing anything?

Cleaned surfaces, an ultra thin coat of silicon and I'll be ready to install the new pump in a few minutes. I'll report on progress and hopefully resolution soon!

Thank you everyone for the help

 

Problem solved!

New pump in, no big leaks (that I could see anyway), drove out for 20 min, long uphill on the way back, no problem!

Thank you everyone.

By the way, silly question; should I be worried that a plastic part from the broken pump may have escaped to cause problems later?

 

That's something I was concerned with when I bought my car. I knew the original pump had been changed, but no idea when or why. There is no way you will ever be able know for certain, but chances are good stray pieces will be caught by the radiator core with minimal risk of overheating.

It would be wise to purchase the Realgauge mod offered by Steve (whitexkr) on his website wwwthejagwrangler.com. so that you read the actual engine temp. and have the warning alarm.

 

That's good advice RJ237.. Thank you.

By the way, the first thing I did with the new pump was yo undo the hose returning coolant from the top of the thermostat tower back to the reservoir. No exactly gushing, but a nice steady stream. Before changing the pump there was nothing at all coming out. Useful diagnostic test for a faulty pump?