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yj-guy 12-04-2010 07:12 PM

Water pump bad?
I thought I'd be real smart and place cardboard in front of the radiator in my YJ in an effort to increase the temperature of the heater. It worked. too well. I was watching the temperature closely and had to remove the cardboard after driving for just 10 to 15 minutes. The temp gage was slightly above normal when I removed the cardboard but the temp continued to climb. I quickly got it home and shut it down before the needle reached the red. There were some gurgling noises from the boiling coolant and I shined my flashlight on the water pump. There is a small hole just above the shaft on the water pump which was blowing bubbles. There was coolant leaking from somewhere and everything was wet. I had lost about 3/4 gallon of coolant. I'm not sure where from but I suspect the water pump? In the case of overheating, is it normal for the "vent hole" on the water pump to spew anything or blow bubbles? Or does that mean my pump is bad for sure?


60mg 12-04-2010 07:36 PM

Is it a 2.5 or 4.0?
In any case, make sure it's not the thermostat before you go on the pump, although at this point it sounds like you need to change it too. Just my .02 :)

scott howard 12-04-2010 08:49 PM

sounds like the thermostat stuck close and overheated causing pressure to build up and blow the seal on the water pump.
the good news is a water pump is cheap and not to hard to replace.
when you buy a thermostat make sure you get a fail safe one and this will never happen again. they cost 5 dollars more than the cheap ones.
a fail safe will open if it goes bad instead of close when they go bad like the cheap one , best 5 bucks of insurance you can buy.
and blocking off half the rad. will not hurt, never block the whole thing.

sppfields 12-04-2010 08:49 PM

Yep, bad water pump. X2 on change thermostat also.

yj-guy 12-04-2010 08:54 PM

The thermostat is opening. I'm sure of this because when I topped the radiator off, I left the radiator cap off to watch the coolant level as I reved the engine. The coolant immediately sucked down about an inch and rose back up immediately when I let of the throttle. The heater is also working so I'm getting flow throught the core. There seems to be great circulation. The reason for my overheating was the loss of nearly a gallon of coolant at which point, the heater went cold and the engine temp began rising. So I guess I should clarify my original question. I'm losing coolant from some where fast but I can't locate the leak. I read in my haynes manual that coolant leaking from the "weep hole" on the bottom of the water pump means the seal is blown. What's got me confused is, I was trying to find the leak and I saw bubbles being blown from a hole above the shaft on the water pump (not below). I'm not sure that coolant was coming from this hole or if it was simply blowing bubbles in the coolant that had leaked onto it. Does anyone know if there is supposed to be airflow through the "vent hole" or is it a sure sign of the pump needing replaced?

Thanks again

yj-guy 12-04-2010 08:57 PM

Also, I forgot to mention it's a 4.2L

I'll go ahead and replace the thermostat anyway though. That's not a bad recommendation and It's so simple to do.

scott howard 12-04-2010 09:53 PM

no the weep hole does not vent air . it is there to tell you the pump is bad before it leaves you on the side of the road or trail from a totally useless pump.

pull the dip stick and make sure your oil is not milky from a blown head gasket and filling the crank case with water.

call me if you have more questions

yj-guy 12-04-2010 10:33 PM

Thank you Scott, I'll replace the water pump and thermostat tomorrow. I'll also check the dip stick for milky looking oil.

I appreciate your help and I'll post tomorrow about what I find when I check the oil.

markharmon 12-05-2010 10:28 AM

I had a similar prob with a car. I was loosing fluid but couldn't find any leaks not even on the ground. Found blown head gasket was forcing fluid back into overflow bottle. When that filled up it was push out. The only way I found it was I noticed green drops on the bottle after I had wiped it off.

scott howard 12-05-2010 09:18 PM

No problem yj guy.
give me a call or pm if you need a fast answer on something.

chensley 12-05-2010 10:02 PM

Unscrew your radiator cap- if the water is not greenish/orangeish then your out of anti freeze...which acts as a lubricant for your water pump. Bad water pump=high temp.

yj-guy 12-05-2010 11:33 PM

Replaced thermostat with a fail-safe thermostat and replaced water pump. Problem solved. Oil is clean, dodged a bullet this time. Thanks for all your help.

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