rebuilt water pump runs hot

oldwoodsman

oldwoodsman

Senior Member
I rebuilt my water pump with a stainless shaft with impeller installed and replaced my fan with a aluminum one and now the engine is running hotter. The old shaft was worn and I couldn't keep it sealed. Any thoughts on why it is running hotter?
 
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I am guessing, but could the new impeller move water at a different rate than the old one? Also, the aluminum fan may let air move a at different rate too. Could you compare parts; old versus new?

You state it runs hotter; is this from a reading using a temp gauge, or some other method?

Good luck figuring it out. I am sure others can give you more info.
 
The old impeller was pitted and the corners of its the blades were chipped. I noticed the temp on the motometer and checked the engine and radiator temp with a infrared thermometer.
 
Do you have a thermostate installed? Those seem to help quite a bit.

oldwoodsman said:
The old impeller was pitted and the corners of its the blades were chipped. I noticed the temp on the motometer and checked the engine and radiator temp with a infrared thermometer.
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Was your old fan a 2 or 4 blade? You said the old impeller was chipped. Maybe it was ground down to slow the circulation rate.
 
Is this the first time you have checked with an infrared thermometer? Motometers are good for dressing up your radiator. Not very accurate when it comes to measuring temperature.
 
Joe It was a 2 blade. It's hard to tell if the impeller was chipped or ground down.
Duffy yes I checked it before and was typically around 145* to 150* now it's running about 180* to 185* I first noticed the change on the motometer though.
 
Was the temp. out side the same . Each time you measured it . My car runs 140 in the winter and 185 in the summer.
 
Mine runs between at 160 to 180. 180 mostly if I idle it for a while but cools to 170 when I drive it in 95 degree temperature. That is what my gauge reads. I don't think you have a problem.
 
I have a climb of 500' in about 2 miles to my house last week it overheated in that climb with 3 people at about 82*ambient temp going 40 mph. I hadn't seen it do that before. I'll have to do some more testing. thanks for the response.
 
This might be a long shot but check to see if your points have closed up a few thou.
If they have then that would retard the spark and it would run hotter.

John Cochran
 
thousands run a 2 blade fan with no problems. So if you replaced it with the 2 bladed fan that looks like an original and not the fan that is a flat blade the fan is not the problem. My vote is that the shaft is too long in the head and is rubbing on the boss in the head. Quick check is to add another gasket to the pump/head connection.

The impeller could be creating bubbles (cavitation) as well.

It could also be that the fan belt is too loose and the fan is moving fast enough.

If the car if driving more than 20 MPH the fan does nothing to more air through the radiator.

As another note, there are many here on the Fordbarn that have driven many miles with no fan (after breaking fan blades) with no over heaning.
 
Like Mike, I discovered that the pairing of a head to a water pump is unique to each pair. When I installed my old pump in a different head it bound. Took me a while to determine whether it was the shaft hitting the back of the head or an impeller hitting the opening around it. I painted the impeller and shaft with bright paint and refitted the pump. Spun it a few times by hand to see where the paint rubbed off and ground that area of the impeller down a bit.
You may have a binding impeller as I did, which made the pump bind and slip on the belt, or you may have a worn head with too much clearance between the head and the impeller blades, thus not moving as much water through the system. (I assume you carefully cleaned off the old gasket so you don't have two on there somehow.)
I can think of a number of ways to find the problem, as I'm sure you can, but I'd refit the old pump to see if the pump is the problem at all. Could be some rust was knocked loose when changing pumps and now the radiator is clogged. If you determine it's the new pump that is the problem you'll have to start making some measurements comparing impeller widths and the distance from the pump housing to the impeller. Could be the new impeller is not mounted on the shaft properly.
Hope you don't get frustrated, and enjoy tracking down these kinds of things. Kinda goes with owning 80-year-old cars.
 
I'd put in a 160 degree thermostat---Maybe with the new impeller, the water is going through the radumator too fast to dump the heat. The Dog agrees! AND, don't forget to drop a loose fitting, large head nail in the top of the overflow tube.
Bill W.
 
I agree with Bill. A good possibility is that the new impeller is so efficient that water passes through the system more quickly and thus not transferring enough heat through the radiator. One way to slow the rpm of both the water pump and the generator is to go to a wider fan belt. Sounds insignificant, but it made a difference on my coupe.

You said the car overheated, and I don't doubt you. However, once I spent weeks trying to get my pickup to stop over-heating on the way home. Turns out what I thought was a radiator boiling over was just water splashing out the cap because I'd overfilled the radiator.
 
check the distance off the impeller on the shaft,should be 8 and 29/64 from fan end,also did you put that tear drop washer in?
 
Thanks for all the input guys. I'll be looking into these suggestions. I did check that and the fan belt is tight, the pump doesn't seem to be binding, the points and timing are correct, the radiator seems to be clean inside and out, I tried a drain down test on the radiator and it drained in 4 seconds, the teardrop shaped washer is on the pump and in the right position. I think maybe the thermostat Bill suggested might be a option an old Ford rod guy thought that maybe the problem as they used to put a pipe with a washer welded to it in a hose to slow down the flow in the old V8 flatheads. I'll spend some time this weekend on it. thanks again for the advice.
 
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