Can a water pump work if it runs backwards

88 mustang 302.I put a front cover and water pump off 72 302 v belt my car is set up for a serptine belt so the water pump is runing backwards does it matter

Depends on the pump. Maybe, maybe not. What kinds of fins did it have on it? Did you happen to take a picture?

Yes it matters.

Instead of pumping the hot coolant out of the engine past the thermostat to cool the coolant in the radiator, the water pump will force the cold coolant out of the radiator towards the thermostat causing it to close so no coolant enters the hot engine to cool it off. Can you say "overheat"?


If the water pump is running backwards, it will not circulate the coolant and will overheat. Generally speaking, water pumps are directional, so you need to correct this problem.

Most automotive water-pumps are the centrifugal type and if spun backwards they will hardly work at all…It’s like spinning a turbine backwards. The blades just stall and splash the water around inside the pump…

The V-belt driven 302 pumps turn one way and the 5.0 serpentine pumps are made to turn the other so yes it will be a problem. Back to the drawing board.

Tester nailed the answer.

Attached is an operating diagram of a typical water pump setup. Best case, you’ll be doing what Tester described. And that ain’t good. Worst case, your pump will have spiral type impellar blades with correspondingly designed chambers and it’ll just cavitate.

Get the right pump. Oy you’ll be posting the question “my engine keeps overheating, is my engine ruined?”

usually the design of the vanes in water pump are directonal- i cant recall a water pump that didnt have directional vanes - so yes the effeciency of the water pump will suffer dramatically if the rotation of the water pump is not followed. SO, the water pump is not working to it’s full potential. and its rotation direction should be fixed asap. especially if you are in Texas

What should have been done to avoid confusion on this issue would have been for Ford to use a different bolt pattern on the water pump hub where the pulley mates.

As it is, the serpentine and V-belt pulleys will interchange and seeing as how the early and late pumps look identical except for impeller vane direction it would be easy to cross them up.

Some water pumps are ‘bi-polar’. They seem to work as well in one direction as the other. But most are designed to work in one direction only and reversing them will reduce or totally eliminate their pumping ability.

The water pump is turning the same direction as the old one did.But this one was off of a v-belt engine witch turned the other way.The fins one the old one were different than this one this one the fins are strait the old one kind of twisted.

I drove it last night about 30 miles an no problems so far i just wanted to know with it getting hotter now if i may have problems later on

Water pump test: Remove the thermostat. Reinstall the housing. Remove the upper radiator hose from the radiator. Hold the open end in a bucket and start the engine. The water should shoot out of the open hose with considerable force…An unrestricted automotive water-pump can pump a lot of water…

If you put the serpentine belt on the wrong side of the pump would it pump the correct direction?

Providing you could do it in such a manner as to still allow everything else to turn correctly, AND get the friction required on the water pump itself to keep it going, yes. I’d imagine that could be quite difficult of a redesign…far easier just to change the pump. You can get a reman W/P for as low as $20, and a new one for around $30.

If it’s working for him (and apparently it is), then let it go. While every post above has valid information, follow Caddy’s test. That’s the only way you’ll know if the pump is really putting out the volume it should…or some decent volume, anyway. The only way to know it’s truly putting out enough - and running correctly - is to replace it.

Good Lord man, a water pump for this engine is less that $100. Just get the right pump and you won;t have to worry about it.

Normally before installing a part I look it over very carefully and make sure it’s identical.

At AutoZone a reman pump is 20 bucks and new one outright is 35 so time expended swapping a used part like this is just wasted in my opinion.

It may work OK now, but not when you’re out on a hot day, going uphill in traffic, that kind of thing. And don’t trust the temperature ‘gauge’ in your car, many are now just glorified idiot lights, with three positions: cold, ok, and hot. The fact that yours reads ‘ok’ doesn’t tell you much.

Get the right pump.

mine seems to be pumping the water when cold pushes back thru the top with enough force to push the water out i just bought the truck and the pump was on it i changed the thermostat and it dd not help still runs hot on the road so it think they put the wrong pump on it 302 ford f150 1993 model i guess thats why i got it so cheap’