Water pump specs

[mplafleur]

I've looked everywhere, but can't find any.

What is the rated output of the water pumps on our diesels? More specifically, the OM693.

I was messing around with the cooling system over the summer as well as yesterday and today, I've hooked up an aftermarket cooling system tester and the flow output ball doesn't even move.

I've disconnected the upper hose and looked at the output flow on the SDL at idle (and no thermostat), it is little more than a trickle. At about 2000 rpm, it's much better, but not much more than a gallon per minute in my estimation. It kind of pours out, in waves. I expected a pretty good steady flow.

I had compared this to my '85 SD, and it's no different. I have no cooling problems with the SD.

[Brian Carlton]

Originally Posted by mplafleur

I've disconnected the upper hose and looked at the output flow on the SDL at idle (and no thermostat), it is little more than a trickle.

Why should this be surprising? Without a thermostat, most of the coolant goes down the bypass and back to the pump (as if you had a cold engine).

The only way to ensure that all the flow goes to the radiator is to install a thermostat that is always "open"...........meaning the passage to the radiator is open and the passage to the bypass is closed.

[mplafleur]

That bypass is only closed off when the temperature reaches 100*C.

This means that we never have maximum flow to the radiator. For flushing and cleaning, the FSM mentions using a forcibly opened thermostat, part number 000 589 74 63 00. This closes off the bypass.

BTW: I noticed that the FSM mentions that with the newer 1.4 bar expansion tank caps, that the maximum allowable temperature is now 129*C. Wow.

My testing over the summer had the thermostat in place. I would have had no flow until I hit operating temperature and the thermostat started to open. At operating temperature, flow is not very strong. I was led to believe (by my flow tester) that normal flow rates for a car are in the order of 30 - 50 gpm. I wasn't seeing anything like this. I'd rev the engine to 3000 rpm and the meter still wouldn't budge.

An estimate that I found is 0.2 USgpm/bhp. For my engine, this would be almost 30 gpm. Now I didn't run the car at 5400 rpm to verify this. Maybe a couple of gpm at 2000 is ok, I don't know.

So the question stands, but I'll rephrase it.

Does anyone know the expected flow rate of our water pumps at operating temperature
at idle or 2-3000 rpm?

[Brian Carlton]

Originally Posted by mplafleur

My testing over the summer had the thermostat in place. I would have had no flow until I hit operating temperature and the thermostat started to open. At operating temperature, flow is not very strong.

Operating temperature at idle with no load is likely to be very close to the temperature of 87°C. Most of the coolant is still headed down the bypass and very little is going to the radiator.

Making a judgment of coolant flow under these conditions would be a mistake.

If you really need to test coolant flow, you'll have to get that special thermostat that you mentioned. With it in place, you'll be flooded with coolant via the upper hose.