My restoration (to date !)

Cooling system stuff

The car came with no pipe work at all - although the previous owner was kind enough to leave me with a water pump. I had to work out (from those oh-so-descriptive manuals) which hose went where and what the circuit was. I eventually deciphered that the heater matrix and cooling system were two separate systems, using the same water flow. I connected it all up and, after about 5 minutes, boiling water gushed out of the header tank. After a bit of head scratching and refilling, I did it again, assuming that there was perhaps a water bubble in the system somewhere. But no - more bubbling. I disconnected the heater matrix, taking a hose directly from the header tank through to the inlet manifold. Engine boiled. Took off the water pump (4 times !!) Engine boiled each time. Replaced the thermostat. Engine boiled. I was about to put an ad. in the paper to sell the stupid car when a very helpful E-Mail came through....

It appears that the 907 engine is thermostat dependant (as below) and the previous owner had replaced the pump with the wrong thermostat. I had no way of knowing this and, were it not for the following information, I'd have given up and gone home !

Jubilant, I fixed the problem, started the engine up and....the water boiled. I kicked the car, bashed my head against a wall kicked the dog, shouted a lot, kicked the wife...and then cried when she hit me back. I was despondent.

Until a friend came round and suggested that I might have the fans wired up incorrectly. They were moving air, but he thought that they were a bit 'tame' and suggested that, as they were d/c motors and I had had to guess at a lot of the wiring, I might have come out on the wrong end of a 50/50 guess at which way the wires hooked up. Tentatively I snipped the wires, swapped them round, and started the engine.....and kissed the dog and the wife. My cooling system worked.

The normal circulation enters from the lower radiator hose to the centre of the front of the impeller. Radially outward through the impeller into the scroll housing. The back half of the scroll housing is cast into the front face of the engine block. On the right side (carb side) of the block/scroll housing there is a rectangular hole that leads into the block's water jacket. Coolant passes through there, into the block, up into the cylinder head and out into the intake manifold's water passage. A rubber hose connects that passage back to the thermostat housing.

When the engine is cold and the thermostat is closed, the coolant can't leave the engine and go to the radiator. Instead it is shunted back to the front of the impeller and recirculated.

The proper thermostat has a round disk added towards the bottom. When it's installed, the disk blocks off (partitions) the internal water discharge passage in the pump. Water leaving the impeller hits the bottom of that disk and is forced to turn 90 degrees and go through the rectangular opening that leads into the block. Water returning from the intake manifold hits the top side of the disk and a portion is diverted back to the front of the impeller and is recirculated.

With the THERMOSTAT REMOVED from the housing, there is nothing to force the water from the impeller to turn and flow through the rectangular hole and into the engine. It would rather just recirculate. Flowing water does not like to turn and it will take the path of least resistance. That does not include a 90 degree turn into the engine. When the thermostat finally opens, the water has a second alternative path through the radiator and back to the pump inlet. Most of the pump discharge water will either recirculate or go directly through the radiator. Relatively little will circulate through the engine. The engine is not sufficiently cooled and quickly overheats.

That's why it's important to never run a 907/ 910/ 912/ etc. without a thermostat installed. That little diverter disk is vital. My thermostat was 1" long in a 2" hole. The diverter disk couldn't reach where it was supposed to go !

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