My 1931 coupe has to have coolant added about every 100-125 miles.
There are no leaks, but rather at highway speeds the water pump seems to be
pumping more volume to the top of the radiator than which is being drawn
back to the block. This excess is then running out of the overflow line
eventually requiring it's replacement at said intervals. The engine was
overhauled last year the block completely flushed and the radiator core
replaced at that time. The water pump I note is not stack as it has not a
stuffing box but rather employes sealed bearings and a lip seal. I did not
measure the impeller diameter but it did fit the stock hole in the head. There is
a baffle in the top tank of the radiator that prevents viewing the tops of the
tubes through the cap hole. Could this be the issue?
Is this a stock 31 coupe of an after market engine? If it is an after market engine, and you have a serpentine belt system, the radiator runs backwards. Check and make sure it is rotating in the correct direction. If it is stock, are all the holes for collect flow open and not blocked by the gaskets? How about the thermostat? Is it on upside right? Is it even working correctly? It would appear you have a blockage and causing the overflow to remove the built up coolant. Did you replace the radiator hoses? If they are old, they may be collapsing under pressure and restricting the flow of coolant.
It is a stock engine built in September 1930. The engine rotation is clockwise as viewed from the front. There is no thermostat in the circuit, and there is no blockage caused by any gaskets on the return. The hoses are new and note that this is an atmospheric pressure system.
If it is not a stock pump, just could it be pumping too much coolant through the radiator to coolant? Same as the newer engines that remove the thermostat and the coolant does not have time to cool down? Was the radiator repair/overhaul done correctly? Sometimes modern day equipment works too efficient for the older vehicles. It sounds from what you're tilling us, it is either a blockage issue or the coolant is not getting a chance to cool down. If you can employ a heat gun to find where the hottest part of the engine is, it may help pin pointing the problem. My grandpa, an old farmer, would just hit it with a hammer to fix it, but this may not be the case. Old cars may have used straight water and caused rust on the coolant journals, and now after years of care and driving, may of let go some and causing a blockage. Probably not the problem, but just guessing without looking. With no thermostat, my money would be on the rapid flow through the radiator and not allowing the coolant to cool down. Just a guess.
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