Sudden rush of water from the radiator

[Taylerdi]

My 1936 Rover 12 has developed a nasty habit of suddenly releasing a gush of water from the radiator cap. This occurs when the engine is just warming up , done about a mile on a gentle gradient uphill. The water level is about 2 inches below the filler cap. The event occurs well before the engine is up to temperature and does not occur every time. Peter Duffell writing in the current Freewheel seems to have had a very similar problem in Australia. Has anyone any further ideas? Is it a sticking thermostat? Thank you David Tayler.

[47p2]

It could be an air lock in the cooling system

[roverdriver]

I have had a similar problem with a P4 100 engine, so this might not be the answer, but it might help. The car in question would lose water after only about two miles of driving from cold. Top off the water and it was right for the rest of the day. I blamed the thermostat, tested it and it was not behaving properly so bought a new one.

New thermostat didn't fix the problem. Examined that thermostat to find there was no 'bleed hole' in it, so reasoned that air/steam was building up behind the thermostat and releasing when the thermo opened, pushing all the water ahead of it. I drilled a one sixteenth hole in the thermostat and refitted it. The car was much improved, but still lost water.

Pulled out the thermo again, and while checking, discovered that the by-pass from the water pump to the thermostat housing was blocked. I cleaned that out, and have had no more trouble.

My problems was obviously there mainly because of the blockage, however, the bleed hole in the thermostat certainly improved things. I do hope that is of some help,

Dane.

[Phil - Nottingham]

If not an air lock which should sort itself it is likely to be blocked full or partially waterway drillings in either head or block. Once corrosion starts buliding up they quickly block causing localised boiling round the exhasut valves. Descaling/flushing is unlikely to help but worth trying otherwise its head off