Jaxhome

Starting up a freshly rebuilt '65 327 in my 60 Vette. Engine continues to blow water pump lower hose after it heats up. This water pump outlet is totally smooth with no lip at the end. Tried double clamping the hose. Tried running without the cap and after a few minutes it starts overflowing. Did a test to see if combustion gasses were coming out of the radiator (thinking head gasket) but not the problem. This engine ran fine before the rebuild. Also has a new radiator.

JohnZ

Sounds like there's a blockage somewhere - the lower hose on the water pump is the INLET, and is not under pressure with the cap off - even with the cap on, at highway speed, it creates enough suction to collapse a weak lower hose. Did you change the water pump? If it's a late-model pump, it may be a reverse-rotation model (made for serpentine belt usage), which would explain why you have pressure instead of suction at the inlet; can't come up with any other explanation for why you're seeing pressure at that point.

andy60

Hello,

Could you have left a shop towel in the radiator?

Andy

simard

Make sure that the portion of the water pump that the lower radiator hose covers is FREE of paint. My experience is that antifreeze dissolves the engine paint and makes an excellent hose lubricant. I lost a few gallons of antifreeze that way before I learned. The next time my waterpump is off, I'm going to rebuild the 'ridge' around the lower hose connection with solder.

pittsaj

Seems strange to be blowing off the bottom hose, That is the suction side of the pump..
Almost sounds like the pump rotating backwards and forcing the therostat shut..
Just a thought...

Tony