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[Marv Cowden]

I have the coolant bypass open in my water pump so it sucks a small amount of water through the hole in the water pump mount. If that is the only bypass I use, the motor will heat up, then cool down,up,down until it finally gets to a happy medium (180 degrees). I don't like it to cycle like that, can't be good for the motor. I finally cured it by connecting the hole in the top of my water pump to the coolant hole just under the thermostat housing in the intake manifold but that connection looks kinda bad under the hood. What am I doing wrong that the bypass in the mounting flange doesn't function properly or should I plug it? Come to think of it, what exactly is the purpose of the bypass hole in the water pump and block anyway?

Marvin Cowden

[acardon]

It sounds like you may have had air in the cooling system that was causeing the temp to fluctuate. Bypassing the thermostat allowed the air to escape. If it still does it after removing the hose, run it for a good while after the thermostat opens, with the cap off to let any air out. Some thermostats have small holes in them around the valve, to let the air out while filling, or you can drill a couple of 3/16" holes in it.

[Marv Cowden]

I plugged the water pump bypass hole, removed the elbow from the w/p to the intake manifold, problem solved. Many thanks to our Guru and grand Sahib of all things automotive, Don Andre.