Porsche Repair: 1984 944, upper radiator hose, air bubbles

Question
R&R water pump and timing belts. Car overheats, took thermostat out, top hose gets hot almost all the way to raditor bottom hose stays cold. removed raditor hoses from engine. water runs thur raditor and water runs thur engine too. We now think that the pump is not working. Whold like your input. Thanks Don

Answer
Hi Don,

If I understand you question...you're looking for a second opinion as to whether to remove the newly installed water pump... because you think it is not working.

I suppose first it would be helpful to me to know why you replaced the first water pump?  I'll assume it was leaking or squealing...or you were overheating, right?  And what was the conditon of the water you removed...pretty green or nasty brown?

Like you are probably thinking, it seems unlikely the new water pump would spin, yet not cool the engine.  If its seals aren't leaking, this is virtually impossible...unless there is blockage elsewhere...or unless there is insufficient water supply because of air bubbles.  When you refilled the water supply, you bled the system right?

Don, since you wrote, I'll assume you don't want to go through the effort of replacing that pump again...I can certainly see why.

So...here are some ideas: let's make sure its nothing else is causing the problem before you attack that pump again.  

1.  Remove and have the radiator inspected for flow/blockage issues.
2.  Remove the block's water drainplug (under the right hand manifold) and re-flush the block as best you can.
3.  Test the thermostat on your kitchen stove.
4.  Put everything back, refill the system, and be sure to let all the air bubbles out using the bleed screw located on the upper radiator hose water outlet.

That's it for the moment...let me know how you do.

Dave