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Posted by David Sherman [24.32.202.83] on Monday, December 21, 2009 at 14:05:31 :
In Reply to: Water Pump Pressure posted by frostysnoman [198.178.8.81] on Monday, December 21, 2009 at 10:28:13 :
The pump doesn't make the pressure you feel in the lines when the engine is hot. That pressure comes from the heat of the water. In a system that's working perfectly, the upper hose still feels soft until the pressure builds up. If the pump is not working, the water in the engine will get boiling hot, which will make so much pressure in the system that the cap will open and release the excess steam.
Also, what do you mean by "overheating"? Do you mean the temperature gauge is pegged, or do you mean steam's coming out from under the hood? What I'm getting at with all this is that if the radiator cap isn't sealing, or there's some other leak in the system, it'll never get pressurized, and so the hose will always feel soft, and when the engine does get up to operating temperature, the coolant (at normal temperature) will exit through the leak or the non-sealing cap. A pressurized system runs at above atmospheric pressure in order to raise the boiling point of the coolant, which allows the engine to run hotter and more efficiently.
Every time I've thought that the water pump must not be pumping, I took it off and it was fine, and the problem was something else. Check out all the other suggestions too -- look for clogged tubes in the radiator, and feel it for cold spots (on the front side) with the engine hot. The real clue in your problem, though, is that you're not feeling any pressure in the lines. There are a lot of things that can cause overheating, but they all result in plenty of pressure in the system. Look to see where the coolant is coming out from when it's hot. That, I think, will point you towards the real problem.
One last thing, if no coolant is coming out anywhere and there's no pressure in the lines, and your only clue that it's overheating is that the temperature gauge says so, then the gauge/sender has to be bad.
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