I'm having some coolant problems. Recently a coolant hose on the side of the block, right next to the oil pressure switch started leaking and it eventually tore off while on the freeway. The temp when way up and I stopped the car and pulled over and fixed the problem. I ran the car for about 2 weeks after that and then my temp all of a sudden rises. I replaced the cap with an OEM one and before I replaced it I checked to see if I had the 'dreaded' bubbles in my system, and I let the car run until normal operating temp and no bubbles were coming out.

I looked for other possibilities and found a test to check if the water pump was faulty. I turned the car on from cold and let it warm up and then I pinched the uppper radiator hose and it was very hard and I felt now change, not even a slight surge in pressure as I released it. So this led me to believe my thermostat was not opening. So I also replaced that with an OEM one and still does the same thing. After I shut the car off I can hear boiling by the thermostat housing. Some water going back into my overflow tank. I might have an airpocket since that last hose tore open and made me leak a lot of coolant, because all I did was just top off the anti freeze. So I'm wondering if it could be a bad water pump? Does anyone have any symptoms/observations they have seen from personal experience?

I could be wrong but I think it could be the water pump because when I turn the car on and let it sit there and temp does not go up at all over normal. Not until I drive the car is it that the temp rises above normal, and I give it a nice rev and temp comes back down (not even sure if I should have done that). So im thinking maybe the pump fins/rudders are so corroded that they are getting stuck and causing the water to stay above right where the thermostat housing is. I bought the car a few years back and the original owner said the pump was replaced but to tell you the truth it might have been replaced with a used one , because the motor looks spotless no grease/oil no leaks nothing and the pump looks really old and rusty.

BTW: The car is an 89 Gtu.

Thanks in advance...

 

I read everything...

Make sure you are using an OEM thermostat
The normal operating temp on an s5 is 1/2 way up the temp gauge
Unless you paint the water pump housing when you by a rebuild or new one it will rust in no time..Its bare cast iron.

 

Yeah its always been halfway up and it stays there when its not rolling. Once I get it moving the temp moves up after like 5-8 mins of driving... anyone? Water pump and maybe air pocket? Something?...

 

http://www.aaroncake.net/rx-7/cooling.htm