Contour Enthusiasts Group Archives Forums General Troubleshooting Runs too hot and too cold

My 98 SVT is very slow to warm up and also runs too hot in steady highway driving. 12K miles ago the car ran really hot and I replaced the waterpump with a metal impeller one from NAPA so I don't think it's the waterpump.

Seems like something is impeding coolant flow. This doesn't sound like a fan issue, does it? I'm suspecting either the thermostat or just a random clog in the system. I also didn't change the belt on the WP when I changed it, though I don't think a faulty WP would cause the car to be slow to warm up.

Thanks for any suggestions.

What is your water to coolant mix?

Too high a concentration of coolant can cause that. There should be no more then 50% coolant.
I actually prefer only 40% coolant because water has a much better heat transfer ability.


Were all the pieces of the impellar still attached when you changed the pump?

I have the same sort of situation. Last summer I installed the napa metal impeller pump after my plastic one broke. all the peices were still there the plastic just came "unglued" from the shaft. I also installed the mustang 160 degree thermostat at that time. I have since had problems not with warm-up time but it warms up too much at idle. If I let it idle it will steadily go up to the high m to l range on the "normal" gauge. If I run the rpms up to 1500 or 2000 and hold for a minute it comes back down. Also if I am cruising at 60 or so it stayes fine. Just idle and low speed it runs warm and the fans are constantly on. it hasnt been as much of a problem in the cold weather but I want to do sometinh about it in the spring. I was trying to do some research into if the metal impeller impedes or does not flow quite as well as the plastic one. The plastic one to me seemed to have much more defined fins on it. the metal was like a sloppy cast metal with a little machining done to it. Are there any other brands that make a metal impeller pump. I would like to see if there are any differences. As far as your long warm-up time that could be a thermostat slightly week or sticking open a little.