Replaced the water pump and thermostat on my 03 GMC Yukon the other day and now the temperature on the gauge only goes to about 185. Before it would go near 210. The coolant in the reservoir remains at the full/cold mark. This is bad, right? I've read that there may be air trapped in the system. If this is the case, how do I get it out on this particular vehicle?
2003 Yukon 4.8L - water pump replaced, now low temp reading
- Thread starter ajscala
- Start date
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strutaeng
Full Access Member
Maybe you bought a thermostat with a lower temperature? They'll usually ask if the parts counter guy is paying attention and there are different options.
In my experience, trapped air is almost never an issue on these engines the way the steam vents and of the coolant hoses work.
Actually, the opposite happens if you have trapped air: you get hot temperature readings.
In my experience, trapped air is almost never an issue on these engines the way the steam vents and of the coolant hoses work.
Actually, the opposite happens if you have trapped air: you get hot temperature readings.
I read before about some kind of flow restrictor in the return hose to the overflow tank. If it is missing that would cause something this. Do not know if that applies to this vehicle or situation. Just throwing it out there.
180 seems better than before? I'd just get a new thermostat that is a 190F and see what it does. Have you checked the upper and lower hose with an IR gun to see what the delta is? If your lower hose is close in temp to the upper hose, then you have bypassing. If it's a large spread, especially in cooler weather, you're probably OK.
If you didn't replace anything but the pump and t-stat, I'd focus on that before looking at other things.
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rockola1971
Full Access Member
You didnt end up with a highly efficient water pump that none of us have..... Its your thermostat and its the wrong one. The opening temp is stamped right on the flange of the thermostat. Check your old one if you still have it. Otherwise lookup what yours takes and make sure you have that value.
I took the new one back to the store. Sure enough it was the wrong one! The guy must have put 5.3l motor not 4.8 or something. They gave me the correct one and I just installed it and it is working properly. Glad it was something simple. Thank you all.
