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Chevy s10 heater problems and possibly still blown head gasket

Chevy s10 heater problems and possibly still blown head gasket. I just bought the truck and the guy says he just replaced the head gasket. It ran fine except for leaking oil while driving. No smoke, no coolant loss, and idles fine. The temp dropped down to 45 degrees last night and I discovered that the heater doesn’t blow hot air and the temp gauge is always strangely low. My question is, if the head gasket was still blown would it mask the problem if he just removed the thermostat? That would explain the low temp and no hot air. I read somewhere that removing the thermostat would lessen leaks due to compression loss??

How low is “strangely low”? On a lot of newer cars and trucks, the coolant temperature gauge is highly dampened, and designed to stay on the 50% mark, and not move once the engine has warmed up. On many older models, the temperature gauge is not dampened, and will fluctuate somewhat based on load and outdoor temperature. I would say that if the gauge reads anywhere between 40% to 50%, you are doing ok.

Also, a lot of things can cause poor or no heat inside the cabin. This could be something minor such as a defective/mis-adjusted HVAC blend door or defective heater proportioning valve, or it could be something more difficult such as a plugged up heater core, or it could be an engine problem, but I doubt that because you say it’s running ok.

It should be possible for you to determine if the engine is even reaching normal operating temperature by letting it idle with the hood open, and observing whether or not the top radiator hose becomes hot, and whether or not the cooling fan eventually comes on. It is possible that there is some air in the cooling system, which can prevent the coolant from flowing properly, and result in an incorrect temperature gauge reading.

First step: replace the thermostat. Use one with the temperature rating recommended for your vehicle.


I don’t know which engine you have but in my V6 TBI S10, the thermostat is very easy to change. I would think you’d still be getting warm air out of the heater with no thermostat. It could be just an issue with the heater controls or the heater core may be clogged. I’ve had to change mine twice when it leaked.

Thanks man. Definitely going to plan on changing the thermostat, flushing the coolant system, and flushing tje heater core. Temp wise it doesn’t get over 150. Isn’t that pretty low?

150 is low. It should be 195 or so, you can check the right temp. at the parts store online though. I’ve seen a 160 thermostat listed as an “alternate” temperature for my truck, not sure what that’s for, but that could be what you have in it. But go with the stock thermostat. You can touch the outlet hose for the heater core to see if it’s getting hot.

The thermostat on the 2.8L engines that I am familiar with and I have owned several and worked on many required installing the slotted O ring on the thermostat and using the gasket as well. Without the O ring the engine will never reach operating temperature.

Thanx guys. I plan on flushing the coolant system, flushing the heater core, and changing the thermostat on Saturday

Have you checked the coolant level in the radiator (cold)? Not the level in the recovery tank. If this is one of the GM designs with no cap on the radiator and a pressurized remote tank, remove the bolts holding the tank and raise the tank as high as you can. If the radiator is low on fluid the tank will drain into the radiator.