Well, I feel like I'm a decent mechanic. I just bought a 91 Civic DX from a woman who said she just had the top radiator hose replaced. I bought it fairly cheap, and figured I would have to make some repairs. Overall, the car is in good shape. It has 117k miles on it. I know these engines are known to blow head gaskets or warp heads due to just lack of maintenance. Here's what this car is doing. It starts up just fine and will set at an idle for up to an hour without heating up. I checked the lower radiator hose, and it heats up after a while, so the thermostat is opening just fine (it's new). If I let it set and idle it runs cool until I drive about 200 yards. After that , it heast up very fast. If I take the radiator cap off while at idle (thermostat open), it seems to bubble and spit out of the radiator. There is no water in the oil , because I also changed the valve cover gasket and the oil was black. My question is this. Could the head gasket or head still be bad and not get water in the oil? Could it just be that the radiator is blocked and not letting water pass through? Thanks for any help in advance.

 

Yes you can have small leaks in the head gasket that let combustion gasses push the coolant out of the engine but otherwise no other problems (no water in the oil, no steam in the exhaust). My car was like that and I fixed it by replacing the head gasket. Test it cold with the cooling system completely full, there should be no bubbling out of the radiator when you rev the engine. (Don't take the cap off with the engine hot).

The radiator in a '91 is really oversized compared to what they had in later models. It would have to be really blocked. You can test that by taking the bottom hose off and run water into the top of the radiator with a garden hose. It should flow out of the bottom freely.

 

I will let you know what I find out. Thanks