My 97 civic just got a GSR swap done and I have a problem. There is no heat when you move the temperature lever to the red. It blows cold air. Even after driving the car for over an hour. I've checked all the fuses related to the heater, those tested ok. I've checked the cables from temperature lever to the heater control valve, they are fine and connected. I've checked the heater control valve by manually opening the valve (pushing lever towards the firewall), still cold air comes out. I've checked the heater hoses at the firewall. They are connected pretty snug and I don't think they're swapped around. The upper and lower radiator hoses are hot to the touch. With the heater control valve open, both heater hoses are just warm. I'm thinking they should be hot too. The car is not overheating, the coolant level is fine and the fan comes on ok.

I did a search and found this thread https://honda-tech.com/zerothread?id=679705 . I'm going to try draining the coolant and then flushing the system. Hopefully after refilling the coolant and bleeding the system, the heater blows out hot air. If not, I guess the problem will be narrowed down to the heater core or thermostat. Any other ideas?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by studio78 &raquo;</TD></TR><TR><TD CLASS="quote">My 97 civic just got a GSR swap done and I have a problem. There is no heat when you move the temperature lever to the red. It blows cold air. Even after driving the car for over an hour. I've checked all the fuses related to the heater, those tested ok. I've checked the cables from temperature lever to the heater control valve, they are fine and connected. I've checked the heater control valve by manually opening the valve (pushing lever towards the firewall), still cold air comes out. I've checked the heater hoses at the firewall. They are connected pretty snug and I don't think they're swapped around. The upper and lower radiator hoses are hot to the touch. With the heater control valve open, both heater hoses are just warm. I'm thinking they should be hot too. The car is not overheating, the coolant level is fine and the fan comes on ok.

I did a search and found this thread https://honda-tech.com/zerothread?id=679705 . I'm going to try draining the coolant and then flushing the system. Hopefully after refilling the coolant and bleeding the system, the heater blows out hot air. If not, I guess the problem will be narrowed down to the heater core or thermostat. Any other ideas? </TD></TR></TABLE>

The FIRST thing I would do is verify the cooling system was bled correctly. Doesn't sound like it was. You MUST have the heater valve set to hot when bleeding the system. Wait for the car to cool down, remove the radiator cap, move the temp selection to HOT and then run the car with the cap off for a few mins. This should purge any air left in the system. Top it off as needed and try again.

 

I bled the coolant system today but the heater is still blowing cold air. I'm going to replace the thermostat. I think it's stuck open.