78 monte carlo 305 no heat

[bigsez]

Hello everyone.Newbie here. i just bought a 78 monte carlo v8 305 and the car has no heat. The blower motor works on all speeds but its just blowing cold air. I let it run for 10-15 minutes and the upper hose is hot..I didnt check the bottom hose. I didnt check the heater core lines either as of yet. I was wondering if possibly the thermostat is bad? Should I change that first and see if that does the trick? Any help would be greatly appreciated. Thank you in advance

 

[bracketchev1221]

Check to make sure the lines are hooked up and that there is no blockage. Even if the thermostat was running cold, you'd still have some kind of heat. If it's an ac car there is a vacuum operated heater control valve as well.

 

[crotchss]

Coolant level could be low enough where it doesn’t get pumped to the heater core. If there is enough coolant in the system grab the heater core lines, if one is hot and the other is cold, then the core is plugged and needs changed out.

 

[bigsez]

I took the radiator cap off and the radiator is filled with coolant. I will check the lines to make sure if one is hot and the other is cold

 

[oldsofb]

Coolant level could be low enough where it doesn’t get pumped to the heater core. If there is enough coolant in the system grab the heater core lines, if one is hot and the other is cold, then the core is plugged and needs changed out.

Agreed! Do a thorough diagnosis first before turning a single wrench. Both intake and outlet hoses should be hot. If the outlet (or intake for that matter) is not hot, then check the Heater Valve as Bracketchev1221 and PontiacGP stated. If that checks out ok you should check the mix door in the car and make sure it's moving correctly from Cold to Hot.

Hutch

 

[bowtiebutler956]

Could just be a bad heater control valve. If the heater hoses are hooked up, and the system is full of coolant, its likely juster the heater valve. Less than $20 at the local parts house, and installs in under 10 minutes. Coolant should flow through the heater core even if your thermostat is stuck shut. (although that wouldn't be good for the health of your engine!)

Matt

 

[bigsez]

Thank goodness for you guys .I checked the heater control valve . There is what appears to be an arm on the top side that was pushed all the way in and rusted .I pried it back with a screwdriver and bam the heat came right on .I am going to take your advice and swap it out Matt . I cant thank you guys enough .I will post pics of the car this week