No heat, what could it be?

[Joey Link]

Anyone? Headed to the shop soon :)

[KenC]

Aren't 1 and 8 the same thing?

I'm not sure if there's a way to easily check the heater valve... I think you just have to rule out other things and narrow it down to it.

I'm very suspicious of the thermostat.

[jlevie]

That rather looks like the temperature/pressure relief valve that is on later production cars. Its purpose is to prevent a failure of the heater core in an extreme overheat situation. I suppose it could be clogged, but removing and inspecting it will tell if that is the case.

[Joey Link]

Just got back from the shop after a long day of cleaning and fixing little things. We did some more investigating into the heater issue, using a laser heat meter, and found some good information. First of all, it appears the thermostat is closed and, like Ken said, it'd take some actual driving to warm the car up enough to open it.

Focusing our attention on the thermostat valve thing mentioned above, we noticed there is no flow going through it and the hose going from it to the firewall/heater core was 54 degrees. However, the hose going from it to the head is around 150 degrees. We then tested the other hose that goes (from the thermostat?) to the firewall/heater core it was 154 degrees near the thermostat and 54 degrees at the firewall, indicating no flow. So, what this is telling us is we have coolant going to the thermostat valve and coolant going at least a little way down the hose to the firewall. Since there's definitely hot coolant at the thermostat valve, my guess is the valve is the problem, yeah?

Does anyone know any more about this valve? Is it a mechanical check valve? Where does that little hose (#11) connect to? Is this a vacuum hose or a coolant hose? If it's vacuum actuated, maybe there's a vacuum problem? It seems like a HUGE pain to get to back behind the engine there, so I want to make sure before I tackle this.

[Joey Link]

Anyone have any more info on that valve? Can anyone tell me the correct way to install it (just to make sure it's installed properly)?

[jlevie]

Just got back from the shop after a long day of cleaning and fixing little things. We did some more investigating into the heater issue, using a laser heat meter, and found some good information. First of all, it appears the thermostat is closed and, like Ken said, it'd take some actual driving to warm the car up enough to open it.

If the car idles long enough, the thermostat should open if it working. But that has no affect on the heater, providing the thermostat isn't stuck open. The flow to the heater bypasses the thermostat so that you have heat even when the radiator is cold.

Focusing our attention on the thermostat valve thing mentioned above, we noticed there is no flow going through it and the hose going from it to the firewall/heater core was 54 degrees. However, the hose going from it to the head is around 150 degrees. We then tested the other hose that goes (from the thermostat?) to the firewall/heater core it was 154 degrees near the thermostat and 54 degrees at the firewall, indicating no flow. So, what this is telling us is we have coolant going to the thermostat valve and coolant going at least a little way down the hose to the firewall. Since there's definitely hot coolant at the thermostat valve, my guess is the valve is the problem, yeah?

Does anyone know any more about this valve? Is it a mechanical check valve? Where does that little hose (#11) connect to? Is this a vacuum hose or a coolant hose? If it's vacuum actuated, maybe there's a vacuum problem? It seems like a HUGE pain to get to back behind the engine there, so I want to make sure before I tackle this.

I've never had my hands on one of those valves (they were only used on late production and I think maybe only fitted during a recall). As far as I know the valve operates only when the coolant flowing through it is excessively hot, like in a serious overheat. I suspect that the small hose is a vent.

As a quick fix, eliminate the valve.

[Joey Link]

I have heat! I pulled the valve to replace it and noticed a blockage in the hose between the valve and the firewall. I cleared the blockage, buttoned everything back up, warmed up the car, did a few laps around the parking lot. It's not as hot as it could be, but I think there's still a bit of air in the system. Thanks a ton for all the help guys.