No water shut-off valve for heater core?

[ron123]

Noticed warm air (much warmer than outside) was flowing out the dash registers even when the temp control was all the way to the cold position
and a/c is shut off. Car not sitting in sun so dash is cool. Others commented about this condition on occasion in the forum when talking about various hvac issues.

Using only flow-through ventilation without a/c running, on other cars I own, the dash register temp matched outside.

Investigated this weekend - followed the heater core inlet and outlet lines from the firewall to the point where they connect to the pipe nipples on the metal junction block attached to the engine; adjacent to where the goose-neck for the lower radiator hose attaches (on same junction block). Did not see any water shut-off valve in the input or output heater supply lines. Most vehicles have a vacuum operated valve on the inlet side right before the connection to the heater core.

Now I am wondering if Chevy is trying to ensure there is always water flow in the coolant circuit for the heater core to act as an "auxillary" radiator. Much of the length of the heater core supply lines in both directions through the engine compartment are aluminum; only have rubber hose crimped on right at the junction of each end where it connects to fittings. This setup would allow additional cooling verses all rubber hoses. Also wonder if this circuit is used to prevent over-pressure when the main thermostat in the upper goose-neck is closed (which normally is done on other vehicles via a bypass at water pump).

Thinking of installing a shut-off valve on the inlet to the heater core because I use the flow-through ventilation a lot without a/c.
Has anyone discovered a hidden shut-off valve in their Camaro, that I may have missed seeing on mine?
Or if none is on the car have you installed one?
Ron

[TooCool5]

Originally Posted by ron123

Noticed warm air (much warmer than outside) was flowing out the dash registers even when the temp control was all the way to the cold position
and a/c is shut off. Car not sitting in sun so dash is cool. Others commented about this condition on occasion in the forum when talking about various hvac issues.

Using only flow-through ventilation without a/c running, on other cars I own, the dash register temp matched outside.

Investigated this weekend - followed the heater core inlet and outlet lines from the firewall to the point where they connect to the pipe nipples on the metal junction block attached to the engine; adjacent to where the goose-neck for the lower radiator hose attaches (on same junction block). Did not see any water shut-off valve in the input or output heater supply lines. Most vehicles have a vacuum operated valve on the inlet side right before the connection to the heater core.

Now I am wondering if Chevy is trying to ensure there is always water flow in the coolant circuit for the heater core to act as an "auxillary" radiator. Much of the length of the heater core supply lines in both directions through the engine compartment are aluminum; only have rubber hose crimped on right at the junction of each end where it connects to fittings. This setup would allow additional cooling verses all rubber hoses. Also wonder if this circuit is used to prevent over-pressure when the main thermostat in the upper goose-neck is closed (which normally is done on other vehicles via a bypass at water pump).

Thinking of installing a shut-off valve on the inlet to the heater core because I use the flow-through ventilation a lot without a/c.
Has anyone discovered a hidden shut-off valve in their Camaro, that I may have missed seeing on mine?
Or if none is on the car have you installed one?
Ron

A mopar I had came with heater shut off valves, GM cars do not.

The heat you are feeling is just after the car sits and you get in and restart it. It should cool off after the air runs through the vents a while.

If not you have a damper adjustment / linkage issue, Maybe check with the dealer if still on warranty.

[ron123]

Originally Posted by TooCool5

A mopar I had came with heater shut off valves, GM cars do not.

The heat you are feeling is just after the car sits and you get in and restart it. It should cool off after the air runs through the vents a while.

If not you have a damper adjustment / linkage issue, Maybe check with the dealer if still on warranty.

My Chevy van V8 and Buick had water cut-off valves. If near boiling water is going in to the Camaro heater core the whole time the engine is running it explains why I am feeling warm air (not hot) out the registers even when the car dash is not sitting out in the sun and outside temp is relatively cool.

Some others on the forum have also noticed this behavior.
Ron

[cajun1le]

The heater core runs on a coolant loop that exists before the thermostat. This allows the coolant routed to the heater core to warm up before the thermostat opens. When it comes to how the air is heated, a servo actuated flap controls how much air is diverted past the heater core to warm up the cabin air.

[ron123]

Originally Posted by cajun1le

The heater core runs on a coolant loop that exists before the thermostat. This allows the coolant routed to the heater core to warm up before the thermostat opens. When it comes to how the air is heated, a servo actuated flap controls how much air is diverted past the heater core to warm up the cabin air.

Thanks for the feedback.
Looks like what I see is correct then ... there is no water shut-off valve on the inlet to the heater core. On the other cars I own (owned), when temp control is set to the blue dot (heat setting all the way turned down), water is cutoff to the heater core.

On Camaro this means the heater core is sitting inside the hvac box behind the dash heating up to near boiling temps even in summer. Kind of defeats some of the purpose of flow-through ventilation fresh air vent. The hot hvac box housing will preheat the air to some extent even when the air valve flap makes the air flow bypass the heater core. Chevy probably saves $40 a car leaving the water valve out. For me, the plus sides of driving the Camaro far outweigh this relatively minor annoyance.
Ron

[Dale_K]

This is pretty normal for modern cars. There are aftermarket kits to add an electrically operated valve to shut off the water flow if you are really bothered by the design.