No heat issue:Resolved

[AriK]

Timing belt was done two weeks ago. New thermostat installed. Coolant flushed. Cracked open flushing tee while gone through several fan cycles. However, after all that no heating in the cab, even after a 2 hour drive cold air full time.I believe all the air is bled. Cold/hot wire is calibrated properly and controls the heater valve as it should. The inlet coolant tube through the firewall burns hot while the outlet tube out of the heater core is slightly warm, all this while in the heat position. What should i suspect? Defective heater valve? Blocked heater core? Should i try flushing the heater core through the flushing tee while i disconnect the outlet hose or do i risk blowing its brains out?
Prior to timing belt job i would get constant heat as long as i didnt turn the fan on. Once on, air would eventually turn cold and stayed cold.
Now always cold.
Suggestions? Further tests?

[vandor]

Sounds like even before you had marginal heat. When working properly Spider heaters will roast you out.
I'd check that the lever on the valve is actually turning the shaft. It's either the valve not opening or a clogged heater core.
If it's clogged this bad I doubt flushing would do much.

[AriK]

Thanks Csaba. The cable in fact does spin the shaft. Even the position marker on the heater valve moves. I disconnected the outlet hose and attached the garden hose to the T valve and clean coolant spilled out the outlet hose. Therefore, heater core not blocked. So what gives?

[vandor]

Does the engine reach normal operating temperature? Have you tried to put everything together since you flushed it (while leaving the lever in the same position) and checked for heat?
If you still have the original valve with the capillary tube then it could be a bad valve.

[AriK]

The engine in fact still runs cool even after changing the thermostat provided by AR. Reaches operating temperature only while sitting in traffic, rad fan cycles as it should. The lever has been in the heat position all along during bleeding of the system, air is continually cold. Can't tell if valve is original. Although i see shaft changing positions does it not do the same thing internally?

[vandor]

The original heater valve had a capillary tube going to the heater core and it would regulate the air temperature depending on how much the heater was turned on. Kind of an early form of automatic temperature control.
If it has gone bad it may turn off at the sign of any heat at all. If you post a pic we can tell.

Was the t-stat installed correctly? The port that is closed when cold goes toward the radiator.

[AriK]

The original heater valve had a capillary tube going to the heater core and it would regulate the air temperature depending on how much the heater was turned on. Kind of an early form of automatic temperature control.
If it has gone bad it may turn off at the sign of any heat at all. If you post a pic we can tell.

Was the t-stat installed correctly? The port that is closed when cold goes toward the radiator.

Selector in the heat position


Selector in the cool position, notice position marker at 12 oclock shifted.


Thermostat


Filled and bled at flushing T with a high funnel bubbling air from cold engine until 2 fan cycles.

[131]

The engine in fact still runs cool even after changing the thermostat provided by AR. Reaches operating temperature only while sitting in traffic, rad fan cycles as it should.

Drive the car until it's at operating temperature, with the engine running, feel around the heater core, it should be too hot to touch, if not, you have no flow through the core. As you've checked flow to the core outlet, you may have a restriction between there and the water pump.

[AriK]

After a very long drive only one pipe is hot, the return isn't. As i said i flushed and water came out the other side whether selector was on hot or cold. On a short drive neither pipe burns hot unless it's near the firewall. It's as if there is no coolant pressure pushing past the firewall. (The heater hoses are healthy and are not choked or collapsed, beyond that there's a straight metal tube leading under the manifold to the pump) So can we say that even if we see the heater valve shaft moving on the outside, something else is happening (or not happening) on the inside?

[131]

As i said i flushed and water came out the other side whether selector was on hot or cold.

So now you need to make sure you have flow through the pipe to the pump. I recently removed the pipe from my car, a previous operator had used enough silicone on the pipe/pump gasket to almost block the hole. Not saying that's your issue, but you need to prove your flow path.

[vandor]

That's a replacement heater valve, it's a simple on/off type valve. The t-stat looks correctly positioned.
Try what 131 suggested, as I'm stumped.

[AriK]

As i said i flushed and water came out the other side whether selector was on hot or cold.

So now you need to make sure you have flow through the pipe to the pump. I recently removed the pipe from my car, a previous operator had used enough silicone on the pipe/pump gasket to almost block the hole. Not saying that's your issue, but you need to prove your flow path.

I had a chance to look at it again.
I ran a long heater hose from metal tube under the manifold into a bottle. Plugged the heater hose inlet to the core in order to restore pressure when the engine runs. No flow between the water pump and the firewall. The engine ran from cold through a fan cycle. I feel a slight vacuum when i squeeze the rad hoses but no liquid gurgling into the bottle. I rechecked coolant level, the system is full, when i overfill it flows out the long hose into the bottle, but still no circulation when engine runs. Peculiar. Too hot under there to do anything now but the next step is to dismantle the metal tube and look inside.

[131]

The steel pipe is on the low pressure side of the water pump, it draws hot water from the head, through the heater core, to the pump.

[AriK]

The steel pipe is on the low pressure side of the water pump, it draws hot water from the head, through the heater core, to the pump.

131, You are correct. Not peculiar anymore. Thanks for the heads up. I will test the flow according to this schematic.

[DanD]

The last water pump I replaced was put on with a gasket and silicone. The silicone was totally blocking the heater pipe, like a rubber plug.