Barely warm heat

Good morning,

The overflowing is not normal.

https://www.2carpros.com/articles/head-gasket-blown-test

I would start with checking the head gasket. You may have compression leaking into the cooling system causing no heat. The air from this leak goes to the highest point which is the heater core. The pressure is what pushes out the coolant.

Roy

I disagree. If both heater hoses are hot, the blower motor should blow out hot air. I think the problem has to do with the blend and/or temperature doors under the dash. You could have a bad actuator or a vacuum hose, cable fell off the door.

There are no bubbles in the radiator, also the coolant doesn't move dramatically with each rotation of the engine, I was running it with the cap off and much like the tide at the beach, the coolant made its way up to the top of the radiator, overflowed, then went back down, and again made its way back up to overflow again. This was what I thought an "old school" way for the radiator to push air out of the system.

I have heard of the blend door motor or whatever going out, and also I heard there are 3 different kinds on this truck. One to move the door to switch fan direction, one for temp, and one for something else. The parts online don't seem to differentiate between the three.

Okay, no, that is not old school at all and it is not bleeding air.

You need to do a leak down test on the cylinders. Looks like you have a head gasket issue. It should never surge out of the top of the radiator. That is pressure, not air.

Roy

let me repeat. if both heater hoses are hot at the heater core, then the heater core is hot enough. the problem then with the no heat is under the dash. there could still be a problem with the overheating but there should still be heat.

Sorry. This heat problem did not occur until after the repair. Possibly a bad thermostat?

You could start there and see if it improves. When you remove the thermostat, fill the radiator until the coolant is full where the thermostat is located. Then install it. That will eliminate any issue of air. If it still bubbles up, then you are back to square one.

I know my colleague disagrees with my assessment but I would not eliminate it at all.

Roy

If both heater core hoses are hot, that means that the heater core has hot coolant in it, therefore it should blow out hot air. The problem is under the dash.

What's the procedure to get to that actuator behind the dash? I know there are three. I guess I'm after the temperature blend actuator, behind the ash tray. I'm stuck at what plastic pieces to remove.

The procedure below with some pictures.

Roy

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1995 Chevy Truck C 1500 Truck 2WD V8-305 5.0L VIN H TBI
Temperature Door Actuator
Vehicle Heating and Air Conditioning Air Door Actuator / Motor Service and Repair Procedures Temperature Door Actuator
TEMPERATURE DOOR ACTUATOR
Temperature Actuator Location
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Temperature Actuator Replacment
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Remove or Disconnect
1. Negative battery cable.
2. Roll instrument panel forward.
3. Electrical connector.
4. Screws.
5. Actuator.

Adjust
A. Electrical connector to the actuator.
B. Turn the ignition key to the run position and let the actuator position itself.
C. Turn off the ignition key.
D. Remove the actuator from the electrical connector.

Install or Connect
1. Actuator.
2. Screws.
3. Electrical connectors.
4. Instrument panel compartment.
5. Negative battery cable.
^Check circuit operation.

That one in the picture looks like the floor mode actuator.

That is the temperature actuator listed in Alldata.

Roy

Is that attached to the heater core box?

Correct. It is attached to the blend door for heat and cool air.

Roy

How come everything I read it says behind the ash tray? Or is that just a general area that's misleading? Cause I have the dash apart now, lol

I think it's a general area. Remove it and move the door by hand and see if the temperature changes.

Roy

See the red rag? That's it. Removing the door for the heater core will do nothing but reveal the heater core. I don't know what it means to "roll back" the instrument cluster. Looks like the entire dash needs to move. I wish the instructions were more clear

What is that picture?

It says to release it and roll it forward.

You remove the actuator, not the case. Then move the door by hand from cold to hot.

Roy

That's shining a light behind the ash tray. What I did was remove the glove box, the panel around the glove box, and the panel around the ashtray and removed the ashtray. I could move the glove panel out enough to get an elbow extension to reach it and replace it. Heat works now.

Good.

Roy

Returning to this thread because I still have some coolant loss. But no obvious leaks.

Roy mentioned a possible head gasket issue. I attached here a bubbling video to describe what I wrote above. It will slowly rise until it just comes out of the radiator.

Yep, I see.

I would have the leak down test done to check the head gasket.

Roy