88, no heater.

[Blue109]

Haven't posted in a while. Slowly replacing worn out stuff on my 2dr as I find it on sale lol. Ive done some searching but haven't found an answer. Truck has never had heat. Not even a slight bit of warm air. Heater core has good flow at the firewall with a hose and I can hear a solid clunk when I move the lever from cold to hot on the dash. Of the two lines going into the firewall, the one that comes off the drivers side of the block flows fine. I just did a coolant flush and spraying water in that line forces water out the bottom of the radiator no problem. The other line from the pass side of the engine to the firewall has zero flow. If I blow into it I get nothing. Should that line be blocked like that or should it have flow? Both hoses are new between the firewall and the Hardline off the engine.

[Slartibartfast]

Can't say I blew into that hose when I had mine apart, but fully blocked off doesn't sound right. Looking at the cooling circuit in the '89 manual, I'm not seeing anything that should be blocking it. Looks like to get to the heater, coolant has to flow from the head to the manifold, where it branches, then to the heater core, then back to the thermostat housing. If I had to guess I'd say the passage in the intake might be blocked up (though I can't see which hose is which from the diagram).

[Blue109]

Thanks! My technical terminology leaves something to be desired. I can't see any aftermarket valve or any external reason for it to be blocked. It's pretty hard to see back there but it's clear through the heater core all the way to the Hardline between the engine and firewall.the coolant was rusty as well which is why I got new hoses and flushed it. Plan in water pump and timing belt when I get a few days off in a row so I'll just be cold for now and try and figure it out then

[V8path]

Here's a check list of what to check...

 

• Get a "coolant flow diagram" to understand the routing of the coolant flow.
• Check if there are any check valves that control direction of flow.
• Once that is understood, then it would be easier to focus on the area or part that may be blocked.

As far as I know, coolant should be able to flow in the system at all times. I'm guessing there is something blocking flow (damage, debris, or ?) in the system.

 

 

 

 

 

[Slartibartfast]

^ Debris is my guess as well, and I'm not aware of any heater valves. I had another look at the manual and it looks like that passenger's side hose that's blocked is the return. It goes down a long pipe under the intake to the thermostat housing, so hopefully you'll find whatever the problem is when you're replacing the thermostat. If you don't find a lump of something in the thermostat housing, you may have enough access to run a wire or something into that pipe to try and poke out whatever might be in there (assuming the clog is between the heater hose and the thermostat). Here's the diagram from the service manual, for what it's worth.

[Blue109]

Awesome guys. Thanks