No heat conundrum

[jeffncs]

No heat coming out of heater. Chevy blower motor that move a LOT of air. Stays ambient temp.

Bypassed the temp valve and no change.

Thinking it’s a clogged heater core as the return hose doesn’t seem to get very warm compared to the supply side.

 

[serial car restorer]

Sounds like you've pegged it to me. Clogged core is about the only cause I can think of, given that you bypassed the valve with no change.

 

[Broncobowsher]

Pull the valve first and make sure it isn't plugged first. Sometimes the valve inside will break free of the actuator and stick shut. Or just crustify into a clog.
When that proves to not be the problem, you will already have one of the hoses off the heater anyway and you can try to blow through the heater core (lung power is all that is needed). You will confirm the heater core is plugged, or we will be very confused.

 

[jeffncs]

Pull the valve first and make sure it isn't plugged first. Sometimes the valve inside will break free of the actuator and stick shut. Or just crustify into a clog.
When that proves to not be the problem, you will already have one of the hoses off the heater anyway and you can try to blow through the heater core (lung power is all that is needed). You will confirm the heater core is plugged, or we will be very confused.

I pulled the valve last night and just added in a straight tube connector. No change. I didn’t check the core while it was apart though.

Maybe I’ll tinker on it later tonight after the day job.

Wife’s truck - doors and a safari top only.., she wants heat! Lol

 

[SLOWnEASY]

I'd say you tested it sufficiently. No heat with a bypassed core I would already be ordering a core.

 

[nvrstuk]

I pulled the valve last night and just added in a straight tube connector. No change. I didn’t check the core while it was apart though.

Maybe I’ll tinker on it later tonight after the day job.

Wife’s truck - doors and a safari top only.., she wants heat! Lol

She wants heat??? Best heat in a Bronco w/o it being sealed up are HEATED SEATS! Seriously , deal breaker. I don't run doors or a solid back or bulkhead on my 1/2 cab in winter and we have winter here for 6 months but with heated seats it is toasty! (well toasty can be defined differently by others but it's nice!!)

 

[DirtDonk]

Are you running a 160 thermostat by any chance? That usually means little to no heat even with a stock set up.

And just so we are all on the same page, did you “pull for heat“ by any chance?
I know you’ve been around Broncos a long time now, so that’s probably not the issue here. Besides, you said no heat, not no airflow.
But I had to check! You know, for the new Bronco owners reading this.

I think this was the first chance this season that we’ve had, to bring up the pull-for-heat issue.

 

[jeffncs]

Are you running a 160 thermostat by any chance? That usually means little to no heat even with a stock set up.

And just so we are all on the same page, did you “pull for heat“ by any chance?
I know you’ve been around Broncos a long time now, so that’s probably not the issue here. Besides, you said no heat, not no airflow.
But I had to check! You know, for the new Bronco owners reading this.

I think this was the first chance this season that we’ve had, to bring up the pull-for-heat issue.

Great questions. Food call on the heater control. Def pulled the knob for heat - no change. I sort of wish I had a senior Monet though - easier than taking out the heater box by far!

Not sure on the t-stat TBH... I likely installed stock temp (not sure of the temp) but really can’t remember now. I’ll change if I have to…. I will say the hose leading to the core was getting hot; return hose didn’t seem to be hot enough in my opinion.

 

[DirtDonk]

Yeah, that’s one of your most direct clues anyway.
The T-Stat can be “tested“ by simply looking at the coolant temperature gauge. Does it go up to the normal range, or does it stay low.
If low, then you might have to change the stat anyway. If it goes to 180 or higher, then the thermostat is not your issue.
But it’s all still leading to the direction you’re going.

 

[Oldtimer]

Before I pulled the heater box, I would disconnect heater hoses from water pump and intake manifold, hook a garden hose up, and try flow in both directions thru core.

 

[blade]

Before I pulled the heater box, I would disconnect heater hoses from water pump and intake manifold, hook a garden hose up, and try flow in both directions thru core.

That's good advice! I had to do that on my ford focus, no heat so I disconnected the hoses and ran water from the hose in both directions and out came about a cup of junk when I backflowed the core. Heater worked great after that.

 

[DirtDonk]

Every time I flushed the cooling system in my '71 I would do the heater core manually like that as well.
The one and only time I used one of those 2-component flushes (acid and neutralizer?) I never really had to do another flush.
Judging by the condition of the inner surfaces of the engine and the visible portions of the radiator (original one too), it was still sparkling clean 15 years later!
But the first time.... Ugly stuff!

Paul

 

[jeffncs]

I installed a new heater core but the engine water jacket was / is full of rust and garbage. Thinking I could have blinded the heater core with garbage but hose test will soon help determine that too!

 

[jeffncs]

Flushed the “old” heater core and bunch of junk came out. Hooked it back up…. No heat.

Threw in a new HC. No heat.

Checked the heater box doors while it was out - all move freely. Valve is clear snd moves freely.

Next step is to get a hotter T-stat. I have doing that bit it’s only thing left aside from flushing the engine block to remove the rust chunks which may be clogging the HC.

 

[Oldtimer]

What style heater hose elbow do you have in the intake manifold and is it all there?
It installs at the high point of the engine, and if it does not extend below coolant level you don't get hot water, just air bubles.

 

[DirtDonk]

And in my long-term experience, the first thing to rust out in an engine is the siphon tube extension on that particular fitting.

 

[SLOWnEASY]

I installed a new heater core but the engine water jacket was / is full of rust and garbage. Thinking I could have blinded the heater core with garbage but hose test will soon help determine that too!

I would think a cold/ faulty thermostat would show up as the valve side hose not getting warm. Are you sure the hot coolant is even getting to the heater core with sufficient flow? I would disconnect the hose just before the valve and fire the engine for a second. You'll know immediately if you have a plug on the engine side of the valve. Also disconnect the return hose at both ends and see if water will flow through as suggested by Oldtimer.