Heater Help???

[big dump]

So, I'm trying to get some hot air blowing in my '72, and I've got a real head scratcher in the works. So far, I've flushed the block, put in a new T-Stat, water pump, and had the radiator dipped and re-built. I also flushed the heater core, which to my understanding is just an in-out, so if it flushes and water passes through without obstruction it's good right? The inlet hose for the heater core isn't getting hot. It gets slightly warm to the touch, but not hot like the upper radiator hose. I'm certain there is water flowing through it, just seems like it's not hot enough. I would think that the inlet for the heater core should be really hot. I removed the vacuum valve, and replaced with a straight through just to make sure that I had hot water running through the core. Any suggestions? I'm really starting to get frustrated with this because its supposed to be such a simple system. I've got some issues with the cables and doors inside the cab as well, but if I understand how this system works, the core should be getting hot water through it all the time, and when the blower is on, the air should be hot. The vacuum valve is to shut off the hot water going to the core, correct? Help me out here guys.

Thanks in advance.

[Yukon Jack]

That has me confused too - doesn't make sense why your inlet hose isn't hot to the touch. Doesn't sound like it is flowing right. Would be a bit messy but you could always grab a 5 gallon bucket and yank the hose and see how it's flowing. Hmm.

[big dump]

I tried that before I pulled the water pump and took the radiator down to be re-built. I figured that there was a small chance that the water pump impeller was spinning on the shaft (very uncommon) and that water was just coming out because of gravity. Turned out that the old pump was fine, replaced it anyway. I really don't know where to go from here. My neighbor is a technician and its got him stumped as well. I don't know. The radiator shop said that it was about 25% plugged up, so I thought that could have been it. However, now it's back together will all new parts, and that hose still isn't getting hot. Any chance it's the core? I mean, like I said initially, I thought if you can run water in and it comes out with no leaks inside, then the core is good. There's gotta be someone that has experienced something similar.

[bigbadchev72]

where do you have your heater hoses hooked to?

[DANTES JIMMY]

If Heater Hoses Are Hooked Up In A Spot Before Or After T-stat It Might Not Get Hot Until T-stat Opens Up??
If Hot Water Is Flowing Through The Block And Not The Heater Core You Have A Issue With The Flow To The Core

[RustyParts]

Connect the two heater hoses together to bypass the heater core and if they get hot the heater core has to have some kind of obstruction.

I never did trust cleaning radiators and heater cores.

Good Luck

[big dump]

Well, the heater hose going into the core is coming directly off of the water pump. The return line from the core dumps back into the radiator. I might try to tie them together as Rusty suggested, however, when I flush the core, water flows freely through. Is it possible that if there is even a minimal obstruction in the core, the lines wouldn't be getting hot? I would think they should be hot either way. Thanks for the suggestions, keep em coming.

[Huck]

If your temp gauge is reading that the coolent temp is up there --around 180+degrees and your thermostat is in correctly--then the water pump should be pushing 180-195 degree water thru the hose to your heater. if that is not happening--it isn't your heater!! remove inlet hose to your heater with engine running---should have a gusher of water coming out HOT. Be careful and don't burn yourself.

[Critter]

I wonder if there is an obstruction in the hose or the water pump outlet? I believe you said the pump was changed recently, but what shape are the hoses in? Sometimes rubber hoses can implode where the inside ruptures and closes off, but the outside looks fine. Just a thought…

[DANTES JIMMY]

Maybe Move The Hose Going To The Radiator To The Intake
Does Not Make Sense To Me But What If You Were Getting Thet Same Amount Of Positive Pressure On Both Lines Then You Wouldnt Get Much Flow
Much Like Hooking Up Two Positive Pressure Hydraulic Hoses On A Snow Plow
Lots Of Pressure But No Flow

[jaros44sr]

Originally Posted by Critter

I wonder if there is an obstruction in the hose or the water pump outlet? I believe you said the pump was changed recently, but what shape are the hoses in? Sometimes rubber hoses can implode where the inside ruptures and closes off, but the outside looks fine. Just a thought…

, but it's just my guess. Wouldn't cost much to find out. Seems like the only logical solution

Looping it from the intake back to the water pump mite work as well, see if that hose gets hot

[old man jimmy]

Just a thought. But their is more to getting heat out of your core than the water running through it. You also have to move air through it. So if your fins are clogged up, no air can get through, and no heat. How hot a stat are you running? Also could be some of the tubes in the core are clogged. I had a blown head gasket on my burb. years ago. Put stop leak in it to get by. When I dropped the new motor in, the heater core was open to the air for a couple days. (Stop leak is activated by air.) could only get luke warm air after that. Back flushed core with garden hose, didn't clear it. New core did. They are a pain to get to, but I'd say you need a new heater core. If it's original, it's done good to last 35 years. Good luck. Almost forgot. My inlet hose didn't get hot either, due to lack of flow.

[big dump]

These are all good thoughts. To answer a couple questions, it is a brand new pump, and 195° thermostat. It runs dead on 210°. My hoses are in decent shape and are all clear. I've flushed the whole system multiple times now and I can't believe it's an obstruction anywhere. The core could make sense if it needs ventilation and good air flow through the fins to work properly. I always just thought that if it flowed water, it was good. Is that not correct? Does it really need good air circulation through it as well? Could it just be that the inlet hose isn't going to get hot?

[jaros44sr]

The fins and fan are needed to move the hot air produced by the hot water, you aren't getting hot water to the core. You do have the hoses hooked up 5/8" to 5/8" and 3/4" to 3/4", rite? Do let it run long enuff to open the thermostat?

This may get messy, but I don't have any other ideas! Make sure your system is cold before you break open any rubber hose connections, 210 degrees hurts for a long time.

I wonder if you have pockets of air in it??

[big dump]

Yeah, it's definitely running long enough to open up the thermostat, and the correct sized lines are hooked up where they should be. I thought maybe I had an air pocket also, but I've drained it and filled it twice now, and I'm fairly certain there's no air. Maybe the fins on the core are clogged with debris not letting them breath or whatever. If that were the case though, I would think it would run hotter, not cooler. ????

[jaros44sr]

Originally Posted by big dump

Yeah, it's definitely running long enough to open up the thermostat, and the correct sized lines are hooked up where they should be. I thought maybe I had an air pocket also, but I've drained it and filled it twice now, and I'm fairly certain there's no air. Maybe the fins on the core are clogged with debris not letting them breath or whatever. If that were the case though, I would think it would run hotter, not cooler. ????

I'd start by figuring out why the inlet hose isn't hot

[big dump]

Are you saying you think there's some sort of obstruction? Or are you just saying in general you'd start with the inlet hose temp? I agree if your saying chase it under the hood first, however, I've done everything I can under the hood. I'm certain there is good flow.

[old man jimmy]

When you say you flushed the heater core. Using a garden hose, right? The hose has a bunch more pressure than your pump will ever kick out. So water will flow through the core with the garden hose, where your pump don't have anywhere near that kind of pressure to push water through a clog. When your lines are hooked up, water will flow to the easiest path. So it don't take a big clog in the core for your pump to say. Heck with it, I'll just push this water the other way. From what you say. Still think it's the core. But would check everything else first. As it's the hardest one to get to. But it sounds like you've covered all the other bases. If you haven't seen a heater core. All they are is a baby radiator. Good luck.

[jaros44sr]

Originally Posted by big dump

Are you saying you think there's some sort of obstruction? Or are you just saying in general you'd start with the inlet hose temp? I agree if your saying chase it under the hood first, however, I've done everything I can under the hood. I'm certain there is good flow.

The system will not work unless that top hose is hot, why it is not getting hot is what you have to figure out. The only reasons that I can think of are, blockage, air bound or a valve closed. I haven't had my system apart yet to know if there is a valve in there, nor have I put a heater core in it yet.

Since the inlet tube on the heater core is higher than the radiater cap I'm leaning more towards air bound, you seem confident in your claim of good flow. They used to sell a kit for flushing that was a 'tee'. You would splice this tee into your heater hose and flush away, then just replace the cap on the tee and be done. Let me think, this mite take awhile

[old man jimmy]

If water is not flowing through the core tubes, the hose won't get hot, the water will just set thier. And their is no valve in the core itself. It's just in through the tubes and out. Their is a vaccumm valve in the hose. But I think he said he alread bypassed that. An easy way to find out is to take off the return hose at the intake, stick it in a bucket, plug the intake, and start the truck. If no water their, put it back on. take the other hose off at the core, put it in a bucket, and start it agein. If you are getting water to the core, but not throught the core. You will know the problem.

[old man jimmy]

Just read and eirlier post that said your "heater hose dumps back into the radiator" You shouldn't ever have a nipple on your radiator for the hose, unless someone has put different radiator on it. It should go into the intake.

[big dump]

Looks like a factory radiator, however, it's not a factory engine. PO could have put a different radiator in when they did the engine. I'm leaning more towards the core now. It makes sense that the pump is not going to put out nearly as much pressure as the garden hose. I'll post a couple of pics later to show you what I've got going on. Thanks,

[TonyJohnson]

So, does one hose go from the waterpump to the core inlet and the core outlet hose go to the intake? Pics?

[big dump]

Ok, the first image shows the 5/8" inlet hose coming out of the water pump which goes into the heater core. It also shows the thru valve I put in temporarily so that I was sure the valve wasn't closed and hot water was getting to the core.



This shows the 3/4" return line coming from the core to the radiator.

[jaros44sr]

I think Ol' Man Jimmy nailed the problem, never seen a hose go to the radiator, that area over there is usually for the trans. cooling lines. Yours is A/C equipped and I am not familiar with that setup, so someone with that knowledge will have to chime in. Which leads me to another question, how do you cool your trans.? My blue hose is the 3/4" water pump to core feed... also I'm confused on the temp. bypass valve