84 with no heat

[ALedbetter1]

I've got a 1984 k20 with a 350. I've replaced the heater core an made sure the door closes all the way. The hoses to the core both get hot. My thermostat is a 195 and I've got the radiator blocked off with a piece of cardboard. Its a non-a/c truck so it just comes out on the floor. The air isn't even slightly warm. Even after a 200 mile road trip me and the girlfriend had to wrap up in a blanket to stay warm the whole way. Any ideas on how to get some heat flowing? My coolant overflow tank nipple broke off my radiator and i just patched the hole and did away with it. Now my antifreeze sits about 3 inches down in the radiator even after filling it full it eventually goes back to the 3 inch mark. Could this have something to do with it? Thanks in advance

[Rubble]

That might be part of your trouble,if your coolant level is low it won't be able to circulate thru the heater core properly.If you have access to a temp gun,shoot sone temps on your hoses as well.When the heater is working right in these trucks,they will cook you out!!

[willett]

Is your fan working?

[rs74]

Non A/C trucks are cable operated aren't they? I know this will sound stupid but make sure the cable is hooked up and make sure it is operating properly. I assume that you are getting alot of air out of the heater when on high just not warm? Also make sure you don't have any obstructions in the system keeping the air from getting to where it needs to go.

[Wellgeo03]

When you said you replaced your heater core, I sure hope it wasn't with one of these. I put this in my non AC 86 last winter.

It did make some heat, but barley warm air and the air flow was terrible. It is a jobber parts store core. Aluminum with much finer fins then the original. The outer dimensions are basically the same, but the core itself is much smaller in all dimensions.

I finally repaired the leaky original and swapped it out.
I now have HOT heat. Jobber parts are JUNK, and this one wasn't even cheap. Around $90 for this POS up here in Canada.

[ALedbetter1]

Yes it was one of the aluminum ones it was only $30 though here in the midwest. The fan works like it should and the cables move freely and open both the doors ok.

[Wellgeo03]

I wouldn't be surprised if that was your problem. I had terrible air flow and only luke warm heat. Both heater hoses were hot and heat gun confirmed that the engine was running 195-200 deg, and the heater hoses were about 175 in and 165 out. It just plain didn't flow enough air, and coolant and transfer heat like it should.

You can see in my picture how pinched the inlet and outlet tubes are at the tank. I should have taken a comparison pic with the original style. There is a big difference.

[Rubble]

[QUOTE=Wellgeo03;6507314]When you said you replaced your heater core, I sure hope it wasn't with one of these. I put this in my non AC 86 last winter.

It did make some heat, but barley warm air and the air flow was terrible. It is a jobber parts store core. Aluminum with much finer fins then the original. The outer dimensions are basically the same, but the core itself is much smaller in all dimensions.

I finally repaired the leaky original and swapped it out.
I now have HOT heat. Jobber parts are JUNK, and this one wasn't even cheap. Around $90 for this POS up here in Canada.
Quote..
What parts store did you get it from? I replaced the one in my crew last fall with a core from napa & it works great.Can't remember for sure,but I think it was copper & it was around 55.00. We had a spell of -40C stuff middle of Dec,I ran into town with it (7miles) and halfway there I was turning fan to low & temp to cold...was cooking me out!!

[rs74]

I was going to ask if there is a definate supplier of copper heater cores anymore. Seems like I am hearing it is hit and miss even with the same brand and part numbers. I hear that you may either get and aluminum or copper core with no rhyme or reason to it. Unless I go with the vintage air I am going to need to buy one for putting my short bed back together. So is there a company that sells nothing but copper heater cores?

[Rubble]

Originally Posted by rs74

I was going to ask if there is a definate supplier of copper heater cores anymore. Seems like I am hearing it is hit and miss even with the same brand and part numbers. I hear that you may either get and aluminum or copper core with no rhyme or reason to it. Unless I go with the vintage air I am going to need to buy one for putting my short bed back together. So is there a company that sells nothing but copper heater cores?

I replaced the core in my 86 two years ago with a napa core as well & it will cook you out of the cab too!! Looking back now,pretty sure it was copper too..

[Tdubbyount]

Make sure there's a good seal between your firewall and your heater box. I had trouble with that after I put mine back together.

[motornut]

Mine leaked swapped to a new aluminum,I roast in the Jimmy
but the other day i felt a cold draft,noticed the pass side foot vent had opened a bit
big boots may have caught it,pulled it open
but you are going to need to fix the "hole"
I find you won't get good heat unless the pressure can build
and if the mix is too weak,it will ice up,cool down when driving,have you checked the "mix"

[Wellgeo03]

Rubble, I got mine at a local S. Saskatchewan parts chain. I find that my non AC truck puts out less airflow with the smaller fan. Defiantly won't cook you out. The poor weather stripping, small hole in the pass. floor board, and rusted out cab corners don't help though!

My 83 6.2L Silverado reg. cab will cook you out. My 90 Silverado crew has good heat too, although the bigger cab does take quite a bit longer to heat up.

The AC equipped trucks just have much better air flow. I haven't had the chance to compare the heater cores on the two styles. Maybe the cores on the AC trucks are bigger along with a bigger fan?

[wilkin250r]

I've seen hose routing problems cause this. Both hoses were routed to the low-pressure side of the pump, so there was essentially no water flow. I say "essentially" because there was just enough pressure difference to flow a tiny bit, so the hoses would indeed heat up. This made it difficult for the owner to diagnose because the hoses would indeed get hot, it just wasn't flowing enough to transfer any useful heat to the heater core and into the air stream.

The problem was simple, but the owner didn't understand the flow characteristics, so he had no idea. If the hoses hadn't gotten hot, he may have figured it out much faster.

[Rubble]

Wellgeo03,I don't notice much difference between my a/c& non a/c trucks,what really helped the airflow in the crew was removing the evaporator when I replaced the heater core.Most of the a/c stuff is long gone anyway,this really helped the airflow.Been using my 86 reg cab last couple days & it's a bit cooler out..-35degC.Going down the road,had to turn fan to low cause it was getting warm in cab,so ya they are both pretty close.My 82 6.2 is about the same as well,throws lots of heat too.

[Rubble]

As far as the cores,I can't remember if any difference in size..thing they were pretty close.I think the fans are the same,pretty sure I have swapped fans around over the years.

[Wellgeo03]

Originally Posted by Rubble

As far as the cores,I can't remember if any difference in size..thing they were pretty close.I think the fans are the same,pretty sure I have swapped fans around over the years.

I wonder if there are different air boxes then? I tried to swap the fan in my 86 custom deluxe (plane jane no options or air) and the fan is only about 4" deep. The AC truck fans I have are about 6" deep. There is not enough depth in the non AC air box to install the AC fan.

[Rubble]

Originally Posted by Wellgeo03

I wonder if there are different air boxes then? I tried to swap the fan in my 86 custom deluxe (plane jane no options or air) and the fan is only about 4" deep. The AC truck fans I have are about 6" deep. There is not enough depth in the non AC air box to install the AC fan.

I might be wrong too,maybe it was a non a/c truck the fan came from too..

[fourfiftyfour]

I figured all the years were the same? I put an 85 a/c in my 78 a/c and it fit fine. Even wit ha huge hole in my floor the thing kiiicks heat out like crazy.

[imjeff]

Definitely replace your overflow tank. It keeps air (corrosion) out of your coolant system. Low antifreeze will affect the heat output, but if it's pretty full and you're rolling down the road it should still blow hot. If it blows cold at idle, but heats up when it's revved you have a low coolant issue.

[ALedbetter1]

I replaced the thermostat with a 195 acdelco from chevy, which fixed my misbehaving temp. gauge. Got the overflow fixed, pulled the heater box out put expanding foam around the core, blocked off the passage for air to bypass the core, put plenty of silicone around the box and bolted it back up.... I dont know which one fixed it but it gets pretty toasty now.