A different kind of "No heat" conundrum

[XLCOR_65]

Ok, I have searched Google and this forum and have not seen anything that closely resembles my current heat problem. I will lay out the basics:

New radiator

New thermostat (180 degrees)

New water pump

Heater core has been boiled and pressure tested

No leaves or any other obstruction in the heater box

Engine warms up normally, sticks to 180 like glue after the thermostat opens the first time. The hoses are hooked up correctly. No matter what, there is not ANY heat coming from the heater core. I just get cold air in the cab. The supply line is kinda warm and the return line to the water pump is cool. I checked for air lock and there was no problem.

Now, the heater used to work just fine. I even burned the heck out of my hand on accident one time by letting my hand rest on the heater core pipe when I was leaning over into the engine compartment...

My guess is that the new water pump is possibly the culprit. I think that it is not sucking the water through the core and back into the pump. Anyone else ever have any experience in this problem? I am going to install a new pump possibly tonight and see how it goes, but I just wanted to see what you all had to say.

Thanks!

(Hope everyone has a safe and happy Thanksgiving!)

[thunder71]

When it gets hot with the radiator cap off can you see the water flowing ? It does sound like the water pump is not pumping...

[XLCOR_65]

Originally Posted by thunder71

When it gets hot with the radiator cap off can you see the water flowing ? It does sound like the water pump is not pumping...

Yeah, I can see it moving slightly after the thermostat opens. But maybe it isn't moving it enough. Can never tell with these dang overseas replacement parts today.

[thunder71]

Does the flow speed up as you speed the engine up...as the rpm's go up the water flow should speed up when looking in the radiator when the temp is up...

[XLCOR_65]

That is definitely something I will look for tomorrow. If the rate of flow doesn't pick up, then I bet that will almost guarantee that the pump is at fault.

[jtrichard]

was it working before water pump change? do you have V belts? and we are talking small block?

[firemanjimtfd]

A friend of mine 66 would not heat after changing the heater core. It was air locked. He pulled one hose loose and started motor. Pushed the air out and it worked fine .

[XLCOR_65]

Originally Posted by firemanjimtfd

A friend of mine 66 would not heat after changing the heater core. It was air locked. He pulled one hose loose and started motor. Pushed the air out and it worked fine .

Yep, I did the same thing last week to make sure that there wasn't an air lock. It's definitely a mystery. I still think there is something funky going on down at the water pump where the heater hose returns. The water flows into the core just fine, but the return line is cool. (and yes, the heater core is perfect. I had it boiled out and pressure tested just to make sure....so no worries about blockage inside...plus, I turned the engine over until water came out of the other side)
I think maybe the return at the pump either isn't drilled through all the way or there just isn't enough suction to pull the water back through the core.

Originally Posted by jtrichard

if you have V belts you may have been sold a water pump for a later engine/truck with serpentine belt a friend of mine a few months ago ( summer in the desert) bought a 1988 3500 with a 454 and drove it from the sales lot about 5 miles and the temp was red lining come to find out someone had put a serpentine belt water pump on a V belt drive engine don't pump much water when its turning backwards

I don't think there is a problem with the pump being backwards....I actually had that problem the FIRST time I replaced the pump this summer. Guy had sold me a serpentine style one. Truck overheated fast. Got a better one on there and then had the heat issues....so deductive reasoning tells me it may be at the pump, but murphy's law tells me it could be anything! hahaha

Gonna probably work on it this afternoon after I have successfully glutted myself on turkey and pumpkin pie!

[thunder71]

Did you ever get heat inside the cab?

[XLCOR_65]

Originally Posted by thunder71

Did you ever get heat inside the cab?

I did! It was late Friday night. I was going to post, but I lost track of time and then forgot to last night when I was on.

I changed out the water pump and decided to get new hoses to replace my cracked out ones. When I was cutting them to fit, I decided to poke around the opening for the hoses. When I put the screw driver in the intake port, it stopped way short. So I grabbed an angled pick and started digging crud out of the port. Eventually removed it from the intake and cleaned it all out and checked the intake for more crud.

Long story short, there was blockage at the intake. I imagine this is due to the intake I used was OLD and CRUSTY and probably could have used a good cleaning before I gave it the Krylon touch and then slapped it on a couple years ago. Something obviously broke loose and got lodged. Now the awesome anticipation of it happening again....at least I will know where to look if my heat goes out again!

(But that won't be too long, because I am slowly refreshing the awesome 292 and 4 speed I got from sigshooter. Great guy!)

[66Submarine]

Is it possible that the flow through the heater core is restricted? Maybe there's a rat nest in there or something.

[jtrichard]

if you have V belts you may have been sold a water pump for a later engine/truck with serpentine belt a friend of mine a few months ago ( summer in the desert) bought a 1988 3500 with a 454 and drove it from the sales lot about 5 miles and the temp was red lining come to find out someone had put a serpentine belt water pump on a V belt drive engine don't pump much water when its turning backwards

[chevyrestoguy]

Originally Posted by jtrichard

if you have V belts you may have been sold a water pump for a later engine/truck with serpentine belt a friend of mine a few months ago ( summer in the desert) bought a 1988 3500 with a 454 and drove it from the sales lot about 5 miles and the temp was red lining come to find out someone had put a serpentine belt water pump on a V belt drive engine don't pump much water when its turning backwards

Yep, seen that before. I would try the trick that firemanjim mentioned first, though.