Heater Help???

[big dump]

Well there is a separate transmission cooler that cools the trans. The bypass is just a 5/8" flush adapter that I put in because the vacuum a/c valve that was on there wasn't functioning properly, and was stuck closed. It just has a cap that you can unscrew and hook a garden hose up to for flushing the coolant system. Rather than buying a new a/c valve, I had this one laying around and put it on there just to use as a temporary solution to make sure that I had water flowing through the core first.

[Kager67]

Here is the heater hose routing on my '72 blazer w/ a/c. Heats great. The bottom hose goes to the water pump.

kage

[jaros44sr]

OK, so does the water pump hose go to the top off the heater core? Well, I quess I'm wrong, according to Kage, and the PO switched the nipples on me

I'm totally confused now, I gotta go read a book on the subject(service manual)

[Old Chevy Mech]

Both my 70's have the 5/8" hose going from the water pump to the top of the heater core then off the bottom (1/2" hose) to the top of the intake manifold. Makes tons of heat. That is the way it should be set up.

Now I could be wrong, but I always thought that the water pump pulled the hot water through the core, drawing the hottest water out of the top of the engine at the manifold through the core and out the top. Kinda hard for me to imagine how the rad hose which is right next to the heater hose is being sucked by the pump and 1" away on the pump "head" the heater hose is not.

Frank

[Kager67]

OK, hold up, I screwed up. I went out to check it over and I was wrong. The upper hose goes to the radiator, below the trans line. The lower connection on the heater core goes to the intake. Sorry bout that. One thing that hasn't changed though, it heats great!

[big dump]

Ok, so Kage, you don't have a line coming out of your water pump for the heater? Now I'm really confused. Does your pump have a plug on it above where the lower radiator hose is?

[Kager67]

Originally Posted by big dump

Does your pump have a plug on it above where the lower radiator hose is?

Yeppers. See circle in pic.

kage

[big dump]

Well, I suppose that I can put the nipple that is coming out of the pump onto the intake, and try to use a plug from the intake for the pump. This is really a pain. I guess it makes sense that you'll get hotter water from the top of the engine than the pump. I don't know.

[da-burb]

I think what you have is your 5/8" line hooked up to the suction side of the waterpump. In fact I would guess that all fittings on the waterpump are likely to be negative presure.

Your 5/8" hose should come from the intake manifold to the shut off valve and then to the heater core. Your 3/4" line will go from the core to your radiator. Your radiator is stock. Some automatic tranny trucks came with this. I have seen many of these. Most replacement radiators no longer have this fitting. Without the fitting you would route the 3/4" line to the waterpump, just above the lower rad hose connection. Just like you have your 5/8" line now.

[big dump]

Well, that makes sense. I suppose that I'll go ahead and fix/re-route those lines and see if that makes the difference before I pull the core. I'll probably try to do that tomorrow and see if it helps. I'll keep you posted. Thanks for all the input, keep it coming.

[pumpkin]

Sounds like a bunch of confusion. Start with the basics. Hot water flows out of the intake manifold and returns to either the water pump fitting, or the radiator. If you have the two heater hoses to the water pump and the rad, then you will have little or no flow through the hoses. With the hoses connected correctly, if the hose from the intake to the heater is hot, and the other hose is cool, or cold, the heater core is plugged. If both hoses are hot then you have an air flow control problem. If both hoses are cool, with the engine hot, the you have a water flow problem. If the rad is getting hot, then the water pump is working.

[big dump]

Well, I took Kage and Burb's advice and re-routed the line from the water pump to the intake. I plugged the pump and used the nipple on the intake manifold instead. Lots of heat now. Now I just have to hope that the core is good and not going to leak (fingers crossed). I think the key was either way to have the inlet drawing water from the manifold where it is hot, and returning either to the pump or the radiator. I figured I'd leave the return on the radiator since I had a plug that fit the pump and the radiator nipple is brazed on rather than a mechanical fitting. Thanks for your help everyone. This has been a frustrating project, only because I knew that it had to be something simple, but I kept referring to the way it was hooked up by the PO, not how it should have been hooked up to function correctly in the first place. I guess I also didn't have a strong grasp on the direction of flow with the whole system. Anyway, thanks again, I'll keep you posted and post some pictures once I get the new valve in there and hook up all the vents.

[big dump]

p.s. Are you a fan of The Office? What did I tell you about yeppers?

Yeppers. See circle in pic.

[big dump]

Quick update and follow up questions. Heater blows very hot, almost too hot, however, now I'm concerned that my temp sending unit is mounted in the wrong spot. My temp guage is pegged after the engine runs for a minute, but it's not boiling over or steeming, so I think that it's just the temp guage reading improperly. Because I relocated the core inlet hose to the intake manifold, I had to move the temp sending unit from the left side, to the right side, right by the T-stat housing. Where are you guys mounting yours? There are a couple other ports that are plugged on the manifold, and a couple others on the drivers side of the block below the exhaust manifolds. Does anyone know where the factory location is? Kage, where is yours mounted?

Thanks,

[Old Chevy Mech]

I think the factory location is the same as mine, my temp sending unit is in my passenger side head.

Frank

[big dump]

Ok, I'll have to take a look and see if there's a free port. I have the Vortec heads on this motor, so I'm not sure if they're the same or not. Thanks,