Looking for some guidance on the water routing for the heater core on my 20r. Before I got the truck is had been played with quite a bit and I’m not sure what all had happened other than some kind of eBay carb. I had since replaced with a Weber and I am desmogged. I have clean flow of water through my valve and through the core. I believe my problem is that I’m not actually getting hot water to the core from the engine. Here are some pictures of how the lines are, Any tips and knowledge are appreciated. I don’t believe the lines are properly routes around the manifold but I have no clue how they should look.

 

Not too sure what that red hose is doing there. I don't have anything like that on my '78 20R. Could it be bypassing your heater core? I'm assuming that red hose is coming from a port on the radiator, below the large lower radiator hose, but where is it going in the near side of the picture? The hose on mine from that port on the radiator goes straight back to the driver's side heater core port on the firewall. The passenger side heater core port has a hose from it to a port on the block, below the intake manifold, towards the rear. I would assume that to be the "hot feed" to the core. Sorry no pics on this, as the camera in my "dumb" phone is garbage.

The second pic shows the 2 short hoses that used to go to the "water choke" of the old stock 20R Aisin carb. The choke was operated via coolant temp. Toyota went to an electric choke starting with the 22R's.

 

Sorry, the red line is not a hose it’s the power for the GM alternator setup I’ve got going and I have cleaned up the wiring really. I hate it when a problem goes away with no clear answer but this one did. Turns out I could clearly see the lines under the manifold but they were routed correctly. The water choke lines confused me but I understand now, he didn’t want to buy the delete blockoff plates so he just looped then, no big deal. I flushed everything well with no effect. I pulled all the lines and checked for flow, I had it. Gave up and drove it to work yesterday. Half way to work I noticed the defroster was hot as hell. I think there was blockage somewhere and all my fiddling busted it loose. Anyways, yeah the hose from the timing cover on passenger side is pretty much going back into the top of the manifold because the water choke isn’t there. Thanks for the help.

 

Could be that the valve was just stuck closed, or blocked with some hardened sediment that the poking around & flushing cured. Curious if you just straight water flushed it or used the flush chemical tho. Given the age & lack of service history I'm sure there is/was some sediment in the system.

I also don't like it when a problem goes away and I don't know why.

 

lol yeah this old truck is just a beater wheeling rig so while I’m fixing things in it I’m not investing the money into it that I have my 4Runner restoration. My flush was simply a garden hose shoved into the inlet until I had clean flow out the other side, then I swapped it to the outlet and back flushed it haha. I guess it worked.

 

Wish I had my 78...a photo of a working hose setup in an engine bay would really help. I can't tell from the photos but it sort of looks like your heater core might be bypassed. I see one hose going through the firewall but don't see another. If there's only one, it's probably the return line, and there's nothing going in. But you'll have to verify if there's a hose going in, and a hose coming out, and trace them to their origin and end. Shouldn't be too hard on that old engine. Easy to see stuff.

 

the send line is the one going into the heater valve, and then through the firewall. The return is the one leaving the firewall then running to a “T” at the water pump. Turns out the heater lines were all correct there was just either air or blockage somewhere and I fixed it. The only weird lines I have are the hoses that would have gone to the water choke. Looks like LCE makes some block plates and plugs but it’s a giant PITA to get to that timing cover hole.

 

Ah great, I didn't read that post all the way through where you mentioned that it started working.