Heater core replacement

[Jerry Carson]

Inconsistent heat like that indicates an air pocket.

While the engine is cool, pull the front end uphill, like onto ramps or uphill and onto a curb. Open the radiator cap to check fluid level. Fill to top of neck.
Open the heater valve to full hot.

Start engine and let it run up to full temperature. As the fluid starts to expand and puke out the neck , install the radiator cap. After driving it, park it back uphill and let it cool.

Repeat the process. You should see lower coolant levels the first time or two, then you will see it stabilize and no longer lower levels.

It's possible that someone did not install the thermostat bleed hole at the top to allow the bubbles to move out of the system freely.

Fill your overflow tank to the proper line after each time you do this. You should see both levels stabilize.

The higher you place the front end the better. I have a slanted driveway, so I put mine on ramps facing uphill, so it was way up. (Bottom of the front tire was about 14" higher than the bottom of the rear tire)

If you are seeing a loss of coolant, then you may have a leak somewhere. I had a leak on the o-rings for the coolant bypass pipe above the thermostat and it took almost 12 months of looking until I finally saw the wet evidence of where it was leaking. As you fix one place, it may start leaking elsewhere, as you get the system better sealed.

Oh, and change your radiator cap.

Thx will try this

 

[Malleus]

It is producing inconsistent heat. I had a shop flush and flush the system it at times puts out very hot air but also produces very luke warm air. Will continue to live with it. Thought it is a time consuming task. Thinking I might drive it some more then flush the system again. Who knows what the previous owner ran it

This could also be a blend door position failure. The A/C section of the FSM is in the Resources section as a stand alone resource. I recommend downloading it, so you know what the system looks like and then go through the troubleshooting steps, before trying to "fix" anything. You might find the solution is simpler than you expect. You also might find you need to remove the dash panel to get at the heater core itself. You won't know until you have completed the troubleshooting procedure.

I've removed a couple of dash panels, and it's never gotten easier than the first time, although I didn't think it was all that hard. I do agree that you need to print the pages of the FSM related to the removal and installation of the dash and use the fastener chart to keep yourself organized.

FWIW, I know a lot of old cooling systems have the potential for trapped air, but given the fact that the upper radiator tank is above the outlet at the head, which is also above the head cooling jacket, I'm not sure I understand how this can happen to a 1FZ-FE engine. I also make a point to fill the block through the outlet and not the radiator, so that may have something to do with the fact that I've never had this happen.

 

[Mrtwooooo]

Can you explain what steps you took to make a 96 heater core work

You'd have to look at the diagrams for a 96 and then the diagrams for a 97. I really don't know if a heater core for a 97 is still available at this point. From what I think remember the piping coming off the earlier version heater core were one piece with the core. Like in the photo. and the 97 version of the core did not have the pipes attached to the core so you'd have to buy them separate. I would think if you could source a 97 core you'd also have to source the hard pipes that attached to the core also. Also believe the 97 cores were aluminum. When I replaced mine I was lucky that Beno was able to get me the proper heater core. Probably one of the last ones at the time. The project was a complete pain. The dash removal part was not that bad. Removing the assembly you see in the photo was the paint. The one tab coming off the assembly at the bottom of the photo overlaps the assembly that houses the evaporator. I didn't want to have to discharge my AC system to get the evaporator out.