TinMan

I know this has been beat to death around here, but have been looking for another post that matches what my heater symptoms are, and just have not found a match.

When my runner warms up, I can turn on the heat and it will blow hotter than fire for about 2 mins, then gradually get colder until it is just like the vent blowing air from the outside.

When I got the truck the dash lever for cool/heat would not move. After a little looking I found that the valve on the firewall was corroded shut. A little wd40 and some love and it moves freely now and does not leak.

I have let it run without the radiator cap on several different times to ensure there is no air in the system.

You can plainly hear that the different doors in the heater box are working properly, and there is very little resistance in the switch to change between modes. Have taken the dash apart and looked at all the cables and ensured that things are working properly.

The temp guage runs right were it should. But I have not taken the thermostat out and tested it on the stove. I can take the radiator cap off and watch antifreeze move throught the system as the thermostat opens and closes so I am reasonably sure it is working right.

This hot to cold happens both on the heater in the dash and the one in the console between the seats.

Right now I am leaning toward the heater cores being clogged and when I turn the heaters on, once the fluid starts moving is plugs up. Any of you think this may be right.

If this is so what is the best way to back flush the system. I picked up one of the prestone back flush systems at AZ, but have not done it yet because I am not sure which line the T fitting would go in. If anyone has done this and can post a picture here it would be great.

Any input is always appreciated.

myyota

If your heater cores were plugged you would get very little heat all the time, but it wouldn`t hurt to back flush the whole system, and to do that you need to unhook the heater from the heater valve under the hood and the other heater hose next to it. The heater hose that conected to the heater valve is the inlet hose and the other heater hose is the outlet hose, you need to conect your garden hose to the outlet hose and turn it on, and that will back flush the system. Run water through the system until it comes out clean and clear and your done.

TinMan

Had a long lounch today so I thought I would back flush the heater cores.

I cut the fire wall heater core outlet hose and put in the prestone T fitting. took off the end of the tubing that goes to the Y pipe, and clamped it shut with a pair of vise grips. Hooked up a garden hose to the T and flushed out the heater core. Good lord the amount of funk that came out of it was amazing. I let it run for about 5 min after the water turned clear.

Did the same thing to the rear heater core. Not as much funk, but still a good bit.

After seeing that much funk in the hear cores, and knowing that the antifreeze ratio was way low, I decided to back flush the whole system. There was so much rusty funk that came out, and for so long that guys were coming out to watch in amazement.

After about 5 min of clear water, I put it all back together and noticed there was still a lot of stuff in the radiator. So went to AZ and got a tub of coolant system cleaner, put it in. I still have to run it for about 4 more hours before I back flush it again. I am driving it around with the heaters wide open that way the cores can get a good cleaning also.

Also back flushed out the heater valve on the fire wall.

So far the heat is blowing hot enough for you to have to pull your hand away from it. And it is constantly that hot.

After the next back flush I plan to fill it with Toyota extended life red.