I've been driving my '88 4Runner with 22RE for almost 9 years and the heater has never blown very hot. It's gets warm, but I'm about to move to a colder climate so I need it to start working properly.

New thermostat didn't help. I haven't looked closely but do the coolant hoses that run through the idle air control valve or anywhere else bypass the thermostat? (The IAC valve has also never worked in the time that I've owned the vehicle, so it's got no choke either.)

There was some corrosion in the cooling system that warranted head gasket replacement before I bought the truck. I can see some hard white deposits in the radiator hose pipes, etc., still. The hoses going into and out of the heater core seem to be about the same temperature and seem pretty hot, but I don't know what they're supposed to feel like. I even bypassed the valve on the firewall to make sure it wasn't restricting flow. Nothing seems to get the heater to blow hot.

If I do need to replace my heater core, must I remove the evaporator or is there a way to do it without discharging my air con?

Thanks!

Try back flushing the heater core. How? Run water through the core backwards to normal flow and see if anything comes out and how well it flows. I used a garden hose and nozzle shoved into the heater lines to do mine. Could also try something in the core to dissolve any buildup and see if that helps.

Maybe the blend door is not opening, therefore bypassing the heater core?

Are you running a hot-enough thermostat? What temp thermo does your truck need? I think mines uses a 185.

If you back flush use low pressure. House wter pressure can easily get to 60 lbs.
that will blow up a heater core....

I've had three of those model trucks and none of them has given me adaquate heat. On the last two I did a generic back flush and switched the heater hoses around at the core. Both gave me 25% better heat. I'm sure there will be posts that say don't do this but I can tell you it worked for me 2 out of 2.

I have a 1990 that you have to keep on low all winter long because it'll melt your tennis shoes! I sure wished they'd have figured the cores out in the 80's. I just bought a 84 that the heater couldn't melt a snow cone on the 4th of july!!!


Let me know how you come out !!


Jeffro

It's a pretty common fix actually. <img src="/forums/images/graemlins/cyclops.gif" alt="" />

One thing to check... The heater hose / control valve on the firewall is the highest point on the cooling system and it will airlock the heater core if you don't bleed it.

With the engine COLD and running and both front and rear heaters set to hot, loosen the hose clamp on the contol valve hose and pull the hose off the valve a bit until coolant comes out. This fixed the same problem with my '89 after a rad swap as there was just too much air in there to flush out.

I should have replied months ago, but backflushing blew a whole heap of old gasket material out of the heater core! I can't believe I didn't think of trying that before. I guess that's what forums are for! Thanks to all who replied!

I figured this had to be an old post, seemed kind of odd for August!