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87 4runner , Heater not working

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Old 10-12-2005, 05:58 PM   #1
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87 4runner , Heater not working

I've flushed the heater core ,till all that came out was nice and clean from both sides. I replaced T-stat , and radiator cap. The switch moves the valve on the fire wall open and closed. The hose on the passenger side does not feel like it has water in it. What else can I look for ?
On a further note . I had been lossing coolant intermitantly, with no sign of leaks anywhere . I put some bars block sealer in , and now the fluid seems topped off fine. If it was ( is ) a head gasket would the sealer be a decent temp fix ? Thanks David.
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Old 10-13-2005, 09:29 AM   #2
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Have seen the gen 1 & 2 heater cores fill with gunk.. the new enviormently friendly cooling system flush on the market today will not (to the best of my knowledge) clean it.. but the old stuff with an acid base did..

Buddy had to replace his..

and yes you can pass clean water through it but there is not enough surface open to make heat..

my buddy's theory, after changing his (85 pick-up) is that the first guy on the assembly line sets the heater core down and the truck is built around it...

Good luck..

If I remember the name of the acid in the old flush I'll post it..
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Old 10-13-2005, 09:37 AM   #3
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If you have an exhaust-cooling system HG leak, then stop leak will do no good. What happens is that the combustion pressure in the cylinder forces itself into the cooling system, partially filling the cooling system with exhaust gas. The gas rises to the highest point in the system, which happens to be the heater valve and heater core. If this happens, you may be able to hear a gurgling or whoosing sound when you rev the engine with the heater valve open. A cooling system pressure test can be used to check if this is happening, you look for the system pressure to rise with engine RPM. Or you can do a chemical test of the coolant looking for exhaust contamination:

I found lack of heater output was almost always one of my first signs of a HG leak on my 22RE.

You might also inspect the heater valve inside, remove the hose and make sure the valve is not clogged. I did have that problem on my old Landcruiser. The valve was almost totally clogged with deposits. A new valve and the heater output was much improved.

Last edited by 4Crawler; 10-13-2005 at 09:38 AM.
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Old 10-13-2005, 10:19 AM   #4
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Find a hose clamp connection on the firewall at the highest point. Warm it up, long enough for the coolant to warm and the thermostat to open and the system to pressurize. THen crack the hose clamp and let the air burp out. BE CAREFUL not to burn yourself.

Another thought is that the bars leak might've clogged up something, like the heater core. That stuff is bad news and should never be used. If there's a leaking problem -fix it, don't stuff debris in the hole.

Last edited by Flamedx4; 10-13-2005 at 10:21 AM.
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