no heat!!!

[cale]

I have a 1986 GL10. It sat for about 3 years with a broken timing belt,
in extreme washington weather. I recently got the title signed over to
me and had it fixed. It has been running great with one exception. It
overheated once. I filled it up with coolant, and it runs great again.
But now that its getting colder, I need the heater to work. It doesn't.
It blows air, just medium temperature. Any ideas? I am thinking a
sticky thermostat? Thanks

 

[johninKY]

Get the engine up to operating temperature and then touch both heater
hoses. If both are hot to the touch then this rules out an air pocket.
The controls are vacuum operated. Check that white cannister under the
hood over on the passenger side of the firewall.

 

[Robert L Wilson]

Given the history, there is a good chance the heater core is plugged up with
junk that was circulating in the coolant. The suggestion to feel both hoses
is a good idea. If only one is hot that might indicate water is not flowing
through the core. I don't know how easy it is to remove the core on a 1986:
On many recent cars it is terrible, requiring removal of most of the dash.
If it appears to be plugged (you can disconnect the hoses and see how freely
air or liquid moves through) and you can get it out easily, take it to a
radiator repair place. Otherwise you can hope there is a slight trickle
through it and that some strong radiator cleaner will gradually eat out the
blockage.
But before going to that trouble, do check the hoses for how hot they get!
Bob Wilson

 

[Rick Courtright]

Hi,

The fact it overheated once since you've gotten it back together tells
me there may have been air in the system. Heater cores are generally
higher than most of the rest of the engine, so there could still be air
in there.

After doing the checks already suggested to see if the hoses are hot on
both sides (if I'm not mistaken, you car has a "constant flow" heater
core, w/ heat to the cabin controlled by the vacuum linkages mentioned),
you can try this drill:

Disconnect both heater hoses. Run water at pretty good pressure both
ways thru the core to make sure you ARE getting good flow. Then hook up
ONE hose to the core. Make sure the end of the other one's close to its
connector, but leave it disconnected for now. Take a small length of
appropriate sized hose and hook to the other side. Remove the rad cap.

Now, get a funnel and put it in the open end of the disconnected hose,
then begin to fill the system "backwards" while trying to keep the
funnel at a point higher than anywhere else in the system. If you start
getting coolant flowing out the radiator cap fitting, install the cap.
Then, when you start seeing coolant coming out of the temporary hose,
you can take it off and hook up the real one. Jack up the front of the
car as high as you can, take the radiator cap back off if you had to
install it, and run the engine at idle w/ the heater on full to finish
burping the system. Turn it off, let it cool for a while, then refill
the radiator as necessary and install the cap. Sometimes it takes a few
"burp" cycles to get all the air out.

Sticky t-stat? Does the temp gauge register in the normal range? Does
the upper rad hose get nice and hot? If yes on both, the t-stat is
PROBABLY working ok, but since the car's been sitting so long, it
wouldn't hurt to install a new one. OEM is best there!

Good luck!

Rick