re: help--overheated 86CGT

[Ken <kkeith@qnet.com>]

Jeffrey A Blanchard <jblancha@u.arizona.edu> wrote:
> 
> My 1986 Coupe GT overheated on the way to the university this morning.
> I opened the hood and noticed coolant was coming out from the expansion
> tank but didn't seem especially hot.  The temp gage was in the normal
> range.  After sitting there for 30min, I started it up and the temp. gage
> immediately read "HOT", but no rad. fan.  I shorted out the radiator fan
> thermoswitch and the radiator fan came on but didn't seem to have much of
> an effect on the temperature (I didn't leave the engine running long since
> it was so hot).

Sounds strange.  I know engines are supposed to "get hotter" after
sitting, 
as the heat soaks into the engine from the coolant.  That might be what 
happened here, but that doesn't explain the overflowing coolant.

I suspect that if there is steam, the motor is either actually
overheated 
and hot enough to overcome the caps overpressure relief valve, or the 
cap is bad and needs to be replaced.  Is the reservoir cap black or
white?
 
> Is it possible that the water pump is bad?  It is on the timing belt, so
> it must still be turning.

A problem I've heard of with the waterpumps is that the impeller will 
actually *slip* on the shaft.  So, everything is turning except the part 
that really needs to be.  That might be a possible cause.

Also, I think on the '86 Coupe GT's, you should have an "after-run" fan 
switch, which should cause your radiator fan to come on when the
ignition 
is switched off if the head is hot enough.  If that's not happening (and 
your car actually has this feature, earlier one's didn't) then you might 
have a problem with the fan and/or it's electrical circuit.

> I will short out the rad. fan thermoswitch
> after it cools down and try idling it and see what happens.
> 
> BTW, Yesterday I was working on the car but only changed the oil,
> tranmission oil, and spark plugs.  

I wish it was that easy for me.  I still have a "plugged" tranny, and 
can't get the plug out.

Just kinda throwing it out there, HTH.

Good luck,

Ken