1990 Honda Accord runs hot sometimes

I have a 1990 Honda Accord. It usually runs with the temperature
guage in the middle range. Frequently the guage will quicky go up
to close to, but not at the high end red mark. This happens even
when its 50 degrees out and I am going 45 mph. If I turn on the
heater the temperature usually goes back to middle. It goes down
very quicky, within 10 seconds of turning on the heater. I dont
believe the heater could cool things off that quickly.

I have a new radiator and antifreeze. I am not loosing coolant.

Could it be a hose or chamber that is blocked/pinched, and turning
on the heater is allowing the coolant to byupass the blockage ?

Any helpful comments appreciated.

G

 

Head Gasket ?

 

I'm thinking thermostat.

 

I hope u are right.

 

I doubt its the head gasket. It never gets too hot. Most of the time it
runs fine and doesnt get hot. Why would turning on the heater make the
temperature go down immediately if it were headgasket.

Thermostat sounds interesting. Does the heater somehow bypass the the
thermostat ? How difficult is it to replace the thermostat ? How much
should it cost to have someone do it (ballpark) ?

Thanks

G

 

The heater doesn't bypass but redirects heat. Those coolant lines go
through the heater core. With the heat on, a fan blows across it sending the
heat into the cabin.

For how to change it...
http://wiki.answers.com/Q/How_do_you_replace_the_thermostat_on_a_1990_Honda_Accord_LX

 

New radiator sounds like a clue. Check for air bubble in the system. I
believe a '90 has a "burp" screw.

 

It can indeed! Considering there's only about 20F or so difference between
"normal" and "overheat", the heater doesn't have to do much to cool the
engine down sufficiently.

Why was the old rad replaced? And how old was the coolant that was in there
before?

Sure does sound like a sticking thermostat. I'll bet it's crappy
aftermarket, too.

The heater feed is independent of the thermostat, so it will work even when
the engine is cold and the thermostat is closed.

Try a new OEM Honda thermostat. About $40 or so and worth every penny.

 

Where is the burp screw ? How do you use it ?

G

 

Look in the vicinity of the top radiator hose connection on the engine for
either a small hex head bolt/screw. Set the heater to max, open it a couple
of turns until coolant comes out in a steady stream without bubbles. Close
the screw, top it off & idle the engine until the radiator fan comes on
twice (heater still at max) then open it again (VERY slowly) and let any
trapped air out.

For the next several days, check & top off the radiator & overflow tank
before the first start in the morning & it should get rid of all the air.

 

Is this the same thing as using the drain screw at the bottom of the
radiator? Not sure if this Honda has one but some cars had it.

 

I doubt Honda manufactures their own thermostats -- instead buying them from
one of the high quality specialty manufacturers-- as they do for so many
parts and subassemblies of the car.

Why not just buy a high quality well designed/manufactured aftermarket
part -- not just some Big Box POS-- and save the extra dough?

 

They don't. The ones I see are made by Nippon Thermostat, are marked
"NTCL", and are of superlative quality.

Because OEM is built to Honda's exacting and stringent specs. Aftermarket,
even from the same manufacturer as the OEM stuff, is built to be cheap.

Aftermarket is crap, and aftermarket thermostats are crappy. There is no
acceptably "high quality" aftermarket thermostat available for Hondas.
Anything other than OEM is a step down.

 

OK, thanks. You convinced me...

 

You gave in quick.

 

how do you KNOW the aftermarket part is "well-designed/manufactured"?
At least with a true Honda part,you know it meets all specs.

Now,if you could find out who is Honda's OEM manufacturer for that part...
then you could go buy it aftermarket.

--
Jim Yanik
jyanik
at
localnet
dot com

 

And that makes ALL the difference in the world.

It's why a FRAM oil filter is of excellent quality when purchased with a
blue can and the "Honda" logo on it, but an aftermarket FRAM has a
questionable reputation.

Honda thermostats are made by Nippon Thermostat (NTCL).

AFAIK, NTCL is like Showa, in that they do OEM-only. No aftermarket.

 

No, air goes up. You can't drain air from a system at the bottom.

 

I replaced the thermostat in my 91 Accord. It still gave me no heat. I
replaced it again, no heat. I gave up and took it to Honda. They
replaced the thermostat. I got heat. I learned my lesson.

 

You probably were putting it in upside down to begin with. OEM SchmoEM
, a thermostat is a thermostat. Company A bids on a contract to supply
Honda with them , Honda jacks price by 30% . You are buying the exact
same aftermarket product 9 out of 10 times in most parts.