98 sohc overheating 105K miles

The check gage light came on today after a short trip and when I looked my
temp gage was pegged at the high end. I pulled over and turned on the heater
on high and the temp dropped down enough to turn the trouble light off and
drive home on.



I just recently moved back from a warm climate and have been driving and
parking outside (Chicago) in very cold temps for the first time in years.



I pulled in it in the heated garage to let everything thaw for a few hours
and then started it and let it idle and it went back to the high end after
about 15-20 minutes.



Coolant reservoir is at the proper level. When I turn on the heater it heats
up and blows hot air and the engine temp drops so that tells me that the
waterpump is at least providing flow. At the same time the top radiator hose
is warm but not as hot as I would expect.



This all leads me to believe that the thermostat is stuck.



My repair manual is packed up in some warehouse right now so I can't check
it. Do all of these indications make sense for a stuck thermostat? How hard
is it to replace on this car (I've done them on several other cars).



I also did a google search and found a thread that recommended using only
original for thermostats due to a better design for this model. Anyone else
know about this.



As always thanks in advance for any help,



Steve

One other important thing that I forgot to mention:
The Fan does run but it starts running as soon as the car starts. Is that
normal?

Thanks Again
Steve


"sehaare" > wrote in message
news
> The check gage light came on today after a short trip and when I looked my
> temp gage was pegged at the high end. I pulled over and turned on the
> heater on high and the temp dropped down enough to turn the trouble light
> off and drive home on.
>
>
>
> I just recently moved back from a warm climate and have been driving and
> parking outside (Chicago) in very cold temps for the first time in years.
>
>
>
> I pulled in it in the heated garage to let everything thaw for a few hours
> and then started it and let it idle and it went back to the high end after
> about 15-20 minutes.
>
>
>
> Coolant reservoir is at the proper level. When I turn on the heater it
> heats up and blows hot air and the engine temp drops so that tells me that
> the waterpump is at least providing flow. At the same time the top
> radiator hose is warm but not as hot as I would expect.
>
>
>
> This all leads me to believe that the thermostat is stuck.
>
>
>
> My repair manual is packed up in some warehouse right now so I can't check
> it. Do all of these indications make sense for a stuck thermostat? How
> hard is it to replace on this car (I've done them on several other cars).
>
>
>
> I also did a google search and found a thread that recommended using only
> original for thermostats due to a better design for this model. Anyone
> else know about this.
>
>
>
> As always thanks in advance for any help,
>
>
>
> Steve
>
>
>
>

The fan will run if the AC is enabled.... the AC is enabled if air blows on
glass....

First thing is to check the strength of the coolant.


"sehaare" > wrote in message
...
> One other important thing that I forgot to mention:
> The Fan does run but it starts running as soon as the car starts. Is that
> normal?
>
> Thanks Again
> Steve
>
>
> "sehaare" > wrote in message
> news
> > The check gage light came on today after a short trip and when I looked
my
> > temp gage was pegged at the high end. I pulled over and turned on the
> > heater on high and the temp dropped down enough to turn the trouble
light
> > off and drive home on.
> >
> >
> >
> > I just recently moved back from a warm climate and have been driving and
> > parking outside (Chicago) in very cold temps for the first time in
years.
> >
> >
> >
> > I pulled in it in the heated garage to let everything thaw for a few
hours
> > and then started it and let it idle and it went back to the high end
after
> > about 15-20 minutes.
> >
> >
> >
> > Coolant reservoir is at the proper level. When I turn on the heater it
> > heats up and blows hot air and the engine temp drops so that tells me
that
> > the waterpump is at least providing flow. At the same time the top
> > radiator hose is warm but not as hot as I would expect.
> >
> >
> >
> > This all leads me to believe that the thermostat is stuck.
> >
> >
> >
> > My repair manual is packed up in some warehouse right now so I can't
check
> > it. Do all of these indications make sense for a stuck thermostat? How
> > hard is it to replace on this car (I've done them on several other
cars).
> >
> >
> >
> > I also did a google search and found a thread that recommended using
only
> > original for thermostats due to a better design for this model. Anyone
> > else know about this.
> >
> >
> >
> > As always thanks in advance for any help,
> >
> >
> >
> > Steve
> >
> >
> >
> >
>
>

Jim,

I flushed the system and replaced the coolant less than 6 months ago. I did
a > 50/50 mix with prestone. The coolant level is fine, I have no leaks so
I haven't had to add any water and haven't diluted the mixture.

Does the fact that running the heater will cool off the temperature make
sense with a stuck thermostat?

Steve


"Jim Warman" > wrote in message
news:2JLDd.57091$dv1.44931@edtnps89...
> The fan will run if the AC is enabled.... the AC is enabled if air blows
> on
> glass....
>
> First thing is to check the strength of the coolant.
>
>
> "sehaare" > wrote in message
> ...
>> One other important thing that I forgot to mention:
>> The Fan does run but it starts running as soon as the car starts. Is that
>> normal?
>>
>> Thanks Again
>> Steve
>>
>>
>> "sehaare" > wrote in message
>> news
>> > The check gage light came on today after a short trip and when I looked
> my
>> > temp gage was pegged at the high end. I pulled over and turned on the
>> > heater on high and the temp dropped down enough to turn the trouble
> light
>> > off and drive home on.
>> >
>> >
>> >
>> > I just recently moved back from a warm climate and have been driving
>> > and
>> > parking outside (Chicago) in very cold temps for the first time in
> years.
>> >
>> >
>> >
>> > I pulled in it in the heated garage to let everything thaw for a few
> hours
>> > and then started it and let it idle and it went back to the high end
> after
>> > about 15-20 minutes.
>> >
>> >
>> >
>> > Coolant reservoir is at the proper level. When I turn on the heater it
>> > heats up and blows hot air and the engine temp drops so that tells me
> that
>> > the waterpump is at least providing flow. At the same time the top
>> > radiator hose is warm but not as hot as I would expect.
>> >
>> >
>> >
>> > This all leads me to believe that the thermostat is stuck.
>> >
>> >
>> >
>> > My repair manual is packed up in some warehouse right now so I can't
> check
>> > it. Do all of these indications make sense for a stuck thermostat? How
>> > hard is it to replace on this car (I've done them on several other
> cars).
>> >
>> >
>> >
>> > I also did a google search and found a thread that recommended using
> only
>> > original for thermostats due to a better design for this model. Anyone
>> > else know about this.
>> >
>> >
>> >
>> > As always thanks in advance for any help,
>> >
>> >
>> >
>> > Steve
>> >
>> >
>> >
>> >
>>
>>
>
>

"sehaare" > wrote in message
...
> Jim,
>
> I flushed the system and replaced the coolant less than 6 months ago. I
did
> a > 50/50 mix with prestone. The coolant level is fine, I have no leaks
so
> I haven't had to add any water and haven't diluted the mixture.
>
> Does the fact that running the heater will cool off the temperature make
> sense with a stuck thermostat?
>
> Steve
>

http://auto.howstuffworks.com/cooling-system10.htm

H

Yes... the heater is just like a little radiator and can help in cases like
this. As you had opined, thermostats are pretty cheap and not too hard to
change (even if that's not the root cause, I don't trust overheated
thermostats - been bitten before). Tale a look at the AC condenser and
another at the radiator front (between it and the AC condenser). Lots of
crud can gather in here.... most of it can absorb moisture and still flow
acceptably when above freezing yet turn into something impenetrable when
below freezing.


"sehaare" > wrote in message
...
> Jim,
>
> I flushed the system and replaced the coolant less than 6 months ago. I
did
> a > 50/50 mix with prestone. The coolant level is fine, I have no leaks
so
> I haven't had to add any water and haven't diluted the mixture.
>
> Does the fact that running the heater will cool off the temperature make
> sense with a stuck thermostat?
>
> Steve
>
>
> "Jim Warman" > wrote in message
> news:2JLDd.57091$dv1.44931@edtnps89...
> > The fan will run if the AC is enabled.... the AC is enabled if air blows
> > on
> > glass....
> >
> > First thing is to check the strength of the coolant.
> >
> >
> > "sehaare" > wrote in message
> > ...
> >> One other important thing that I forgot to mention:
> >> The Fan does run but it starts running as soon as the car starts. Is
that
> >> normal?
> >>
> >> Thanks Again
> >> Steve
> >>
> >>
> >> "sehaare" > wrote in message
> >> news > >> > The check gage light came on today after a short trip and when I
looked
> > my
> >> > temp gage was pegged at the high end. I pulled over and turned on the
> >> > heater on high and the temp dropped down enough to turn the trouble
> > light
> >> > off and drive home on.
> >> >
> >> >
> >> >
> >> > I just recently moved back from a warm climate and have been driving
> >> > and
> >> > parking outside (Chicago) in very cold temps for the first time in
> > years.
> >> >
> >> >
> >> >
> >> > I pulled in it in the heated garage to let everything thaw for a few
> > hours
> >> > and then started it and let it idle and it went back to the high end
> > after
> >> > about 15-20 minutes.
> >> >
> >> >
> >> >
> >> > Coolant reservoir is at the proper level. When I turn on the heater
it
> >> > heats up and blows hot air and the engine temp drops so that tells me
> > that
> >> > the waterpump is at least providing flow. At the same time the top
> >> > radiator hose is warm but not as hot as I would expect.
> >> >
> >> >
> >> >
> >> > This all leads me to believe that the thermostat is stuck.
> >> >
> >> >
> >> >
> >> > My repair manual is packed up in some warehouse right now so I can't
> > check
> >> > it. Do all of these indications make sense for a stuck thermostat?
How
> >> > hard is it to replace on this car (I've done them on several other
> > cars).
> >> >
> >> >
> >> >
> >> > I also did a google search and found a thread that recommended using
> > only
> >> > original for thermostats due to a better design for this model.
Anyone
> >> > else know about this.
> >> >
> >> >
> >> >
> >> > As always thanks in advance for any help,
> >> >
> >> >
> >> >
> >> > Steve
> >> >
> >> >
> >> >
> >> >
> >>
> >>
> >
> >
>
>

Jim,
Thanks for the advice. I replaced the thermostat and the problem appears to
be fixed. When I first had the problem I thought that maybe I had an ice
problem with the radiator and did not find anything on an initial inspection
but I'll take another look when its daylight tomorrow just to be sure.

One thing that still puzzles me is that the radiator fan appears to be
running continuously even with the engine cold and the Heater/AC controls
set to Off. I pretty sure that it should only run when the temp goes above a
setpoint or when the A/C is turned on but the Haynes manual that I have
doesn't show any schematics of the fan circuit so I can't trouble shoot it.
Do you have any advice on that one?

Thanks
Steve
"Jim Warman" > wrote in message
news:0K2Ed.9518$06.9116@clgrps12...
> Yes... the heater is just like a little radiator and can help in cases
> like
> this. As you had opined, thermostats are pretty cheap and not too hard to
> change (even if that's not the root cause, I don't trust overheated
> thermostats - been bitten before). Tale a look at the AC condenser and
> another at the radiator front (between it and the AC condenser). Lots of
> crud can gather in here.... most of it can absorb moisture and still flow
> acceptably when above freezing yet turn into something impenetrable when
> below freezing.
>
>
> "sehaare" > wrote in message
> ...
>> Jim,
>>
>> I flushed the system and replaced the coolant less than 6 months ago. I
> did
>> a > 50/50 mix with prestone. The coolant level is fine, I have no leaks
> so
>> I haven't had to add any water and haven't diluted the mixture.
>>
>> Does the fact that running the heater will cool off the temperature make
>> sense with a stuck thermostat?
>>
>> Steve
>>
>>
>> "Jim Warman" > wrote in message
>> news:2JLDd.57091$dv1.44931@edtnps89...
>> > The fan will run if the AC is enabled.... the AC is enabled if air
>> > blows
>> > on
>> > glass....
>> >
>> > First thing is to check the strength of the coolant.
>> >
>> >
>> > "sehaare" > wrote in message
>> > ...
>> >> One other important thing that I forgot to mention:
>> >> The Fan does run but it starts running as soon as the car starts. Is
> that
>> >> normal?
>> >>
>> >> Thanks Again
>> >> Steve
>> >>
>> >>
>> >> "sehaare" > wrote in message
>> >> news >> >> > The check gage light came on today after a short trip and when I
> looked
>> > my
>> >> > temp gage was pegged at the high end. I pulled over and turned on
>> >> > the
>> >> > heater on high and the temp dropped down enough to turn the trouble
>> > light
>> >> > off and drive home on.
>> >> >
>> >> >
>> >> >
>> >> > I just recently moved back from a warm climate and have been driving
>> >> > and
>> >> > parking outside (Chicago) in very cold temps for the first time in
>> > years.
>> >> >
>> >> >
>> >> >
>> >> > I pulled in it in the heated garage to let everything thaw for a few
>> > hours
>> >> > and then started it and let it idle and it went back to the high end
>> > after
>> >> > about 15-20 minutes.
>> >> >
>> >> >
>> >> >
>> >> > Coolant reservoir is at the proper level. When I turn on the heater
> it
>> >> > heats up and blows hot air and the engine temp drops so that tells
>> >> > me
>> > that
>> >> > the waterpump is at least providing flow. At the same time the top
>> >> > radiator hose is warm but not as hot as I would expect.
>> >> >
>> >> >
>> >> >
>> >> > This all leads me to believe that the thermostat is stuck.
>> >> >
>> >> >
>> >> >
>> >> > My repair manual is packed up in some warehouse right now so I can't
>> > check
>> >> > it. Do all of these indications make sense for a stuck thermostat?
> How
>> >> > hard is it to replace on this car (I've done them on several other
>> > cars).
>> >> >
>> >> >
>> >> >
>> >> > I also did a google search and found a thread that recommended using
>> > only
>> >> > original for thermostats due to a better design for this model.
> Anyone
>> >> > else know about this.
>> >> >
>> >> >
>> >> >
>> >> > As always thanks in advance for any help,
>> >> >
>> >> >
>> >> >
>> >> > Steve
>> >> >
>> >> >
>> >> >
>> >> >
>> >>
>> >>
>> >
>> >
>>
>>
>
>