Thermostat failure ?

odyssey wrote:
> 1994 4cyl. 198k.
> Now that it is much colder outside. The temp. gauge reads very low, but
> after awhile it goes up to the normal reading of approx. 185 , but it fluxs
> from normal to low. When it's in the low reading it gives less heat. I had
> changed the waterpump this spring w/timing belt. Changed the antifreeze
> also. Hadn't changed the thermostat, would this be the problem? Or is it the
> temp. sensor ? Either way it's not reading the correct temp. to the
> computer. It running very good but its got low heat. Any idea what is wrong?
> Thanks, Dan
>
>

Because the heat output corrresponds to the reading, I think the
sensor is ok and the thermostate is sticking at least partly open.
 >> Stay informed about: Thermostat failure ? 

Because the heat fluctuates, change the thermostat. Use Toyota Red and
distilled water. If you can't find Red use Toyota Pinko pre-diluted
coolant. The pinko is supposed to last longer, but the 2-year Red is
better in fighting corrosion.

Use a Toyota thermostat. Thermostat is a part I won't use aftermarket
for any car (jiggle valve for one, heavy duty spring that resists pump
pressure another, more solid looking heat engine the third, and it
doesn't cost a whole lot more).






On Dec 2, 1:29 am, "odyssey" <nos....RemoveThis@msn.com> wrote:
> 1994 4cyl. 198k.
> Now that it is much colder outside. The temp. gauge reads very low, but
> after awhile it goes up to the normal reading of approx. 185 , but it fluxs
> from normal to low. When it's in the low reading it gives less heat. I had
> changed the waterpump this spring w/timing belt. Changed the antifreeze
> also. Hadn't changed the thermostat, would this be the problem? Or is it the
> temp. sensor ? Either way it's not reading the correct temp. to the
> computer. It running very good but its got low heat. Any idea what is wrong?
> Thanks, Dan
 >> Stay informed about: Thermostat failure ? 

Because coolant temp is such a vital parameter in so many aspects of the
operation of your EFI engine, my recommendation would be replacing the
thermostat at a MINIMUM of every 2nd year. Thermostats are simple mechanical
controls. Your thermostat will begin functional failure in one of two ways.
It will bind in the more open position causing cooler than required temps
.... or it will bind in the more closed position increasing temps. Both types
of partial failure have a significant effect on a number of critical ECU
measured parameters.

Maximum two years on a thermostat ... coolants formulated for the system
construction and design ... a little attention to this very important closed
system ... and you're doing right by the people who sweated to develop the
technology.

Oh yeah. Since the foundation of your cabin heating system is also your
engine cooling system, you can't even address your "comfort" complaint until
you ensure the health of the cooling system that everything is based on.


"odyssey" <nospam DeleteThis @msn.com> wrote in message
news:YXu4j.13801$so3.7622@newsfe18.lga...
> 1994 4cyl. 198k.
> Now that it is much colder outside. The temp. gauge reads very low, but
> after awhile it goes up to the normal reading of approx. 185 , but it
fluxs
> from normal to low. When it's in the low reading it gives less heat. I had
> changed the waterpump this spring w/timing belt. Changed the antifreeze
> also. Hadn't changed the thermostat, would this be the problem? Or is it
the
> temp. sensor ? Either way it's not reading the correct temp. to the
> computer. It running very good but its got low heat. Any idea what is
wrong?
> Thanks, Dan
>
>
 >> Stay informed about: Thermostat failure ? 

RACEGUY wrote:
> Because coolant temp is such a vital parameter in so many aspects of the
> operation of your EFI engine, my recommendation would be replacing the
> thermostat at a MINIMUM of every 2nd year. Thermostats are simple mechanical
> controls. Your thermostat will begin functional failure in one of two ways.
> It will bind in the more open position causing cooler than required temps
> ... or it will bind in the more closed position increasing temps. Both types
> of partial failure have a significant effect on a number of critical ECU
> measured parameters.
>
> Maximum two years on a thermostat ... coolants formulated for the system
> construction and design ... a little attention to this very important closed
> system ... and you're doing right by the people who sweated to develop the
> technology.


That seems a little...anal. Thermostats typically last many years,
and when they fail you can tell it's happening. 5 years would be more
like it for preventive maintainance on Toyota thermostats. Our '95 sedan
still has the original, and it still works fine. Uisng Toyota coolant is
a good idea.


(...)
 >> Stay informed about: Thermostat failure ? 

"RACEGUY" <xspamxraceguy RemoveThis @nbnet.nb.ca> wrote in message
news:475c3aa5$0$5276$9a566e8b@news.aliant.net...
> Because coolant temp is such a vital parameter in so many aspects of the
> operation of your EFI engine, my recommendation would be replacing the
> thermostat at a MINIMUM of every 2nd year. Thermostats are simple
> mechanical
> controls. Your thermostat will begin functional failure in one of two
> ways.
> It will bind in the more open position causing cooler than required temps
> ... or it will bind in the more closed position increasing temps. Both
> types
> of partial failure have a significant effect on a number of critical ECU
> measured parameters.
>
> Maximum two years on a thermostat ... coolants formulated for the system
> construction and design ... a little attention to this very important
> closed
> system ... and you're doing right by the people who sweated to develop the
> technology.
>
> Oh yeah. Since the foundation of your cabin heating system is also your
> engine cooling system, you can't even address your "comfort" complaint
> until
> you ensure the health of the cooling system that everything is based on.

The thermostat in my 99 Camry CE 6 cyl. is almost 9 years old and the temp.
guage shows EXACTLY the same reading for a warmed up engine as it did when
the vehicle was brand new. Changing out thermostats every 2 years is a giant
waste of money, increasing the odds that you will get a dud.



>
>
> "odyssey" <nospam RemoveThis @msn.com> wrote in message
> news:YXu4j.13801$so3.7622@newsfe18.lga...
>> 1994 4cyl. 198k.
>> Now that it is much colder outside. The temp. gauge reads very low, but
>> after awhile it goes up to the normal reading of approx. 185 , but it
> fluxs
>> from normal to low. When it's in the low reading it gives less heat. I
>> had
>> changed the waterpump this spring w/timing belt. Changed the antifreeze
>> also. Hadn't changed the thermostat, would this be the problem? Or is it
> the
>> temp. sensor ? Either way it's not reading the correct temp. to the
>> computer. It running very good but its got low heat. Any idea what is
> wrong?
>> Thanks, Dan
>>
>>
>
>
 >> Stay informed about: Thermostat failure ? 

"mjc13<REMOVETHIS> @verizon.net>" <"mjc13<REMOVETHIS> wrote in message
news:xXY6j.1669$ki7.578@trndny06...
> RACEGUY wrote:
>> Because coolant temp is such a vital parameter in so many aspects of the
>> operation of your EFI engine, my recommendation would be replacing the
>> thermostat at a MINIMUM of every 2nd year. Thermostats are simple
>> mechanical
>> controls. Your thermostat will begin functional failure in one of two
>> ways.
>> It will bind in the more open position causing cooler than required temps
>> ... or it will bind in the more closed position increasing temps. Both
>> types
>> of partial failure have a significant effect on a number of critical ECU
>> measured parameters.
>>
>> Maximum two years on a thermostat ... coolants formulated for the system
>> construction and design ... a little attention to this very important
>> closed
>> system ... and you're doing right by the people who sweated to develop
>> the
>> technology.
>
>
> That seems a little...anal. Thermostats typically last many years, and
> when they fail you can tell it's happening. 5 years would be more like it
> for preventive maintainance on Toyota thermostats. Our '95 sedan still has
> the original, and it still works fine. Uisng Toyota coolant is a good
> idea.

Agreed, I should have added that I always use Toyota RED.




>
>
> (...)
 >> Stay informed about: Thermostat failure ? 

Thanks for all your help. It had turned out that it was the rubber seal
around the thermostat, it had corrosion around the edge of the housing
causing the coolant to leak past the thermostat. Changed it out with Toyota
brand (with the "Jiggler" in it ) blasting warm comforting heat. Thanks
again. Dan

"odyssey" <nospam DeleteThis @msn.com> wrote in message
news:YXu4j.13801$so3.7622@newsfe18.lga...
> 1994 4cyl. 198k.
> Now that it is much colder outside. The temp. gauge reads very low, but
> after awhile it goes up to the normal reading of approx. 185 , but it
> fluxs from normal to low. When it's in the low reading it gives less heat.
> I had changed the waterpump this spring w/timing belt. Changed the
> antifreeze also. Hadn't changed the thermostat, would this be the problem?
> Or is it the temp. sensor ? Either way it's not reading the correct temp.
> to the computer. It running very good but its got low heat. Any idea what
> is wrong? Thanks, Dan
>
 >> Stay informed about: Thermostat failure ?