Rapid cooling on downhill - thermostat problem?

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Old 03 Mar 2005, 09:15 pm   #1 (permalink)
bauz
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Default Rapid cooling on downhill - thermostat problem?

1991 Camry DX, 4cyl, 97K, auto

when I drive down the hills on the way to/from LA (Grapevine), the engine
temperature goes low, and it appears in the same level as the car just
started in morning. It happens in the summer too. In the winter it gets so
low that the transmission is disengaging the overdrive, and it takes some
time until OD is available again. Usually it happens in the last downhill
slop into the flat hwy 5, and when everyone drives 70mph around me, I am
restricted to 50-55mph, because above that the engine start screaming for
help. I noticed that some members are from southern CA, and I wonder if it
is normal.
about a year ago the coolant was changed with Toyota's 50/50 mix
(according to the mechanic), even though I always had this problem. While
going downhill, I let the engine do most of the braking.
Could it be the thermostat? any other possibilities?
I don't want to ask my mechanic, because he recognizes my limited
knowledge, and volunteers to replace any part that I mention in my
questions.
Thanks for your comments suggestions.

BTW - thanks to all the members who responded to my previous post about
the vibrations in high speed. It was the wheel bearings, as suggested by
davidj92 and robmurr. Before I knew about this NG, I asked the mechanic if
the vibrations are from the trans, he right away became certain about it,
and told me that I better change it immediately unless I want to get
stuck. Thanks to this NG, $185 solved the problem.

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Old 03 Mar 2005, 09:18 pm   #2 (permalink)
Mark A
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Default Re: Rapid cooling on downhill - thermostat problem?

"bauz" <b_avta@nospam.hotmail.com> wrote in message
news:b97d32a01ded4a044c8a4ad37407867a@localhost.ta lkaboutautos.com...
> 1991 Camry DX, 4cyl, 97K, auto
>
> when I drive down the hills on the way to/from LA (Grapevine), the engine
> temperature goes low, and it appears in the same level as the car just
> started in morning. It happens in the summer too. In the winter it gets so
> low that the transmission is disengaging the overdrive, and it takes some
> time until OD is available again. Usually it happens in the last downhill
> slop into the flat hwy 5, and when everyone drives 70mph around me, I am
> restricted to 50-55mph, because above that the engine start screaming for
> help. I noticed that some members are from southern CA, and I wonder if it
> is normal.
> about a year ago the coolant was changed with Toyota's 50/50 mix
> (according to the mechanic), even though I always had this problem. While
> going downhill, I let the engine do most of the braking.
> Could it be the thermostat? any other possibilities?
> I don't want to ask my mechanic, because he recognizes my limited
> knowledge, and volunteers to replace any part that I mention in my
> questions.
> Thanks for your comments suggestions.
>

Yes, could be the thermostat.


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Old 03 Mar 2005, 10:17 pm   #3 (permalink)
Jason James
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Default Re: Rapid cooling on downhill - thermostat problem?


"bauz" <b_avta@nospam.hotmail.com> wrote in message
news:b97d32a01ded4a044c8a4ad37407867a@localhost.ta lkaboutautos.com...
> 1991 Camry DX, 4cyl, 97K, auto
>
> when I drive down the hills on the way to/from LA (Grapevine), the engine
> temperature goes low, and it appears in the same level as the car just
> started in morning. It happens in the summer too. In the winter it gets so
> low that the transmission is disengaging the overdrive, and it takes some
> time until OD is available again. Usually it happens in the last downhill
> slop into the flat hwy 5, and when everyone drives 70mph around me, I am
> restricted to 50-55mph, because above that the engine start screaming for
> help. I noticed that some members are from southern CA, and I wonder if it
> is normal.
> about a year ago the coolant was changed with Toyota's 50/50 mix
> (according to the mechanic), even though I always had this problem. While
> going downhill, I let the engine do most of the braking.
> Could it be the thermostat? any other possibilities?
> I don't want to ask my mechanic, because he recognizes my limited
> knowledge, and volunteers to replace any part that I mention in my
> questions.
> Thanks for your comments suggestions.
>
> BTW - thanks to all the members who responded to my previous post about
> the vibrations in high speed. It was the wheel bearings, as suggested by
> davidj92 and robmurr. Before I knew about this NG, I asked the mechanic if
> the vibrations are from the trans, he right away became certain about it,
> and told me that I better change it immediately unless I want to get
> stuck. Thanks to this NG, $185 solved the problem.


The thermostat is not regulating the coolant temperature by closing
partially to limit coolant flow thru the radiator on those down hill runs
when the hot coolant is pumped thru the radiator with little heat transfer
from the waterjacket.
New thermostat time.

Jason


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Old 04 Mar 2005, 06:54 am   #4 (permalink)
m Ransley
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Default Re: Rapid cooling on downhill - thermostat problem?

Definatly the thermostat, use a Toy thermostat my last three non Toy
have failed fast and the last one had to narrow a gasket always allowing
some water to bypass. If your overdrive disengages you are running at
110-120f, running below 140f increases friction, oil contamination, and
Decreases milage, oil life. Fix it now and change the oil. Spend the
extra buck for a Toyota thermostat.

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Old 04 Mar 2005, 08:10 am   #5 (permalink)
Daniel
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Default Re: Rapid cooling on downhill - thermostat problem?

I don't want to ask my mechanic, because he recognizes my limited
knowledge, and volunteers to replace any part that I mention in my
questions.
------------
You _definitely_ need to find a new mechanic.
Sounds like this guy is out for your money rather than the proper
functioning and maintenance/ repair of your automobile which _should_
be his first concern.
There are many mechanics in Southern California familiar with Toyota.
Look for a clean shop when you feel comfortable with the way you are
treated and can develop a level of trust with the service personnel.
Try reading the Haynes manual to familiarize yourself with the
mechanical aspects of your car. It is an easy an inexpensive way to
learn.
You don't have to do any of the procedures, but they have pictures to
show you what the components look like, and some sections that describe
how things work to help you be more informed when talking to a
mechanic.
By the way, it is _their_ job to diagnose what is wrong with your car -
not yours.

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Old 04 Mar 2005, 12:41 pm   #6 (permalink)
bauz
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Default Re: Rapid cooling on downhill - thermostat problem?


Thank you very much - all your comments are very helpful, and answered all
the questions I had.
I had been going to the same autoshop for few years because it is close to
my home and they were the least expensive I could find. Some of the
mechanics are honest, some are less, the problem is that they keep on
changing.
I will take ransley's advice and get the Toyota part - you answered my
question before I asked it.
I am now not sure whether to hand it to an autoshop or try replacing it
myself. I just hope that my university would not kick me out after I would
accidentally spill antifreeze in the parking garage...
I have the Haynes manual, and looks pretty straight forward - or do you
recommend to leave it to the pros?
- does anyone know where can I recycle the coolant in Northern or Southern
CA? it seems that no one would accept anything but motor oil.
Thanks again for sharing your knowledge and advice!


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Old 04 Mar 2005, 12:57 pm   #7 (permalink)
timbirr@mailcity.com
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Default Re: Rapid cooling on downhill - thermostat problem?

Los Angeles County operates four permanent hazardous waste disposal
sites, as well as a number of "one-day" only sites. These are
specificially for people like you and they accept antifreeze, motor
oil, paint, pesticides, etc.

Here is their website: http://www.lacsd.org/HHW/HHWFLIER.htm

Swapping out the thermostate isn't tough, However, in a few models the
space to work in can be tight. I remember in my '84 toyota, I had to
remove the radiator to be able to get enough space to get the
thermostat out. Sounds like yours is not so bad.

Just follow the instructions in the Haynes, remember to remove all of
the old stuck on gasket material, use a new gasket -- and in a few of
those models, if I remember right, the thermostat has to go in a
particular way -- "this end up" or something like that. Your manual
should make note of it.

Finally, most antifreeze is toxic to animals, so you really want to
collect it and you really want to clean up any you spill. I've used
cheap cat litter.

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Old 04 Mar 2005, 02:49 pm   #8 (permalink)
m Ransley
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Default Re: Rapid cooling on downhill - thermostat problem?

You can do it yourself but the housing should be wire brushed off and
check it is clean and smooth where the gasket seats, to do that you will
twist the hose and possibly break it if you leave it on, my friend just
did mine and twisted and broke my hose so I know it is a good idea to
remove it. If hoses are over 3-4 yrs old replace them both while you are
at it, hoses usualy go first and are cheap insurance. Use some
penetrating oil a day or so before on the bolts. Actualy a 90 you
should completly flush the system with a flush kit, it is after all 15
yrs old, use distiled water not tap and a 50 - 50 mix.
Also motor braking is hard on the motor and trans, Use your brakes
they are cheaper to fix.

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