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.

Reply to
bauz
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Yes, could be the thermostat.

Reply to
Mark A

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

Reply to
Jason James

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.
Reply to
m Ransley

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.

Reply to
Daniel

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!

Reply to
bauz

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:

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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.

Reply to
timbirr

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.

Reply to
m Ransley

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