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View Full Version : so is this bad for the engine



85gtsblackman
01-23-2005, 11:05 PM
ok ill let the car warm for a min or 2, drive on the back roads till i get to I-295. Ill get on 295 and as soon as i get over 65mph the temp needle will drop. If i stay at 80 ,which is the normal flow of traffic, it drops down all the way to 1 notch above C, and the heater just blows luke warm air.

also it does this if i floor it in each gear , so i guess it starts to drop when i go past 3500 rpm.


even when its warm it does the same but not as much, maybe just drops a notch

saved_1992
01-24-2005, 12:01 AM
sounds like you have a thermostate stuck open, warms up while idling cools down when driving. is you gas milage getting worse too?

Punisher
01-24-2005, 12:26 AM
yes.. thermostat is stuck open or hell you might not even have a thermostat in there!

I had the same issue.. when I bought my celica.. the temp would never go anyway.. idling after 10 minutes.. it might be at the C mark.. what the hell.. so anyway I pulled the water housing and found there wasn't even a thermostat.. previous owner must've removed it for summer driving.

85gtsblackman
01-24-2005, 01:17 AM
i just put a thermostat in and its less than a month old

gas milage is the same

oh yeah umm ive had no thermostat, it would take 30 mins for my car to warm all the way up if that was the case

TRDmkII
01-24-2005, 01:45 AM
well you may have a faulty one....thats usually the only thing that would cause that...or you have a temp gauge switch malf...

saved_1992
01-24-2005, 03:06 AM
you got a defective thermostate, the thermostate will open at approx 195 and keep the temp there opening and closing in conjunction with the radiator fans on and off.

in the winter time if you had no thermostate your car would warm up at idle then cool back down when you started driving. because of the air keeping the radiator cool.

Doc
01-24-2005, 03:16 AM
I had some cheapie thermostat from who knows where in my celica for 25k miles or so and it would almost always stay a notch and a half above the middle. Replaced it toyota OEM and temps went back to normal.

There's just some things I will always go OEM with, and this is one of them.

But I agree with everyone here, it sounds like your coolant system is circulating too much, causing the engine to cool too much.

Hooligan
01-24-2005, 06:45 PM
It's possible that you have a perfectly functioning thermostat, but it's just opening too early and the coolant stays too cold.

Yes, coolant can be too cold. Hot engine (after it's warmed up) + cold coolant can cause cracks in cylinder heads.

saved_1992
01-25-2005, 02:16 AM
Hoooligan, What? if the thermostate is operating correctly it will not open early. the coolant too cold? the coolant is in the engine, when warmed up it opens the thermostate too cool down engine.

you must be talking about another make of car not Toyotas

Lagos
01-25-2005, 02:29 AM
i forgot to change the tstat when i did the swap. is there any chance that the tstat can get stuck closed and cause any overheating issues?

85gtsblackman
01-25-2005, 02:32 AM
ok i feel completely stupid now

my fan runs constantly because some part that tells the fan when to turn on and off burnt out (not a fuze or relay) and its some multi hundred dollar part.

that probally does it because of this

cold air + constant fan+ summer mix antifreeze (60/40)+ speed = over cooling

didnt do it much hardly today even though it was really cold and windy (felt like chicago)

saved_1992
01-25-2005, 02:51 AM
that is usually the temp sensor at the bottom of the radiator that causing the fan to run all the time.

yes a thermostate can get stuck closed or partially closed causing overheating problems

Hooligan
01-25-2005, 05:30 AM
i forgot to change the tstat when i did the swap. is there any chance that the tstat can get stuck closed and cause any overheating issues?

Yes - if this happens, the coolant flow will be severely restricted and the car will overheat.


Hoooligan, What? if the thermostate is operating correctly it will not open early. the coolant too cold? the coolant is in the engine, when warmed up it opens the thermostate too cool down engine.

you must be talking about another make of car not Toyotas

Different thermostats open at different temperatures. Some need to open at a lower temperature in order to make up for smaller heat exchangers (this is becoming more and more popular as it is cheaper to have a smaller core on a car).

I haven't heard of this problem with a Toyota in particular, but I'm sure it could still happen to one. When the engine is put under high load and gives off a lot of heat and you already have very cool water coming from the core, there are very large thermal differences between the coolant jackets very near the combustion chamber and the coolant itself. Over time, these large temperature differences can distort the head or block, or cause the gasket to crack.

saved_1992
01-25-2005, 03:19 PM
dave what cars are you talking about? i have been in the automotive repair field for 23 years servicing all different models and never have run into the problem you are talking about. have seen overheating causing a crack in the head.

Hooligan
01-25-2005, 04:34 PM
I have heard about it in a couple of engines that were kind of accidental, cult-favorite cars. Think the original minis, etc. They were intended as econoboxes but got turned into racecars by many. The problem that I'm talking about isn't really a daily driver problem (not very common and you probably wouldn't see it as a mechanic, but I'm assuming you repair at a dealer or independant service shop), but more for cars that get really hard track use.

I will see if I can find any articles on the good ol' 'net and get back to you.