So - the question is: if a motor runs below it's regular operating temperature at speed for extended periods of time will it be damaged. And if so, how will it be damaged?

The inspiration for this question is my current situation. Today I swapped my coolant (flush / replace) and put in a brand new radiator on my 1993 SC400. I took a test drive around town to dinner and back and I noticed that temperature never rose above the first indicator line (not the very bottom complete cold mark, but the very first mark upward from there). Later on I decided to take a longer drive from Tampa to Sarasota and back. the entire drive @ 70 or 75Mph with an RPM of 2500 to 2800 the temperature gauge only once rose above that mark while I paid a toll going up to the Skyway Bridge. The outside temperature was between 52 and 60F during the drive...

I'm not dull, yet I don't know everything in the world either. But what knowledge I do have of how lubrication works in an engine give me cause for concern. If the oil isn't being brought to the right temperature because the engine as a whole is being cooled TOO efficently, then I'd have to guess that the oil would not be able to spread across the engine components correctly and this could potentially lead to mechanical failure as result of improper lubrication.

Am I right or am I totally just worrying about things too much?

 

ur just worrying too much.

sounds fine. now, if the heater doesnt work after the motor's been on for a while then you may have a dead thermostat.

 

I rather feel better to see my temp gauge points at regular level!

For me working at a repair shop, I see cars with similar "problem" oftenly. A radiator flush (with special vaccum/pushing machine) and refilling coolant (proper ratio mixed), or replacing the thermalstat/gasket usually take care the "problem".

Hope this help you some.

 

the engine will see a lot more friction when it's cold, and as a result it won't run nearly as efficiently since the oil is never getting to the proper temperature. Fix the problem and don't leave it like that.

 

In modern engines its not really a problem and it does depend on temperature. A cold start in Alaska is much worse than one in Georgia.

That is an advantage of synthetics...the oil bonds to the engine so under cold starts there is less friction than traditional oil....

 

Most machines run most efficiently at operating temperature, maybe lower mpg. The only problem I can see is if the coolant temp is too low, the thermostat could remain closed. I had an old Mazda 626 and the temp would go all the way back down on a cold winter day on the highway. It lasted almost 10 years before we sold it. So I wouldn't worry.

 

cars have to run around their designed operating temperature, they designed the car to lubricate and seal up at those temps

 

It's not so much a "bonding" effect with synthetics that gives them their advantage; it is the fact that they remain fluid and viscous at more extreme temperatures than regular dino oil. For instance, at -20F, regular dino oil is so thick it is practically like jelly ( the higher the viscosity number, the worse it gets with cold ); but synthetic oil, at the same temperature, flows almost as easily as it does on a summer day. That is why synthetic used extensively in polar cold and desert heat conditions...it doesn't cook and crystalize into carbon particles at high heat conditions like dino oil does either.

 

I guess then that possibly my antifreeze to distilled water ratio is off? This is a 1993 SC400 and if I'm not mistaken the entire cooling system is 11.8 Quarts including the heater core in the dash (Nearly 3 gallons). I'd put in 1 gallon of Toyota RED and almost two gallons of Distilled so I thought I had it right..... should I have put in more antifreeze than I did? Is that what's causing this? I have to assume that antifreeze doesn't let the motor get *as* cold due it not being as efficient a cooling agent as pure distilled water.

 

Using a 67/33 water to antifreeze as you effectively are using shouldn't cause that much of a temperature difference. In a worked Mustang, using pure water and some RL water wetter caused a very small movement in the needle so your ratio shouldn't have caused any change. Antifreeze and coolant, besides at the obvious extremes of temperature, main job is corrosion protection more than anything else.

 

My temp gauge didn't work normally after I changed radiators. I asked the tech who did the install about it and he said that was normal. If it didn't return to normal after several days, bring it back in. It started working normally after a week. I forgot the explanation. Sounds like you're okay.

 

Your fine, a cooler running engine is far better than a hot running engine, as long as your not revving it cold (just after startup like in the mornings after your car has been sitting)... you'll be fine...

 

Today it was *slightly* higher while driving around town. We'll see if it rises closer to the normal halfway point tomorrow. Since this is my first radiator replacement that I've done I'm learning as I go. I would be interested in knowing just what the reason for it taking a few days for the car to register a normal temperature after a new radiator + flush was Always good to have as much database car knowledge in your noodle I always say.

 

Haha. Trust me, your engine isn't running cold. That's a hot day.

I have a '93 SC as well, and for the last month I've been starting it just fine at a temperature of 5 - 15 degrees F and a wind chill factor of about 0 to -15degrees. THAT'S cold.

What would people in Florida do if it got down to -15 degrees F.? lol

 

Sounds like your thermostat is stuck open if the engine temperature is not rising to its normal operating range. With the engine cold, you should remove it and make sure it is in the fully open (cold) position.

Two ways to fix it:

• The John Deere Method - give it a couple of whacks with a hammer with the engine running and fully warm to dislodge the valve. This requires a good deal of intestinal fortitude.
  
  
• The Right Way - the old trick of removing the thermostat and putting it in a pan of boiling water to watch the operation of the valve. It should close it fully (or at least partially, depending on rating) in a couple of minutes.
  
  Hint: Don't let your wife catch you doing this with one of her good saucepans - you may be wearing it. Even if she doesn't catch you, there has to be some kind of plausible denial for the odd taste of the hollandaise . . . sorta like Prestone.

If you have any doubts that it is functioning properly, replace the 'stat with one of the proper temperature rating for the vehicle - with a new gasket. (I assume your engine uses one.)

Back in the '50's it was a common practice down here in the Texas tropics to remove thermostats for the summer and reinstall in winter to get the blockage of the thermostat body out of the coolant stream, making the cooling system operate at higher efficiency. That's not a good idea anymore since modern engines are designed to operate at coolant temps somewhere between 210 and 225 degrees, and actually need to rise into this range before emissions controls and fuel delivery are operating properly.