Car running @95 C = 203 F !!!!!!!!!!!!! - PeachParts Mercedes-Benz Forum

JimSmith · #1 03-08-2003, 10:05 AM

rickjordan,

When the car was new, and probably for a decade or more thereafter, it likely ran at about 80 degrees C or just a hair less.

Others on that frequent this site have noted in the manual that it says it is ok to run up to the red zone without damaging the engine. That may be true, but I believe there is some system degradation when the car starts running at 90 or 95 degrees C.

My Diesels have always had the needles seemingly glued about a needle's width below the 80 C mark, regardless of outside temperature and load when all is well. If my cars run hotter than this I take it to mean something is not correct, somewhere, something changed. With the simpler models, the W123 and earlier 240D and even older 220D, this was never more than a bum thermostat, leaking radiator cap or leaking water pump. The newer models have some complications with fan operations and automatic climate controls. I have not had the pleasure of having to dope these out yet on one of my cars, so I am not much help there.

So, I would figure, since the system used to be able to hold you at 60 degrees C, that the part you put in to regulate temperature, the new thermostat, is either faulty or somehow the installation was faulty. These thermostats are a little more complex than the average, as they have two sets of moving parts to control flow bypassing the radiator and flow returning from the radiator. Also, the system is pretty sensitive to venting, and any trapped air can cause problems with the operation of the thermostat.

So, I would try to make sure the system was fully vented. I usually do this by parking on a pretty steep uphill rise (which I have in my yard), with the radiator cap at the high point (right side of car more uphill than left). Then I fill the system, run the car with the heat on full and the radiator cap off until the temps get to their normal maximum temps. I fill with MB antifreeze and distilled water until the system takes no more, then I squeeze all the hoses a few times and do the filling exercise again, until it will take no more fluid.

By the way these thermostats go in one way, and they usually have a little vent hole that is aligned with the high point in the housing. With a bubble of air or steam on one side, thermostat will have a great deal of difficulty responding to the hot side water temperature.

I hope some of this helps, Good Luck, Jim

rickjordan · #2 03-08-2003, 10:32 AM

Recently changed the thermostat in my TD, which was causing the car to run at a mere 60 C. With the new OEM Behr 80 C thermo., she is now running at about 95 C. I recently figured out what that is in F., 203 degs. That is hot, but apparently not for these engines, because the red line is up at 120+ deg C, which is something like over 220.
Is everyone else running at this temp? Here it is I thought diesels ran cooler than gasoline engines, but I guess I was wrong. My VW Passat with a 1.8 liter turbo runs at a solid 190F.

psfred · #3 03-08-2003, 10:37 AM

Thermostats have been known to be bad out of the box, more common now that it used to be.

Should run right at 80C, or 85, depending on application, 95 is too hot.

Check hose condition, fill state (you could be low on coolant if the engine "burped" air after you filled it), and the rad could be crudded up. If you have an aluminum radiator, suspect it as the culprit. You can remove it and have it checked at a radiator shop for flow, or CAREFULLY check to see if it is uniformly warm after running. Cold spots indicate plugging.

Also check that the visco clutch is working -- you should hear the start to roar as the engine gets above 90C, and the aux electric fan must come on at 100C or so.

Peter

Stevo · #4 03-08-2003, 11:17 AM

I read a message over on the other forum having to do with over heating that I had never heard of before. The "seat" in the T stat housing that the bypass part of the S stat seats against had corrosion, allowing coolant to flow past when it should be flowing through the radiator. I wonder if that is a common problem ? It sure wouldn't, hurt to check it out if your replacing the T stat or before spending the $ for a new radiator.

Also I read someplace that MB started using T stats that ran hotter because of emissions and folks were having better luck with Auto Zone or Pep Boys T stats. Totally to be taken with a "grain of salt", Just thought I would mention it in case anyone had ever heard of such a thing

Holson Adi · #5 03-08-2003, 11:29 AM

The same thing happened to me at one night when it was like 0F or something extremely cold.

The water temp would hover at 95C?!@ But if I drive it more the temperature would go back to 80-85C again. It's when I baby the throttle (drive gently) that it goes back to 95C..

it hasn't done it ever since. I'm guessing it's the T-stat.

84300DT · #6 03-08-2003, 02:34 PM

my gauge usually hovers about covering the top loop of the '8' in the 80 mark ie. horizontal. this is the usual driving mode. on hills or xtra hot outside conditions on the highway it sometimes goes slightly higher. i consider this normal for the car.
i am running a bosch t-stat.

JimSmith · #7 03-08-2003, 04:50 PM

Peter (psfred),

Considering his initial complaint, the car was running at 60 degrees C, it would seem the problem really is a thermostat, or a trapped air, issue. Hardly seems reasonable that after changing the thermostat the car now overheats due to either a viscous clutch issue or a crudded up radiator. If that were the case he would have had the problem before as well, or do I have this picture out of focus?

rickjordan,

A question. Does the car get to this temperature under load or while idling? Do you get any gurgling or other noises when the car is running with the heater on (listen from inside the car near the center dash vents)? How does the interior heater work? If you turn the heat all the way up does the temperature drop?

A little more information will help figure out where the problem is. Good luck, Jim

rickjordan · #8 03-08-2003, 07:30 PM

I really didn't think there was a problem per say. I was just commenting on how hot 95C is in farenheight (sp). My problem WAS the car would not get above 60c, regardless of what type of driving. The air from the vents was luke warm, and the radiator was only warm to the touch. So the engine was running too cool. Also, my fuel economy was in the very low 20's. I presented this problem to the "collective" here and everyone said it was the thermostat. I changed it and all my problems went away. The radiator on this car has been replaced, it doesn't look too old. Again, I didn't realize that there may be a new problem. Since redline is just above 120 C, I figure 90-95C is fine. Nothing is leaking, my coolant level is fine. Even when I am driving 75 mph, the temp stays on 95C.

rwthomas1 · #9 03-08-2003, 07:41 PM

Mine runs at what I assume to be 90-95*, the needle is straight accross to the 9 o'clock position, maybe a little higher and it never moves from there. New T-stat was installed right before I purchased the car. I do still have a wierd "invisible" coolant leak though. Leaves a small, like quarter sized puddle of coolant when it sits for more than a day. No traces of coolant anywhere on the engine, hoses, etc. Its a "magic" leak.... RT

psfred · #10 03-08-2003, 09:04 PM

Jim:

Possible, not very likely, unless the outside temp came up at the same time, to where the rad won't cool enough once the engine comes up to temp.

Just commenting that 95C is rather hot, and if fill problems weren't the cause, what else to look at.

And there is such a thing as a bad thermostat in the new box, there have been several reported on this forum!

Peter

rickjordan · #11 03-09-2003, 10:44 AM

OK, now I am confused. Back when I originally posted my problem on another thread, alot of people were saying their cars ran between 85 to 90C and that my 60C was definetly too "cold". Now that my car is running at 90+ C, everyone is saying that is bad, despite the fact that the redline is some 25degs. higher than that. Is the "collective" saying that the thermo. is bad and not opening until 95C? Being it that one can't actually look into these radiators, how do you tell if she is plugged? As I mentioned before, even cruising at 75 mph, for 45 minutes, the temp stays at about 95C. Obviously as it gets warmer out, I will keep an eye on it.

JimSmith · #12 03-09-2003, 11:14 AM

rickjordan,

The point I was making is the car comes from the factory running at about 80 degrees C. This has been the case for all my cars, gas or Diesel. Gas cars will heat up a little in stop and go traffic, especially in the summer and you can hear the various cooling aids come on to keep temps under control - the viscous clutch for the main fan and the auxilliary electric fans. At running speeds, especially highway speeds, even my gas cars run at an even 80 C in all weather.

If your car is running above 80 degrees C, it is not the factory normal temperature and there is a reason. The most common candidates are the thermostat operation being out of specification, or low coolant level.

Now to your question. The manual says all is ok as long as you do not run in the red zone on the temperature gage. So, I guess it is ok to run at 95 degrees C.

I can tolerate a lot of little, non-vital stuff on the car being out of whack, like cracks in the dash or knobs that have developed idiosyncracies that I have learned to live with to turn things on and off. After all I have wrinkles on my face and joints that have developed noises and other idiosyncracies over the years too. But I cannot get used to the temperature gage pointing above horizontal. Drives me nuts because for thirty three years of driving these cars the gage spends 99% of its time horizontal after the car has warmed up. So, 95 degrees C would unnerve me, and I would have to find out why the car decided to run hot. Even if it is not too hot.

Sorry if I am alarming you needlessly. Good luck, and I hope this helps, Jim

ck42 · #13 03-09-2003, 02:41 PM

I thought factory TS spec was for 87C ?

Everything I've heard and read says that NORMAL operating temps will vary from ~85-105C with 85C being casual driving on flat roads, etc. and 105C being perfectly normal when chugging up a mountain side.

My car, coincidently, ran for the longest time smack at about 87C (from best I could tell from the gauge) and would maybe get to about 90C in the summer with the A/C, etc.

Just the other day, I looked down while at a stoplight and noticed the gauge sitting at 110C. Long story cut short, I had recently changed out the waterpump and coolant and introduced air in the system that gave me the gurgling heater in the dash noise.

I think that this air pocket worked it's way out yesterday and ended up leaving my system about 1.25 gallons short of coolant. After filling it back up, the temps have come back down.

So...anyway Rick, my opinion on temps are anything from 85C to 105C are *normal* under their given driving conditions. Although, I would have to say that a car running consistently at 95C during normal driving conditions warrants a second look...I'd even go so far as to verify that the temp sender unit isn't lying.

rickjordan · #14 03-09-2003, 03:22 PM

How does when verify what the temp sending unit is indicating? When I drive the car again, I'll check the radiator for cold spots. Since she is not running near over temp, I am not too concerned, but as Jim has alluded to, it's worth looking into.

ck42 · #15 03-09-2003, 03:57 PM

Rick,

The only way I know of to verify the existing sender w/o removing it is to get ahold of one of those laser temp readers and take a temp reading RIGHT WHERE the sender is sitting.

Otherwise, I think you'd just have to replace the sender with a new one (but this doesn't mean the new one is correct either :p )

I think that there's a voltage-temp conversion and you could measure the voltage output from the sender and see if THAT voltage corresponds to the temp your gauge is reading.

Otherwise, dunno

...and yes, I agree. Constant 95C temps certainly justify your suspicion.

Chris
'85 300SD