LOGIC REQUIRED -Engine Temp What Is Normal??????
 

In the thread "lowering coolant temp -Success Story" Tkamiya states"The only problem with the "boil test" is that most MB cars (gas) has 87C thermostat. 87C is a start-to-open temp. It won't fully open until 102C. "
Those familiar with old threads know that many members in the heat of summer say their cars never go over 90C. There is also many members, including myself, who complain that their cars run too hot 100C-110C. Some say the higher temps are normal some say not. Some of us have spent a lot of money trying to get the temp down to no avail.
Now if Tkamiya is right about the thermostat not being fully open until 102C - is THAT temp considered normal?? If the thermostat is rated at 87C shouldn't it be fully open at that temp. On my older NA cars in the past when I bought a 165F thermostat - it was open at 165F. If Mercedes only START to open at 87C - then how in heck can people in hot climates be running at 80-90C???
I AM TOTALLY CONFUSED NOW! Any way we can nail this down once and for all??? I normally use logic to troubleshoot - but something does not make sense here - how can a car run at 80-90C in hot weather when the thermostat only BEGINS to open at 87C???

Over 100C is normal in hot climates. The temp on MB thermostats is the temp at which they start to open. A lot of the time, as thermostat gets old, it starts to open at a lower temp.

If your temp is holding steady at 80C, you need to replace the thermostat. I replaced mine when I changed the coolant, and now it is back in the upper 80s to 100 range. Before I replaced it, the temp was running 82C on the highway.

Think about it, if MB thought that running 100C was not normal, then why did they design it so that a properly functioning thermostat should still be restricting coolant flow into the radiator at 100C? The fan clutch doesn't even start to pull mass air through the radiator until 95C.

Like most of us, I suspect, I too have labored under this issue of "Is my engine running too hot?" I wish I could really remember what mine was like when I first got it (3 years old, 25 k mi on the clock) but I was not as finnicky or observant then as I am now. The preponderance of the data I've read lately is that just about anything under 110 is OK. Even then, I am not reassured. This winter, it's been mild here, so we have been getting lots of 40 degree F days. On those days, on the interstate, my temp is around 85-90. Seems to me that it SHOULD be 80, like it is when the ambient temp is 35 or below. But then I read that 87 degrees on the coolant gauge is perfectly normal, and that running cooler puts more wear on the engine.

Part of the "problem", if there is one, is that MB uses a linear gauge. Most other manufacturers fudge on gauge readings, probably to prevent owners from complaining and running up needless warranty claims. Every Ford and Toyota and Honda I've owned has had a rock-steady temperature indication once the engine is at operating temperature, every day of the year. THis is an artifact of the electronics used, since I'm pretty sure just about any engine should show some variability in temp depending on season, stop-and-go vs. 75 mph, etc.

MB engineers apparently think we "CAN handle the truth" to paraphrase Jack Nicholson.

Thank you all for forging through all of this.

Living in N. California, where the temps can range quite a bit-(Sierras in the winter to the valleys in mid-summer), I too have watched the temp gauges on my diesels (past cars) and with the current ones ('91 300E & '95 E320 Wagon) and wondered what was OK and what was not.

I have driven through Death Valley during a "mild" summer where it was "only" 129 in the old '82 240D. I have also driven through a -15 night in the high peaks. What I have always come back to was what Mercedes recommends.

I have been educated through your comments, research and postings. I was never quite sure where MBZ's temperatures were supposed to be.


Thanks again for this.

Specs for my C280 are all exactly the same as tkamiya posted except for the aux fan control:

Low speed cuts in at 100C and off at 95C coolant temp or
Low speed cuts in at 16 bars and off at 13 bars refrigerant pressure

High speed cuts in at 115C and off at 107C coolant temp or
High speed cuts in at 20 bars and off at 17 bars refrigerant pressure.

So, for my car, they modified the aux fan so that it will run on high speed under high refrigerant pressure. They also added a low speed cut in based on coolant temp, and changed the high speed cut-in so that it does not come on until 115C.

If my car ran 80C on the highway, I would immediately change the thermostat due to the fact that it would have to be broken for this to be possible. My car should not run under 85C, and if it did, I would correct the problem.

I can say that with my car, when outside temps were 25F and I was going around 70 MPH on the highway, engine temps stayed steady right at 87C.

I while back I saw an older article (see link below) stating that engine wear increases rapidly at temperatures under 170 F (77 C). What I think is the most damaging to an engine is cold start owing to the pistons expanding faster than the cylinders. I always try to get my engine to temperature a.s.a.p. without revving it over 2500 rpm or so. Also, I believe synthetic oil goes a long way in reducing wear during cold starts. Quite frankly I'm more concerned about hot running engines than cold running ones.

http://www.gi.alaska.edu/ScienceForum/ASF7/747.html

GREAT DISCUSSION!! - So those of us who are at 100 -110 should (pardon the pun) chill out. It is normal. So if we can accept that up to 110 is normal (depending on outside temp - & air cond on) I have only one other question before my queasy stomach relaxes. When someone says their Mercedes overheated and the engine was damaged --- what temperature did it hit to do the damage??? As a side note- my car(88 560sel) is in storage for another 2 months. As soon as I get it out - I have an infra-red non-contact laser guided temperature reader - I am going to check the temperature on the motor, rad and hoses and compare them to the guage in the dash. Maybe those whose gauges read 80-90C normal are off or maybe ours at 100-110C are off - when I find out I will post results.
I think I speak for a lot of us when I say all we trying to do is ensure we don't unintentionally damage our prized cars by running them too hot.

Hi Moedip,

For one thing, the higher the temperature the faster the oil degrades and loses its lubricity. One has to be more conscientious about oil changes and fluid level checks (engine coolant and oil) with hot running engines. Also, heat damage being cumulative, check for operating temperature creep over time as this is a sure sign that something is going wrong. As you said, temperature gauges are not very reliable in absolute terms but they can tell you, in relative terms, if your maximum operating temperature is creeping up.

TO: Tkamiya
 

Makes sense to me. My 560,if outside temp is about 88F or lower with air cond on never goes above 100C - 90C max with air off. However- I drive down to Indiana to visit my sister every summmer and the temps there are usually 95-100F. Under these conditions cruising down the highway at 70MPH my max temp is 100-105F if I put the air on it starts climbing over about 3-5 minutes to 110 at which point I turn the air off, sweat, and continue till it drops again. In my worries about overheating, I have had the rad flushed and tested (it is 100%), new hoses, thermostat (twice), new water pump, new viscous fan, new rad reservoir cap. All changd with absolutely no difference with the temps. All I have left to try are the temp sensors. But if you are saying that if I let the engine go past 110C to maybe 115C - there would be no engine damage and I might be surprised to see the aux fan kicking in. At 110c now it does not kick in. I hot wired the aux fan so it is on full time and under the worst outside temp conditions with air on the engine will not climb over 100C. That is why I worried about 110C. Thank you very much for your input -- I am feeling more comfortable about higher engine temps.

To: Tkamiya
I sent you my email - please forward the article -I'd really appreciate it. Unfortunately you are wrong where I live. I live on the cold Canadian Prairies where we can get up to -45F tempertures, so my antifreeze has to be set for -50F protection as I have unheated storage. My daughter's car had a slipping alternator belt the other day - by the time she drove home with her lights on(45 minutes) it was too late. At -35F the battery froze. New battery time.
There are 2 temp. sensors I believe - 1 on air cond pressure and one for coolant ( I think) - since car is in storage till spring -that was my next step)to look up in cd manual and change.Are you referring to the coolant sensor when you say it can drift? Changing the air cond. one scares me as up here it is illegal to use R-12 as of Jan 1 this year. To change the air cond sensor means to convert to R-134, maybe change compressor to proper type - yadda - yadda -yadda - In other words - I really don't want to change it unless it is absolutely necessary as my air cond works great!

To :Tkamiya
Thank you for your help. Please don't forget to email me the article.
Many Thanks
Maurice

send to: mdepiero@mb.sympatico.ca

YES YES YES
 

To Tkamiya::D :D :D :D :D
I got the article - Thank you very very very much. The work I could have saved plus the money!!!! Unbelievable - IT REALLY IS NORMAL to hit 115C!!! May I quote from the article " if the outside air temperature is in the 90's and you have the air conditioning on full blast with 5 people in the car - you can expect to see 110C on the guage" NORMAL NORMAL NORMAL. Please contact the Moderator of Tech Help and see if you can upload the one meg file to a thread - I guarantee you there are many Mercedes owners out there who are just as paranoid as I was. I think it would be a great service to make this article available to ALL members who request it. I now firmly believe after reading that article that anyone who has a Benz that is running at 80-90C when the outside temp is 100F - has a faulty guage or sensor. Oh Man - the hours I wasted - Phil should stock up on Red Line Water Wetter and try to get Mercedes Antifreeze - Never thought of the Ph factor!! Sorry for rambling - I am so relieved!!! If the Jpeg files are too large to post - let me know and I have text recognition software that can convert the images to text . If there is too much text I can post the three pages individually. I can do it early next week. Have a Great Week end!
Maurice

Jimf has done extensive research on this :) Perhaps his website might help.

http://pages.prodigy.net/jforgione/MB_S500.html

Kuan

Interesting note from article - NA antifreeze is has higher Ph value than MB antifreeze which attacks the plastic top of MB rads. Article states that the plastic becomes crumbly which causes neck of rad to break off. Could this be the reason for the threads on this site about broken rad necks??? Has anyone been using MB antifreeze and still have their rad neck break??

The newer radiators have a metal insert in the neck to prevent them from breaking off, however, I am unsure of the year that the changes were made.

Does anyone know what year they started putting the metal insert in the neck of the radiator?

I'm not buying that bit about Ph crumbling plastic. In pool chemicals both Ph increaser and decreaser come in plastic bottles and I've never seen one crumble. Plastic is impervious to ph. What it isn't impervious to is heat. And hoses suffer from extreme heat also. I think what scares me most about the elevated temps is that we have this old mindset that we need a "safety" range. In the old days of 180F engines, we didn't sweat until they reached 210F. That was a long way on the old mechanical temp guages. Now, "green" engines are already set at 195F so there goes half of our "safety" range. After all is said and done, the engine that operates closest to it's thermostat setting will live the longest.

AH - But Cap'n - the containers for the Ph stuff for your pool is not subjected to ongoing temps of 90-110C plus 20 lbs pressure. I don't know if MBUSA is right (but I think they should know). That is why I asked if any one out there was using MB antifreeze consistently and still had the rad break. If most people reply that they used NA antifreeze and had broken necks - there may something to what they say. Any takers for comments on using MB antifreeze exclusively??

I think the radiator neck problem is stress related, If Ph were the culprit, then the entire top cap of the radiator would fail, not just the neck.

Not sure if this is related or not, but I just had to replace a plastic thermostat cap on my 190-16v. It had started to leak from the plastic 'nipple' that is the begining of a hose back to the resovoir, and the piece broke off completely when i tried to examine it. This is not a 'stressed' part in any way except incorrect anti-freeze and high temps. Just for the records, my h20 runs about 85-90, but my oil goes to 100-110. Go figure.

Dan

Well, all plastic rads are subject to wear, and will break at some point.

It's common on Japanese cars. We use MB coolant in ALL our cars. We recently replaced the rad on our old 1988 Mazda 626. The dealership couldn't believe how long the rad lasted. Many of the mechanics have started using MB coolant in their own cars after seeing our 626.

I don't care why it works. It does, and costs little extra per mile, so I use it.

As to temperature, MB is one of only a few makes that has a REAL temp gauge, so ignore what you know with other cars.

My 1998 C230 reads a constant 83C at highway cruise with the AC compressor only pushing 2.5 bar at an ambient temp of 10C.

At an ambient temp of 32C, with the AC compressor reading 16.0+bar, my coolant temp reads about 97-101C, falling if highway speeds are reached consistently. Not much below 87C though.

Our 1998 E300 reads pretty much the same. Most late model MB's exhibit similar temp behaviour.

Think about this for a moment. The role of the thermostat is to force the engine to operate at a minimum temperature, i.e. the degree setting on the thermostat. It opens when that temp is reached. Now, whether it's beginning to open or all the way open is irrelative, because everything that happens from this point on, lock up of fan dampers, startup of aux fans etc. is for the purpose of lowering the coolant temp down to where the thermostat closes. Then the process repeats. If you're thermo is open all the time, then your cooling system is inadequate either by design or malfunction. A good cooling system, be it on a Mercedes or an earthmover should keep the engine near the thermostat setting whether it is at idle or under load. If a manufacturer wanted the engine at 100C, they would put a 100c thermo in it. ;)

would it be advisable to cover ones rad grill in winter to induce higher engine temps? mine wallows between 40-80 on the highway...

Sounds like you just need a new thermostat.

To Mercedes Fred
What kind of outdoor temps are we talking when you get 40-80 on your gauge on the highway???

the outside temp varies from -10C to -20C. Once im in town in stop and go traffic the temp guage goes past 80

WoW!! You don't need a thermostat, you need to move south! :D I have no experience with that kind of cold. Our freezers don't even get that cold down here. I'm out of this one.

here on the cold Canadian prairies - we have winter fronts with flaps. It is going to be below -15C close flaps - Daytime temp over -15C - open flaps - and always keep an eye on your temp guage.
Sounds a little strange that your guage will go below 80C at only -10C on the highway. Have your thermostat checked before resorting to a winter front. If your engine is not at aperating temp - excessive wear, poor gas mileage and other problems will exist. If you read higher up this thread you will see that the thermostat BEGINS to open at 80 to 87C.-engine is not holding temp - check your thermostat

Engine Temp what is normal????
 

Very interesting discussion. My 600SL runs at approximately 95-96 at steady cruise. But, the least amount of acceleration or a hill sends it 98C and the Viscous fan comes on 96-97. This fan is extremely loud and for top down driving it destroys the ambience. Any way to quiet it down but retain its efficent operation?. I wonder if the noise is the fan proper or the clutch.