"Normal" operating temps (560SL's) - What is normal? - PeachParts Mercedes-Benz Forum

rgnprof · #1 08-26-2008, 02:14 PM

I don't think this is just limited to 560SL's, but what are your everyday operating temps? I am new to this car, so I'm just wondering...

Mine is consistently around the 100 degree mark (halfway between the 80 and 120 marks). So far anyway - and that is driving in mid 80's to mid 90's ambient temperature with the A/C running.

I have read thru the archives - mixed opinions about what is normal here...

ryan

dugald · #2 08-26-2008, 03:35 PM

Mine never budges from 80.

rocky raccoon · #3 08-26-2008, 05:23 PM

See my post in your other thread.

Walrus · #4 08-26-2008, 09:50 PM

you sound about right. I have read situations where folk who report lower figures have stuck (open) thermostats. It has been reported on other boards as well... When the thermostat is changed during normal maintenance, suddenly, they find a car "running Hot"!

Incidentally, If I recall correctly, the thermostat in the 560SL is around 80...
(and not fully open until 94C). excursions above 100 are common.

Don't get me wrong... I'm sure there are cars that run 80, and I'm sure no one on this board would report a false or fictitous number to mislead...

EDIT: I just read your other post... White smoke concerns me! I stand by my above statement, but would be interested to hear from you on the condition of the coolant level over time.

Walrus · #5 08-26-2008, 10:13 PM

My ramblings from "another" forum...

I see quite a few posts about the W107 running "too hot". Often times, it seems the reports are of the engine running above 100C at times, etc, etc. Also, I often see the results best described as the "shot-gun approach" when it comes to diagnosis, ie replace this, replace that, etc.

First, let me suggest it be determined IF overheating is actually occurring at all. The W107, and many other MB engines are designed to run "hot" compared to what us USA folk are used to from Detroit/Japan. It is not uncommon for these engines to run close to the 100C mark, with occasional excursions above also common. Anecdotally, this seems "hot" when compared to the iron I'm used to, but it is normal and by design. If the excursions above 100 are frequent, and near/into the red, then you have cause for concern. While its true a 560Sl has an 80C thermostat, it is not fully open until 94C. Realizing this, its easy to see how the gauge in the dash could rise above 100 while the thermostat is reacting, assuming the two react equally for a given temperature, and hover near 100 during normal operation.

If an engine is overheating (really, to be accurate, we should say the coolant temperature is above design criteria), the obvious question is WHY? Really, there are only two reasons... Either the engine/tranny is generating too much heat for the cooling system, or the cooling system is not functioning adequately. Often, the assumption (and more often than not, correctly), is that the cooling system is "faulty"; however, this may not always be the case. One should consider the state of tune of the engine among the lists of items to check. An engine that is out of optimum tune, ie running very lean, or otherwise compromised will be guilty of generating more heat than the cooling system was originally designed to accomodate. The engine timing is also critically important to the state of tune, and the heat thereby generated. The tranny's health must also be brought into the fray as it can contribute directly and indirectly to cooling system inadequacies: directly by tranny fluid running above normal, transferring heat directly to the cooling fluid, and indirectly by inducing strain on the engine if not coupling/shifting correctly. Given that we are considering vehicles around 18-30 years of age, there may be more heat in the system than originally designed due to mechanical weakness in the drivetrain. Another list of things to consider can be called extraneous causes and can be related to dragging brakes, missing/mal-adjusted fan shrouds, tire aspect ratio and inflation, ratio of antifreeze/water, etc. Even the type and grade of oil can contribute to an engine producing higher levels of heat than originally designed.

If one accepts the above postulates, then it becomes incumbent upon the examiner to consider many factors aside from only the cooling system parts, ie clutch fan, thermostat, radiator, etc. In reality, for equipment of the age and mileage we are concerned with here, the cause will likely be a combination of these factors. The holistic approach must therefore be utilized in ascertaining a solution.

I suggest the following:
1. reSEARCH to determine what "normal" should be (expect a range).

2. Test to be certain overheating of the cooling fluid is actually happening. By test, I mean, utilize measurement devices beyond the gauge in the dash.

3. Check for extraneous causes. Focus on anything that has been changed recently, or serviced, etc.

4. Examine the systems, heat generating (engine/drivetrain) and heat exchanging (cooling system).

Somewhere within, the answer lies...

Author's note: The opinions expressed here are belonging to the author, and have been developed from years of mechanical experience with engines from motorcycles to freight locomotives and are by no means all inclusive or solely limited to the items mentioned.

meltedpanda · #6 08-27-2008, 01:43 PM

mine sits around 80 -but these guys are designed to run hot a horizontal temp quage is good going beyind that may be cause for concern

rmadja · #7 08-27-2008, 08:35 PM

My 1988 runs about 80C or slightly above. Even with summertime temperatures.

rgnprof · #8 08-29-2008, 10:06 AM

The small responses to my original question kind of sum up my confusion...

I did some looking around yesterday and made a few observations. Using my laser thermometer, I measured temps around the head and the radiator and did not measure temps as hot as my gauge was reading - radiator temps around 80 degrees C - from top to bottom of radiator and temps around 95 - 100C at the thermostat housing.

Also, the fan does not speed up when engine is revved to 4000-4500 rpm - and when I shut the car off the fan continues to spin several revolutions until coming to a stop. Although, if I try and spin it by hand - when warm - the fan only rotates about 1/2 turn or so.

Any thought?

ryan

meltedpanda · #9 08-29-2008, 11:09 AM

the fan has a clutch, higher speeds it may actually allow it to turn slower as wind causes cooling. it should be hard to turn when engine is hot. Change out your senders ,they are cheap, see what happens

SL Lover · #10 08-31-2008, 07:25 PM

I just completed the water pump installation on my 380SL. I also change out the thermostat.

After pouring Zerex coolant, I allowed the engine to "burp". It burped as the engine temperature hit 100 C. I turned off the motor and allow the coolant to fall back into the expansion tank. Added more Zerex coolant.

My engine continues to run slightly over 100C. The radiator fan kicks in at higher speed. At this point, my engine is boiling. AT this point, it seems as though my temperature sending unit just failed. The gauge now reads 0. Now, I have to replace my temp sending unit.

I can't recall if my engine ever hit 100C PRIOR to my malfunctioned water pump. I think it was somewhere near 80-90C.

The only thing I have not done yet is put the A/C belt back on.

I'm perplexed as to why my engine still runs 100C...?

meltedpanda · #11 09-01-2008, 09:42 AM

This happened to me on my 300SD, not sure why, some thermostats have an orientation ( up /down) make sure you have it in correctly. Also you may still have air in the system, park it nose up over night

Walrus · #12 09-01-2008, 10:43 AM

Quote:

Originally Posted by SL Lover

I just completed the water pump installation on my 380SL. I also change out the thermostat.

After pouring Zerex coolant, I allowed the engine to "burp". It burped as the engine temperature hit 100 C. I turned off the motor and allow the coolant to fall back into the expansion tank. Added more Zerex coolant.

Now, my engine continues to run about 100C. I can't recall if my engine ever hit 100C PRIOR to my malfunctioned water pump. I think it was somewhere near 80-90C.

The only thing I have not done yet is put the A/C belt back on.

I'm perplexed as to why my engine still runs 100C...?

If you do not find the "cause", I suspect you have become one of the many.
Reading my response above, you'll see I report that I have had this exact experience , and have read many reports across BB's from others as well. You just added more credence to my assertion that reports of low operating temps. ie 80, are due to stuck open or faulty stats. Did you check your thermostat before changing it, ie put it in a pan of water and measure the temp it opens? Was it stuck open already? What temp stat did you install? Remember, a stat is an analog device. The temp listed on the stat is the temp it starts to open. For a stock 560SL, the stat is a 80, but not fully open until 94.

Anyone who has recently replaced their stat, please wade in... If you have replaced, or know your stat is functioning properly, and you are experiencing low operating temps (80 or so), then God bless... My response is not meant to call your experiences into question.

meltedpanda · #13 09-01-2008, 04:27 PM

I redid the 72 450 , complete , new hoses , stat , fluids drained block recored radiator runs 175 F , solid, never moves even on hottest days

Walrus · #14 09-01-2008, 07:16 PM

Quote:

Originally Posted by meltedpanda

I redid the 72 450 , complete , new hoses , stat , fluids drained block recored radiator runs 175 F , solid, never moves even on hottest days

Excellent!

79.4c ... Do you recall what temp stat you put in? I only remember the stat for the 86-89 560SL.

4 years ago, I re-did my 560 due to a broken rad neck. I installed a new rad, (had my old one re-tanked and repaired for later...), hoses and t-stat, and Zerex. Prior to the job, I was running 80-ish. With new rad, hoses and stat, I was seeing near 100 on summer (90+) days with A/C running, with excursions above 100whne spirited driving. I researched, burped, drained and refilled, etc and still experienced the same. That is when I discovered others posting similar (Hell, I even began to question my new rad). Infrared temp gun readings were in agreement with, and a bit lower, like the other poster wrote earlier in this thread. I quit worrying about it when I read information from sites, and discussed with learned people that all seemed well. I wish I had chacked my old stat, but I dropped it during the removal, which would have rendered any test invalid (and any visual of condition also suspect).

This temp thing is not specific to the 107 either. I can't remember what site it was posted, but the author even supplied pics of how he modified his stat in a sedan, drilling holes in the perimeter of the body, to let more fluid thru during closed stat operations. The 560, as well as the other 107's IIRC, use a stat with a valve on the bottom. it closes off a bypass route while opening and vice/versa (I'd have to look at my dwgs in my manual(s)to confirm).

280sleuro · #15 09-01-2008, 08:08 PM

Has anyone read their owners manual. My manual for the 280sl,380,sl and the 500sl states: "The coolant temperature may rise to the red marking in case of high ambient temperatures and when traveling in mountainous terrain" . The red mark begins at 120. My 280 mostly stays at 80 and may climb to 95 in 90+ days in traffic.