What is the CORRECT engine temperature for '88 560SEL?
 

Hello all,

I've searched around, both on this forum and others. All that I can find are peoples' opinions on what the correct engine temp for this car should be, and it varies between 80c and 100c.

Does anyone actually know what the correct spec engine temp for the 560SEL is?

I have an indie mechanic who put what I believe to be a bunk thermostat in there, and he's telling me my temps are normal. I've owned this car over 5 years and I've never seem them this high.

Thanks in advance!

80 degrees C unless under load/high heat conditions.

Every Mercedes I've owned has always run at 80C unless you put the a/c on and it was very outside or you were doing a hill climb then it would run up a little hotter.

What is your car running at now?

It was overcooling when I took it in, barely getting to 60 because it's so cold outside. I know that was wrong, because as you noted, I'm used to my cars running at 80c in almost any conditions.

After the T-stat swap, they gave me back the car a GALLON LIGHT on coolant, which I caught thankfully. Anyhow, the thing is now getting up past 90, hard to tell exactly on that style gauge, but I'd say like maybe 95?

Anyhow, I think it's too hot. He gave me some BS about how the Mitchell book says that is normal closed-loop temps.

Can I now tell him he's full of it?

93.33C loaded. On those analog gauges they will rome between the 80 and the 100 C marks.

So the t-stat failed,probably in the open position, resulting in your over cooling?

Then he replaced it? Was the coolant flushed? Why wasn't the coolant level resolved? Is this a MB familiar shop?

How old is your radiator, fan clutch, etc?

Yeah, old T-stat was stuck open for sure.

I have no idea why the hell it was a gallon light on coolant when I got it back. They really effed me around this time. I had been very happy with them until now, but not so much anymore. They also managed to knock my timing out because the forgot to tighten the distro clamp.

Oh, the radiator is maybe 4 years old, and the FC is old, but I know it's in pretty good shape because you can really hear the fan roar when you accelerate. If anything, the fan clutch isn't slipping enough....

Anyway, I am pretty much DONE with them at this point.

But that 80c you're talking about, that I'm used to... Is that documented anywhere? Already there is somebody saying 93.3C is normal.

Can anyone actually cite a source for this?

Thanks very much!

Best documentation I can find:

This is from the 560SL service manual that MB hosts. I'd have to look at my W126 data for it.. but it looks like in general 90+ is for "full load operation"

http://www.startekinfo.com/StarTek/outside/11883/PROGRAM/Engine/107/M117_56/20-005.pdf

While I don't have any documentation, my Indy mech of 10 years has always told me that one of the best things I can do for the health of any MBZ that 20 or more years old is put a thermostat that's set for 80C vs. the normal 87C. His belief is that as these cars age, they're not as adept at dealing with the higher temps. Made sense to me so it's something I've always done with no ill effects- ever!

AL

Thanks, that's somewhat enlightening, although it does not list the engine I have and appears to contain older cooling circuits. My car is a 560SEL (not SL) and has the 117.968 if I'm not mistaken.... I will try to find the page for my car. Thanks for posting this, and if you happen to know where the one for my car might be, that would be fantastic. I'll hunt around.

I wonder if he stuck an 87c stat in there instead of an 80c stat....

I looked at my W126 service manual it did not mention the 117.968 either.

All the thermosats I've ever put in are the normal 87C units.

I wonder what brand they put in too.

Somewhat related but radiators really should be changed out after 10-12 years of service. That definitely helps.

tp:

The FSM engine manual that covers that series of engines (incl. 117.968) describes the operation of a nominal 80C thermostat as follows:
Up to coolant temp of 80C - stat main circuit closed, bypass open
Above 80C, below 94C - main circuit opening, bypass closing
At or above 94C - main circuit fully open, bypass closed

The correct operating temperature? Depending on load, and ambient air temp, an engine that is "up to temperature", may, in fact not reach 80C (Jan. in International Falls), or may go over 100C (Aug. in Death Valley).
With the exception of such extremes, anywhere between 80C and 94C should be considered as "normal"; good judgement counts.

tp, where are you located?