1991 560sel temparature problem

I think I need to replace my fan clutch due to temp problem, but before I do anything I would like to ask your advise.

My car had overheating problem a week ago.Temp went up very close to 120C and boiled over(coolant spilled out of the expansion tank).

I have since replaced the thermostat(I used 89C T/stat), and had the radiator serviced (rodded out).

Today at about 75F outside temp as shown on my dash, here are the temp readings I observed:
*Freeway driving:85C to 90C
*City driving with minimal traffic:90C to 95C
*City driving with stop and go traffic:95C to 100C

Are the above temp readings normal for the outside temp of 75F?

Do I need to worry about my Fan clutch not working properly? Should I replace the clutch? Is there a simple way to test whether or not the clutch is working properly?

Can you suggest some tips for a DIY in replacing the clutch?

How much do I expect ot pay for a fan clutch?

TIA

[stevebfl]

We would have installed t-stat MB# 116 200 03 15 which is an 80deg C. The actual temp in an engine will always be 3-10 degs higher than your t-stat is rated at. The device starts opening at the temp its rated (actually I think it is rated at a partial opening at the quoted temp) and controls the bottom (min operating)temp from there on. The cooling capacity (of the system including the fan clutch)is responsible for keeping it cool from that point on.

Your car seems to be running at the right range for the t-stat you used. If it handlles the extra heat when it gets to 90 then you are OK. At around 100 or whenever the A/C gets working the additional fan will be added and help. I don't like to see the engines running above 100 even though MB says its OK.

The fan clutches very seldom fail and are a little pricey MB# 116 200 11 22 list $224.

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Steve Brotherton
Owner 24 bay BSC
Bosch Master, ASE master L1
26 years MB technician

thank you for the quick response. anyway, what is the MB spec as far as what T/stat to use? Is it 80C or 89C or other? Also, just to clarify that the temp readings i mentioned above are with the A/C running...

[stevebfl]

The MB parts film gives the number I gave and identifies it as an 80deg theremostat.

It is the only option for a 5.6 liter. They do give a 84deg option for the 5.0 M117 engine.

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Steve Brotherton
Owner 24 bay BSC
Bosch Master, ASE master L1
26 years MB technician

[JoeB]

Strongly recommend you replace the 89 degree thermostat with the 80 degree thermostat...made a world of difference in my 420 SEL.

JoeB:
so what temp rating was the T/Stat that you replaced?

thx

[JoeB]

Emmy, I had a MB mech change the thermostat, and didn't ask what rating the old one was. It was stuck open, so during last winter the engine water temp never got above 40-45C. So not sure if the old one was the wrong rating or not.

JoeB

thx for the update. my car does not get hot anymore. it stays at about 85-90C and up to 100C if traffic. i guess my tstat is 80C afterall...