Author Topic: 6.9 (Euro) Running Temp  (Read 151 times)

Woganator

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6.9 (Euro) Running Temp
« on: 19 September 2020, 02:45 PM »
Apologies if this has been asked/answered previously.  I have a '77 450 SEL 6.9 and it is running fine albeit at a temperature of circa 85c on an open highway but up to 95c in London traffic.  Given we aren't known for our balmy climate and the fact this is significantly hotter than the other classic Benz's i have owned (R129 & W216 sat at circa 82c) I asked the garage about bringing it in to check/change the visco fan clutch  and/or radiator (no sign of any coolant leaks and it has a brand new water pump) but they reckon the dry sump means the thermostat might be set hotter than normal.  Any thoughts on this would be greatly appreciated. 

raueda1

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Re: 6.9 (Euro) Running Temp
« Reply #1 on: 19 September 2020, 04:58 PM »
1976 Euro 6.9 here.  To me that says it's working well-to-perfectly though you're not really in a stressful environment.  Mine does about the same whether it's 18°C or 35C and pretty much independent of speed and altitude.   It will go up to about 100° up a mountain grade at 3000m.  Nothing so bad about 95C in traffic IMO ("traffic" being a stop-and-go crawl, not idling for 10 minutes at a spell before going one car length). I do have new visco-clutch, thermostat and freshly descaled radiator.  Cheers,
-Dave
Now:  '76 6.9 Euro
Before that:  1966 230S, 1964 220SE coupe, 1977 Carrera 3.0

TJ 450

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Re: 6.9 (Euro) Running Temp
« Reply #2 on: 20 September 2020, 09:52 AM »
That sounds optimal to me, but it does of course depend on the thermostat installed.

Mine operates at between 85-95 degrees normally but will creep up to 100 in hot weather and stop-start conditions in Australia with the A/C on.

The temp should stabilise when cruising at speed. If it doesn’t then this could indicate some blockage in the radiator.

I’m surprised the 129 would run cooler as most of the more recent models are set to run on the hotter side presumably to reduce emissions.

Tim
1976 450SEL 6.9 1432
1969 300SEL 6.3 1394
2003 ML500

slfan

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Re: 6.9 (Euro) Running Temp
« Reply #3 on: 20 September 2020, 10:07 AM »
1976 Euro 6.9 here.  To me that says it's working well-to-perfectly though you're not really in a stressful environment.  Mine does about the same whether it's 18°C or 35C and pretty much independent of speed and altitude.   It will go up to about 100° up a mountain grade at 3000m.  Nothing so bad about 95C in traffic IMO ("traffic" being a stop-and-go crawl, not idling for 10 minutes at a spell before going one car length). I do have new visco-clutch, thermostat and freshly descaled radiator.  Cheers,

Hello Dave,

Hope everything is going well.  Another question for you:  is the visco-clutch in the 6.9 unique to the model or is it the same as the “standard” 450 SEL?  I am asking because this is the only component of my 6.9’s cooling system that has not been changed/re-done.   For your information,  my 6.9 runs in the 85 degree temperature until I get stuck in serious stop & go traffic for more than 10-15 minutes (in 30C/86F with the AC on). During these occasions, temperature reading surpasses 100 C on the temperature gauge (and gets close to 110).  Nevertheless, as soon as I get out of traffic and the car starts moving at 35-40 miles per hour the temperature decreases immediately.  Is yours behaving in the same way?

Best regards,
Angel
1978 - 450SEL 6.9 - 3170
1978 - 450SEL 6.9 "Parts Car" - 2973

raueda1

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Re: 6.9 (Euro) Running Temp
« Reply #4 on: 20 September 2020, 11:17 AM »
1976 Euro 6.9 here.  To me that says it's working well-to-perfectly though you're not really in a stressful environment.  Mine does about the same whether it's 18°C or 35C and pretty much independent of speed and altitude.   It will go up to about 100° up a mountain grade at 3000m.  Nothing so bad about 95C in traffic IMO ("traffic" being a stop-and-go crawl, not idling for 10 minutes at a spell before going one car length). I do have new visco-clutch, thermostat and freshly descaled radiator.  Cheers,

Hello Dave,

Hope everything is going well.  Another question for you:  is the visco-clutch in the 6.9 unique to the model or is it the same as the “standard” 450 SEL?  I am asking because this is the only component of my 6.9’s cooling system that has not been changed/re-done.   For your information,  my 6.9 runs in the 85 degree temperature until I get stuck in serious stop & go traffic for more than 10-15 minutes (in 30C/86F with the AC on). During these occasions, temperature reading surpasses 100 C on the temperature gauge (and gets close to 110).  Nevertheless, as soon as I get out of traffic and the car starts moving at 35-40 miles per hour the temperature decreases immediately.  Is yours behaving in the same way?

Best regards,
Angel
No, never near 110.  Maybe 100C in traffic with AC on and 36C outside.  As for visco clutch, I don't know if it's unique.  Not sure why it would be.  But it's easy to test.  With engine cold turn the fan by hand.  If it's quite stiff and damped you're probably OK.  If it's easy to spin or spins freely then it's kaput.  Cheers,
-Dave
Now:  '76 6.9 Euro
Before that:  1966 230S, 1964 220SE coupe, 1977 Carrera 3.0

slfan

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Re: 6.9 (Euro) Running Temp
« Reply #5 on: 20 September 2020, 02:15 PM »
Dave,

Thank you! Will check this out when I go pick-up the 6.9 at my storage place.

Best regards,
Angel
1978 - 450SEL 6.9 - 3170
1978 - 450SEL 6.9 "Parts Car" - 2973