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2003 E500 Avantgarde
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186 Posts
Discussion Starter #1
I`ve searched and there seems to be a wide variety of opinions on what it should be.
Mine runs at 80 up to 85 on long climbs.
My other car at 90 up to 95 on long climbs.
80 seems too low to me, being that according to one thread that I read, that the warm up regulator keeps on putting fuel in till the block / water temp is 84.
Which could account for my ongoing (but not overly) rich condition.
Is there a general consensus ??

Cheers Mike
 

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1986/1990 W126
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14,158 Posts
80 is definitely a little too low. 85 is ideal. But its fine if they run hotter. Cooler equals less efficient and more engine wear. Surely the warm up regulator isnt doing anything at all at 84deg?? I could be wrong but i'd have thought that highly unlikely indeed.

New radiator, new thermostat and new temp sensor and my M116 is at 85 no matter what the weather and it gets there quickly and stays there. High summer with A/C on, maybe 90 degrees is all it will go to. But the manual says hotter is fine on hill climbs, just not in the red.

Before radiator, stat and sensor replaced (All at different times) it went to 100 easy in traffic or on hills esp in hot weather. Ran great though. Stat is obviouly the first thing to check/replace. (Apologies if you've done all that already!)
 

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93 190E 2.6; 82 300 SD Turbo
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1,686 Posts
80C is mercedes standard. all of my mercedes run at 80C.

Your m117 should as well. The car should not normally run over 100C. Even in the Texas heat a friend of mines cars never get much past 85C

How old is the radiator? Thats what ended up being the problem in the 420..It would climb to 100C when at idle for a while. T-stat did nothing. Coolant flush did nothing. New radiator, problem solved.
 

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1986/1990 W126
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Totally agree with the radiator thing. Changed my climbing trafdic temps completely. But the OP has possibly lowish temps, so stat would be first to check.
 

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MB 1985 W126 300SEL, 1991 MB W124 260E, 2007 MB W209 CLK200, 1999 Skyline R34 GTT Veilside,
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342 Posts
Mine is always on the first click below the 80C, will only increase slightly when i turn off the A/C which also turn the electric fan off during start stop traffic. Time to change the Thermostat?
 

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93 190E 2.6; 82 300 SD Turbo
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80C-85C isnt low. Thats right where it should be.

driftmeister, yes if your car never gets to 80C then either you have an air bubble in the system or your thermo is stuck open.
 

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1989 mercedes 420 sel & 1995 volvo 850 t5 (just in case)
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244 Posts
i've had 80 Degrees C at winter time as the constant temprature. Now that it's summer it usually sits at 90. it did go to 100 few times.
 

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Mercedes 300 SD, 1985
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10 Posts
Same here as driftmeister. Mine does not reach 80. Sometimes barely under 80, but most a little after the first strip under the 80. So replace thermostat first? Have a new radiator in the car. Any tips on replacing the thermostat? Never done this before.

thanks, and this is a great forum by the way.:)
 

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MB 1985 W126 300SEL, 1991 MB W124 260E, 2007 MB W209 CLK200, 1999 Skyline R34 GTT Veilside,
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Gonna change my thermostat & radiators tomorrow...planning for a long trip. I was told the same thing...thermo stuck opened. Heard replacing it is a simple job, try searching some threads on it. Cheers!
 

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2001 E55 AMG
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3,294 Posts
Sorry to jump in.....I know it's a different engine but the principle is the same, it's to do with a possible half stuck open thermostat.....Below is what I posted in the correct section but had no reply...What do you think?
Well the weather is +5* here today,car never went above 80* on temp gauge....Still thinking possible half stuck thermostat. With 15*-20* outside it runs at 95* and the fans come on....After reading various threads I'm still unsure about normal operating temp?....It also took ages to get to 80*,it was staying around 60* 'till I hit some traffic.....I think I will just go and buy a thermostat and see it makes any difference,although I'll have to wait to next year for the full results.
 

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93 190E 2.6; 82 300 SD Turbo
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1,686 Posts
M116/M117 thermostats are NOT FUN, at least I didnt think so.

The thermostat housing is mounted so that the three screws are horizontal to the engine, two of them are decent to get to, the third one is best accessed by socket wrench with extension behind the alternator bracketry.
 

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2003 E500 Avantgarde
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186 Posts
Discussion Starter #12
OK .. in my case .. thermostat operation was dodgy at best, and radiator / header tank cap knackered completely. New ones. Temp settles nicely now at 85C, I`m happy with that. Also replaced filthy PS fluid. Big difference. Hoping to go on a 1300k trip north and back late next week, so we`ll see how it behaves ..

Next on my list of deferred maintenance issues is engine mounts, rear main and TC seals. And make the drivers seat a bit more comfy, I can`t believe someone paid so much for this car in 1983 ($NZ305k) and didn`t get lumbar support !!
 

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1986/1990 W126
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Well done. 85 is what my local specialist reckons is ideal.

Possibly the seats are so saggy by now, originally i expect they were firm and supportive maybe. I didnt like my '86 seats, but my latest '89 seats are blissful.
You could try the pool noodle thing on the base. Helped loads with my previous seats. Back support i dont know though.
 

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MB 1985 W126 300SEL, 1991 MB W124 260E, 2007 MB W209 CLK200, 1999 Skyline R34 GTT Veilside,
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Update : Changed thermostat for almost a week now. First 5 minutes after the changed the temp went up while stationary at almost 80c. Then it would drop back to 60-65c, so my Indy check the temp sensor and did a few test to check whether it actually move when connected & disconnected. He won't sure it was faulty but ask me to changed to changed the sensor (still haven't done that yet). Temp is still at 60c so I am planning to changed the radiator because Im not sure how old has it been on the car. Only had my 300SEL for 6 months now.

Anyone know why the temp is still so low?
 

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2003 E500 Avantgarde
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186 Posts
Discussion Starter #16
OK .. I`m back ..
Car did 13.5 litres / 100k`s .. 21 mpg. A/C on the whole time, the off button doesn`t work !! Not including city driving ..
Pretty much on the money I reckon, considering the long climbs to the top of the Central Plateau both ways.
Temp stayed constant at 85 .. with small climbs to 90 on aforementioned climbs.
Not even crawling in traffic did it deviate.
Has developed a small exhaust / manifold leak somewhere .. I can here a little ffft ffft ffft on acceleration .. but I can`t see where ..
Seats were much more comfy than I thought, now that its adjusted properly.
Used a litre of oil each way plus city driving .. approx 1500 k`s all up.
All in all a successful trip in a car that has barely been driven for the last ten years ..
 

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Mercedes 300 SD, 1985
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10 Posts
Changed my thermostat and voila, temp is back to 80. Car is running better to.
Now I have to change my glow plugs, ordered the updated one's and ordered the reamer tool from Mercedes source. Valve adjustment is coming soon.
 

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MB 1985 W126 300SEL, 1991 MB W124 260E, 2007 MB W209 CLK200, 1999 Skyline R34 GTT Veilside,
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342 Posts
Definitely change the sensor first.
Will do that on Saturday, will standby my parts guy for a BEHR radiator if it stills stay at 60c.

OK .. I`m back ..
Car did 13.5 litres / 100k`s .. 21 mpg. A/C on the whole time, the off button doesn`t work !! Not including city driving ..
Pretty much on the money I reckon, considering the long climbs to the top of the Central Plateau both ways.
Temp stayed constant at 85 .. with small climbs to 90 on aforementioned climbs.
Not even crawling in traffic did it deviate.
Has developed a small exhaust / manifold leak somewhere .. I can here a little ffft ffft ffft on acceleration .. but I can`t see where ..
Seats were much more comfy than I thought, now that its adjusted properly.
Used a litre of oil each way plus city driving .. approx 1500 k`s all up.
All in all a successful trip in a car that has barely been driven for the last ten years ..
Wow! Nice to hear problem free trip, mine is coming up next month from Kuala Lumpur, Malaysia to Phuket, Thailand with an estimated 2500km to/fro. I am gettin more nervous each day as the day for my travel getting closer.

Changed my thermostat and voila, temp is back to 80. Car is running better to.
Now I have to change my glow plugs, ordered the updated one's and ordered the reamer tool from Mercedes source. Valve adjustment is coming soon.
I just changed my plugs (not sure which spec & type) recently with BEHR ignition cables. My engine now shudders during idle. What plug for 300SEL would you recommend?
 

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2003 E500 Avantgarde
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Discussion Starter #19
I`ve done the trip from KL to Alor Setar .. with a brief excursion into Thai territory because we could .. when I was 10 years old !!
We were living in Petaling Jaya at the time, my Dad was there a couple of years on a Colombo Plan appointment ..
We did the whole round Malaysia trip, at one stage I recall the car had to go by rail between 2 points because there was no road !!
 

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MB 1985 W126 300SEL, 1991 MB W124 260E, 2007 MB W209 CLK200, 1999 Skyline R34 GTT Veilside,
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I`ve done the trip from KL to Alor Setar .. with a brief excursion into Thai territory because we could .. when I was 10 years old !!
We were living in Petaling Jaya at the time, my Dad was there a couple of years on a Colombo Plan appointment ..
We did the whole round Malaysia trip, at one stage I recall the car had to go by rail between 2 points because there was no road !!
I can imagine back then there was no highways, just trunk roads and overtaking tiny cars, trucks and tankers were the norm but very exciting. Looking at your present ride and highways now, probably you will drive from KL to Bangkok without breaking a sweat.

Car going in for radiator and water temp sensor check tomorrow. Hope to get rid of my vibration during idle at the same time if possible.:confused:
 
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