Hotter Thermostat for - PeachParts Mercedes-Benz Forum

tvpierce · #1 10-26-2005, 11:08 AM

I just installed a new thermostat in my ’92 201(4 cyl. 102 engine).

The reason I replaced it is that since the ambient temps around here have been getting lower (in the 40 degree F range) the car has been running at about 78 degrees C – too low.

The only thermostat available at FastLane was rated for 87 degrees, so that’s what I got. With the new thermostat, it now runs at about 82 degrees – still too low in my humble opinion. I’d like the engine to run at about 90 degrees. Is there another engine in the MB family that runs the same physical thermostat, but rated for something higher – maybe 92 degrees?

Thanks in advance.

Jeff Pierce

yal · #2 10-26-2005, 12:53 PM

Go 90-100% antifreeze.
Beck Arnley makes a 195 (90C) degree thermostat.

By the way why do you think 82 degrees is too low?

tvpierce · #3 10-26-2005, 04:48 PM

Quote:

Originally Posted by yal

Beck Arnley makes a 195 (90C) degree thermostat.

Where would I find one of these?

Quote:

Originally Posted by yal

By the way why do you think 82 degrees is too low?

A few reasons. In the warmer/summer months, the engine runs at about 90 degrees. It runs well, and gets better fuel economy.

The cooling fan's electric clutch engages at well over 100 degrees. This tells me that MB engineers fealt it was fine to run the engine much hotter than 87 degrees. My guess is that the 87 degree thermostat is a safe compromise from the standpoint of MB. They have to spec a thermostat that will keep the car from overheating if it's sold/operated in the South (say Texas or Arizona) with the A/C running full blast. Well I'm in Maine, I don't need that kind of protection. (and my A/C doesn't even work anymore)

Maybe someone with more knowledge will chime in here, but my guess is that the ideal temperature range for this engine (max power and efficiency) is somewhere in the low 90s.

Jeff Pierce

Nate · #4 10-26-2005, 04:56 PM

I cant help you much, but I do know that antifreeze turns to jello when it is in 100% solution, below (I THINK) 0* F, that cant be good...

I wouldnt go more then 75 antifreeze, and 25 water (distilled only)

~Nate

lkchris · #5 10-26-2005, 06:01 PM

Quote:

Originally Posted by tvpierce

This tells me that MB engineers fealt it was fine to run the engine much hotter than 87 degrees.

Actually what they did is specify one and only one thermostat for your car.

Why not get that?

Believing what your temp gauge tells you is pretty silly.

After you put in a new thermostat and the temp gauge doesn't read the thermostat spec, replace your temp gauge.

t walgamuth · #6 10-26-2005, 06:39 PM

that winter fuel gets poorer economy. also in my case i leave it running more so it is warm when i come out. are you planning to change it back in the summer?

i think i wouldnt put in a warmer stat. but prob one is available. i would also as noted above check the accuracy of your guage.

tom w

tvpierce · #7 10-26-2005, 09:47 PM

Quote:

Originally Posted by lkchris

Believing what your temp gauge tells you is pretty silly.

After you put in a new thermostat and the temp gauge doesn't read the thermostat spec, replace your temp gauge.

The temp guages on these cars are exceptionally accurate. I'd be more likely to believe that a new thermostat is defective before I'd believe that my temp guage was faulty. To think otherwise would be silly ;-)

Running a mixure other than 50/50 is a bad idea... out of the question.

I would change it back in the summer if it was running hot. But my guess would be that it would not run hot... but that's just a hypothisis.

Jeff Pierce

manny · #8 10-26-2005, 11:41 PM

Would you consider leaving the thermostat as is, and get a hot girlfriend instead ?

ksing44 · #9 10-27-2005, 04:02 AM

The dealer replaced my leaking water pump, flushed my cooling system, replaced the thermostat, refilled with all MB stuff, and now my car runs at about 92 instead of 87 or a little less. That is just past half way between 80 and 100, instead of just under half way between 80 and 100. Actually, at the end of my last thermostat’s life, my car was running low 80s. I liked the idea of running just under 90 instead of just over 90. I don’t think hotter is a good thing. I was thinking about trying to get a lower temperature thermostat. I asked the dealer about it and they said only one 87-degree thermostat was available for my car. I gave up on it, but I still wish it were 87 instead of 92.

On these forums, some have commented that it is not uncommon for a failing thermostat to start leaking and allow lower operating temperatures. That may sound too bad, but I would not have been happy if a failing thermostat finally stopped working correctly and let my car overheat.

tvpierce · #10 10-27-2005, 08:02 AM

Quote:

Originally Posted by manny

Would you consider leaving the thermostat as is, and get a hot girlfriend instead ?

My wife might take exception to that... but I'll run it by her.

Quote:

Originally Posted by ksing44

...my car runs at about 92 instead of 87 or a little less.

That's the temperature it should run at. An 87 degree stat BEGINS to open at 87 on the way up, and will be closed completely at 87 on the way down. So the normal operating temp of the engine will be a few degrees above what the stat is rated at.

Excessive heat IS a bad thing. But if your car is designed to run at 92, you aren't doing it any favors by running it at 82. True, it's running cooler, which is good for longevity, but you're causing it to operate less efficently, therefore making it work harder (bad for longevity).

Just to clarify: I'm not trying to make my engine run hotter than it's designed to run. I simply want it to run at the proper temperature.

Jeff Pierce

yal · #11 10-27-2005, 08:50 AM

Quote:

Originally Posted by tvpierce

Where would I find one of these?

Jeff Pierce

www.********.com

tvpierce · #12 10-27-2005, 09:33 AM

Quote:

Originally Posted by yal

www.********.com

Thanks for the link... they have a great selection of parts.
(BTW, I would only buy MB parts from them if it was something I could NOT get from FastLane or Phil -- gotta support the folks who support the community. And in this case, the MercedesShop forum IS the community.)

But the best that Rock Auto could do is a 195 degree F stat. That's only 90.5 degrees C. It's better, but still a little low.

Jeff Pierce

abe g · #13 10-27-2005, 12:16 PM

How about that ol time fix: put a peice of cardboard in front of radiator, cut to fit temp you want ! good luck, Abe G