Need a low degree thermostat: M104 engine - PeachParts Mercedes-Benz Forum

macarose · #1 08-21-2007, 12:28 PM

M104 engines are known to run in the higher degree areas. Right now, due to the heat wave in Atlanta, my 1993 TE300 is running between 99 and 105. Usually it's right around the 90 degree area during the winter time.

I wanted to see if perhaps there is a lower degree thermostat which may be helpful. I know it's not overheating, but I would like to ensure the longevity of this vehicle and if I can do that and sacrifice a small amount fo fuel economy that would perfectly fine.

Thanks, and hope all is well...

macarose

yal · #2 08-21-2007, 01:24 PM

You can buy an 82 degree thermostat as opposed to the 87 degree one the W124's use. You can buy it at your local NAPA store part# THM180 or online at www.********.com.

juribe2 · #3 08-21-2007, 02:35 PM

I think the thermostat will not lower your engine temp. It will open sooner and will take longer to reach the operating temperature but after running for a couple of miles it will be the same.

105C is normal in that engine because at that temperature the high speed aux fan will start.

If you want to modify something, you have to deal with those aux fans starting at a lower temp. Read this 17 and 18 here: http://pages.prodigy.net/jforgione/MB_S500.html

psfred · #4 08-21-2007, 11:58 PM

I would check the aux fan operation and visco clutch first -- likely the visco clutch is bad (assuming you have one, I'm not sure). Temps hanging around 100 C in traffic sounds a whole lot like a bad visco clutch -- both of my cars did that before I replaced them.

A low temp thermostat won't help.

Peter

#5 08-22-2007, 07:37 AM

With the heat we've been having, you have nothing to worry about w/ 100 to 105C, especially if you're in stop and go traffic.

If the "official" temp is 100, sitting in traffic has to be more like 110 or even 120F. If your car is running at 105C, I'd say don't chase a problem you don't have.

Then again, I have an M119 and trying to get her to run under 100 in summer is Mission Impossible.

mbdoc · #6 08-22-2007, 08:04 AM

IN MOST cases a lower temp thermostat won't lower the engine temps!

100C engine temp in 100+ ambient temps is NORMAL on that & most other MB engines

jcyuhn · #7 08-22-2007, 12:59 PM

I bet the low speed aux fan operation triggered by a/c high side pressure is broken. So he gets no electric fan activation until 105C. Fits the symptoms well, as the fans switch on at 105C and off at ~100C.

Try this simple test. Idle the car in the driveway, hood up, with the a/c on. The electric fans in front of the condensor & radiator should engage at low speed within the first minute or so, and possibly cycle off and on. If not, you have a problem.

Of course, this is all predicated on the a/c working. If the a/c is dead or low on charge, then nevermind.

- JimY

ksing44 · #8 08-23-2007, 07:22 AM

http://www.peachparts.com/shopforum/showthread.php?t=193757

Pretty good discussion in the link above. The low speed fan does help a little, so first be sure that your AC pressure and low speed fan operation are OK.

I have the cool harness and it does work to keep the car below 100 degrees, even in stop and go traffic in the heat. The only weird thing is the high speed fan stays on once it comes on. A driver operated switch for high speed fan might be the best solution, but I am happy with my cool harness for now. Jim was easy to work with, even for a goof like me.