"stant thermostats" or "temperature regulation 101" - PeachParts Mercedes-Benz Forum

noMoreGasoline · #1 02-08-2008, 09:45 PM

From looking at other posts on here, i gather that the 617 engine should normally run between 80-90 degrees C. In fact the car did run that way with the OEM (mercedes logo stamped into it) theromstat i "preventatively" removed a few months ago.

However when i installed a Stant thermostat from AZ, the temp is now regulated at 100 degrees C. Even on a 50 degree (F) day, with the engine not working especially hard, it wants to stay at 100. So on the off chance that I got a defective unit, I went to Napa and bought one of their thermostats and the same thing is happening!

(I later learned that Stant makes Napa thermostats. Great. So much for troubleshooting with a different brand.)

I refuse to believe that i got two defective thermostats. Are perhaps the Stant designs flawed? Btw, both thermostats had "174 F" stamped into the bodies... this is roughly 80 C. Anybody else have similar experiences?

Now I am looking at getting one online and my choices are Wahler, Behr, and Calorstat. Any recomendations?

Chas H · #2 02-08-2008, 09:57 PM

I once went through 3 new t-stats (one was a Wahler) before I got a winner. I've had success with Behr. You might want to check the t-stat in a pan of water on the stove before condemning or installing it.

jkoebel · #3 02-08-2008, 09:58 PM

I had a Wahler thermostat I just removed from my car, it had the star and a xx xx xxxx part number stamped into it. It was stamped 80 C and had severely corroded, and one of the two arms holding the back part together had snapped off and so it would no longer actuate. (I think it was probably original with the car.)

I think, based on this, Wahler is an OEM supplier.

fdanielson · #4 02-08-2008, 09:58 PM

I bit the bullet and paid the 20 some odd dollars for a genuine Mercedes thermostat at the dealer the last time I changed the coolant. It's rock steady at about 82 degrees.

Mustang_man298 · #5 02-08-2008, 10:01 PM

I believe I installed a Behr unit in mine when I put my engine conversion in almost 2 yrs ago, (Old stat was grenaded). So far so good, no problems, it runs just a slight bit warmer in the summer, but I attribute that to having a radiator for a 616 with a 617 engine. It -might- reach 100*C driving in the mountains here on a 115*F day, can't really blame it for getting warmer in those conditions though.

lutzTD · #6 02-08-2008, 10:27 PM

i could never get mine to run below the next line over 80 until I drilled holes in the thermostat plate, now it never budges from a needle or two below that line. I hit the rad with a ir thermometer and it was right at 85C

mobetta · #7 02-09-2008, 12:37 PM

I just got a whaler from napa. it was in a stant box, but was a whaler, made in germany- pan tested it first, good2go.

their oring is a waste of money, though. not the right part.

noMoreGasoline · #8 02-10-2008, 12:29 AM

well, i got the mb dealer thermostat and same thing: temp regulated to 100. interestingly i had to give the parts person my VIN because she said it was engine specific (beyond the fact that i told her it was an 82 300d). perhaps mercedes has changed the design spec?

#9 02-10-2008, 01:19 AM

It is engine specific as it only works in the 78-85 300SD, 81 300TD and 82-85 300D/CD/TD.

Your temperature should be between 80-85*C all the time.

noMoreGasoline · #10 02-10-2008, 02:24 AM

it's not. it's now right at 100 with 2 stant thermostats and 1 dealer thermostat. wierd.

#11 02-10-2008, 02:41 AM

Clean out your radiator with a hot water pressure washer (from both sides) and replace the coolant bottle cap if you have not done so already.

If the gauge has ever been jumpy then replace the temperature sender on the head as well.

noMoreGasoline · #12 02-10-2008, 03:19 AM

Quote:

Originally Posted by ForcedInduction

Clean out your radiator with a hot water pressure washer (from both sides) and replace the coolant bottle cap if you have not done so already.

If the gauge has ever been jumpy then replace the temperature sender on the head as well.

Thanks for trying to help out

but i have a new radiator. the coolant bottle cap i have not replaced, but i don't think it is related. i say this because the old thermostat i took out maintained 80 just fine. the only component that changed from when the car ran at 80 versus running at 100 was the thermostat.

i am not the only one having these issues with new thermostats:

Troubleshoot a 617.952 cooling system (84 300TD turbo)

i really think a design/manufacturing spec has changed. whether on purpose or not, i do not know.

i wish now i hadn't thrown the old one away.

vstech · #13 02-10-2008, 04:43 AM

Mine too is showing the same behavior.
Brian C tells me that it is normal.
I ran citric acid and flushed and flushed, drain bolt out, flushed flushed... no change.
rock solid on 100C... GREAT heat, but I don't like running so hot.
there is a 70C Thermostat for the 107 motor... give it a try. I will stick with the 100C temp for now. I may have a weak water pump. I did buy a new one, but have not installed it yet... waiting until I break down and adjust the valves again on her...
oh, and changing the T-stat is not all you did, you also added antifreeze, or changed your antifreeze... your old mixture may have been weak... just a thought.

Stevo · #14 02-10-2008, 10:58 AM

Quote:

Originally Posted by noMoreGasoline

Thanks for trying to help out

but i have a new radiator. the coolant bottle cap i have not replaced, but i don't think it is related. i say this because the old thermostat i took out maintained 80 just fine. the only component that changed from when the car ran at 80 versus running at 100 was the thermostat.

i am not the only one having these issues with new thermostats:

Troubleshoot a 617.952 cooling system (84 300TD turbo)

i really think a design/manufacturing spec has changed. whether on purpose or not, i do not know.

i wish now i hadn't thrown the old one away.

I'm sure you have this covered but, you do know about the little arrow stamped on the T-stat body? Its hard too see and I have seen Whalers that for some reason didn't have it. The last Behr I bought did. The correct T stat for your car will have 80C stamped on it also.

sailor15015 · #15 02-10-2008, 04:09 PM

Try a 75C stat from a late 70's SL. That's what I had to use in mine because I was going through the same things and now it holds rock steady at 82C, and this is with a new radiator, water pump, and flushed system.