Differences in thermostats - PeachParts Mercedes-Benz Forum

MarkM · #1 01-06-2007, 07:45 PM

While in eastern Massachusetts we enjoyed 70 deg. F weather, I did one of the items on my Mercedes to do list ....I took out the Wahler (auto zone) which is marked 80 deg.C, and keeps the coolant temp. at a steady 81-82 degrees, according to the dash gauge. I changed to the Behr, which is also marked 80 deg. C, and did this to "winterize" the car (oddly on a 70 F day in January!), because this thermostat keeps the coolant temp. at a nice toasty 93 to 95 degrees C (better for heat in the cabin)!

I just thought I'd mention it....probably covered in other posts. In case you think your car runs too hot, change the thermostat to a Wahler. If you have a wahler, and want better winter heat, change to a behr.

Mark

#2 01-06-2007, 07:47 PM

If the thermostat is marked for 80* and it keeps the engine 93-95* then it's a bad t-stat or poorly built by the manufacturer.

stephenson · #3 01-06-2007, 07:51 PM

Another consideration is that since this is mechanical device, drawing conclusion from only one sample of each may be a reach.

sailor15015 · #4 01-06-2007, 07:52 PM

I'm waiting on my fifth thermostat, 174 F from Autozone which is supposed to be OE temp. I've gone through three thermostats from Fastlane that were all supposed to open at 80 C, none of which even started to crack till almost 90 and causing my car to run right at 100 C. I got a 180 F degree from Autozone and it also didn't open when it was supposed to. By the way, the radiator and water pump are new within two months and I also did a citric acid flush and made sure to get all the air out of the system.

Biodiesel300TD · #5 01-06-2007, 08:01 PM

Quote:

Originally Posted by ForcedInduction

If the thermostat is marked for 80* and it keeps the engine 93-95* then it's a bad t-stat or poorly built by the manufacturer.

hmmm... I put in a new one and my car runs at 90C. Should I be thinking about puting in another new one?

benzforlife · #6 01-06-2007, 08:15 PM

its, funny, because just yesterday i did a flush and a stat change an while not running hot , my old sta kept it at justa hair over 80c but the new one is closer to (90-100c) i thought this was odd, maybe i just need to wait for the air to get out?

stephenson · #7 01-06-2007, 08:20 PM

I learned a trick about 20 years ago on a BMW 2002 I had which had an external tstat ... have used it on every tstat I have installed since then - I and several other BMWCCA members went through dozens prior to finding ones that actually operated properly - someone came up with this idea and it appeared to work then.

I drill 3-4 tiny holes around the perimeter - the portion of the tstat that is thin (the part that moves) .. while I don't KNOW if this had made a difference since then in the 10-15 tstats I have replaced or simply removed and then reinstalled, I have not had a tstat that didn't appear to operate properly since then.

sailor15015 · #8 01-06-2007, 08:25 PM

Quote:

Originally Posted by stephenson

I learned a trick about 20 years ago on a BMW 2002 I had which had an external tstat ... have used it on every tstat I have installed since then - I and several other BMWCCA members went through dozens prior to finding ones that actually operated properly - someone came up with this idea and it appeared to work then.

I drill 3-4 tiny holes around the perimeter - the portion of the tstat that is thin (the part that moves) .. while I don't KNOW if this had made a difference since then in the 10-15 tstats I have replaced or simply removed and then reinstalled, I have not had a tstat that didn't appear to operate properly since then.

How tiny are we talking? I took one and drilled just one the size that Diesel Giant shows on his page and it kept the car from getting above 60 C. I was toying with the idea of drilling tiny holes in one if the one in the mail doesn't fix the problem.

MarkM · #9 01-06-2007, 08:51 PM

Quote:

Originally Posted by stephenson

Another consideration is that since this is mechanical device, drawing conclusion from only one sample of each may be a reach.

This was the third in a row that did this, two from Fastlane, one from Performance....two were behr (germany) and a third one (bought to try a different brand) was made in France (I forgot the brand)....at $15 to $20 each, and being in the Summer when I did NOT want the car to run hot, this was very annoying.

Finally someone here had the same experience and suggested that I get a Wahler from Auto Zone, and the thing runs slightly above 80...just perfect. So now, I use one of the Behrs for winter.

Mark

stephenson · #10 01-06-2007, 09:00 PM

Sailor,

I had not seen the Diesel Giant trick, but I just reviewed the photos - holes that I have drilled in are far smaller - maybe 1/4-1/2 that size - his look awfully large ... I also just spread the holes at about 90 degree points.

While I can't prove it, I believe the extra flow of water as it heats up assists the heating effect on the tstat itself - perhaps ensure more positive opening?

t walgamuth · #11 01-06-2007, 10:20 PM

i would not drill any holes in my stat.

they are designed by real engineers. benz has been using this style of stat for over forty years that i know of personally. many other european cars use the same style of stat. they work properly left alone.

drilling holes in them is not a good idea, imho.

tom w

Gurkha · #12 01-07-2007, 05:49 AM

The original T stat which comes with the OM616 is 78C, keeps the engine at 90C flat, MB then decided to give out 72C T stats which keeps the engine at 80C flat, 82C under extreme heat conditions.

stephenson · #13 01-07-2007, 10:31 AM

Good inputs - however, consider that there are many, many folks who report having tstats that don't work right. They can be "designed" by real engineers (but, in this case, the design work was done about 80 years ago, I think ... recently simply a lowest cost production issue), but still respond well to custom mods that could not be done to meet the price points in large scale production.

This variety of tstat has stood the test of time pretty well - think about them being virtually unchanged for decades - when everything else on the engine has changed substantively. What if tstats had evolved the same way - imagine a sensor based electric system that measured water in 3-5different places, also using inputs from other thermal sensors and position sensors to anticipate loads so that as you start up a hill, the tstat opens in advance of the load -maintaining temp +/- 1 degree ALL THE TIME. If it is gonna be electric, why not make the coolant pump electric, too (I think this is already in the works with move to higher voltage systems) - and then the pump could work with the sensor system and the tstat to completely control thermal issues without belt drive - it could even operate off the battery when the belt does through itself .... pretty cool!

tangofox007 · #14 01-07-2007, 10:36 AM

Quote:

Originally Posted by stephenson

While I can't prove it, I believe the extra flow of water as it heats up assists the heating effect on the tstat itself - perhaps ensure more positive opening?

The "extra flow" should have the opposite effect on a bypass system. The added flow would be from the radiator.

Now for the $64,000 question. Is an 80 degree thermostat supposed to maintain a coolant temperature of 80 degrees? Or does the thermostat temperature rating describe the temperature at which the thermostat begins to actuate? At what temperature does an 80 degree thermostat completely actuate?

Biodiesel300TD · #15 01-07-2007, 12:30 PM

Quote:

Originally Posted by tangofox007

The "extra flow" should have the opposite effect on a bypass system. The added flow would be from the radiator.

Now for the $64,000 question. Is an 80 degree thermostat supposed to maintain a coolant temperature of 80 degrees? Or does the thermostat temperature rating describe the temperature at which the thermostat begins to actuate? At what temperature does an 80 degree thermostat completely actuate?

Yeah Yeah!!