Ok, my thermostat was screwing up (engine running too cold). I replaced it at the advisment of my local indie, and now the engine is running way hotter than it should.

Before, when the thermostat was running correctly, it was running about 80-82*C. then it was running at about 75*C. The new one makes the car run at about 92*C, no matter if the temp is 35*F or 65*F.

Any ideas?

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http://comp.uark.edu/~dmgill/signature.jpg

Not sure about your model, but some have a "jiggler" valve that should be positioned at the highest spot..ie..12 o'clock or thereabouts.

Perhaps air was introduced into the system when this task was performed?

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Mike Murrell
1991 300-SEL - Model 126
M103 - SOHC
"Fräulein"

I believe this is an OK temp, what does it rise to if left idling when hot, when do fans cut in - I believe up to 105 is OK.

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NormanB
230 TE (W124) 1989 with 153,000 miles on the clock - hoping for at least another 100K

I think you finally found a good thermostat.

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2010 ML350 Bluetec
2012 Mustang Convertible

Moparmike, what brand and temperature thermostat did you buy? It's best that replacement thermostats be the same brand and temperature as the original to ensure similar performance. Some thermostats have a weep hole that must be oriented correctly for proper operation. If yours has a weep hole check that you installed it correctly. Also, check that air is not trapped in the cooling system.

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Fred Hoelzle

What does air in the cooling system do? And how does one know if there is air trapped in the system?

Iggy

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Insanity: doing the same thing over and over again and expecting different results.

2006 - Suzuki Gran Vitara (2.0 L fully equipped) Like this car so far except for trying to put on the seatbelt.
1988 - 190e - 2.3L - 172K miles (It now belongs to the exwife)
1999 - Chevy Blazer LS Fully Equiped - killed it June 2006
2001 - Honda Civic EX - 68K miles (sold June 2004)
1963 - 220S - Dual Carb 6 cyl. (sold)
1994 - Yamaha WaveRaider (fun to ride)

Depends on how much, but:

1. Adversely affects flow and heat exchange.
2. Accelerates internal corrosion.
3. Normally will rise to the highest point of the system but..
4. Can get trapped in the cabin heater - most folks will notice that loss of function first if they live in cold and wet countries like the UK!!

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NormanB
230 TE (W124) 1989 with 153,000 miles on the clock - hoping for at least another 100K

Your engine is now operating where it should operate.

Looks like you found a properly functioning thermostat. Rated temp is 87C. A proper thermostat should START to open in the 87C range and be fully open by 102C.

If your engine were running under 80C, that was because the previous thermostat was broken. It seems that as the thermostat ages, the opening temps seem to creep down a little bit. When my car starts running 80C on the highway, I replace the thermostat and that brings it closer to 90C on the highway.

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Ali Al-Chalabi

2001 CLK55
1999 Dodge Ram 2500 Cummins Diesel
2002 Harley-Davidson Fatboy
Merlin Extralight w/ Campy Record

allright, i'm confused now ! This is the second thermostat I've replaced in two months. both original from mercedes dealer. rated at 87degrees. before I replaced the first one the car ran around 87 to 92 deg. now the temp never goes above 82 or so... any ideas why not ? I replaced the new therm. thinking it could've been faulty. but that doesnt seem to be the case i guess.. what can i do ?

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Whether you think you can or cannot, Either way you're right!. by Henry Ford.

If the new thermostat never lets the car go above 82C and the coolant temp gauge is working properly then the new thermostat is faulty.

REMEMBER, an 87C rating means the thermostat STARTS to open at 87C. The thermostat does not fully open until 102C! In theory with a new thermostat working exactly as it is supposed to, the engine should never be below 87C. When my car starts running a constant 80C on the highway, this is when I replace the thermostat. That brings it up to 90C where it should be.

The old one you replaced was working properly. If you want your car to run at a temperature other than what the engineers decided it should run at, then don't get an 87C thermostat.

I would find that old one that kept the car a nice 90C, put it back in and make sure all the air is bled out.

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Ali Al-Chalabi

2001 CLK55
1999 Dodge Ram 2500 Cummins Diesel
2002 Harley-Davidson Fatboy
Merlin Extralight w/ Campy Record

well the old one was thrown away. so it's not around to be re-installed. it's just surprising how two brand new thermostat rated at 87 would not function properly. I agree with the theory where it should "start" to open at 87. what should i tell the dealer ? to replace it with a different one ? i don't want them arguing with me that's all.

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Whether you think you can or cannot, Either way you're right!. by Henry Ford.

If the engine is not getting above 82C with the new thermostat, I would take it to the dealer, it is not functioning as it should.

If you want to verify proper operation for sure, or to check a new thermostat before installing it you can suspend it with a string so it does not touch the bottom in a pot of boiling water with a thermometer in the pot. Just put it on the stove and watch it open. Of course, this is easier to do before the thermostat is installed.

I have noticed at least in my C280, that as the thermostat ages is seems to gradually creep towards a lower opening temperature. The last 2 thermostats in my car worked exactly as they should have at first but then after about 3 years or so seemed to be opening about 5C colder.

82C in itself is not that cold and not really a problem, but if the thermostat gradually opens at a cooler temp as it gets older, will your engine be running and 75C in 2 or 3 years? That would be too cold.

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Ali Al-Chalabi

2001 CLK55
1999 Dodge Ram 2500 Cummins Diesel
2002 Harley-Davidson Fatboy
Merlin Extralight w/ Campy Record

i was wondering, give that we all pretty much have to guess where the 82 or 83 deg would be based upon the needle position since we only have the 80 deg mark and then 90. could someone perhaps post a pic of their cluster showing their temp needle. this way we can all compare and figure out exactly what the temp needle should be at and take the guess work out of the equation.

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Whether you think you can or cannot, Either way you're right!. by Henry Ford.

The line above 80C is 100C NOT 90C.

90C is located halfway between 80C and the next line above it.

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Ali Al-Chalabi

2001 CLK55
1999 Dodge Ram 2500 Cummins Diesel
2002 Harley-Davidson Fatboy
Merlin Extralight w/ Campy Record

allright, here's a pic from another car that i copied from the net. now looking at the temp guage, are we saying that if the needle is exactly half way between the 80 and the 100 deg then it's fine. but my needle actually stays just a little above the 80deg mark. it intersects the digit 80 almost half way. now what temp. might that translate into ? 82, 83 ?

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Whether you think you can or cannot, Either way you're right!. by Henry Ford.