My car likes to heat up close to overheating on highways after long stretches (more than about half an hour at highway speed and I'm over 100C...the needle has peaked the meter out once and I shut it down and pulled over and suffered no damage.)

I probably need a coolant flush but until that point in time, I was just thinking of taking the thermostat out. That way, it'll be fully circulating the coolant the whole time, and should run cooler.

Aside from taking longer to get to operating temperature, this can't hurt anything right?

__________________
1983 Mercedes-Benz 240D
Automatic, A/C, Power Sunroof, Power Right Side Mirror
231K Miles FOR SALE MAKE OFFER

No.

The system must have a thermostat at all times to route the coolant where it needs to go. Removing the t-stat will not force the coolant through the radiator.

Take your car to a local car wash and use the pressure washer to wash/blow out the radiator and A/C condenser cores. Chances are they are plugged with road dirt.

You might want to study up on the specifics of a bypass-type thermostat.

Just pick up a new t-stat and coolant and do the whole job in one afternoon. Removing the t-stat might solve your overheating issue, but it can produce new problems. Not getting your engine up to operating temperature can lead to engine hesitation and blowing white smoke while driving. If you were going to take the old one out, why wouldn't you just put a new one in? Even if you didn't want to get into the coolant flush right now, you could still do that another day.

__________________
'95 E300D ("Tank") - 231,000 miles
'79 240D ("Biscuit") - 197,250 miles (Sold)
'83 240D ("Ding-Ding") - 217,000 miles (Death by deer)
______________________________________

"Back off, man. I’m a scientist” ~ Peter Venkman

On the subject of thermostats.....what does it mean if I replaced my T-stat (I did do it properly via FSM methods) and it runs "a bit warmer" than it should now? I mean it runs about 87C driving around in traffic, and will somtimes get to 90C-91Cish on the freeway, then fall back down to 88ish after a while. Never gets above 91 though. Could I have a bad T-stat? It used to barely see 60C....

My dad's car I replaced the T-stat as well as it barely got over 50C while driving, and now with the new one it runs 81-85C, no higher.

Is mine bad perhaps?

My Radiator, Coolant, and expansion tank are OEM and only a year old, so its not that.

__________________
-diesel is not just a fuel, its a way of life-
'15 GLK250 Bluetec 118k - mine - (OC-123,800)
'17 Metris(VITO!) - 37k - wifes (OC-41k)
'09 Sprinter 3500 Winnebago View - 62k (OC - 67k)
'13 ML350 Bluetec - 95k - dad's (OC-98k)
'01 SL500 - 103k(km) - dad's (OC-110,000km)
'16 E400 4matic Sedan - 148k - Brothers (OC-155k)

I went through several "80* C" stats that didn't even begin to open till almost 90* C. They would make my car run at or slightly above 100* C and yes, I had a new radiator, water pump, citric acid flush with new coolant, and I parked the car on a steep hill while filling into the upper hose to ensure that there was no air trapped in the engine. I went through this about five times with three t-stats from Fastlane and one from AutoZoo until I finally came across a thread on here that said to use a 75* C stat from a late 70's SL, I believe. Ever since I put that stat in she's run rock steady at around 82* C, only climbing to 85* after an exit from a freeway run in our 100 degree summers with the a/c on. It hasn't once tried to over heat since I put the 75* C stat in.

__________________
Seth

1984 300D 225K
1985 300D Donor body
1985 300D Turbo 165K. Totaled. Donor Engine. It runs!!!
1980 300SD 311K My New Baby.
1979 BMW 633csi 62K+++? Dead odo

An 80*C Behr thermostat works perfect for me.

Also, if your temperature sensor is more than 5-10 years old, you should change it. They loose their accuracy over time, it only costs $12 and takes 5 minutes to change. I'd bet that most of you complaining of running constantly too hot have a bad sensor.

Oh yeah. That's another thing I forgot to add. I bought an infrared thermometer to verify that the sender was indeed accurate. I know its cheaper to just buy a new sender but this way I got a new tool.

__________________
Seth

1984 300D 225K
1985 300D Donor body
1985 300D Turbo 165K. Totaled. Donor Engine. It runs!!!
1980 300SD 311K My New Baby.
1979 BMW 633csi 62K+++? Dead odo

I took the t stat out of one of my cars and after many miles and
multi hundred mile road trips, the only side effect was no heat.
I probably have in excess of 10k like that.

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81 Mercedes 300SD 289k.......SOLD
82 Mercedes 300CD 252k......slow ride

82 mercedes 300 SD...mi Unknown
83 Mercedes 300D ????ksniff..gone too
84 Mercedes 300D 148k........SOLD
85 Mercedes 300TD 386k and holding some one elses project

You need to put them back in, they should never be driven without it.

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Uhhh yeah, Jack, you are in Florida. Try running a diesel without a thermostat in a cold weather clime. Even here in Tucson winter time temps get down into the 20's and 30's at night. Not getting your diesel up to operating temps results in a incomplete fuel burn with the un-burned fuel "washing" the cylinder walls of lubricating oil causing minor cylinder scoring and decreasing the life of the engine.

Well, my only thought here is that these are diesel engines that require proper heat to function at their best. So, if you are driving around in cold temperatures without a t-stat, then you aren't doing your engine any favors. If it is cold enough out, you won't get up to proper operating temperatures and your engine will probably not be burning fuel efficiently.

__________________
'95 E300D ("Tank") - 231,000 miles
'79 240D ("Biscuit") - 197,250 miles (Sold)
'83 240D ("Ding-Ding") - 217,000 miles (Death by deer)
______________________________________

"Back off, man. I’m a scientist” ~ Peter Venkman

Alright, I'll carwash it.

__________________
1983 Mercedes-Benz 240D
Automatic, A/C, Power Sunroof, Power Right Side Mirror
231K Miles FOR SALE MAKE OFFER

Yeah my gauge bounces around, I will replace the sender the next time I order parts....and if it still reads wrong I'll try another thermostat.

__________________
-diesel is not just a fuel, its a way of life-
'15 GLK250 Bluetec 118k - mine - (OC-123,800)
'17 Metris(VITO!) - 37k - wifes (OC-41k)
'09 Sprinter 3500 Winnebago View - 62k (OC - 67k)
'13 ML350 Bluetec - 95k - dad's (OC-98k)
'01 SL500 - 103k(km) - dad's (OC-110,000km)
'16 E400 4matic Sedan - 148k - Brothers (OC-155k)

An excellent point made!
These cars will run short term with many things as they should NOT be. But you are decreasing the long term engine life that ebay sellers love to brag about.....

__________________
Jimmy L.
'05 Acura TL 6MT
2001 ML430 My Spare

Gone:
'95 E300 188K "Batmobile" Texas Unfriendly Black
'85 300TD 235K "The Wagon" Texas Friendly White
'80 240D 154K "China" Scar engine installed
'81 300TD 240K "Smash"
'80 240D 230K "The Squash"
'81 240D 293K"Scar" Rear ended harder than Elton John