1980 240D manual - coolant temps whats "normal" - PeachParts Mercedes-Benz Forum

stayalert · #1 05-11-2014, 04:31 PM

Please help me as this new to me (was my Dad's) w123 and I get to know each other….

4 door sedan with ~160K miles) with 3 adults, 2 sets of hockey gear, highway miles, ambient temp ~70 degrees F, No A/C used.

highway travel ~70MPH

on longer uphills I'd see the temp climb to 95-100 degrees C (via stock coolant temp gauge) - never went higher….If I backed off a bit or the road leveled out the temp would fairly quickly drop to ~85 - 90 degrees C….When I say hills we're talking Vermont….some nice rollling hills sometimes going uphill for a couple of miles and maybe gaining a couple of thousand feet We're not talking colorado etc. with l-o-n-g passes with BIG elevation changes…..

stayalert · #2 05-11-2014, 04:34 PM

and yes. My geographical references are meek and mild I'm sure some of you live where its flatter, and some of you live where the Mtns. of Colorado seem flat.

uberwasser · #3 05-11-2014, 04:57 PM

Seems pretty normal. 85-90C is definitely normal for cruising. Fluctuations to 95-ish C are not abnormal at higher speeds, especially under heavier use like on a really hot day, or going uphill, especially when loaded down.

I'd only be worried if I saw it cross over 100C and continue to climb.

Deemo13 · #4 05-11-2014, 04:59 PM

I'd say my average was around 80-85 in the flat Central Valley in California. I also owned a 1980 manual 240D, except mine was not Euro.

pj67coll · #5 05-11-2014, 06:14 PM

That's a bit higher than I'd like on the hills but it doesn't sound like it's overheating. I'd start to investigate all cooling system components but keep driving it and monitoring it and if it never get's above 100C and seldom even reaches that I don't think I'd be too worried.

- Peter.

Mxfrank · #6 05-12-2014, 01:18 AM

Unfortunately, this is probably normal. The short explanation is that most cars are designed to run "on the thermostat", so if you have a 185 thermostat, that's about where they'll run. But Mercedes plays some tricks with airflow, which result in wide temperature swings. There are two fan systems...a mechanical fan driven off the water pump and an electric fan in front of the radiator. The mechanical fan will engage only when it's very hot...about 95 degrees. The electric fans engage when it's even hotter...100 or more depending on the model. To make matters worse, the mechanical fan, if it has a viscous clutch, senses air temperature around the middle of the radiator, where the water is fairly cool, the electric fan senses temperature near the water exit, where it's fairly hot, the temp gauge reads from the side of the head, adjacent to a cool intake port, and the thermostat is all the way at the bottom of the system. I don't have an objection to high temperatures for efficiency and emissions. But temperature fluctuations aren't good. Unfortunately, that's the way this system was designed to work, unless you're prepared to mod it.

t walgamuth · #7 05-12-2014, 07:01 AM

I don't believe any 240D ever came with a clutch fan.

Mine always runs right at 82 degrees unless climbing. Getting up to 100 would make me want to start checking things. First I'd take a hose and blast the radiator from behind to get any debris out. Then I'd get a new 80 degree stat and put it in when it was opportune.

funola · #8 05-12-2014, 07:40 AM

Quote:

Originally Posted by Mxfrank

..........I don't have an objection to high temperatures for efficiency and emissions. But temperature fluctuations aren't good. Unfortunately, that's the way this system was designed to work, unless you're prepared to mod it.

Can you please provide details of the mod?

Shortsguy1 · #9 05-12-2014, 07:50 AM

Quote:

Originally Posted by t walgamuth

I don't believe any 240D ever came with a clutch fan.

Mine always runs right at 82 degrees unless climbing. Getting up to 100 would make me want to start checking things. First I'd take a hose and blast the radiator from behind to get any debris out. Then I'd get a new 80 degree stat and put it in when it was opportune.

Strangely enough, the earliest w115 220d cars had a viscous fan clutch. And then within a year or so, they all went to fixed systems.

If BC was here, he might argue against Tom's recommendation of a lower T thermostat. It doesn't do anything to lower steady-state temperature on an extended climb. It only buys you a few more seconds of transient temperature rise, since the starting point is a little lower.

Mxfrank · #10 05-12-2014, 08:06 AM

Quote:

Originally Posted by funola

Can you please provide details of the mod?

I've not worked on a 240, but from what I can see there are extra 22mm water jacket ports on the left side of the head. Use a Porsche fan switch, which comes on at 92C, and wire it to the low speed resistor for the fans. The electric fan will come on at lower temperature, helping airflow.

1985 Porsche 944 Base Coupe - Water Pump, Thermostat & Hoses - Page 2

Maxbumpo · #11 05-12-2014, 08:45 AM

I think those temperatures are too high.

Thermostat seems to be operating fine, so leave that alone.

I like the suggestion of cleaning out the radiator fins. If there is an AC condenser, you may have to remove the radiator in order to do a good job.

If that doesn't work, my next step would be a citric acid flush, see the service manual.

After that, either replace the radiator or take the car to a radiator shop.

cooljjay · #12 05-13-2014, 01:07 AM

So one point I would like to make about the electric fan, not all w123's came with them, and they have been argued to death....the majority of the member stating that the fan only comes on when the ac system is on....not when the car reaches over 100...

I would look into replacing the radiator, while they are still available for a reasonable fee..

For added protection, a clutch fan, can very easily be added.....all you need to do is go to the JY and pull the assembly with bolts off a 300D and it bolts right on.

t walgamuth · #13 05-13-2014, 06:16 AM

Quote:

Originally Posted by Shortsguy1

Strangely enough, the earliest w115 220d cars had a viscous fan clutch. And then within a year or so, they all went to fixed systems.

If BC was here, he might argue against Tom's recommendation of a lower T thermostat. It doesn't do anything to lower steady-state temperature on an extended climb. It only buys you a few more seconds of transient temperature rise, since the starting point is a little lower.

80 degrees is factory on the stat. (if that's not right, I mean to recommend a new factory stat).

Skippy · #14 05-13-2014, 06:26 AM

There seems to have been a run (or more) of replacement thermostats that run hotter than marked. My 240D always ran right around 100 C regardless of how I was driving, including flooring it for hours at a time on long road trips. My 300D came to me with a failed open thermostat and never got over 60. With the replacement one in it's been running 100 or so for the past eight years. I don't consider this a problem, as I've been getting better fuel economy than most, even though I drive like Ayrton Senna. If it starts getting significantly hotter, then I would suspect a problem.

stayalert · #15 05-13-2014, 07:11 AM

Quote:

Originally Posted by cooljjay

So one point I would like to make about the electric fan, not all w123's came with them, and they have been argued to death....the majority of the member stating that the fan only comes on when the ac system is on....not when the car reaches over 100...

I would look into replacing the radiator, while they are still available for a reasonable fee..

For added protection, a clutch fan, can very easily be added.....all you need to do is go to the JY and pull the assembly with bolts off a 300D and it bolts right on.

I am leaning towards this after I look into cleaning rad/condenser, and check T-stat…..My car has an electric fan that I have never heard seen run (havn't looked closely, just havn't noticed it…..