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MB w123 250D om602 10v 1983
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Discussion Starter #1
So the winter cold has "finally" reached my MB 200E which is struggling with engine temp, it takes forever to get the engine up to operating temperature and if I run the fan on even stage 1 or 2 it won't reach ~80C even when driving at 90-110km/h!

I take into consideration that the outside cold will have an affect on this but I still find it strange to believe that the engine would get such penalty from the winter cold, there isn't much difference between -8C or -16C in terms of how long it takes to warm up.

The engine temperature will reach operating temperature if I let it idle and having the fan off (although it takes forever), if I turn the fan on (stage 1 or 2) it won't go over about 50-60C.

I have switched thermostat 2 times and still no effect on the warm-up issue, though the last one allows the engine to reach 80C when the other ones didn't.

I'm starting to wonder if it's a temperature sensor failing or whatever, but I don't know, I recently did a complete service on the car which included, new thermostat, new plugs, new ignition wires, new cap and rotor, motor oil, oil filter, fuel filter.

Any ideas?
 

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Mercedes 300 TE 24v SportLine -91 W124
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Does Your climate temp seem warm enough or does that feel too "cold" also?

It may be the temp sensor if You get good warm air into Your cupé.
 

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MB w123 250D om602 10v 1983
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Discussion Starter #3
Does Your climate temp seem warm enough or does that feel too "cold" also?

It may be the temp sensor if You get good warm air into Your cupé.
That's the problem, sure it's "warm" but not as warm as it should be, the air that comes out the vents are pretty much equal to the engine temp as it should be, the problem is the time the engine takes to reach optimal engine temperature ~80C, and sometimes it doesn't even reach that temp.

If I turn the fan off then sure it reaches 80C but even on stage 1 it takes probably an hour before it reaches 80C on the highway or driving in the town, doesn't really matter.
 

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Mercedes 300 TE 24v SportLine -91 W124
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My first guess would be the thermostat, but as You already have changed it.... just plain weird.
 

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MB w123 250D om602 10v 1983
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Discussion Starter #5
My first guess would be the thermostat, but as You already have changed it.... just plain weird.
I agree, it's really weird! Because the engine should be able to reach temp even with the fan on, right? and I'm sure the engine fan isn't running so that's not cooling it off either..

What I'm wondering is if there's a temp sensor somewhere or something that tells the engine "you're already decently warm" so then engine doesn't struggle getting up to optimal running temp?

Or if it's possible to short some sensor or whatever to see if it helps raise the engine temperature, if the sensor is bad that is.. if it's possible?
 

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Mercedes 300 TE 24v SportLine -91 W124
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Well, the only parts that would automatically cool down the engine is the thermostat and the viscous fan coupling. Unless You have a electrical radiator fan. Then You have a temp sensor that closes a circuit and turns on the radiator fan.

Otherwise the engine would and SHOULD just get warmer and warmer.
 

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About a dozen 1988, 1989, 1990, and 1991 sedans, wagons, 4Matics and 1 coupe
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This is not a control system or electronic/electrical problem -- it's a mechanical problem.
We didn't get 4 cylinder 124s here in the USA so I'm not familiar with the exact layout of the fan system.
Also, we don't see temperatures like you are experiencing.
Fist of all, I would ask the owner of a similar vehicle how his car behaves. IOW establish a normal behavior baseline.
If his car warms up fairly quickly (as I think it should) I would first look at the thermostat again. What brand did you put it, Behr? I would definitely go with that brand given your experience. The rubber sealing ring is in place over the thermostat, right?
Then I would look at the cooling fan operation. If it's a viscous type does it freewheel at cold temps? I can stick my gloved fingers into the fan of my 88s and slowly stop the blades and hold them while the engine is running. IF you have the electric clutch fan it should be disengaged.
If all else fails there's always the sheet of cardboard method. You place a piece ahead of the radiator to block airflow through it. This must be wellknown in Sweden.
My dad bought a new Saab 99? in 1964. 3 cylinder, 2-stroke, 4-speed trans on the column, cooling fan in a cage, and a manually-operated roller blind that you controlled from the driver's seat. If you wanted more heat you blocked airflow through the radiator.
Good luck. Being cold is no fun at all!
 

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Mercedes 300 TE 24v SportLine -91 W124
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Hehehe! Yes, the old cardboard sheet trick is well known here up north.;)

My 300 24v does also take longer to reach 80 degrees now when it's colder and the snow is falling.
I would guess about 1 metric mile before I get 80 degrees. But the engine gets warm anyway.

Check the next time You get to Your car that You can move the fanblades without any real resistance.

Kolla nästa gång du går ut till bilen och se om Du kan snurra din fläkt med händerna utan att det är något direkt motstånd.
 

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I'm unsure as to how the thermostat/cooling system on the 4-cyl engines is laid out/constructed, but they both should be pretty basic.

I found the thermostat on my W126's 4.2L engine broke in such a fashion it could not close. Naturally, I found this out on a winter road trip...at night, in BFE. Fortunately, I found a place with a slab of cardboard!

It's always better to have a thermostat break/stick open rather than shut. Just trust me on this....

Seeing you've already replaced the thermostat, twice, however, I'm baffled. Though, you did test one, even though it's new (hey, new stuff isn't always infallible), by putting it in a pot of water on a stove, then bringing said water to a boil relatively slowly, to make certain it doesn't open at 50C, correct?

Check the one you've already removed, and see how it behaves. If stays closed until the water is good and hot, then, well...we'll figure it out!

Sweden, eh? Maybe you have a W124 which was made for the desert market. ;-P
 

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My dad bought a new Saab 99? in 1964. 3 cylinder, 2-stroke, 4-speed trans on the column, cooling fan in a cage, and a manually-operated roller blind that you controlled from the driver's seat. If you wanted more heat you blocked airflow through the radiator.
That setup is so Jalop, I fully embrace it!

I'm sure the choke was also manual, so you had multiple manual controls due purely to cold.

Awesome... ...at least in concept. In practice? I'll take heated seats!

Oh, and a 4-on-the-tree. Yet more awesomeness!

-10C is 'only' 14F, so it's not totally horrible.

I will say, however, even with a perfectly-functioning cooling/heating system, -20F (-29C), receiving cabin heat is wishful thinking...especially at night.
 

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'92 300TE 4matic 280,000miles, '92 300TE 4Matic 'Ice Blue Metalic' 101,000miles
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One of the m103's strong suits IMO, is that you get heat really fast in the cabin. I've had my car to -10F and had more heat than I needed. Never had it at -20F though! The only winter I had any problems is when the blower motor went out and it became a nightmare for sure-only because it was the worst winter here that anybody remembered...of course.:rolleyes:

I think all the suggestions for his 4 cylinder are spot on....would be nice to hear some feedback on others who own one in very cold climates as well.:confused:

Kevin
 

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MB w123 250D om602 10v 1983
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Discussion Starter #12
The engine fan is indeed a visco one and it spins much slower then the engine "wheels" are turning, I can hold the fan in place with my hand and it's not connected, I've tried shortening the fan to see if the visco works and it sure does.

I guess the only thing I could really try and get somewhere with is to test the thermostat, I agree that new things don't always play along as they should, but hey, 3 thermostat's can't be bad? Oh well.. it's worth a shot, right?

It's not really enjoyable getting into a stone cold car even when you've had it running on idle for a decent amount of time..

I just took the car for a spin and when I was driving around town it got to almost ~80C operating temp but then I turned the fan on stage 2 and it dropped pretty fast to say about ~60C, so it takes a really long time to warm up the inside of the car too when it behaves like this.

The carboard thing is a good one but the problem would still be there unfixed and well, I like fixing things "the right way" :)
 

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MB w123 250D om602 10v 1983
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Discussion Starter #13 (Edited)
So I'm back with an unfixed problem, the heat issue still remains and I've tried boiling 2 thermostats and both show no activity until the water almost starts boiling so there's no problem with either of them, and I've tried using them both mounted in the thermostat house with same effect, the engine doesn't reach optimal temperature!

The thermostat is mounted correctly and the seal is there like it should and it's a brand new one too, I've switched the plastic housing to a aluminum one from an old 190e but I doubt that should change anything? The only way to reach 80C is to let the car idle with the coupe fan off, with the fan on and on idle it will never reach 80C.

I just don't know what else to do, is there something else that could cause the engine to not heat up? I'm all out of ideas, really.. only thing I noticed is that with the ignition on the second water pump thingy is running, but maybe that's normal? I mean the electrical one that's mounted on the left hand fender (facing the engine), I don't really know what function it has, only that it's connected to the cooling/heating system.
 

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About a dozen 1988, 1989, 1990, and 1991 sedans, wagons, 4Matics and 1 coupe
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That second pump is the auxiliary coolant pump and it is there exclusively to augment coolant flow through the cabin heater core during idle and low engine speeds. On a M103 car you'll *know* it if the pump quits. Heater output will be good while the car is moving but as soon as you coast to a stop and idle the discharge air cools off. Start moving again and heater output returns.

The problem your car has is quite interesting. At the most basic level there are two possibilites:

1) the engine does not produce enough heat. I think this can be dismissed as *every* otto cycle engine turns a lot more fuel into heat than it does into power.
2) coolant is circulating through the radiator or other device fast enough to carry away most of the heat. I think that this is where the problem lies. But where exactly?

Again I urge you to strike up a conversation with the owner of a similar car and ask him/her a few questions. At the very least it would be nice to know what their experience is.

After that I would look very carefully at the coolant pump. AFAIK they all have at least *some* internal bypass passage. You may have the wrong pump, a modifiied pump, or a defective pump with a too large passage which allows excessive coolant bypass flow.

Does teh M102 pump look like this:
 

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2000 SL500
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Replace the thermostat. This happened to me last winter. I asked and people said it's probably the thermostat but not to worry as long as it wasn't overheating. Well the car was running around 60C and the heater didn't work well at all. I dealt with it. Finally this past summer, the thermostat went to crap. It's a really easy thing to replace. I bought one from the dealer, as well as a radiator cap. Just get it done as soon as you can so you don't have to freeze your @ss off this winter and so the engine runs at proper temp for fuel economy and less wear on the parts. Also good to flush the cooling system completely while your at it.

Oh and forgot to mention. It's gotten in the 30's lately at night and the car runs at the proper temperature and my heater is working great. I kinda wish I would've just done the thermostat last winter!
 
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