E-Class (W124) 1984-1995: E 260, E 300, E 320, E 420, E 500 (Includes CE, T, TD models)

ANOTHER cooling problem, but this is different...

Old Aug 20, 2004 | 04:42 AM
  #1  
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ANOTHER cooling problem, but this is different...

My '87 300E just get's to 120 degrees C when it's 85 F degrees outside temp while in stop and go traffic. I've had to stop or turn on the heater to prevent it from rising. The single front fan is operational so the thermostat appears to work. The car immediately cools to normal temp when I get up to 30 MPH. Other than hot weather and stop and go traffic, the cooling is a normal <100 C. Anyone have good troubleshooting ideas before I start replacing the w/p thermostat, fan fluid dampener, water pump, or radiator? Which way should the electric fan turn? I can feel air flow toward the front but I thought the engine fan pulls air toward the engine. The "red" mark on the gauge is just north of 120 C. How long of running at 120 C before the engine is damaged?

Last edited by pifcat2; Aug 20, 2004 at 04:46 AM.
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Old Aug 23, 2004 | 05:43 AM
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'00 S320 W220, '98 A160 W168/ sold in 2005 '86 260 E W124 '90 260E W124
Most probably the fluid coupling of the main fan is shot. It is a silicon oil filled element which engages the fan depending on the demand of colling air required. It is hard to tell by looking at the fan. One not very objective test is to try to turn the fan by hand when the engine is cold. When you push the fan (engine cold and OFF) it shall not túrn anywhere close to 90 degree on its own. To replace the fluid coupling is not very complicated. You just need a metric Allen wrench 6 or 8 mm (forgot) and a steel rod 7-8 mm diameter with a 90 degree bending of about 1/2 Inch to hold the coupling when loosening the centre screw.
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Old Aug 23, 2004 | 07:02 AM
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Maybe

My friend had a similar problem on his 190E. For him, it was the small accessory water pump. His was frozen and a new little pump solved the problem. You can disconnect the little pump and connect it to a battery to see if it turns. I would ask for tech help at MercedesShop.com
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Old Aug 23, 2004 | 09:58 AM
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I am having a similar problem. The car gets hot in stop and go traffic too but is fine on the highway. I also notice that there is a hose that goes from the coolant reservoir back toward the passenger side fender and down into a container. This container overflows when car gets hot. Does this mean I need a new cap or what?
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Old Aug 23, 2004 | 10:23 AM
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Thank you 190Eboy

My friend, 190Eboy, confirmed that the symptoms you described are the same as he experienced until he replaced his auxiliary water pump.

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Old Aug 23, 2004 | 11:18 AM
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Aux pump

Ksing44,
Are you sure 300E's have this pump? Where is it mounted?

Bamberger_1,
I will plan to replace it and the thermostat before dealing with the water pump or radiator.

Thanks all,
Felix
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Old Aug 23, 2004 | 04:18 PM
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Originally Posted by bamberger_1
Most probably the fluid coupling of the main fan is shot. It is a silicon oil filled element which engages the fan depending on the demand of colling air required. It is hard to tell by looking at the fan. One not very objective test is to try to turn the fan by hand when the engine is cold. When you push the fan (engine cold and OFF) it shall not túrn anywhere close to 90 degree on its own. To replace the fluid coupling is not very complicated. You just need a metric Allen wrench 6 or 8 mm (forgot) and a steel rod 7-8 mm diameter with a 90 degree bending of about 1/2 Inch to hold the coupling when loosening the centre screw.

Well regarding this main fan which is called the viscous fan clutch:
I have one taken from a 1988 300E. The car was rear ended and had 89k on the odometer. The fan clutch is here at my house serving no purpose. I sold my 300E before I installed it. If anyone is interested in it, PM me or email me at: lmorr004@fiu.edu
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Old Aug 23, 2004 | 04:49 PM
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I'm a BOZO

I am not an expert or even an amateur DIY. I am a BOZO with not experience under my hood, but I think mine is near the battery on my 1995 E320. All I know about my motor is that it is very clean considering it is 10 years old and has 80,000 miles. I think it must stay very clean because of that plastic cover under the car. I never detail the motor or anything. It just stays very clean in there.

Your description of the problem just sounded exactly like 190Eboy's, so I chimed in. I would ask the Tech guys at mercedesshop.com


Last edited by ksing44; Aug 23, 2004 at 04:52 PM.
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Old Aug 24, 2004 | 05:41 AM
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Originally Posted by pifcat2
Ksing44,
Are you sure 300E's have this pump? Where is it mounted?

Bamberger_1,
I will plan to replace it and the thermostat before dealing with the water pump or radiator.

Thanks all,
Felix
Thermostat is worth a try, beause its cheap, but I doubt it is the culprit in your case. The little pump the guys talking about is the water pump to feed the heater radiator. You'll find it below the shock dome on the passenger side. But as you described, you can turn on the heater to prevent the temp. to rise fruther, tells you that the heater pump is working well. In general the heater pump does not have anything to do with the temperature rising beyond limits, since during summer this pump is not supposed to be engaged and the coolant temperature still shall stay inside the design limits.
Bamberger_1
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Old Aug 24, 2004 | 11:46 AM
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Bamberger_01,
Thank you, that makes alot of sense.

I would consider Mike's offer on the used part but I read these fan couplers go bad even new. How do you check these?

Kings44,
I appreciate the chime in and helping me be aware of this part. Someone mentioned 300E's use an electric water pump in another forum and I only knew of the belt driven pump.

Felix
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Old Aug 24, 2004 | 12:53 PM
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The reason these fans go bad sometimes when new is because some of the shops make a mistake and store the clutches horizontally. Than leads to the fluid somehow leaking out, and the fan is rendered useless. It looks new, but because of the way they store them, they are already broken. I have mine in my house stored vertically, the proper way.

still interested in it?
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Old Aug 24, 2004 | 04:10 PM
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You go 190Eboy

Just so you know, the picture I posted of the auxiliary water pump was taken from the 300E section of buymbparts.com. You must have one. 190Eboy also told me that he was able to reduce the engine operating temperature, by running the heater, even though his auxiliary water pump was frozen. I am not saying that you definitely have the same problem. It just sounds like you are experiencing the same symptoms.

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Old Aug 26, 2004 | 04:08 AM
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Originally Posted by pifcat2
Bamberger_01,
Thank you, that makes alot of sense.

I would consider Mike's offer on the used part but I read these fan couplers go bad even new. How do you check these?

Kings44,
I appreciate the chime in and helping me be aware of this part. Someone mentioned 300E's use an electric water pump in another forum and I only knew of the belt driven pump.

Felix
Testing the fluid coupling for a DIY is kind of impossible. The only "test" is what I described in my first post. Just push it (when it is installed) and see how far it moves on its own. Best is to have a new one and the old one to see the differnece. I had mine exchanged after 15 years in my 86 W124 260E. My other W124 260E is going to be 15 next year----see what happens so far the coupling seems to be ok.
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Old Aug 26, 2004 | 03:03 PM
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Bamberger_01,
I tried your test but am unsure of the results. I can push the fan and it has resistance <90 degrees. I can push it harder to make it rotate more. I guess my hand needs calibration!
Felix
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Old Aug 26, 2004 | 08:01 PM
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Originally Posted by pifcat2
My '87 300E just get's to 120 degrees C when it's 85 F degrees outside temp while in stop and go traffic. I've had to stop or turn on the heater to prevent it from rising. The single front fan is operational so the thermostat appears to work. The car immediately cools to normal temp when I get up to 30 MPH. Other than hot weather and stop and go traffic, the cooling is a normal <100 C. Anyone have good troubleshooting ideas before I start replacing the w/p thermostat, fan fluid dampener, water pump, or radiator? Which way should the electric fan turn? I can feel air flow toward the front but I thought the engine fan pulls air toward the engine. The "red" mark on the gauge is just north of 120 C. How long of running at 120 C before the engine is damaged?
I had a very similar problem on my '87 300TD. Replaced thermostat, coolant, water pump, etc. In stop/go traffic, temp would touch 120C; once traveling again, temp dropped back to normal.

Finally, when I had to replace the A/C condensor I found the problem: lodged between the condensor and the radiator was a ton of trash (leaves, pine needles, straw, etc.). I don't know how it got there, but it was preventing airflow through 1/2 of the radiator. Once that got cleaned out, the car rarely exceeded 100C again.

If you can find a way, check between the condensor and the radiator, to see if you have airflow through this area.

Good luck.
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Old Aug 27, 2004 | 06:02 AM
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Originally Posted by pifcat2
Bamberger_01,
I tried your test but am unsure of the results. I can push the fan and it has resistance <90 degrees. I can push it harder to make it rotate more. I guess my hand needs calibration!
Felix
If you can push harder (hot engine) and make it rotate over 90 degrees I consider the thing shot. Remember when the engine is hot the fan shall engange more (make more speed). If I'm not mistaken the fan shall go up to 3000rpm max. speed when the engine is really hot. If you would have strobe on had to measure the speed, this would be the right test to find out.
The other posters comment about a clogged radiator on the air side, between A/C condensor and radiator is a pretty good idea to be checked. But I also have the question how the hell the dirt got there???
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Old Aug 31, 2004 | 01:21 PM
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Originally Posted by bamberger_1
The other posters comment about a clogged radiator on the air side, between A/C condensor and radiator is a pretty good idea to be checked. But I also have the question how the hell the dirt got there???
The debris seemed to be some type of bird/rodent nest. Must've been while the car was sitting prior to my purchase (didn't sit much afterward).
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Old Aug 31, 2004 | 04:56 PM
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My fan and condenser were broken from an earlier accident and the car would over heat in stop and go traffic. So this weekend I took out the condenser and the fan and it doesnt overheat anymore. It looks really nice too (looks like it's turbocharged cuz the radiator looks like an intercooler .)
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Old Sep 10, 2004 | 10:16 PM
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Guys,

What is it with the 300's and this problem. I have the EXACT same problem as described in the original post. Mine came about after replacing one of the aux fans up front (and the sub harness) since the fan froze up melted and took part of the wiring harness with it. Since getting the car back I have had the problem described with no resolution yet.

Has anyone else found a definitive root cause?

Thanks,
bear

Last edited by McBear300E; Sep 10, 2004 at 10:17 PM. Reason: typo
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