Thought I might get some interest with this subject....

I am trying to find out why my car, 92 300D, is running 90-100C. So far I have drained and flushed the radiator-clean fluid, no rust, and replaced the thermastat. I noticed that when I ran the defrost that only one aux. fan came on. Is this right or is one not working? If both should be working, what is most likely the problem? Fusses are good. Thanks for any help.

What's your weather like? During hot weather and AC operation, 95-100C is normal.

One fan is engaged by AC pressure, the other by temp. If memory serves, the second fan comes on at something like 107C.

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John Shellenberg
1998 C230 "Black Betty" 240K

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Blackmercedes,

Thanks for the promt reply. I have heard/read different reports regarding this matter. The dealer said both should engage simultaneously. Although, I have found far greater wisdom on this boad.

PS... weather is in the mid to high 90's with AC on when temp climbs

On my 126 car, they both come on. I have a low and a high speed. The later engages when temps exceed 102C. If your fans sit side by side, it wouldn't make much sense for just one to run. Both side-by-side fans would cover the spans of the radiator.

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

Both fans should run, but 90-100C is normal.

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Ali Al-Chalabi

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

Mike and Ali,

Thanks for the information. I am confident now in thinking that both fans ought to be running at the same time. Any advice on what components to check for potential problem?

It's funny how this temperature thing comes up from time to time.

90 - 100 degrees celsius is not considered hot for these cars.

The stock thermostat on my 93 300E opens up at 92 degrees.

I wonder why everyone freaks out when the gauge hits 100 degrees.....

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Paul S.

2001 E430, Bourdeaux Red, Oyster interior.
79,200 miles.

1973 280SE 4.5, 170,000 miles. 568 Signal Red, Black MB Tex. "The Red Baron".

A previous poster mentioned that pressure and temp. activate one or the other. I do not know where these would be on a 300D. I would follow the wiring from the aux. fans in front of the condensor. I suspect you'll end up in the vicinity of the receiver-dryer if R-12 equipped. Hopefully someone versed in the 300D will offer more exact advise.

I agree about the 100C issue. I recently had a large amt. of work done on a 126 to include new radiator, fan clutch, t-stat, expansion tank, cap, hoses; coolant. My temp. gauge still goes to 100C in stop-and-go traffic, but quickly drops back to about 87C once underway again. This occurs with or without A/C and irregardless of the season. Cold weather is non-existent where I live.

The 126 owners manual says this is normal. I gave up worrying about something for which there is nothing to worry about.

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

On all models I am aware of, both fans should come on at the same time. If one runs and the other doesn't, it almost certainly means either a bad fan or break in the wiring.

I think the reason we (myself included) obsess about coolant temps is we are used to the gauges on other cars, which are not truly accurate and tend to stay at a steady indication despite changes in ambient temp and whether AC is on, etc. MB, on the other hand, wants us to have accurate info, and thus we get freaked out when we see a needle climbing to the 100 mark.

I agree, temps up to 100 or even a bit higher are normal in hot weather with AC on, and mine does this despite having a new water pump and radiator, but reminding myself that this is OK is a daily struggle for me.

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Steve
'93 400E

Suginami,

I am sure you are aware that the variety of metals involved in an engine expand and contract, although minutely, through different temperature ranges. There exists an "optimal temperature" at which these metal surfaces are of a specific size to operate within the tolerances for which they were designed. A swing of a few degrees is negligable. However, a change of 20C, 25% more the "normal" for my car, makes me pensive. Is there something I do not understand? I am by no means an expert and am on this board to learn...

According to my W124 ETM both fans should always operate at the same time. The system does have two speeds, low speed activated by AC condensor pressure and a high speed activated by engine coolant temp. If only one fan responds its a fan or wiring problem with power to the fan. All control components are common to both fans.

I'm also puzzled by people worrying about engine temps - the owners manual is quite clear on the subject. Its OK for the engine to see 100C or even 110 to 120C in really adverse conditions.

I have a 91 300D is operates at 85-95C depending on traffic situations and ambient temps. It rarely gets over 100F here in the mid atlantic region. I also have a 400E that operates at approx 110C in stop and go traffic with the A/C on. The car has NEVER overheated and according to MB this is normal.

If its OK with the factory its OK with me.

Tim

Keep in mind that MB put insulated encapsulation panels under the 300D to help with noise. This in turn does slow the way heat is expelled from the engine compartment.
Your engine temp is considered normal.

I too get puzzled by all the MB owners who are obsessed with having their engines run cold (<80C).

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Scott Diener
89 300E
93 300E
92 Volvo 740 Wagon aka "Mutt mover"

sorry for the contradiction but , for the most part, mine never goes above 84c under any conditions. i would freak if it went to 100! I did notice it was going up one time after changing over to th red antifreeze and it will if the overflow tank is not filled to the proper level..you floks with the needle heading north to 100 check your levels for humor sake, i wonder if your overflow has fluid in it?

My 91 300D's temp was like that too! both fans should work together at low/high speed. 2 weeks ago, I removed the engine/tranny insulation panels. I also took the fan/condenser protection cover off. You can't believe how much junks were collected in that area over 11 years. It's snapped on and completely sealed around the condenser. I end up cutting the bottom half of it and installed it back so that nothing can collect in there. Now, It runs a lot cooler then before. Sometime it will get up to 102°C but it doestn't stay there for long. I would advice you guys remove that panel and clean that area up.
I would think that temp range is normal. If it stays high above 102°C for too long....abnormal!?.

BTW, Both 126s never get over 92°C.(Here in Houston, TX we are at 90's daily). They have bigger fans and no cover in front or below.

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BJ

09 GL320 Bluetec 65K+
07 E320 Bluetec 43k+
05 Nissan Frontier NISMO 4X4 72K+


07 Kawasaki Vulcan 900 5k+ gone
87 300SDL 158k+ gone
91 300D 113k+ gone
83 300SD 220K+ gone
89 300E sold
87 190E sold
83 380SEL sold
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