As far as I can tell, both of my aux fans on the 95 E300D are bad. They look like they're a PITA to replace. My inclination is just to forget about them. Any compelling reason why I shouldn't?

I live in New England, not Phoenix. The AC doesn't work. In driving the car for the last several months I've seen the temp go to 95, maybe 100 on rare occasions, but most of the time it's right in the 83-90 range.

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14 E250 Bluetec 4Matic "Sinclair", Palladium Silver on Black, 159k miles
06 E320 CDI "Rutherford", Black on Tan, 179k mi, Stage 1 tune, tuned TCU
91 300D "Otis", Smoke Silver on Tan, 145k mi, wastegate conversion, ALDA delete

19 Honda CR-V EX 77k mi
Fourteen other MB's owned and sold
1961 Very Tolerant Wife

If your fan clutch is OK and you don't run the AC you shouldn't need them.


Sent from my iPhone using Tapatalk

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1991 350SDL. 230,000 miles (new motor @ 150,000). Blown head gasket

Tesla Model 3. 205,000 miles. Been to 48 states!
Past: A fleet of VW TDIs.... including a V10,a Dieselgate Passat, and 2 ECOdiesels.
2014 Cadillac ELR
2013 Fiat 500E.

If you don't mind the damage resulting by your MB's engine overheating, then no reason to replace them.

I keep ALL my vehicles in nearly perfect condition/repair, so don't go by me.

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'06 E320 CDI
'17 Corvette Stingray Vert

Well, Joe, we're not all blessed with your finances or your quantities of spare time.

On my 87 my aux fan went out the other day and I haven't had the opportunity to replace it yet, been busy getting ready for car shows this weekend.

Even running the AC on a hot day my temperature will stay around 100*C in traffic. On the highway its down around 80*.

I intend to fix it, and I'd advise you to ultimately repair them on your car as well, however its by no stretch of the imagination grounds to park your car.

Use your best judgement and keep an eye on the temp gauge.

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68 280SL - 70 280SL - 70 300SEL 3.5 - 72 350SL - 72 280SEL 4.5 - 72 220 - 72 220D - 73 450SL - 84 230GE - 87 200TD - 90 190E 2.0 - 03 G500

Nissan GTR - Nissan Skyline GTS25T - Toyota GTFour - Rover Mini - Toyota Land Cruiser HJ60 - Cadillac Eldorado - BMW E30 - BMW 135i

when during dire straits turn on the heater and crank the temp to red, it should click as it opens the monojet valve or else only intermittently.
We can get bake for a while, these alloy component heads , blocks can bend!

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Well, DieselPaul, I believe most all of us on an automotive engine DIY fixit forum are blessed with the sense to not drive a car in disrepair. Especially one without a complete cooling system in operation as designed by it's manufacturer. I don't neglect what needs repair, as some do.

I changed out my aux fan in a heartbeat. I'm not one to limp around in my vehicles, nor neglecting them when they need urgent servicing.

Whether we're all blessed with the time OR finances to fix our cars in a timely manner, is not the issue. Nor is it isn't anyone else's concern or fault if/when another doesn't have either the time or finances.

You want to postpone your aux fan(s)? Be my guest. It'll be your blown engine because of overheating not mine. To me, it's not too bright to not have all systems go in especially brutal heat. Heat which can run 100*+ weeks of the year in Texas. Just the way I was brought up, to pay attention to ALL my equipment.

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'06 E320 CDI
'17 Corvette Stingray Vert

Thanks all. Like I say, the car never comes close to overheating.

My other two cars I keep close to perfect....but not this one.

If I'm always watching the gauge, I hardly see how there's any risk to the engine.

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14 E250 Bluetec 4Matic "Sinclair", Palladium Silver on Black, 159k miles
06 E320 CDI "Rutherford", Black on Tan, 179k mi, Stage 1 tune, tuned TCU
91 300D "Otis", Smoke Silver on Tan, 145k mi, wastegate conversion, ALDA delete

19 Honda CR-V EX 77k mi
Fourteen other MB's owned and sold
1961 Very Tolerant Wife

Shertex: Our NE climate is a big help. I live in a rural area, and never (like never) have to line up in traffic on a hot day; that would be my biggest concern. I have working A/C, and could get above 100d if I were trapped in a traffic tieup; my aux fan kicks in at 110d, and I test it every spring when I bring the car out for the summer. In hot RI I would be very wary; I once overheated to 120d (not a fatal overheat) and lost a lot of rubber seals in the process.

So, lets treat this like an engineering problem. Under what circumstances do the fans turn on? Are they triggered by coolant temp or AC high side pressure / compressor trigger? Both? We need a wiring diagram / diagnostic chart to be sure.

Given the AC isn't working, high side pressure won't trigger it so that leaves coolant temp.

Per the OP
" . . .95, maybe 100 on rare occasions, but most of the time it's right in the 83-90. . . "

100C is hardly overheated for a good system and I suspect it occurs only in sub 30 MPH traffic on a hot day. In such a situation, placing the trans in neutral then raising the idle speed to 1,500 RPM would increase air flow and coolant flow.

Given the OPs cool climate location, running without a aux fan does not seem to be an issue.

Mine didnt work when i got my car, well one didnt. First I'd jump power to the fans themselves it might be something simple like a burnt resistor. Barring that the brushes and commuter coil in the fan motors gets dusty corroded and nasty I sprayed mine with contact cleaner and blew them out with compressed air and brought it back to life.

Replace both the aux fans and clutch fan with a pair of puller fans. They're cheaper, quieter and far more effective than the stock fans.

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CENSORED due to not family friendly words

Removing them to replace them is a one afternoon deal, not that bad. Here is a thread on how to remove them. Radiator does not have to be removed, or mechanical fan either. I bought a set of used ones for about $100.

Let's change the Aux Fans on a W124!

I think you will be OK to drive as-is, without AC.

Rgds,
Chris W.
'95 E300D, 398K

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Objects in closer are mirror than they appear.

Thanks, Chris. BTW you're my hero....the further you push up your mileage (now 398k), the more hope I have for mine with 305k!

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14 E250 Bluetec 4Matic "Sinclair", Palladium Silver on Black, 159k miles
06 E320 CDI "Rutherford", Black on Tan, 179k mi, Stage 1 tune, tuned TCU
91 300D "Otis", Smoke Silver on Tan, 145k mi, wastegate conversion, ALDA delete

19 Honda CR-V EX 77k mi
Fourteen other MB's owned and sold
1961 Very Tolerant Wife

when mine seized in Las Vegas I had to use the cabin temperature to regulate around the city. Was able to maintain 80 at highway speeds with air on. In my opinion the aux fans when seized block a lot of air from entering the rad. If you are not going to repair then I would remove them to increase air flow to the cooling system. Just my opinion.

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1999 Mercedes E300TD daily driver sold at 238K miles 106K miles were mine, rust worm got it :-(
2006 Mercedes CDI new daily driver! 56,000 miles May 2016 now 85,625 Apr 2018 and Apr 2019 101,000 miles Apr 2020 109,875. March 2024 135,250, Dec 2024 145,000 miles

Oh word of caution, my friend. I love my diesels, but I also own a 95 e320...same fan system, same gauge system and I can tell you for a fact that those gauges are merely feel goods. My engine was overheating like you wouldn't believe and the gauge didn't move over 100. Don't trust the gauge. NEVER trust just the gauge! However, if you know the other signs of an overheating engine, I'm with ya on simply being careful. Use common sense and you should be just fine.