103 Engine Fan not cooling properly - PeachParts Mercedes-Benz Forum

ps2cho · #1 05-08-2010, 01:32 PM

Got stuck on the I-10 outside Tempe (gun shooting!!) for over an hour yesterday in 105F heat (first time this has happened) and my M103 was touching the red bar the whole time so I was pretty concerned. I had the heater blasting to try and keep her cool.

I did not hear the main engine fan spin up at all. Also, while I was driving (75mph) the car was still over 80C and hitting 85/90C on steep hills. I don't think it should be running that hot while driving 75MPH even if it was 95F ambient outside.

What could be the issue?

babymog · #2 05-08-2010, 01:36 PM

Idling in traffic, try turning on the A/C. Your temps sound normal, and as odd as it sounds, the A/C will keep it a little cooler idling because the aux fan(s) will come on.

JohnM. · #3 05-08-2010, 01:37 PM

Fan clutch most likely. When you stop the engine, does the fan keep spinning or does it stop quickly? You should hear the roar of the fan when the clutch is locked. It will go away after 3,000 or so RPMs. When my engine gets to 90-95C my fan clutch locks and once the engine is back down to 80-82C it is freewheeling again.

EDIT: Oh, and your main auxiliary fan should kick on at ~105C. It's also really loud and noticeable. Between the aux and engine fans, your engine should be coooool.

Your car should not be getting anywhere close to the red range. That is danger-zone for M103!

ps2cho · #4 05-08-2010, 01:41 PM

This is for my 260E...Fan clutch does not lock. No roaring at all, that is how I know it is not turning on. I am familiar with the roaring noise because my wagon does it all the time on hot days -- This car is dead quiet.

Is that just the fan clutch (viscous fan coupling -- same thing?) or could it be anything else?

I replaced my engine temp sensor at the back of the head, so its not that.

Yep it is danger zone which is why was I was very concerned and tried to get off the freeway ASAP and had the heater blasting (No A/C for me yet...as evap is leaking so I couldn't turn on Aux fan). Once I got off the car was sooo...slowww to accelerate. I got her back down into the 85C range quite quickly though where she stayed.

JohnM. · #5 05-08-2010, 01:52 PM

Yes. Absence of the roaring noise can only be the fan clutch. When my last fan clutch failed, it didn't unlock! Therefore when the engine was hot, it would spin the fan up to redline. Fan clutch is supposed to release at certain RPM. It actually overcooled the engine. There were also a few different part numbers which locked at different temperatures. I wish mine would lock at a higher temperature. That roaring noise is really ridiculously loud when you are flooring it after sitting in traffic for a bit.

I would also look into your front aux fan. not working? Even without A/C it still should kick on at 105/110. You can jumper it directly to see if it still works. Then look into why it's not switching on (fuse?). I'm not very keen on how to troubleshoot the AUX fan.

ps2cho · #6 05-08-2010, 01:56 PM

All I know is, it seems it has had some wiring done by the dealership. When I was running the A/C before it leaks out, the Aux fan kicks on as soon as the A/C is turned on. I don't know if that is at the cost of it not working with engine temp?

I am going to make this my priority to get it replaced. Might be a junkyard run for me as $120 + new 9 blade fan is pretty steep.

I'll check later today if the fan stops spinning when the engine is turned off.

I do remember when I took it out a few months back, there was a "little" slack. I believe I posted a thread, but didn't get any responses. Maybe that is why? The slack was inside the engine, not on the clutch though. How much slack should there be?

Do you know where it is to jumper the aux fan? (might be good to know in case this happens again until I can get a new clutch)

JohnM. · #7 05-08-2010, 02:13 PM

You are looking for the fan to continue spinning for more than 5 seconds after engine shutdown. If it does, your fan clutch needs to be replaced. But if it's not roaring, its more than likely worn-out.

One of the two coolant temp sensors on the head (blue) is also called the 105/115 switch. At 105 its supposed to trigger the aux fans,and at 115 it is supposed to shut-off the AC. With KEY ON, unplug the blue temp sensor. It should kick the aux fan on high.

If not, it could be the aux fan resistor (lego sized box on the drivers side engine bay), or it could be the aux fan itself (try applying direct power to fan). There is also a cube relay in the fusebox that is a part of the aux fan system.

babymog · #8 05-08-2010, 02:25 PM

The test in the FSM for the fan clutch, is to idle the car until it reaches the clutch turn-on temp, which IIRC is 105C, then rev to hear the fan.

cliffmac · #9 05-08-2010, 08:35 PM

a fan clutch is to spin the blade by hand with the engine stone cold and not running (of course), the fan blade should spin freely. If it doesn't then the clutch is bad...to be sure run the car around until the motor is completely warmed up and then turn the car off and try to spin the fan again, there should be considerable resistance compared to the cold start test...if seems the same then it's same problem...clutch is bad..I gotta tell you though, I have never ever seen a fan clutch go bad to the point of causing cooling issues.....

babymog · #10 05-08-2010, 08:51 PM

When the car is started cold, the fan is engaged and will run and you should hear it, drops out in a few seconds. If it spins freely with the engine off, the clutch is bad. It should have some resistance to spinning.

There are threads on the diesel forum about how to repair it with new fluid, easier to replace but $$.

Ivanerrol · #11 05-08-2010, 10:04 PM

The fans should have no effect at highway speeds.
Your symptoms are an indication that something is wrong with the coolant circulation.
Are you losing coolant?
Is your serpentine belt at the right tension so as to make sure the water pump operates efficiently and the engine fan operates efficiently when the clutch locks up?
Is your thermostatic alright and working properly?

You should get your coolant circulation system pressure tested.

ps2cho · #12 05-08-2010, 10:34 PM

My coolant levels were fine...
I popped off the coolant cap and it boiled and shot out everywhere (not sure if that was normal because it was so hot?)

I have a brand new thermostat in there and flushed the coolant with new Zerex G-05 (twice) in the last 4 months. No coolant loss.

I have not touched the belt yet, so I'll check tension.

Ivanerrol · #13 05-08-2010, 11:00 PM

How is your radiator? No blockages? You reversed flush this - I assume - when you flushed your coolant out?

Why I mention getting your system pressure tested is that the water pump may be not working properly and circulating water around the system efficiently enough.

The temperature in my city reached 115 degrees last summer. The temp on my 103 reached around 110 degrees - at highway speeds. This was with a leak at the water pump (since repaired).

anthonyb · #14 05-09-2010, 01:24 AM

87-90*C while on the freeway is normal - the thermostat should be an 87*C unit for your car.

The fan clutch is engaged when cold-started first thing in the morning, it should resist freewheeling and give you a nice roar for 20 sec or so when you first get going.

You don't need a new fan - the clutch unbolts from the fan once it's out of the car.

The aux fans have two speed settings, one for the low temp/AC and one for the high temp. My old 300E had been rejiggered by the dealer to run at the high temp speed whenever it was engaged, probably because it tended to run hot in the summer.

pawoSD · #15 05-09-2010, 10:11 AM

My 300E fully engages the clutch around 90C...and turns on the electric fans on high (regardless of the A/C being on) around 105C......