103 Engine Fan not cooling properly
 

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?

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.

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!

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.

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.

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)

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.

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.

the way to test
 

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.....

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 $$.

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.

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.

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).

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.

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......

Bingo! that's the correct operation.

Also at higher revs the fan clutch disengages.

At over 30kms per hour the air movement through the radiator renders the fans redundant. Even at extreme ambient air temperatures the system should keep the engine temperature at or less than 110 degrees - not up in the red. This is why I suggest a coolant circulation problem.

It is my H.O. that the M103 engines should have idiot lights rather than a temp gauge - which seem to worry many people by the temp oscillations.

His car was only barely touching the red after sitting, idling in traffic for a long time. No mention of overheating while driving. The aux fan also did not kick on at 105 as it should have. A very worn fan clutch will definitely affect the small amount of air the engine fan is able to produce at idle.

I know that just sitting in the drive through food lane, my car will shoot up to 100C within 5 minutes of idling. If it's anywhere above 80F ambient, it will hit 105C. Then the aux fans will kick in full force. But if I had a weak fan clutch, and no aux fans, I could see it hitting 115 easily.

Anybody have a pic of the blue sensor on the head? I don't see one on my 87. Maybe different color?

Test the fan clutch by simply turning the fan with the engine off and see if it coasts. If it does, replace the fan clutch.

The electric fan is actuated by high side a/c pressure and will not come on unless the a/c is on and the high side pressure is dangerously high. It's only purpose is to bring down that dangerous high side pressure.

The main fan can be adjusted to come on earlier at around 95 'C.
as can the aux fans.

True, but not the complete answer. It is also activated by the blue base temp sensor on the head, back about cyl 4 (farthest right in the photo). That's what activates the high fan at about 105C, while the pressure switch on the drier responds to condenser pressure (somewhere between 16 and 20 bar, depending on red or green switch).

On my 87 it is not blue....It is a big green sensor with two 'plugs' that go into it...
Anybody done it with this model?

Cal Learners image might be from the later model M103's.

Here's an image from the earlier M103. The ECU temp sensor is a two pole green sensor in this variation. Your aux fan arrangement maybe a single fan and not the dual as per later update W124's.

http://farm3.static.flickr.com/2162/...413ca8f5_o.jpg

So it is the water temp sensor on that image?

If so, that is the one I "attempted" to do. I unplugged with Key ON. Then started the car and the aux fan did not turn on...I thought maybe it was the wrong sensor, but maybe not? I checked the fuse and it looks fine.

Like I said though, when the A/C was functional, the aux fan was working fine.

That sensor is the water temp gauge sensor for the gauge in the instrument cluster.

http://www.ps2cho.net/downloads/phot.../Headimage.jpg

Is it the green one then? If so, which plug do I remove? Is it the same process so I can just do a trial-error to figure it out?

How many sensors do you have there? Three or four?

The green sensor is normally in the very rear of the head. That "should" be the sensor for engine control.

I don't want to second guess here - U.S. Specced cars are different from Euro's and cars specced for the R.O.W.

In the later models with dual fans there are two relays
one actuates the fans at low speed - AC derived operation
one actuates the fans to high speed - sensor derived operation.

I'm not sure it's the same as the diesel, I only have diesel and M104 powered 124s right now.

If it is the same, the green sensor has a single-pin connector, which is for the temp gauge, and a 2-pin connector, which turns on the fans, high-speed, direct / no relay. Low speed goes through a ceramic resistor behind the left headlamp and the high-pressure switch on the receiver/dryer next to it.

Babymog is wright.Two pole sensor is the one you looking for. With unpluged sensor,ignition on engine not runing, connect those two wires and your fan should run if wiring is ok.Wiring goes over resistor (lego look) at driver side near by head light. Position of the sensor is different with year and market.

Gotcha. Then yes my very rear one is for the KE-Jet coolant temp sensor. Do I need to bridge them or just unplug? Should the fans kick in right away or when the car is started if it is functioning correctly?

once unplugged, fans should ideally come-on at full speed..if not, something is not right (resistor or relay)

Check your fan resistor. The connectors often get corroded - break off or wont condcut the fan current through the corrosion.

Fan resistor is underneath the ABS module. Caveat this is for the later M103 update version.

http://farm3.static.flickr.com/2703/...506723a4_o.jpg

Pulled the two connectors with Key ON to ignition and fuel pumps energized....Nothing happened. I checked that resistor and I don't see any corrosion on the leads.

Is the relay one of the metal square boxes under the fuse box? I wonder if I can switch the one from my 88 300TE as I know that functions right as a test?

Slightly off-topic, but does anyone else feel that 105 is a bit too high for the aux fans to come on? My 300SD plants itself at 80 degrees and does not move a millimeter when in traffic, hot, cold, etc. When I got my 300E I was extremely concerned when it hit 100* in traffic and then went down to 60* on the highway. I have never seen a cars temp fluctuate so wildly. I take it 105* is "fine" then and will not hurt the engine? I get nervous when it hits the 100 mark.

Edit: yes, I do realize that diesels create less heat than gas engines, but in comparison to other gas cars, the temp gauge is wild.

The relays should be interchangeable. If you pulled the 2-pole connector off the temp sensor (the farthest right one in the earlier photo) with key all the way on, engine off and the fan did not spin, there is a problem in the circuit somewhere. Have you tried bridging the pigtails coming off the drier pressure switch? That gives you low fan (KOEO), and would be a test of fan function. Other components to test: 2 fuses. I think they are 7 and D, one is for the coil side of the relay (labeled C in the attached photo) and one is for the load side. Then there's the relay itself, the ceramic step resistor in Ivanerrol's photo, and the wiring from there to the fan motor.

http://www.peachparts.com/shopforum/...1&d=1243511924

You can just bypass the resistor.
Yes I agree. 105c is too hot. I'm eliminating the clutch fan on my 2.6 and triggering the aux fans at 90c with a 700 ohm parallel resistor in the coolant sensor plug. But it sounds like your thermostat has failed because the temperature shouldn't drop to 60c. I would replace it with a 79c thermostat.

I have the reverse problem
 

My 300E engine can never reach 80*C on the highway. It can in the city. With the engine not running the fan can still move. But when the engine is running it seems to run at the same speed. I notice that there is no electrical connection to the fan.

Is my engine running too cold? Is the fan clutch activated by electricity? If so then how can I test whether the clutch is still working and how to get its correct connection wire?

Not if he wants low fan speed.

If the temp gauge sits just a hair below 80c on the highway, you probably have a 79c thermostat. I wouldn't worry about it. If its much lower than that, your thermostat probably failed.
I don't see the benefit to having a low fan speed. On my car low speed is only used by the AC pressure trigger and the resistor is another potential failure point. After 100k+ miles all our radiators are stuffed full of dirt, rocks, debris etc. Run a high pressure water jet through the back of the back of the radiator fins and you'll be amazed at the crap that comes out. The more air you can flow through the radiator at lower temp, the better.

[QUOTE=tjts1;2465815]If the temp gauge sits just a hair below 80c on the highway, you probably have a 79c thermostat. I wouldn't worry about it. If its much lower than that, your thermostat probably failed.

Thanks, tjts1. To be exact the needle is roughly 2mm below 80C on the gauge on the highway. Another question: is there any control wire to the fan clutch? I don't see my fan have it.

The 300e should have a regular viscous clutch fan so no wire. When they fail, the clutch doesn't engage as the engine warms up. An easy test is to allow the engine to warm up (~90c on the gauge), pop the hood and try to stop the fan with a rolled up news paper. Be VERY careful with your fingers. If you can stop it or slow it down substantially with the newspaper, the clutch is probably toast. If you're temperature gauge never goes above 100c, the clutch fan is probably fine.

When the engine doesn't run the fan is movable. When the engine does I can still keep the fan from moving by holding it but when I release it it seems to run with the same speed with the crankshaft meaning it always runs as if it is always engaged with the pulley of the crankshaft.

My car occasionally reaches 90C when running under the sun with the A/C on. Most of the time it is around 80C in the city and less on the highway. And the funny thing is my aux. fan starts when the temperature gauge reads slightly above 80C. Is there anything wrong here?

Running a too hot engine is definitely not good but what is the down side of a cold engine? I heard someone say normal operating temperature of Merc engine is 90C.

Which one is it?

When spinning it dead cold, it only spins about 1/4 of a turn. It definitely is not free spinning. Quite some resistance.

I bought a used working fan coupling either way(Seller showed video of it working and it is only 2 years old), but just curious as to the correct test procedure.

Standard is an 87C thermostat. You should be running around 90C or so most of the time. Is your gas mileage poor? If so, then you may be running with the cold start injector going all of the time.

That doesn't sound right. Maybe the temp sender or the temp gauge on your dash is bad.

Sounds like it is probably still good. Does the fan clutch engage with a roar when you first start the engine (and for the next 20 sec or so)? Does the car temp stay relatively stable when idling? If all of the above are true then your clutch is probably in good shape.

I spun it again with a lot more force this time and I got it 5/6 of a turn...Not quite one full rotation, but close.

Temperature stays OK when idling, but it does not roar at all -- ever not even first start. I thought it was strange when I first got the car because of it, but I thought it was because the cooling system was OK...but now ever since the scary stuck in traffic red line event, I need it to be functional.

My aux fan does not engage either, but I'll tackle that once the VFC is functional.

Just wanted to post the tool which I have been using to lock the fan clutch:
Not sure what the item actually is...but it works!

http://www.ps2cho.net/downloads/phot...or/clutch1.jpg

All I did was bend the tip as shown and it works 100% perfect :)