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Braingears
Expert
Date registered: Apr 2006
Location: St Petersburg, FL
Vehicle(s): G320 & ML320
Posts: 1450
| Need Help !!!
About two weeks ago, I shredded my V-Belt (aka fan belt). Over the past day or so, I noticed that the temperature has been running a little hot. When I popped the hood, I noticed that the cooling fans were not running at all.
I looked all over the engine compartment and cannot find any plugs that are loose or wires that are broken.
I have checked all of the fuses, and everything is looking fine.
I suspect that I am having problems with one of the relays. I have no idea which one it can be or how to test them. Does anyone have any pictures or wiring diagrams?
Chuck |
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Braingears
Expert
Date registered: Apr 2006
Location: St Petersburg, FL
Vehicle(s): G320 & ML320
Posts: 1450
| RE: Need Help !!!
i just pulled and checked the connection at the temperature sensor. It looks fine. When I take a wire and short the connection, the fans come on. How do I check the temperature sensor to see if this is actually the failure point? Will it hurt the fan if I "hotwire" the fans to stay on? On my 300D, I have them permanantly on. Living on Florida, it never hurts to be a little cooler, and it makes the A/C about 5-10 degrees cooler too (it is always cooling the A/C condenser).
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 IMAGE_015.jpg (50KB - 9 downloads)
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AlanMcR
Expert
Date registered: Apr 2006
Location: US, CA, Los Altos
Vehicle(s): G300DT E300DT 230SL
Posts: 3500
| RE: Need Help !!!
Shorting the plug is a good short term solution. I carry a short cable with bannana plugs just for this reason. (bannana plugs fit perfectly). Living in relatively temperate California and having a diesel, I removed the engine driven fan completely and depend on the electric fans for cooling. I've modified the circuit to turn on 50% at 90C, 100% at 95C.
I'm not sure that you want these fans running constantly. Testing the sensor should be as easy as letting the engine heat up and waiting for contact close. I recall the setting is 110C (aka smoking hot).
Most likely the real problem is that the flapping fan belt broke/bent the bi-metallic strip on the front of the engine driven fan clutch. If it is gone, you need a new clutch. If it is merely bent then you can gently bend it back. Write back with the situation and I'll try to give some more assistance.
...Alan
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Braingears
Expert
Date registered: Apr 2006
Location: St Petersburg, FL
Vehicle(s): G320 & ML320
Posts: 1450
| RE: Need Help !!!
When I went into my garage... I truly found a solution. I actualy had a replacement sensor on the shelf! I ordered it last year when I was having A/C compressor problems (with the high temp cut-off). It took me 5 minutes to replace the sensor. The truck was even leaning in just the right position so that coolant wasn't even spilling out of the hole. When I installed the new sensor, I also used some teflon tape to make sure that I didn't have any leaks. I will drive the truck again tomarrow. I'm pretty sure that fixed it. I will carry a jumper wire just in case....
 (Sensor.JPG)
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Sensor.JPG (46KB - 12 downloads)
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AlanMcR
Expert
Date registered: Apr 2006
Location: US, CA, Los Altos
Vehicle(s): G300DT E300DT 230SL
Posts: 3500
| Fan clutch
Still, I'd be testing the fan clutch. Get the truck good and hot and see if the fan roars. Fully engaged they truly roar.
...Alan |
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Braingears
Expert
Date registered: Apr 2006
Location: St Petersburg, FL
Vehicle(s): G320 & ML320
Posts: 1450
| RE: Fan clutch
AlanMcR - 4/24/2006 7:46 PM Still, I'd be testing the fan clutch. Get the truck good and hot and see if the fan roars. Fully engaged they truly roar. ...Alan Mine does not have a clutch like your diesel. Mine uses a viscuss/hydrolic clutch instead of an electric clutch. It would be great if I could tighten/stiffin this style clutch. |
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Brent
Expert
Date registered: Apr 2006
Location: SW Colorado USA
Vehicle(s): '13 Wolfsburg GTI
Posts: 1754
| RE: Need Help !!!
No, the two trucks have the same type of viscous clutch. The spring Alan was referring to controls the viscous clutch lock-up. He is right, it will really roar when locked. You can even get it really warmed up, stop and let it idle, pop the hood and manually run the throttle. You will know if the fan is working, it will be loud and move serious amounts of hot air in your direction.
I know this because my fan clutch failed on my G320. You can also temporarily lock the fan clutch by bending a few of those little metal fingers into the alum finned clutch housing. I had to do this when mine failed, that is what they are for. It was a sure cure for hot running. If the mechanical fan clutch goes the electric fans will not keep up at higher speeds (75 mph+) or working at low speeds. |
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fernweh
Date registered: Apr 2006
Location: Calabasas, CA - Centenario, BCS - Luebeck, Germany
Vehicle(s): Few Mercedes-Benz, a Toyota Amphibious and a Vespa
| RE: Fan clutch
Hi,
Your viscous fan clutch is part of the thermostatic engine temp control. It's very simple to test the clutch - when the truck/engine is cold you should be able to turn the fan by hand easily and when hot it should have a quite resistance to turn (engine off!!!). This system helps the engine getting quickly to operation temp. At normal highway driving speed, for sure with low engine rpm, the viscous fan clutch allows the fan to be driven with only partial power while at higher load = higher temp or idling with no forward speed, the clutch will drive the fan with more power - also improved gas milage compared to fixed fans.
The temp sensor should kick-in at high temp around 195F(or as marked on it) to turn on the electrical aux fans, cycling on/off as needed by the coolant temp. Turning on the A/C will also activate the aux fans already at normal engine operation temp. So, if you drive through the desert with your A/C on - most likely your aux fans will run constantly for hrs and they are designed for it.
We used to test the temp sensors in a pot of water on the stove top, connect a multi-meter to the contacts, thermometer in the water and ajusting the stove heat up&down to see the sensor contact close and open at the correct temp.
Karl |
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Braingears
Expert
Date registered: Apr 2006
Location: St Petersburg, FL
Vehicle(s): G320 & ML320
Posts: 1450
| RE: Need Help !!!
I have not driven the truck to temperature since I've replaced the sensor. Until everything comes up to temperature, I do not know what works and what doesn't. When the V-Belt shredded, it was REALLY wrapped in and behind the circulation pump where the viscous fan is attached. I did not feel any springs or wires behind the pulley. Does anyone have any pictures or diagrams of what this looks like?
Brent, do you have any pictures of your failed part? When I pulled over today because the engine was running hot (115°-120°C), the viscous can was pretty loose. That was before I changed the sensor... |
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fernweh
Date registered: Apr 2006
Location: Calabasas, CA - Centenario, BCS - Luebeck, Germany
Vehicle(s): Few Mercedes-Benz, a Toyota Amphibious and a Vespa
| RE: Need Help !!!
Hi Chuck,
the little bi-metal spring in front of the viscous clutch (a little torque converter) , Alan is talking about, being influenced by the airflow temp through the radiator, changes the power/load from the clutch to the driven fan. If this bi-metal spring got damaged or it's even missing your viscous fan clutch is not able to increase the fans power/torque output (roaring noise) and pull more 'cold air' through your radiator.
If your noticed that you can move the fan blade very easy at your stated temp(115-120C) the viscous clutch needs to be replaced.
The temp sensor you have already replaced, has nothing to do with the viscous clutch, turns on the aux fans for additional airflow through the radiator.
Karl |
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fernweh
Date registered: Apr 2006
Location: Calabasas, CA - Centenario, BCS - Luebeck, Germany
Vehicle(s): Few Mercedes-Benz, a Toyota Amphibious and a Vespa
| RE: Need Help !!!
Hi Chuck,
I found a wiring diagram for a G320 w/ M104 engine.
M4 = Aux fan
K9 = Fan Relay
S32/1 A/C Intake line pressure switch 16 bar on(triggers Fan Relay) - 12 bar off
S25/11 Coolant Sensor 100C switch (triggers Fan Relay)
S25/16 Coolant Sensor 120C switch (shuts off A/C via Control Unit)
S25/11 & S25/16 are combined in one three pole sensor unit - your picture!
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scan0003.jpg (92KB - 11 downloads)
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AlanMcR
Expert
Date registered: Apr 2006
Location: US, CA, Los Altos
Vehicle(s): G300DT E300DT 230SL
Posts: 3500
| Pic of similar fan clutch
See attached pic. The bi-metallic strip is the rectangular item in the middle. This bends ever so slightly to push on a pin (hidden) that controls the flow of the fluid. If you take off the clutch, make sure that it stays in a vertical orientation. They can leak if left on the front or back face.
...Alan
 (FanClutch.jpg)
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FanClutch.jpg (29KB - 9 downloads)
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Braingears
Expert
Date registered: Apr 2006
Location: St Petersburg, FL
Vehicle(s): G320 & ML320
Posts: 1450
| RE: Need Help !!!
The fan belt did not get anywhere near that area. To add insult to injury... I think that I found a new coolant leak today. It is somewhere under the intake manifold. I was not able to find the actual location of the leak yet. |
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