[vallemail]

Hi All! I haven't asked for the wisdom of the forum since about July, but now I'm back with a new problem (fortunately all the old ones have been resolved - thank you!)

New problem: My 2001 ML430 with 126k miles is running hot, not in the red zone, but definitely hotter than it used to, and I want to be proactive and solve this problem before it gets much worse and causes big problems.

Here are the symptoms and here are the things I checked: If I'm driving along at normal highway speeds the rushing air is sufficient to keep the temperature about 100 deg (I have a temp gauge bolted to the engine to give me an overtemp alarm inside after this happened on another car, burst radiator, etc.) But if I get stuck in traffic the temperature creeps up quickly. For the last month I've been turning on the A/C to run the aux fan which brought the temperature down nicely. But today even the aux fan wasn't enough and sitting in traffic it got to 107 C with the aux fans running too. I think that's too high so I think something is going bad.

I've looked at the fans and they're all running. I've spun the cooling fan by hand and it turns one full revolution (I put a white dot on the top blade) before stopping, so it doesn't seem like the clutch is slipping.

I've felt the radiator hoses to check the thermostat. When the top hose is quite hot the bottom one is warm, definitely not cold or cool.

I do NOT hear any kind of squeal or noise to indicate a water pump problem, nor is there any leak from it.

The oil was changed at 124k, Mobil 1 0w40. The cracked expansion tank was replaced and the radiator was flushed at 119k and filled with MB fluid. There is NO loss of coolant, and no leaks anywhere (I am OCD about leaks.)

Could it still be a sticking thermostat, or what should I check? Thanks!

 

[RJV]

You mention a few temperature readings and I'm left wondering if these are from the factory gauge in the instrument cluster or from an aftermarket gauge you have fitted. If the latter, then you need to eliminate a scenario where its just a gauge going faulty or reporting inaccurately.

So can you just explain which gauge you are reading from, and if I am correct in assuming you have two gauges are they BOTH showing increased temperature over what you have previously experienced?

 

[mattml430]

Are you saying 107f or 107c if it's Fahrenheit that is only 46 Celsius I could be reading your post wrong.


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[43sqd]

When you post information, make sure it is correct. You have a 2001 430 listed in your profile and in your post you list it as a 2000.

When you say "the fans are all running", what does that mean? The fans are running when? When the temp. is high? Are they running all the time? Be specific.

When you say "I spin the fan blade one full revolution", what does that mean? When the eng. is cold or when it is hot?

When the fans come on at 107°C, do they stay running and does the temp. gauge drop to the 90° range and then shut off? If so the fans and the system values are are working properly.

It would seem from what can be gathered, that you have a faulty fan clutch.

 

[Hirnbeiss]

Check the aux recirc pump too.

 

[vallemail]

Thank you for the responses and I apologize for a few typos in my posting. Yes, it's a 2001 and the temp is 107C. I did say that I've added an after market temp gauge and it's very accurate, and it agrees with the gauge on the dash (but is more accurate) so it's not a gauge problem. The temperature is real.

I did NOT say the fans come on at 107c, I said that the car reached 107 on the freeway and when i pulled over to check it, all 3 of the fans were running and it was at 107c with all 3 fans running. It used to be in the past few months that when the extra temp gauge got to 105 (where I have the audible alarm set) without the A/C on that I could turn on the A/C and it would bring the temperature down quickly to about 90 (it's digital and I can watch it drop by tenths of a degree), but not anymore, that's why I'm trying to figure out what to do to fix it. If I start the car cold the aux fans are not running.

Regarding spinning the fan it doesn't seem to matter whether it's hot or cold. I have spun it both hot when I got home from the 107 drive and today first thing in the morning without starting it up and it spins exactly 1 full revolution in both cases.

I tried to answer all the questions, did I get them all?

 

[art_arev]

Regarding spinning the fan it doesn't seem to matter whether it's hot or cold. I have spun it both hot when I got home from the 107 drive and today first thing in the morning without starting it up and it spins exactly 1 full revolution in both cases.

As 43 pointed it is your fan clutch. When the engine is cold you might be able to turn the fan with your hand. But when hot the clutch is supposrd to be engaged and you wouldnt be able to spin it.

 

[vallemail]

Wow! From Zimbabwe! I was hoping it was the aux pump as that seems so much easier to replace. I am going to check it anyway by applying B+ to the white lead, ground to the other on it's connecter as 43sq recommended in a different thread, and see if it's running. Just now with the truck at 100 I turned the A/C on, the 2 aux fans came on (they weren't on before) but I felt absolutely nothing when I put my hand on the aux pump, although both it's hoses are very hot. I can't hear anything over the engine noise, so I don't know how people hear a humming from this pump!

 

[bula]

Wow! From Zimbabwe! I was hoping it was the aux pump as that seems so much easier to replace. I am going to check it anyway by applying B+ to the white lead, ground to the other on it's connecter as 43sq recommended in a different thread, and see if it's running. Just now with the truck at 100 I turned the A/C on, the 2 aux fans came on (they weren't on before) but I felt absolutely nothing when I put my hand on the aux pump, although both it's hoses are very hot. I can't hear anything over the engine noise, so I don't know how people hear a humming from this pump!

Aux pump does not run all the time. With engine at normal running temp shut the car off, aux pump should start running for few minutes

 

[43sqd]

Here is the way the cooling fan/s system works.

1. driving without the A/C on, providing everything is in working order, the belt driven fan w/clutch provides enough cooling to keep it at 80°C.

If one or more components are not in working order, the temp. will rise and when it reaches 105° (221°F) the two electric fans will kick in and lower the coolant temp. until it reaches 94°C and the elec. fans will turn off. It will repeat this process until the component problem is resolved.

2. driving with the A/C on, the fans will constantly run until you turn off the A/C. This is why while you have the A/C on you can maintain 90°C, but not 80°C, because the clutch fan is not spinning fast enough.

 

[vallemail]

Thank you for the explanation! My truck has NEVER held at 80C since purchasing it just under 2 years ago. It's always seemed hot (which is why I got the extra gauge with audible alarm) usually 95-100, almost never less than that. I guess the clutch fan has been degrading gradually?

Today I could tell that my electric fans turned on (because the temperature started dropping quickly) when the digital gauge read 102c, so I guess it's off by 3 degrees which is not bad.

Could you expand the explanation to include how the aux pump fits into the picture? Thanks!

On partsgeek I see Behr and Beck/Arnley fan clutches for about $100 and then Sachs, Hayden and 4Seasons for $250, big difference. Any opinions about that? I would have thought Beck/Arnley and Behr were good brands. Do I need the thermal fan clutch, those seem to be the expensive ones?

Is there a DIY for replacing the fan clutch? I couldn't find it in the thread.

 

[art_arev]

A fan clutch is a critical part for the well being of your car. Look into buying a MB part or at least Sachs.
You dont need the thermal fans.
It is just the clutch. You use your own fan blades.

 

[43sqd]

Thank you for the explanation! My truck has NEVER held at 80C since purchasing it just under 2 years ago. It's always seemed hot (which is why I got the extra gauge with audible alarm) usually 95-100, almost never less than that. I guess the clutch fan has been degrading gradually?

Today I could tell that my electric fans turned on (because the temperature started dropping quickly) when the digital gauge read 102c, so I guess it's off by 3 degrees which is not bad.

Could you expand the explanation to include how the aux pump fits into the picture? Thanks!

On partsgeek I see Behr and Beck/Arnley fan clutches for about $100 and then Sachs, Hayden and 4Seasons for $250, big difference. Any opinions about that? I would have thought Beck/Arnley and Behr were good brands. Do I need the thermal fan clutch, those seem to be the expensive ones?

Is there a DIY for replacing the fan clutch? I couldn't find it in the thread.

Below is an explanation of the Coolant Circulation Pump.

To check if it is working, turn the key to pos. #2 and feel the pump with your hand. You should also hear an audible hum. The pump runs continuously whenever the key is turned on or the engine is running. Then upon eng. shut down the pump will run approx. 2 mins. and then shut off.

If it's not working, you need a new one. Stay away from Beck/Arnley. Behr is good but it has a roar to it.

 

[vallemail]

I'm very suspicious of this coolant pump. I turned the key to position 2 and listened with a stethoscope on it and felt the pump and there is no discernible vibration, mechanical motion or hum. With the engine running there is still no vibration. And when I shut off the engine there is nothing at all, even for the first 2 minutes, no hum, no vibration. I disconnected it and applied battery voltage/ground to the pump terminals (they're marked +/- so I'm sure I didn't get it wrong) and nothing at all. I'm sure it's completely dead. I think single failure modes are most likely so I'm going to replace this first, before the clutch, and see if it fixes the problem.

 

[B&kML350]

Vallemail.. Seach this forum. There are a couple a threads on how to repair the pump for under 10$$ or use a Volkswagen pump for around 70$$

 

[43sqd]

I'm very suspicious of this coolant pump. I turned the key to position 2 and listened with a stethoscope on it and felt the pump and there is no discernible vibration, mechanical motion or hum. With the engine running there is still no vibration. And when I shut off the engine there is nothing at all, even for the first 2 minutes, no hum, no vibration. I disconnected it and applied battery voltage/ground to the pump terminals (they're marked +/- so I'm sure I didn't get it wrong) and nothing at all. I'm sure it's completely dead. I think single failure modes are most likely so I'm going to replace this first, before the clutch, and see if it fixes the problem.

Suspicious is not the word. You need a new pump, but I still believe that your overall problem is with the fan clutch.

 

[vallemail]

Okay, but one thing at a time. Thank you for all the input! I found the thread about using the VW Bosch pump instead and have found it in numerous places very reasonable, but I can't find anything about repairing the old one. Can someone point me in the right direction?

 

[43sqd]

Okay, but one thing at a time. Thank you for all the input! I found the thread about using the VW Bosch pump instead and have found it in numerous places very reasonable, but I can't find anything about repairing the old one. Can someone point me in the right direction?

Bend back the 6 crimping fingers at the lower cap and remove. It's probably the brushes that are gone but it could also be that the motor is seized.

If it's the brushes then you will have to send away for them and perform the repair.

http://www.benzworld.org/forums/w163-m-class/1610389-auxiliary-water-pump-funcitionality.html

If you want to do that instead of spending of spending $90, then go right ahead.

Amazon.com: Bosch 392020039 Electric Water Pump: Automotive

 

[Wragie]

Consider the vw pump. I just did mine using that. It saves a lot of time and you wont even have to undo the hoses. Slide it off the mount, undo the power connection, loosen the 4 screws on top of the old pump, remove old motor and swap in your cheapy vw one and reverse the steps. Takes less time to do than it did to tap out this reply on my tablet. Plus you can then at leisure replace the brushes on the original and have a ready to go spare. And a functional aux makes a lot of difference to how it heats up, cabin heat and it does not sound like a 3.2 litre percolator on shut down ;-)

 

[vallemail]

I really like the idea of not even having to disconnect the hoses! I hadn't thought of that! I did order the VW pump, it should be here tomorrow so I'm glad to have read this tip before doing it (although I made a good dent in a bottle of wine in preparation for the job (for the cork of course, which now I don't need).

I also figured out how to test my fan clutch further to evaluate it. With the engine cold I hooked a rubber band around one fan blade and the dipstick tube, then started the car. The rubber band held the fan in place as I expected. Then I let the car idle and watched my digital temp gauge and the rubber band, expecting the rubber band to break when the clutch engaged. I let it get to 95C and then gave up and decided my clutch was basically non-existent. Am I missing something? Does the clutch engage at an even higher temperature? I feel more confident now about needing to buy a new fan clutch. On FCP Euro's website I see the Sachs clutch and Meyle for half the price. Does anybody have experience with Meyle clutches? They're the only 2 they carry so I suspect it must give Sachs some serious competition.

Thanks for all the input!