X3: white smoke while puhing heavy trailer in reverse

[Niloc]

X3: white smoke while pushing heavy trailer in reverse

Hi,

I own a 2004 X3 3.0 manual + sport package (17500km) - love it so far!

I also have the BMW class II hitch (3500lbs) installed...

Last weekend I had to push, uphill and in reverse, my tent trailer which weight 2500lbs. After about 10 minutes of going back and forth to have it properly positioned, some white smoke that smelled like burnt rubber started to come out of somewhere under the engine, more toward the front wheels, I'd say between the front wheels and the front doors.

It was definitely not the tires, they did not spin. The engine did have to work hard in reverse to have the trailer move up.

Absolutely no signal came up in the dashboard. The engine temp did not move.

[Edit: no signals came up in the dash after after I noticed the smoke- while pushing in reverse I obviously did not look at the dash...]

Does anyone have any clue on what could be the cause of this?

Thanks,
Colin.

 

[Big Daddy]

I assume it is an automatic? The forward/reverse may have burned some clutches in the transmission as in effect you had the fluid running one way than back the other, back and forth, very hard on a transmission. Pull your auto trans fluid dipstick and smell the fluid, if it smells burnt have it replaced.

 

[Niloc]

Hi,

No, sorry, forgot to mention, it is a manual transmission. (... I just added it to my original msg).

When I said "back & forth" I didn't really mean quick back & forth, like say you are stuck in snow and trying to get out. It is just that I had to push it in reverse and then go back in forward a little bit to realign the trailer - did that 4-5 times.

 

[bmw046series]

White smoke; that means a popes been elected.

 

[Big Daddy]

Sounds like a clutch than. The location you describe is right on for smoking a clutch.

 

[Niloc]

If it is the clutch, should I have it checked? Is this something I should worry about? Is there a way for me to make sure it is the clutch?

If this is a "real" mecanical problem, and not something like some fluids that overflowed on the manifold or some plastics that melted, I'll be really puzzled that the X3 cannot handle this kind of load.

Thanks,
Colin.

 

[Stitch]

Take it back to the dealer & tell them what happened. They would be happy to check the whole car up for you. You have the 4yr/50,000mile plan, right?!

 

[Niloc]

Took it to the dealer this morning. Service guy told me it looked (and smelled) like a clutch problem - mecanics will check it later today. He also told me that the clutch was not under warranty... so if it is indeed the clutch it might be bad news for me...

At 17000km (10625mi) I don't find it reasonable not to assume the clutch must be defective. I don't think it is normal that this vehicule cannot handle this kind of duty. We're talking about a 4x4 SUV, not a Toyota Echo.

Anyways, more news later!

Colin.

 

[Big Daddy]

I would not call the clutch defective I would call it burnt. A clutch is only as effective as the foot that operates it. Don't take this wrong, but I too have burned a clutch. If the clutch was not totally engaged and put under a severe load it will spin and burn. By not totally engaged I am saying that the engine rpm's were greater that the transmission and as the clutch disc came against the flywheel it created heat burning the clutch.

 

[mjbst111]

It could have been how you drove it. If your foot was on the clutch at all while you are pushing a heavy load up hill you can put wear on the clutch. Unless the clutch is fully depressed it is getting wear and burning to some degree. If you were doing this long enough or having the clutch pressed a significant amount it got hot enough and wore enough to smoke. Any manual would do this.

 

[Kirby]

At 17000km (10625mi) I don't find it reasonable not to assume the clutch must be defective. I don't think it is normal that this vehicule cannot handle this kind of duty. We're talking about a 4x4 SUV, not a Toyota Echo.

I agree with Dan and Michael's comments. A clutch on a tractor trailer will burn up if it is slipped too much, and they are designed for 100,000 lb loads. It's not an issue of design or quality, it's essentially misuse. Heat was the enemy here.

Think of it this way. If you got stuck, and burned up a tire by spinning it to get unstuck, would you hold BMW responsible for the tire?

 

[Niloc]

I am totally aware of the consequences of slipping a clutch, especially under high load. While pushing the trailer I was very careful not to use the clutch to control my power - I really used the gas to control the climb.

What I meant about the possibly defective clutch is that I find it hard to believe that the clutch on the X3 is not capable of handling this kind of load - defective or maybe just factory equipped with a too gentle clutch model? For example - and I really don't know - if they put a series 3 type of clutch in the X3 instead of putting a X5 type of clutch maybe the series 3 clutch is not rated for this kind of load.

While thinking about all this while coming back from work (in the oh so nice Buick Allure loaner I thought: why didn't I spin the wheels since the load was heavy and the ground was gravel, wouldn't my wheels spin before slipping the clutch? ... Traction control!!!!!!

Woah. Isn't the traction control capable of reducing the engine torque directly with the transmission? (using the clutch??) Is it possible that what really happened is that I was in fact fighting against the traction control by giving more gas for more power but the traction control was slipping the clutch to avoid wheel spin?

While manoeuvring the trailer I was looking backward all the time so I did not see if the traction control light came up in the dashboard.

Is this plausible?

And thanks for all your feedback this is really appreciated.

Colin.

 

[Kirby]

As far as I know, traction control does not modulate the main clutch. But you bring up an interesting question that I don't think has ever been mentioned - does traction control work in reverse?

I found this:
"Receiving inputs from the DSC's sensors, xDrive factors the rotational speed of each wheel, steering angle, brake use, yaw and lateral acceleration, and then seamlessly alters the distribution of torque according to the situation at that second. Most extreme real world example: if both rear wheels are on ice, almost 100 percent transfers to the front axle. The actual transfer is via a multi-disc clutch that can be completely open, completely engaged, or engaged at any level in between. That's why the torque transfer is seamless, or in BMW parlance, "steplessly variable." "Think of xDrive as controlled transmission of torque," said xDrive Product Manager Bert Holland. "One-tenth of a second is all it takes, even in the most severe circumstances."

I think they are talking about a separate xDrive clutch in the transfer case. However, it sounds like it could be this clutch that you smoked?

Question: Does you trailer have surge brakes? That is, hydraulic brakes that automatically apply via pressure on the hitch assembly when you brake the car? If so, when you back up, the trailer brakes will be applied, especially if you are backing up hill. My boat trailer surge brakes have a slot to insert the safety chains when backing up. This prevents the surge brakes from activating. Just a thought.....

 

[andreyiv]

Also, another thing with traction control. As far as I know at first it just applies brakes to the wheels and only when that is not enough, it backs off the engine. Maybe the brakes were working against you before anything else and thats what did the clutch in?

 

[Niloc]

Hm. This is interesting.

To answer Kirby's question, no my trailer doesn't have surge brakes.

I think that smoking the transfer case xDrive clutch would make sense. My X3 is still at service, they only started working on it at the end of the day. I'll definitly bring up that theory tomorrow morning and see what they think.

I wonder how much the dealer's mecanics really understand about xDrive. I really had to insist on having the X3 checked - their first reaction was that if no problem light came up I should just continue on and come in if something show up later (this was the advisor, not a mecanician I was talking to). I have the feeling they will not be willing to open that up and carefully look for potential premature wear. If they don't I'll have to hope that the damage wasn't too bad and that it won't break the day after the end of the warranty (or during the road trip all the way to the Florida Keys planned in August...).

We'll see what they have to say tomorrow.

Colin.

 

[MrElussive]

When you were going forward and reverse, were you half-clutching, or did you fully engage the clutch each time? It SEEMS like you didn't have your eye on the tach when you were reversing, so you were probably giving it way too much gas and the clutch was just being grinded against reverse and first gears while you were going forward and backward.

The X3 can handle towing and stuff like that, but usually people who know they are going to do a lot of towing, go with an automatic transmission. The fluid-based operation of an automatic makes it perfect for starting off when hauling something, especially since you need that low-end torque.

I highly doubt you burnt up the xDrive clutch as the system is designed to work hard such as when drive off-road or in deep snow.

 

[epj3]

The clutch probably wasn't completely bedded in either.

I wouldnt worry too much at this point, if it drives fine for now let it alone, and don't do any towing for a few weeks. Let the clutch bed itself back in to match up with the flywheel/pressure plate.

You should also check on the actual towing capacity of the car itself. Just becuase the hitch is capable of 3500 lbs doesn't mean the engine and drivetrain is. If you had your family in the car with a bunch of gear, PLUS the trailer (which I would assume was loaded up), and the weight of the car, You're looking at what, around 8,000 lbs if not more for that drivetrain to move? Add in that it probably has a clutch delay valve.