Possible Tansmission Problems

[7builder]

I posted a while back that I had problems with my X5 when I towed for the first time. Basically if trying to pull away the car would refuse to move. The engine bogs down and plumes of black smoke appear from the exhaust. This has happened in forward and reverse and the car doesn't move an inch.
The confusing part is that I drove all the way to Cornwall without an issue including hill starts in stop start traffic with no sign of a problem. I got to the camp site and as soon as I tried to reverse onto the pitch it refused to budge again. I moved forward a couple of feet and was then able to reverse again.
I have removed and cleaned the EGR valve, checked for split hoses, lose hoses etc, replaced the air filter as part of a full service and oil change and plugged in the BMW scanner to check for error codes but there were none.
The only thing I can think could be causing the problem is the automatic transmission but there are no error messages and gear changes are as smooth as greased weasle shit so I am confused. Any suggestions on what could be causing this problem as I am getting worried that I have an expensive gearbox related bill just over the horizon?

[X5Sport]

Not certain that the scanner can read the gearbox fault codes.  Try a Bosch Autocentre which has an Autologic system.  That should be able to read any gearbox codes that may have been stored.

Richard

[Steamyrotter]

Cant remember if you tried it with the electrics unplugged??

Did you have a bash??

[7builder]

[quote="X5Sport"]
Not certain that the scanner can read the gearbox fault codes.  Try a Bosch Autocentre which has an Autologic system.  That should be able to read any gearbox codes that may have been stored.

Richard
[/quote]
Thanks Richard, I'll give that a try.

[7builder]

[quote="Steamyrotter"]
Cant remember if you tried it with the electrics unplugged??

Did you have a bash??
[/quote]
Hi Steamy I did try with the electrics unplugged but I couldn't travel far so it was inconclusive so in the end I fitted the OEM wiring kit from PF Jones. I towed all the way to Cornwall without a problem so though it has fixed the issue but it has happened twice since. Imagine connecting a thick chain to the towbar that is wrapped around a giant oak and trying to pull away. The car won't move and the engine will not rev, just bogs down and chucks out epic amounts of thick black smoke.

[X5Sport]

OK here's an off the wall thought.  Is the gearbox getting too hot according to the temp sensor in there and the signal to the DDE says 'cut power'?  Now I would expect that to cut fuel but it may restrict air instead - these things being drive by wire.  It seems if I'm reading your experience correctly that if you let the car cool down it's fine.

Lots of comments on line about towbar equipped X5's needing larger cooling fans and/or different oil coolers.  Is something triggering an over temp signal, which won't bring the light on, and that is the issue?

I know my X6 has a more powerful fan (850W in place of 600W) but I can't remember what was done for my E53 when I specced a factory bar.  Might have had a different oil cooler & fan from the factory.  Early E53's are reported to need both, but not later ones though no info on when the change happened.  Could be another part of the Facelifted models?

Richard

[X5Sport]

And here's another off the wall suggestion.  That it's nothing to do with the X5 but might be the overrun brake system in the hitch is locking the van brakes on?  I'm assuming you have overrun brakes on the van?

My currency on newer hitches is out of date but on some of our 'heavy' trailers (over 1.5T MGW) we had a reversing switch to lock out the overrun brakes.  If it wasn't used you could move everything just far enough until the brakes locked on and no further unless you shuffled forward a bit and tried again - with the same effect!  Is there an automatic system in your more modern hitch that might be causing this issue - say a broken/weak spring or damper, and by doing so locking the caravan brakes on?

Just trying to think what else could cause the X5 to baulk?  It pours smoke but won't move.  It moves a couple of feet and stops again.  That could point at the trailer being the 'problem' not the tractor.  Does the X ever do it when no caravan is attached?

I'm trying the KISS approach.  Keep It Simple Stupid - in case it's something really simple, like the hitch itself?

Richard

[7builder]

Some interesting thoughts and observations there Richard and food for thought. The X never has a problem when there is nothing hitched up only when my caravan is attached. The caravan does have override brakes but even if there was a problem with them locking up I cant see that would be a problem for the X. The reason I say this is because I once towed the caravan with the handbrake fully on with my previous vehicle, a 2.7Tdi Grand Cherokee and only realised the error of my ways when the caravan brakes overheated and started to protest via the medium of smoke signals. I didn't feel any difference in towing performance at the time or anything to hint that the brakes were fully applied. As such I couldn't imagine the X suffering whilst in the same predicament. Maybe I will hitch the caravan up tomorrow and try to pull away with the brakes on and see how it behaves and see if it replicates the problem I occasionally have.
I don't think it is a temperature issue as I have had it lock up as soon as I hitched up one morning and tried to reverse off of a pitch. Hmmm I'm thinking as I type and to be honest it has nearly always happened as I reverse the rig. Only once has it happened when pulling away and that was after I stopped on a slight incline and that would have activated the overrun brakes. The caravan is an old bugger so it could well be a braking issue on it but surely a 3.0D X would have enough grunt to overcome any problem and drag it regardless? The Grand Cherokee could.

[X5Sport]

Auto or manual?  It certainly ought to be able to move it, but perhaps if it senses a problem then the reverse gear ratios are not enough.  It may be that the brakes bind on harder in reverse?  I might be way off the mark, but it just occurred to me that it happens too often when you're hitched up.  Perhaps the gearbox on the E53 runs differently with a trailer connected?

I know modern 'tin-tents' come with ATC and other anti-sway gizmos.  Mrs X5Sport had me looking at said beats this morning so I guess we'll be joining that most hated club ourselves soon.

Richard

[7builder]

It's an auto Richard and due to torrential rain and unexpected visitors I was not able to hitch up and try the caravan with the brakes firmly applied. The caravan is an old beast of 1993 vintage so nothing new and fancy when it comes to the braking system. In fact old , worn and problematical is more likely the order of the day. The caravan has seen it's last outing and will be replaced soon with a newer model so who knows the problem may disappear with the introduction of a newer model. I'm just not convinced the 3.0 beast would struggle even with caravan brake issues. In normal conditions it feels like the X could tow a caravan up a cliff, I just hope there isn't an expensive and catastrophic failure just around the corner. Very worrying  :'(

[X5Sport]

Know anyone else with a similar sized 'van' you can test with?

The one SWMBO would like weighs in at nearly 1850kgs so I will be looking very carefully at everything to make sure I have my calculations correct.  I have an uphill learning curve for a few months until 'she decides'!

I can't think of anything else that as yet hadn't been tried.  I'd be surprised if the X couldn't move the van, but if the brakes are binding hard on, even momentarily, it just might be enough.  It could also be something really silly - and obvious - once worked out!    :-[. I'll keeping thinking.

Richard

[7builder]

Thanks Richard our next caravan will be around that weight as well. We have always had big twin axle vans and the next will be no exception. When towing normally the X deals with the van without any fuss, it's effortless and you wouldn't know you had anything attached if it wasn't for the rear view mirrors so I wouldn't worry too much about the weight of the caravan your wife is looking at.

[7builder]

Jeez, I've just noticed you own a 4.0D X6. Cease your worrying immediately 

[TimX5]

t sounds to me as though the caravan brakes are jamming/ binding when reversing , the brakes have a cam in them  which should release when reversing and when braking whilst towing the brakes will work , have a look at the caravan brakes and eliminate them first , I tow a sterling eccles sport 586 2014 which has a gross weight of 1550kg which I think I will be about 100kgs over that (oops)and the x5 plays wwith it.

[Horizon]

t sounds to me as though the caravan brakes are jamming/ binding when reversing , the brakes have a cam in them  which should release when reversing and when braking whilst towing the brakes will work , have a look at the caravan brakes and eliminate them first , I tow a sterling eccles sport 586 2014 which has a gross weight of 1550kg which I think I will be about 100kgs over that (oops)and the x5 plays wwith it.
[/quote]

Sounds like if the problem only occurs when, and around times when you are reversing with the caravan, as mentioned above the trailer brakes are designed to release when the trailer reverses. Years ago we had to get out and put a physical bar that stopped the piston / damper pushing backwards and applying the brakes.
Best option is to get the caravan brakes serviced/ checked out first. A lot cheaper than second guessing on the X.
Hope you get it sorted .