540i towing weirdness - auto drops to 3rd after a while
Discussion
This has been happening for a while. Never see it when driving normally, only when towing (600kg trailer, 1200kg car on it, boot full of tools, spare wheels in back seat). So quite a lot of weight
After about an hour the car will drop to 3rd gear, and stay there. Putting it in manual and telling it to change to 4th or 5th is a waste of time; it ignores me. After a while (5, 10 minutes maybe) it will decide its happy again and drop back to 5th. Then it will happen again after a while.
I changed the gearbox oil last year when i bought the trailer; just seemed sensible. I just put 4 new tyres on it and got the gemoetry done. No change.
Any ideas?
ta
Andy
First, let me say that I have never even driven a BMW, so I'm no expert on BMW autos......
Many auto boxes will not use top gear until a certain temperature is reached. I wonder if they also refuse the higher gears if a certain temperature is exceeded.
Many auto boxes will not use top gear until a certain temperature is reached. I wonder if they also refuse the higher gears if a certain temperature is exceeded.
Edited by gareth_r on Tuesday 30th June 00:42
Due to the time iot takes before it does it, i do think temperature is something to do with it, but i don't see how dropping to a gear where higher revs are used helps at all.
Either way, people must tow with these cars without it happening, so there must be a problem with mine that can be fixed...
Either way, people must tow with these cars without it happening, so there must be a problem with mine that can be fixed...
Perhaps the gearbox is overheating? From what I've seen on searches, 3rd gear is its "limp home" gear. Bit weird that no indicator light comes on.
You say you changed the oil, did you do it exactly as per procedure (refilling at the right temperature etc) as I guess the oil level is critical.
A specialist will be able to read the fault codes from the gearbox - may be worth a visit but I suspect you're operating the gearbox at the very extreme of its capacity and it's just getting pissed off with you
You say you changed the oil, did you do it exactly as per procedure (refilling at the right temperature etc) as I guess the oil level is critical.
A specialist will be able to read the fault codes from the gearbox - may be worth a visit but I suspect you're operating the gearbox at the very extreme of its capacity and it's just getting pissed off with you
General consensus seems to agree with my own logic; its getting hot. It was my specialist guy that changed the gearbox oil and it didn't start doing it until a few months after that, and now its getting worse e.g. its less time each journey before it starts.
http://www.kenlowe.com/oil-coolers/engine/index.ht...
In touch with the above peeps about this extra oil cooler kit which will get fitted at the same time as new fluid. I'll report back with how i get on.
Andy
http://www.kenlowe.com/oil-coolers/engine/index.ht...
In touch with the above peeps about this extra oil cooler kit which will get fitted at the same time as new fluid. I'll report back with how i get on.
Andy
peebee said:
I tow a 950Kg caravan with my 530i Auto touring (E39) and don't have this problem, although it does tend to hold gears longer than when going solo it alwys changes up to top eventually.
I'd be interested in how you get on with the Kenlowe rad and how much it costs to buy and to fit.
£126 inc vat and delivery. Will let you know about fitting (though its worth mentioning I'll be changing the trans fluid at the same time, so it will be more than just fitting). Apparently finding somewhere for it to go is the problem on the V8s....so the Kenlowe guy said.I'd be interested in how you get on with the Kenlowe rad and how much it costs to buy and to fit.
If not under the front, i see no reason it couldn't go under the rear bumper; gets plenty of airflow as well. The towbar itself hits the floor before the bumper so the cooler would be well protected. Its a thought.
We shall see.
peebee said:
I tow a 950Kg caravan with my 530i Auto touring (E39) and don't have this problem, although it does tend to hold gears longer than when going solo it alwys changes up to top eventually.
I'd be interested in how you get on with the Kenlowe rad and how much it costs to buy and to fit.
bear in mind i am towing double the amount you are....maybe more...I'd be interested in how you get on with the Kenlowe rad and how much it costs to buy and to fit.
john_p said:
Does it not already have an oil cooler? Or is this an uprated one?
Yes, it has one thats at the bottom of the radiator. Quite small apparently. Lots of manufacturers fit larger ones when adding tow kits, though i am not sure if BMW do. Mine is an aftermarket tow kit so I only have the standard one. Follow the link i posted and you'll see what this is; an add-on 'proper' oil cooler. You plumb it in after the existing one, on the 'return' pipe, somewhere where there is airflow. Even within the engine bay (if you can't get it in direct airflow) is supposed to be an advantage.
Andy
OK, we have success
The oil cooler on a 540 is pitiful. Its not, as was thought, a pipe that runs through the radiator and heat exchanges with the rad water. It is actually a tiny little oil cooler that lives under the car near the front suspension arm. Its looks like a tin of sardines, and isn't much bigger. Not in direct airflow, just what comes under the car. Here is a poor picture of it, taken on phone:
So....I fitted the Kenlowe kit which came with a new pipe to plumb it into the existing setup (you add it on the return pipe), all the fittings for doing so, and a selection of ways to mount it.
The 540 has a nice space under the number plate, behind the bumper but in front of the front panel. I thought it would fit nicely in there....it turns out its a perfect fit; height-wise it slots beautifully inbetween two rubber flaps, one of which (the top one) you cut two holes for the pipes to go into. I then pushed a sharp thing through it and just used zip ties to locate it:
As you look at the front of the car the pipes go to the right and actually go over the top of the brake ducts; when you offer up the bumper there is the duct in the bumper and you marry it up wth the socket; they go down the side of it. Over the suspension arms and splice into the existing pipe about half-way along. A few zip ties more to make sure the pipes don't catch anything and stay relatively where they start (but not tight). Then start the car and top up the gearbox oil.
Bob is your uncle:
I'll get some fine mesh for the front i think, to stop any stones flying up. I'll go all the way along that grille i think, so it doesn't look weird.
This was all a few weeks ago as i hadn't towed anything since then. The acid test was yesterday when i went to get the RX-7 from Portsmouth where it was getting its turbo rebuilt. All the way home and it didn't drop into 3rd once; problem solved!
So...that finishes this off nicely i think; E39 gearbox (or anything else really) overheating, or planning to pull a lot of weight? Plonk one of these Kenlowe oil coolers on and worry no more
Andy
The oil cooler on a 540 is pitiful. Its not, as was thought, a pipe that runs through the radiator and heat exchanges with the rad water. It is actually a tiny little oil cooler that lives under the car near the front suspension arm. Its looks like a tin of sardines, and isn't much bigger. Not in direct airflow, just what comes under the car. Here is a poor picture of it, taken on phone:
So....I fitted the Kenlowe kit which came with a new pipe to plumb it into the existing setup (you add it on the return pipe), all the fittings for doing so, and a selection of ways to mount it.
The 540 has a nice space under the number plate, behind the bumper but in front of the front panel. I thought it would fit nicely in there....it turns out its a perfect fit; height-wise it slots beautifully inbetween two rubber flaps, one of which (the top one) you cut two holes for the pipes to go into. I then pushed a sharp thing through it and just used zip ties to locate it:
As you look at the front of the car the pipes go to the right and actually go over the top of the brake ducts; when you offer up the bumper there is the duct in the bumper and you marry it up wth the socket; they go down the side of it. Over the suspension arms and splice into the existing pipe about half-way along. A few zip ties more to make sure the pipes don't catch anything and stay relatively where they start (but not tight). Then start the car and top up the gearbox oil.
Bob is your uncle:
I'll get some fine mesh for the front i think, to stop any stones flying up. I'll go all the way along that grille i think, so it doesn't look weird.
This was all a few weeks ago as i hadn't towed anything since then. The acid test was yesterday when i went to get the RX-7 from Portsmouth where it was getting its turbo rebuilt. All the way home and it didn't drop into 3rd once; problem solved!
So...that finishes this off nicely i think; E39 gearbox (or anything else really) overheating, or planning to pull a lot of weight? Plonk one of these Kenlowe oil coolers on and worry no more
Andy
Edited by papercup on Sunday 26th July 15:58
eliot said:
Interesting, I've just looked up my 540 on etk and it shows this:
If you get yourself an ediabas cable from ebay along with an old laptop with a real serial port, you can read the fault codes and display the real-time temperture of the box (and the whole car for that matter).
is yours an E39? Funnily enough, Kenlowe said that was what i would find in the way of an oil cooler (hence why i put that in the beginning of the thread; an 'oil to water heat exchanger').....but see the pictures above for what i actually found. The gearbox end of things, and the pipes coming from it, did look like that, even down to the pipes being 'over-and-under' rather than side-by-side. But the cooler side of things was that strange 'can of sardines'-looking thing, which was obviously not up to the job.If you get yourself an ediabas cable from ebay along with an old laptop with a real serial port, you can read the fault codes and display the real-time temperture of the box (and the whole car for that matter).
By the way, we did fault-code the gearbox.....and found nothing. We did it twice, though at my BMW specialist guy, not while it was doing it. We thought there'd be a fault code for 'been hot recently', but there was no codes whatsoever.
Andy
papercup said:
phumy said:
It might pay you to put some kind of "stone guard" in front of your cooler, it wouldnt be nice to get hit by a stone on the motorway to find all your oil lost and needing a new gearbox 20 miles up the road.
See above does anyone actually read this threads properly?
Looked at the pics and thought, thats going to get a stone in that is, so have you done it yet, because if you dont you know what will happen
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