On a tour thru Europe where I've on a couple of occasions only have been able to find diesel with upto 7% biodiesel additive. I dont know if that's what's responsible, but my otherwise revhappy very powerful 535d is suddenly unable to maintain cruisecontrol speed of 80 km/h with a caravan in tow so i have to force a downshift to maintain speed. Also, throttle response is very sluggish, feels like it lost 2/3 of its power though it intermittently then returns. No problems starting, no warnings, everything seems normal. Any ideas?

 

I think BMW specifically recommends against the use of bio diesel - I can only suggest you fill up with premium diesel as soon as you can to see if things improve.

 

I mentioned to my mechanic a while ago about a place in my city that was doing bio diesel, and how it was a lot cheaper then the stuff at the stations, and he'd told me he had been fixing (ie, fitting new filters and such) to a few cars recently and he told me they'd used this bio fuel..
Personally, I didn't think it was worth risking to save a few pence per fill up.
Ps, happy caravaning

 

Check your vacuum hoses. On the 535d the vacuum hoses that control the turbo are very prone to go brittle and break after a few years. They're rubber and they wrap round the hot exhaust manifold.

You need to remove the 5 allen bolts and lift off the acoustic cover. Look at the all the pipes around the exhaust manifold and turbos.

The symptoms are various loss of power scenarios depending on which hose has gone.

If it's not the hoses you need to get the fault codes read to see what they flag up.

 

Just returned and drove another 2000 km on premium diesel without bio additives but that didn't return the power. Tried to unhook battery for 10 mins to reboot electronics after I drove thru 2 tankfulls of premium fuel and also reset the gearbox with the little trick of 25 secs on full throttle with ignition on, engine off but all to no avail.

Had my sprintbooster in red mode and sport button engaged to get a semblance of normal power but had to shift manually at around 2800 rpm every time to get it moving; thank god i got steering wheel shifter paddles installed the week before as they got a workout..

The vacuum hose issue sounds very plausible as it feels like the big turbo does not engage. I've advised my mechanic to look at that first and it goes to the shop tomorrow so keeping my fingers crossed.

 

As a special loaner arrangement, I'm currently enjoying my mechanic's e46 330i coupe with aftermarket turbocharger which sound racy and feels about as powerful as my 535d - fun to drive and the 3 is definetely more nimble than the 5. Meanwhile he's busy working on my car. All the vacuum hoses were replaced as they were apparently not in good shape, but not yet faulty. Then he discovered that the wastegate on the large turbocharger is stuck in the open position. Getting to the turbo is difficult and it may not be possible to repair (bmw dealer recommends replacement) but after just 72k km (45k miles) I hope it still has life in it and just need a cleaning!

 

When I review the thread, I find that I didn't accurately describe the car's behavior earlier, but it was difficult to do so, compared to normal behavior, given I had a heavy caravan in tow. So here goes, for the benefit of those who may run into a similar problem in the future.

The car starts normally, there is no significantly different sounds eminating from the engine and there are no errors reported on the idrive. Mileage is about normal and throttle response and gearshift is also about normal until I hit 2800 revs where it becomes distinctly sluggish - the rush of power from the big turbo is missing and the fun is gone.. above 3000 rpm it accelerates like a 1971 morris minor going uphill in top gear and it tops at 3400 rpm. The gearbox doesn't know how to deal with the absense of engine power and keeps waiting for the turbo to kick in; resultantly it does not downshift but stays in the same gear and I have to manually force it to a higher gear to drop revs and resume a reasonable accelaration. As I've now driven with it for a few days I know it is the engine power (turbo) that's the problem but one could be forgiven for thinking that there was a problem with the gearbox and as mentioned earlier, I have done the 25-sec gearbox reset trick which obviously had no effect on the current problem.

 

13 days in the shop. Had the large turbo renovated; that is to say, the waste gate was stuck so had it scraped out/cleaned. All the vacuum hoses were replaced as a precaution. It then went on to BMW for testing/calibration, and they had a waiting list, hence the long time. They changed a valve and some pushrod I understand and there were a couple of solenoids (magnetic switches) replaced as well. With a lot of bargaining it ended up costing me 12k DKK (usd 2,150), which included a cleaning of the diesel particulate filter. Pricy, but it could have been a whole lot worse.

Going forth, I'll be looking into additives to help keep the engine clean. I'm really worried that it was the combination of towing a heavy caravan where the engine had to work hard, but never really got to stretch out - coupled with a couple of tankfulls of fuel with upto 7% biodiesel. I hope using non bio-diesel fuel and a cleaning additive will still allow me to tow a caravan in the future and I wonder whether anyone else have had problems with the car sooting up when towing a caravan?

In any event, the car is now back in action and it drives better than ever before. It is lightning quick, and the fuel economy is stunning. I ran a good 100 km on an expressway after leaving the mechanic, as he wanted me to ensure the self cleaning got started as well, following his mechanical cleaning with a cleansing liquid. I put the cruise at 110 km/h which I managed almost uninterrupted, save for a couple of U-turns heading back and forth the same stretch of highway. I got an AMAZING 17.8 km/l which bests anything I've ever done before and certainly the averages I saw as late as a month ago where my mixed driving really had fallen to around 12.2 km/l so despite the trouble and the money, I'm again madly in love with my E61.

 

Very interesting, thanks for sharing.

Which cleaning additive did your mechanic recommend?

 

Bell Add. there are 2 relevant products

cleaning of the engine as a special event - this is for the turbo performance: http://www.belladd.dk/eng/home.asp?S...&ContentID=139

additive for regular cleaning and improved fuel economy: http://www.belladd.dk/eng/home.asp?D...&ContentID=373

I'm thinking of going for the additive now, and at least use it when I haul my caravan

found it online at http://www.landberg.dk/shop/bell-add-diesel-473p.html (danish only, I'm afraid) where 2 liter costs dkk 575 incl shiping in Denmark. That's about usd 100 and it covers 2000 L diesel, so putting in about 65L when filling up from almost empty, that's close to 31 tankfulls, and works out to a little over dkk 18, or usd 3 per tankful. If it works, it will be worth it.