Since I bought the car, I had noticed a faint smell of exhaust fumes when the heater blowers were on and the car was stationary, at the lights etc. It gradually got worse until a couple of weeks ago I decided it had to be put right.
After going under the bonnet for a separate reason, instantly from start up fumes appeared in the engine bay, originating from under the air filter intake ducting / near the front right suspension top mount, shown in the picture below.
If the heater fans were on in the cabin, diesel could be smelt almost instantly. When driving along no fumes could be smelt even with the fans on, or so little fumes were getting in that it couldn't be distinguished. When sat at traffic lights or a junction, fumes once again started entering the cabin. Neither distance travelled nor engine temperature seemed to make any difference to the problem.
As the car is my daily commuter, I had to find some temporary fix whilst I found a more permanent one.
I found an extremely crude fix, which saves the unpleasant smell and headaches. Press the recirculate button until the green light is on to the top right of the button, as shown below.
Do this just before you get to the lights or junction to avoid circulating the diesel fumes. Also don't leave it on this setting as the windows start to steam up, or at least they do in my car.
I did some searching on the net and this was the list I drew up as a conclusion.
- Most likely - Flexi-pipe on the exhaust primary cat split - lower section of part 1 on this diagram
- Split or cracked exhaust manifold - part 1 on this diagram
- Badly sealing exhaust primary cat
- EGR pipe split - part 1 on this diagram
- Inlet manifold split (some doubt whether this would cause these symptoms)
Upon inspecting my car, it turned out that my flexi section on the primary cat was indeed blowing. It was pretty evident, as you can see in these photos.
I ordered a new section from Ecotune for £160, a darn sight cheaper than the £800 BMW quoted me for a replacement. This new one is stainless steel with a lifetime guarantee and a 2 year guarantee on the flexi section.
It turned out to be a real pain in the backside getting the old cat off, there just isn't enough room for manoeuvre in and around the turbo. In the end I had to get the whole exhaust assembly off to fit the new pipe. It was a bit of a faff getting it back on as well. At least it didn't have a lambda sensor in though, all pre 2003 models weren't fitted with one. The sensor could have made things very interesting. Here's a shot of the old primary cat with no sensor, if it had one it would be sticking out somewhere in the middle of this shot.
Anyway, after 5 hours under the car it was all back together and running sweetly. No fumes could be detected whilst stationary with the fans on.