Removal/cleaning of dipstick housing a MUST
Having recently undertaken this replacement on my E39, I thought I would add my experience and unequivocally recommend removal and cleaning of the dipstick even if you thought you could do this diy without removing it. This could explain why some owners do not see an improvement in oil consumption after replacing the CCV and tube if they do not do this.
My E39 has now done 158k. She is in very good condition and I am loathe to get rid of her. She is quiet, comfortable and mainly reliable. However, the excessive oil comsumption made me think it was the end of road.
Oil consumption has always been an issue, using 1L every 1000miles from halfway through the service interval. BMW said this was in spec but I think this is appauling when you have to add 6L (costing GBP70) of oil between changes. For the last couple of years though she has used 1L every 1000 miles all the time, but recently this has increased to 1L every 250 miles (local) to 500 miles (long journies). I had a compression test carried out which showed all cylinders ok at 220psi. Internet searches suggested the problem to be valve guides or CCV. I chose the lower (CCV) cost option and hoped!
I decided to replace CCC and all tubing (£120 for all parts) as BMW had to order the parts in, and I didn't want to be short of parts over a weekend or have to repeat this again at a later date for a perished tube.
I decided to leave the inlet manifold in place as my tools capacity is limited these days, and didn't want to get into something deep! This resulted in not being able to get to one of the two mounting bolts for the CCV, so I snapped the old CCV away from the hidden mounting, behind the throttle actuator. Keeping the manifold in place made the CCV extraction tricky, but with a lot of manoevering and twisting and forcing (well it was being replaced anyway) it came out of a tight gap.
Inspection of the removed CCV showed a presence of thick oil at the bottom outlet, though I wouldnt say it was blocked. However, the return pipe (from the base of the CCV to the dipstick carrier) was blocked solid. I decided I didn't have to remove the dipstick housing as the return inlet from the CCV into the housing seemed clear (by proding with a wire) and it had oil in it. But I am SO glad that I had to remove it to make the reinstall easier....
Close inspection and investigation (its a long story!) of the bottom outlet of the dipstick housing confirmed that the oil flow from the CCV into the sump does NOT flow through the big hole in the middle of the dipstick. No... Instead it flows through the tiny weeny little gap getween the dipstick outer and inner walls, which are crimped together in 2 places (See photo of the cleaned housing sump drain). Mine was blocked so solid that I initially thought it was a thick walled tube until I checked for flow through it (sorry no pre cleaning photo). Why oh why did BMW design such a narrow flow channel! I am sure this was where the initial blockage ocurred, then backed up to the tube between the CCV and sump, and then into the CCV.
Having turned the dipstick housing upside-down, I prodded and poked the tiny gaps with wire. Flat metal from an old wiper blade is recommended but I had just thown a set away. I then worked white spirit into the gap with the wire. Others recommend using carburettor cleaner but white spirit was all I had. I finally got some flow to the CCV inlet and from then on it got freer until finally it poured through. I purged and dried all the white spirit from the housing using a pump from a hand sprayer, and alternately blocked the various outlets with my thumb to ensure all the channels were free flowing.
Installing the new CCV meant that I had to break the fixing eyelet on the new one to match the shape of the bit that was left behind (see earlier). This isn't too drastic as its a snug fit and is stable with only one bolt holding it in place. Incidentally, it was much harder to manoever the new CCV into place to the gap under the manifold than it was to remove the old one, and it only slipped into place after I sprayed the CCV casing with WD40 to lubricate it past the manifold.
In summary, the CCV and plumbing blockages explains the varied symptoms of my problem:
(i) Excessive oil consumption (1L every 250-500 miles)
(ii) A slight oil leak from the crankcase gasket due to the pressure forcing oil past the gasket onto the exhaust manifold.
(iii) Oil dripping onto the exhaust manifold after one long journey
(iv) Occasional difficulty starting where, if the engine did not start immediately, I had to keep her turning over constantly for 3-5 minutes until she caught. I suspect this was due to oil in the inlet manifold and/or oil getting past the valve guides (as others have reported with blocked CCV) and filling the cylinders, affecting the plugs or fuel mix.
She hasn't used a drop of oil in 700 miles now, and has a new lease of life and I am so pleased and relieved.
Although the crankcase gasket leak was noticed and replaced by a non-BMW garage, they didn't find the cause of the problem. This was only possible by the postings on the internet. The excessive oil has worried me for several years, and resolving this it is down to all you contributors in the numerous forums.
Thanks a million.