Timm's BMW E63 and E64 N62 Vacuum Pump - Fixing Oil Leaks
As a general rule I’m not too worried by a small oil-leak, after owning seven M62 V8’s you get used to the slight weeps
around the valve covers. The problem with the leak from the vacuum pump on my 650i is that the oil blows back onto the
exhaust manifold - and that stinks. These pumps are a problem on many models of BMW - the leak comes mainly from the
front o-ring which is under the machined front cover. The cover is thin and only has five fixings, a tiny loss of elasticity of
the o-ring and the small bow of the cover between fixings is enough to let the oil out.
As there is very little manifold vacuum, when the throttle is given a good poke the crankcase pressure cannot be relieved
by the feeble vacuum pump. The positive pressure is too much for the thin face plate on the pump and out comes the oil -
it gets blown backwards and onto the exhaust. It is easy to think that you have fixed this oil-leak as during normal driving it
doesn’t leak, but after a good thrashing it can start spewing oil out again.
There are a few routines around on various BMW models for replacement of the o-rings and I looked at quite a few before I
started this job, but using the standard method there is a possibility of breaking the lugs on the pump and other ghastly
hassles that you don’t need. I decided to do the job in an unusual order so that there is no possibility of damaging the
pump - but I’ll explain this as we go along. Firstly, here’s the pump with the front cover off:
The rotor seen above is driven by one of the camshafts via a hinged flat-bladed coupling which forms a universal joint. It
drives the flat bar seen above that forms a seal to the sides, top and bottom of the pump cavity and as this rotates the
displacement-change pulls air from the top connection which leads to the brake booster. The air is pushed into the crankcase
and is evacuated by the crankcase ventilation system.
Anyway, enough blurb, let’s get the blighter off and start fiddling with it - the pump has to come off to replace the rear o-
ring, although this one usually doesn’t leak we might as well change it while we’re here. On the E63/64 there is a strange
bracket that does little more than support the power-steering hose that leads to the cannister. The bracket has a separate
part that supports the hose which is secured with a 10mm nut - so break out the ratchet and a 10mm socket to separate the
two parts - then lift the pipe out of the way.
The rest of the bracket is held in place using the same three long male Torx bolts that hold the pump in place and these
come off next - try not to let the pump pop out of the timing case before you are ready, it is reasonably heavy and fragile.
The remaining connection is the vacuum pipe to the brake booster which is held by a one-use hose clamp.
A grown-up thing to do would be to cut off the clamp and then replace it later, but I don’t have a clamp of that size
around so I decided to leave it connected. So, I got a cloth ready and pulled the pump from the cover, it popped out easily
with a few drops of oil. Below can be seen the flat blade that couples to the camshaft - as the pump popped off the o-ring
immediately fell off - we will use grease to keep the new one in place when we refit the pump.
Turn the pump over, protecting the back using a soft cloth. The cover is held on by five special Torx fixings and are
reasonably tight so use a decent bit. The pump contains a small amount of oil for lubrication and it is best at this stage to
pour it out as we need to refit the pump with the cover removed. When replacing the o-ring give it a good greasing and also
give the cover a bit of a greasing on the mating face.
We are now going to refit the pump to the engine before we refit the front cover. The reason for this is to ensure that the
flat coupling mates with the slot in the camshaft properly - the failure to do this causes the lugs of the pump to snap off
and may damage the coupling. I have seen loads of pumps damaged in this way so I was happier to play it safe.
You will find that as the pump is pushed back into the timing case, the rotor (seen below inside the pump) will move
outwards - so turn the rotor as the pump is pushed in so that the blade coupling mates with the slot in the camshaft and
the pump can be pushed in fully with the rotor flush with the face of the pump. Temporarily refit one of the long male
Torx fittings so that the pump is held in place while the front cover is fitted.
At this point it should just be a case of refitting the cover bolts and everything will be air-tight and lovely - but it wasn’t,
it weeped oil and that’s a bit disappointing. The problem is that the cover is thin, the o-ring compression is minimal and
when the pump heats up (and it gets very hot) there is enough bow between the five fixings to allow oil to escape when
the crankcase pressure increases.
This is the reason that many of the on-line routines recommend using a silicone sealant such as Hylomar. I hate using
sealants, they really shouldn’t have a use here, but I can see the reasoning. But first, before I break out the sealant I’m
going to try a couple of things - first I’m swapping out the tiddly Torx screws for manly Allen bolts
On they go:
That certainly looked like it would do the job, and it almost did - after an exceptionally good blast there was a tiny weep -
so time to go a bit further:
All done, Time for a Cup Of Tea
Update 2018 - 1 year later: All good, dry as a bone!
It’s been a couple of weeks now, including a good thrashing most days, and there is no sign of a leak - it would probably
have been easier to use some sealant, but I’m happier without it!
I usually use a tub of Duckhams Keenol for greasing o-rings so they stay put - but a quick search reveals that this is classed
as a ‘vintage grease’ on Ebay, anyway something thick and gloopy will do nicely. The pictures below show the o-ring groove
and then the new o-ring greased into place so that it doesn’t immediately drop off again.
And that fixed it nicely, the washers spread the load further across the cover, enough to compress the o-ring sufficiently
to form an effective seal. The extra washers can only be fitted on the fixings that are not covered by the bracket as this
gets in the way - so I have two M6 x 10mm fixings under the bracket and three M6 x 15 with the washers.
So, back on with the bracket making sure the pump is not pulled away from the timing cover - you have to ensure the
pump blade stays coupled to the camshaft, and then refit the power steering pipe back to the bracket with the 10mm
nut. All of the fixings need little more than a good nipping up.
