Refurbished 2CV engine breather

After finding out that my engine breather didn’t need replacing it was worth refurbishing it as it had got a bit tatty over the years, the surface treatment having worn off and rust had developed under a layer of grime.

2CV engine breather/ oil filler

2CV engine breather/ oil filler

After a thorough clean up, first with degreaser and then abrasives a treatment with rust remedy had it ready for a protective coat of paint.

The choice of paint was a tricky one, originally it was a coppery gold colour but redoing it in that colour would have looked a bit too gaudy in a 30 year old engine bay so I ended up mixing copper and silver Hammerite to achieve a colour I was happy with.

Painting a 2CV engine breather/ oil filler

There’s an oil return from the breather to the crank case at the bottom of the breather, this is connected to the dip stick tube via a short length of 8mm ID rubber hose.  As the original hose was by now very stiff a trip to the local Piriteck secured some new hose.

8mm ID hose for a 2CV engine breather oil return

The new hose isn’t as thick as the old hose but it’s reinforced and rated for oil so should be good.

8mm ID hose for a 2CV engine breather oil return - original and new

Cut to the same length as the old one it was 42mm.

2CV engine breather oil return hose

The studs fit in the block with a bit of thread lock for good measure – as shown more clearly during this crank case build up.

2CV engine breather/ oil filler mounting studs

Whilst the breather is easier to fit onto the studs than using bolts, it does make fitting the return hose onto the dipstick connection a bit tricky.  However, after some finagling it all went back together and was secured with the 11mm nuts and washers supplied in the stud conversion kit.

V series mounting studs

The 652cc V series engine had a few changes from the M series engine it was based on.  One of these was stud mounts for the fuel pump and the engine breather/ oil filler rather than the bolts used on the M series.

As the stud mounts make it easier to fit the relevant accessories the SPOG produce stud conversions for the M series engines that replicate those found on the V series – as shown below from the Haynes Manual for the Visa.

2CV crank case build up

After removing everything from the crank case I cleaned it up with industrial strength degreaser and a pressure wash.

The dipstick guide had a bit of surface rust so that was cleaned up and painted with a couple of coats of black Hammerite.

The oil filler/ breather normally attaches with a pair of bolts but the V series engine had more practical studsSPOG sell a pair of studs for the A series engine which are easily fitted (with a bit of thread lock for good measure).

2CV engine breather studs prior to fitting

The longer stud with the thicker band goes on the off side as there is an alternator mounting plate on that side in addition to the breather.

2CV enginer breather studs in-situ

A new low oil pressure sender was fitted, complete with washer.

2CV low oil pressure sender fitting

This one needed a 22mm spanner.

2CV low oil pressure sender fitting with 22mm spanner

The oil pressure relief valve piston was liberally coated with fresh oil and inserted.

2Cv oil pressure relief plunger being inserted

When fully home the only the nose stands proud of the housing.

2CV oil pressure relief valve plunger in situ

The spring sits over the nose of the piston and, as I didn’t have a new copper washer, I annealed the old one by heating it until it was red hot and then letting it cool slowly.

2CV oil pressure relief valve fitting

The bolt is a 17mm and I don’t have a tightening torque for this so  I went with a good strong tweak with the breaker bar which should be enough to crush the washer slightly.

2CV oil pressure relief valve fitting

Another SPOG item is the 3/4″ thread oil filter spigot.  A bit of thread lock and this was firmly screwed into the oil filter mounting plate.

2CV oil filter adaptor prior to fitting

With a new o-ring and some sillyfoam sealant the mounting plate was re-attached to the crank case with the two alan bolts.

2CV oil filter adapter in situ

One of the advantages of the much more common 3/4″ thread is that a sandwich plate can be mounted.  In this case I’ve got oil temperature and pressure senders – important information to have available for an air/oil cooled engine.

Sandwich plate with oil pressure and temperature senders on a 2CV crank case

As I’m planning to fit an electric fuel pump I’ve got a stainless steel blanking plate for the standard, mechanical, fuel pump mounting point.  This is important as, without the actuator rod, omitting the fuel pump would leave a hole in the crank case.

2CV fuel pump mount with silicone sealent

After applying a generous amount of high temperature sillyfoam sealant the blanking plate was secured with stainless steel M7 nuts.

2CV fuel pump blanking plate

Testing 2CV crank case vacuum with a manometer

The 2CV’s two cylinder boxer engine configuration means the crank case volume changes with each revolution of the crank, reducing as the two pistons come towards each other on the inlet/power stroke and away from each other on the exhaust/compression stroke.

If the crank case was a sealed system this change in volume would cause resistance to the running of the engine.  To prevent this the crank case has a breather that vents through the oil filler and out to the air box.

The breather is fitted with one-way valves that allow the air out of the crank case but not back in thus maintaining a negative pressure.  This negative pressure has the advantage that the oil has a tendency to be drawn back into the engine rather than leak out.

2CV egine breather schematic

To ensure these one-way valves are functioning the crank case vacuum should be tested with a manometer – the pressure differential here is quite low (~0.1 psi) so a normal vacuum gauge typically won’t be sensitive enough to show a reading.  Per the Citroën workshop manual, this vacuum should not drop below 5cm even at high revs.  (At high revs there is less time for the air to be pushed out of the crank case as the pistons move towards each other before they move out again.)

There are various options for a manometer – from the simplest being a loop of tubing up to one made to the same specifications as the original Citroën workshop tool (MR. 630-56/9a) that is available from Burton.  I went with a generic plumber’s manometer from an on-line retailer.

I also added a liquid trap to the engine side of the manometer to prevent water being sucked into the crank case but another option is to use LHM fluid as this won’t contaminate the oil if it does get into the engine.

Manometer used to test 2CV crankcase vacuum

(The water level doesn’t show up too well in these photos so I’ve highlighted it, a bit of dye would mean the level is more obvious but, when you’re actually stood in front of it, seeing the water level isn’t a problem.)

With one end of the manometer open to the atmosphere the other is connected to the inside of the crank case via the dipstick opening.  The 6mm (inside diameter) PVC tubing I’m using wasn’t large enough to seal so some insulating tape wrapped round the end did the job.

2CV manometer dipstick end 'gasket'

Make sure the engine is nicely warmed up then take out the dipstick and connect the manometer to the crank case via the dipstick tube.

Manometer inserted into 2CV crankcase via dipstick aperture

With the engine idling, gently rev it a couple of times to stabilise the fluid level in the manometer.  We’re now ready to take a reading.

At idle, the water level on the engine side should be at least 5cm higher than the side open to the atmosphere – indicating the pressure in the crank case is lower.

Keeping an eye on the water levels, rev the engine all the way up to full throttle – we’re expecting the water level to fall but it should never get low enough to be level with the side open to the atmosphere.

A vacuum of less than 5cm at idle or dropping to zero at high revs indicates that the one-way valve in the breather has failed and needs to be replaced.

Manometer in 2CV engine showing vacuum

I was pleasantly surprised to see that Judith was showing a vacuum of over 30cm , especially as the breather hasn’t been replaced recently – if ever.

Replaced engine breather exhaust tube

The engine breather exhaust tube runs from the oil filler to the air filter.  Given it’s a rubber hose running near the exhaust manifold it’s hardly surprising it had started to perish after nearly 30 years.

A trip to a local Pirtek and for a few quid they supplied me with some 19mm ID hose that fits perfectly when trimmed to length.

2CV oil breather exhause pipe

Being pressure hose this is thicker walled than the standard hose (which doesn’t have to handle any pressure) but I think works better when fitted.