2cv engine breather – Colonel Sponsz's Shared Items

Refurbished 2CV engine breather

25th February 2017 15:49

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.

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.

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.

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

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

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.

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

14:21

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

16th December 2016 13:07

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 studs. SPOG sell a pair of studs for the A series engine which are easily fitted (with a bit of thread lock for good measure).

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.

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

This one needed a 22mm spanner.

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

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

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.

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.

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.

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

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.

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.

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

Testing 2CV crank case vacuum with a manometer

28th August 2016 13:25

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.

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.

(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.

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.

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.

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

27th February 2016 20:22

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.

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.