Specialist tool

I was doing a bit of tidying up work on the fuel tank which involves inserting some bolts vertically upwards.  The problem with this – as I learned before – is that, under the influence of gravity, they will drop back into the socket which doesn’t leave enough thread protruding to bite into the nut.

Following the principle of the sump plug socket I put a slice of fuel hose into an 11mm socket.

11mm socket with fuel hose in it

The bolt now sits on top of the fuel hose with the full amount of thread available.

11m socket with fuel hose in it holding up a bolt

Citroën Instrument for checking crankcase vacuum MR. 630-59/9a

The 2CV workshop manuals provide “manufacturing drawings for tools not on sale”.  One of these is the manometer used to measure the crankcase vacuum.

Citroen MR 630-59/9a

Usage Instructions

Usage instructions are quite simple:

Citroen MR 630-59/9a use

  1. To check the vacuum in the crank case, use a water manometer RM. 630-56/9a/

    One of the ends will be connected to the rubber guide tube for the oil level dipstick.

  2. While engine is idling, accelerate slightly to stabilize the manometer levels.

    The liquid should climb in the section of the manometer connected to the engine.

    Read the difference in levels :

    It should be :

    – with engine idling : 5cm (1.96 in) of water min.

    Otherwise, the breather must be replaced.

    The vacuum should never fall to zero, no matter the engine speed.

Image credits

The images are taken from the Citroën Repair Manual No. MAN 8161, Volume 1, October 1983.

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.

Setting a 2CV’s ignition timing

Setting the ignition timing on a 2CV is a routine service item, forming part of the D (anual) service.  It will also need doing if the points are replaced or adjusted.

Setting the timing requires the use of a specialist tool – in this case a 6mm rod.  I inherited a bent nail which does the job admirably.

Nail used as 2CV timing rod

This fits through a hole in the engine block on the near side under the inlet manifold.

2CV timing rod in crankcase

The bend in the tool is required as the dipstick tube blocks straight access to the hole.  The tool will come out through the hole and present to the face of the flywheel.

2CV timing point on flywheel

Rotating the engine will turn the flywheel until a hole in the body of the wheel will align with the tool.  Use the tool to lock the flywheel at the timing point and paint some alignment marks on the flywheel and a static part of the engine.  When painting the line don’t forget to take account of parallax.

Now remove the tool – this is important as you will need to rotate the engine to set the timing.

If you haven’t done so already, remove the fan to gain access to the points box.  You won’t need to open it for this job.

2CV points box in-situ

Slacken off the nuts either side of the box and free the box, it might well need a bit of encouragement but be careful you don’t damage the cover behind the points box – it’s relatively thin metal.

With the points box free to rotate connect a test lamp between the positive coil terminal (without fully disconnecting the connector and breaking the circuit) and earth.

Ignition timing light on a 2CV

It really helps if you can position the indicator lamp where it is visible both whilst you are working on the points box and from above when looking at the flywheel timing mark.

With the flywheel set at the timing mark the light should just come on.  Turn the points box back and forth to find the point where the light is coming on and off.  With the light just on move to the flywheel and use a large flat head screwdriver to move the flywheel back and forth slightly through the timing point ensuring the light turns on and off exactly at the mark.  This should allow you to make the last adjustments to the points box to get the timing as accurate as possible.

Start tightening the points box – taking care not to disturb the position – and rotate the engine to check that the light is still coming on at the timing mark each revolution. Fully secure the points box and make a final check to ensure the timing is still correct.

Removing a stuck 2CV fan

As the cooling fan on a 2CV is a friction fit on the taper it can get stuck and be hard to remove.  When we first serviced Judith the fan was stuck and we didn’t get round to removing it.

Originally the 14mm fan retaining bolt was on FT.  As it’s inside the starter dogs a narrow socket is required to access it so, with a screwdriver lodged into the flywheel and the application of a breaker bar, we managed to remove it.  However, the fan remained stuck on the taper.

With a higher priority job needing doing it took me a while to get round to looking at this.  However, it needed removing to access the points box and re-time the ignition.  With the fan retaining bolt removed and over the course of a few evenings I applied WD-40 into the centre of the shaft in the hope some would penetrate.  I also turned the fan each time to help gravity distribute the WD-40 to as much of the joint as possible.

To break the taper a specialist tool is required – in this case a large bolt that fits into the centre of the fan (other lumps of metal are available).  This can then be struck with a suitable percussive tool (mallet) to free the taper.

Specialist tools in use removing a 2CV fan

Strike the tool sideways or upwards – i.e. not downwards – to try and avoid disturbing the points.  Of course, if it’s really stuck and you’re going to be re-setting the points anyway then have at it in all directions!

The WD-40 really did work, after repeated attempts at dislodging the fan before it now came free after only a few good hits this time and there was clear evidence that the liquid had penetrated the join.

With the taper freed the fan will be loose and can be withdrawn whilst unhooking the alternator belt from the pulley that is the rear of the fan.

Removing a 2CV fan

The fan itself is made up of two parts: the metal backing plate that has the pulley and the starting handle dogs, and the plastic fan with blades.  They are held together by three 8mm bolts and three 10mm bolts.

2CV fan parts

When re-assembling the fan put all the bolts in half way then tighten the 8mm bolts followed by the 10mm.

2CV Suspension knife edges

Tonight I made up a pot of suspension knife edge grease. The knife edges are the triangular pivots that form the connecting joint between the suspension arms and the push rods that enter the horizontal interconnected spring arrangement.

It’s designed as a dry joint but as it carries a lot of load it’s recommended to grease it to prevent rust. The trick is to mix grease with engine oil so it penetrates better. Turns out you need quite a bit more oil than I anticipated (about 1:1 oil and grease) so I’ve now got a supply that should last some time.

Applying the grease mixture is pretty straight forward – get under the car and use a paint brush to liberally apply the mixture to the the knife edges.

2CV off side front knife edge

2CV sump plug socket

Got round to sorting out all my automotive tools into a single toolbox and got some rails for the sockets, it’s nice to know that the 11mm socket is to be found between the 10mm and the 12mm rather than hunting through a collection.

I’ve also got a cut down wine cork installed in the 21mm socket for dealing with the sump plug. The only 21mm socket I could find in York was an impact socket which actually works out perfectly as it is hexagonal so will grip the flats rather than the corners meaning it will be much less likely to round.

2CV sump plug socket

The purpose of the cork is to stop the sump plug disappearing into the socket as it will sit on the cork making it much easier to re-fit.

Sump plug socket with sump plug

The gearbox sump and filling/level plugs are also 21mm so this is good for them as well.