Tech Focus: Citroën 2CV Engine

The Burton Car Company shows how to reassemble a twocylinder air-cooled Citroën engine.

Rob Hawkins concludes our feature on rebuilding Citroën’s small, light and quirky air-cooled two-cylinder engine.

In the last issue of Classics, we followed the Burton Car Company stripping down a 602cc engine. This time, we’re finding out how they reassemble the engine with new or overhauled components. The lightness, compactness and simplicity of Citroën’s commonly known 2CV engine perhaps makes it ideal to overhaul for a classic car DIYer. There are, however, a number of tools that can help save time and avoid disasters, many of which are available through the Burton Car Company in the Netherlands. And some jobs do require specialist tools, such as for assembling the crankshaft (should you need to dismantle it in the first place). In other situations, such as fitting the front and rear main oil seals, a suitable size drift is required.

Cleanliness is a top priority when it comes to assembling any engine, so make sure everything is spotlessly clean and that the workbench or area you are using for reassembly is also clean.

3 The camshaft is fitted next, ensuring that the two lines on the side of its drive gear teeth line up with a single line on the crankshaft’s drive gear, as shown here (inset). Add more engine oil for lubrication.

7 Apply a bead of sealant along the mating surface of the casing containing the crank and camshaft. Don’t add sealant inside the holes for the casings’ bolts and studs.

4 Fit the strainer plate into the engine casing half containing the crank and camshaft. Refit one of its 8mm securing bolts– the other will be fitted later when the two halves of the engine casing are put together.

6 Refit the oil outlet plug that was removed in step 21 of part one last issue (it was a 6mm Allen key plug). Fit the oil pump gear into the front of the oil pump (pictured) with lots of engine oil.

1 Reassembly of the crankshaft requires the two halves to be pressed together with new conrod bearings. The crank web in the centre is heated to help with fitting. Burton use a jig to assemble the crankshaft.

2 After fitting new front and rear bearings and the drive cog for the camshaft, fit the crankshaft into the right side engine casing with lots of engine oil (the right side also refers to the right side of the vehicle).

5 Manoeuvre a new oil pump and gasket onto the end of the camshaft, applying engine oil over the camshaft. Secure the oil pump with a couple of bolts threaded into the engine casing.

10 Refit the smaller 12mm nuts and bolts that hold the two halves of the engine casing together. There is no torque setting for them, but Burton recommends 18Nm. Refit the remaining 8mm bolt for the oil strainer plate.

14 Take the oil filter housing and fit a new O- ring, applying petroleum jelly or multi- purpose grease to it and the mating surface of the housing. Refit it onto the engine, using a new copper washer for its longer Allen key bolt and a steel washer for the shorter bolt. Tighten them to 18Nm.

12 Fit a new sump plug with a new copper washer – hand-tighten it with a 3/8in ratchet. Gently tap the face of the oil pump to help locate it. Remove the two bolts locating the oil pump – the cover needs to be fitted.

8 Carefully manoeuvre the empty engine casing half onto the one that contains the crank and camshaft and the sealant that was applied in the last step. Make sure that the conrod protrudes through the hole in the casing.

13 Fit a new O- ring with lots of petroleum jelly or multi- purpose grease into the oil pump’s cover. Fit the cover onto the oil pump and secure it with five 12mm bolts, progressively tightening them to 15Nm.

11 Check that the crankshaft can be rotated. If it cannot, dismantle the casings and check that all parts are correctly fitted and spotlessly clean.

9 Refit the four large engine casing bolts first. After fitting them, tighten them to 20Nm. For older engines with large studs, tighten the nuts to 45Nm.

19 Fit new oil seals onto the ends of the oil cooler’s pipes and apply lots of engine oil. Fit the whole assembly onto the engine and tighten the 16mm pipe nuts. Refit the top M7 mounting bolt and nut.

18 Apply grease to a pair of new front and rear main oil seals. Fit them in position on the engine, ensuring they are evenly seated. Burton have special sized tools to use as drifts and ensure they are correctly seated.

20 New pistons and barrels are supplied assembled with new piston rings, so fit each one over the corresponding conrod. Make sure an arrow on the top of the piston points to the front of the engine.

21 Apply lots of engine oil over each gudgeon pin and inside each conrod little end bearing, then slide the gudgeon pin into position. Block the adjacent hole in the engine case with a cloth before fitting the gudgeon pin’s spring clip – if it falls out and into the engine, the engine will have to be dismantled to retrieve it.

22 Make sure the spring clip for each gudgeon pin has clicked into position and is securely fitted. Next, push each barrel down the long cylinder head studs and into position against the engine casing.

15 Add a smear of engine oil to the rubber seal on a new oil filter, then fit and tighten it by hand onto the oil filter housing. Adding oil to the seal will reduce the risk of the seal catching and tearing when tightening the filter.

17 Refit the camshaft followers with lots of engine oil. Make sure they are refitted in the same positions from where they were taken during the stripdown, with the flat surfaces touching the camshaft.

16 Refit the oil pressure relief valve, adding engine oil to its piston. Use a new copper washer. Tighten the relief valve by hand using a 17mm spanner or socket – there’s no official torque setting.