REPLACING A 2CV EXHAUST SYSTEM
The exhaust system on a 2CV or Dyane consists of four parts - primary silencer beneath the gearbox (sometimes referred to as the cross box), front pipe (swan neck), secondary silencer (torpedo) and tailpipe (of which there are at least three types - (1) the short 'van' type, (2) a full length pipe which exits below the rear bumper and (3) [much rarer] a full length pipe which exits behind the rear wheel). No special tools are needed to change any of the components. As it is so easy to remove the near side front wing of a 2CV you may find this is worthwhile as it means that access to the joint between the primary silencer and the front pipe is considerably improved. As well as the defective part of the exhaust, you will need to purchase the appropriate new clamps.
SECTION 1 - CHANGING THE PRIMARY SILENCER
First remove the clamp which holds the front pipe on to the outlet from the primary silencer. Note that this clamp is slightly smaller than the four similar clamps at either end of the heat exchangers. Now loosen the 11mm bolts which hold the hooks on the top of the primary silencer to the side of the gearbox. Finally remove the clamps which hold the primary silencer to the rear end of each heat exchanger. The primary silencer can now be slid off the gearbox bolts and lowered to the ground. If your car still has the original Citroen chassis you will have to jack up the front of the car in order to remove the silencer from underneath but this may not be necessary if you have a replacement chassis, it depends on its design. Put the new silencer in its place by reversing that procedure, then, if the car is jacked up, lower the car.
It is almost certain that you will need to remove the front heat exchanger clamps in order to get the correct alignment when fitting the new silencer. Clean both ends of the heat exchanger pipes and the end of the front pipe with a wire brush before commencing re-assembly. Make sure all old exhaust paste is scraped off. The joints must be in good condition if a gas proof joint is to be obtained. If there are any defects in the pipes which run through the heat exchangers there is a danger of exhaust fumes entering the car, in which case you should consider replacing the heat exchanger units.
The secret of getting all the joints gas tight is to line them up squarely and as close together as possible before tightening the clamps. When all the pipes are clean, smear the joint faces with exhaust paste. Also run exhaust paste into the grooves of the new clamps and as you fit them, revolve them round the joint to distribute the paste. Connect the front ends of the heat exchangers to the exhaust manifold, leaving them just loose enough that they can be moved. Now offer the new primary silencer up to the rear of the heat exchangers and locate the hooks on the bolts in the gearbox. Take up the gap between the gearbox and the hooks with washers. This will prevent the hooks from being bent when you tighten the bolts which could in turn cause damage to the threads in the gearbox. Do not tighten these bolts yet. As well as the spacer washers, there must be a washer between the head of the bolt and the hook on the silencer. Make sure that the clutch cable is correctly run through the bracket provided for it on the top of the silencer. Now clamp the silencer to the rear ends of the heat exchangers, moving the joints at the front as necessary, so that all four joints are a snug fit and there are no visible gaps. Hold the silencer in this position and tighten the clamps. Getting all four joints to line up perfectly is likely to be a compromise and you may need to lever the silencer forwards (e.g. with a broom handle on the ground levering on the back of the silencer) before tightening the clamps. If you wish, at this stage you can start the motor and check for leaks on the four new joints but bear in mind that the exhaust will soon get hot and noise from the outlet of the silencer will be quite loud! If there is a leak, you will have to loosen some or all of the clamps and try again. Although the joints must be leak proof, over tightening of the clamps will make matters worse rather than better as the clamps will distort. When youíre satisfied, you can tighten the bolts on the gearbox. Finally, if you are not renewing any of the other parts of the exhaust, use a new clamp and exhaust paste to secure the front pipe to the primary silencer and then check that joint for leaks.
SECTION 2 - CHANGING ALL OR SOME OF THE FRONT PIPE, SECONDARY SILENCER AND TAILPIPE
In writing this part of the article it is assumed that at the very least you will be replacing the secondary silencer as that is the bit that usually goes first. Although it doesnít always rust through, the baffles work loose and rattle. It is highly likely that the front pipe and tailpipe are corroded into the silencer and they will be difficult to separate whilst still on the car. So it is suggested that you remove all three sections as one unit.
Remove the clamp holding the front pipe to the primary silencer (if not already removed). Put blocks under the secondary silencer. If you have a full length tailpipe, disconnect the two rubber straps from the chassis. Inside the car, under the rubber mats, you will see two pairs of 11mm bolts which hold the secondary silencerís rubber rings to the underside of the floor. Remove all four bolts. Note that the two brackets are not the same, the rear one being in two pieces. All three sections of the exhaust can now be removed from the car.
You can now try to separate the sections if any of them are worth using again. A hammer and chisel will probably be required, ensuring that you only damage the parts which are already useless.
Now separate the rubber rings from the silencer by unscrewing the 8mm screws at each end of the silencer, lifting out the clip and sliding the rings off the ends of the silencer. If the rings and clips are serviceable, fit them to the new silencer. Otherwise, buy new ones, as neither are supplied with new silencers. You can now hang the secondary silencer to the underside of the floor with the 11mm bolts. Ensure that the rings hang vertically.
Now fit the front pipe. If you are using the old one, clean up both ends with a wire brush. First, loosely fit the pipe into the front of the secondary silencer. The old ĎUí clamp will probably be OK to use again provided the nuts run on its thread easily. Use copper grease to help with this. Before tightening the ĎUí clamp, fit the front pipe to the primary silencer with exhaust paste and a new clamp as in Section 1. Make sure that the rubber rings at each end of the secondary silencer are still hanging vertically - adjust by altering how far the front pipe enters the secondary silencer. Now tighten the ĎUí clamp and the clamp at the primary silencer. You can now start the engine and check for leaks at the two joints you have just made.
When satisfied you can fit the tailpipe. For a short van type tailpipe you have only to transfer the ĎUí clamp from the old system and clamp the pipe to the secondary silencer (see footnote). If youíre fitting a new full length tailpipe you will have to loosen the clamps with the rubber straps still attached, slide them off the old pipe and on to the new one. The shortest strap is the rear one. If you are reusing the old pipe it should go straight on but you may need to loosen the strap clamps and slide them to the correct position. Before tightening the ĎUí bolt or the straps make sure that the tailpipe is routed well out of the way of moving parts such as the rear axle arm and that it canít hit bodywork or chassis. Twist it where it joins the secondary silencer to adjust. Start the engine again and check for leaks between the secondary silencer and tailpipe. It isnít usually necessary to use exhaust paste on the secondary silencer joints.
Footnote: Suppliers of van tailpipes usually warn that using these pipes on a saloon will cause other components of the exhaust system to fracture prematurely. We understand that, when they were fitted to vans, an additional inverted ĎUí shaped piece of metal was secured between the top of the rear rubber ring and the mounting bracket (see photograph) and this stopped some of the lateral movement of the back of the secondary silencer. All we can say is that we know of two cars fitted with this device and neither has suffered from premature fractures of other components. And itís fairly easy to make up such a bracket for yourself.
THE WESSEX DUCKS
THE WESSEX DUCKS