On a 2cv, Dyane, Ami etc, the usual reason for replacing any part of the exhaust is corrosion. However, that is not the only reason.
The ‘crossbox’ silencer, (under the gearbox), often urgently needs attention due to fracturing of the outlet pipe flange, leaving the remaining 3 sections of the exhaust detached, dramatically increasing the noise level and potentially allowing exhaust fumes into the car.
Not many people will carry a spare £80 crossbox in their car, so how easy would it be to find one in a hurry? In the whole of the UK, there are probably only 2 parts suppliers who normally keep them in stock, (plus maybe some of the 2cv repair specialists). If you’re in mainland Europe in a right-hand drive car, you are even less likely to find a right-hand drive crossbox.
The alternative: RetroSpec Parts have produced a repair kit for about 1/8 of the cost of a new crossbox. The kit comprises of a flanged sleeve and a clamp. You will need the hacksaw in your in-car toolkit to remove any remaining parts of the broken flange and then you can slide the new flanged sleeve down over the remaining lower part of the outlet pipe and either clamp it or weld it in place. (See fitting instructions for more details).
Our flanged sleeve is of thicker metal than the original exhaust, so can be considered a permanent repair. You can buy our flange repair kit here
Why does the crossbox fracture at the outlet pipe flange?
There are a few reasons that this happens:
- Alignment is very important on the 2cv exhaust system. If the whole system has not been assembled with every part properly aligned, it can put a strain on the joints and mountings. The flanged joint between the crossbox and the swan-neck intermediate pipe is the weakest point and it is also potentially under the most strain.
- If this joint is not perfect aligned and a solid cast type of clamp is used to pull the misaligned parts together, this can bend the flange towards to close the gap. Even slight bending of this weakest part can lead to it fracturing. The much cheaper standard (Citroen type but wider) 47mm clamps work perfectly well with good alignment and are more forgiving than the solid cast ones where alignment is slightly out, as they will flex, rather than forcing the exhaust flange to flex.
- If a short tailpipe has been fitted without the appropriate AK/AZU/Mehari bracket that restricts the sideways movement of the torpedo silencer, the flanged joint will be under even greater strain.
Fitting a 2cv Exhaust Crossbox Outlet Repair Sleeve
Fitting variations:
We have checked numerous crossboxes from various manufacturers; standard and stainless steel versions. The diameter of the tube below the bell-mouth flange varies slightly. Also, the position of the reinforcing bracket that bridges the outlet and left-hand inlet pipes varies. We have produced our repair sleeve to fit all of the crossboxes that we have checked but the variations do mean that it may be necessary to make some changes to the sleeve before fitting.
If you are including a repair sleeve with your emergency spare parts in the car, we recommend that you make these changes first:
- Depending on the position of the reinforcing bracket that bridges the outlet and left-hand inlet pipes on your crossbox, you may need to shorten the lower end of your repair sleeve, to allow it to slide down far enough to allow the flange to be at the required height.
- Cut two slots up from the lower end of your repair sleeve, so that the supplied 36mm clamp can squeeze the pipe together around the outlet pipe of the crossbox. (Not usually necessary if repair sleeve is to be welded in place).
Fitting instructions:
- Use hacksaw to remove any remaining parts of broken flange from crossbox outlet pipe.
- Clean surface of remaining outlet pipe and test fit of repair sleeve and adapt (as above) if necessary.
- If not welding in place, smear surface areas with appropriate sealant and fit new sleeve onto outlet pipe (ensuring that the flange is at the correct height) and secure with supplied 36mm clamp.
- Check/adjust alignment of other exhaust components, check condition of all mountings and, if a short tailpipe fitted, check for existence of appropriate movement-restriction bracket, (see reasons for fracture, above).
- Re-fit swan-neck pipe to new sleeve on crossbox, with appropriate 47mm clamp, (see reasons for fracture, above), and check for leaks.