cracked exhaust

[Croc]

Yesterday on a nice long run I developed a 4.5 inch crack in the exhaust at the weld where the 4 merge to 1. I have a standard Caterham SV rear exit exhaust. At the same time the muffler started giving off rattle sounds - like something is rattling around inside. I checked and the exhaust is still seems securely mounted so it is not rattling around on the mounts or hitting anything. It also does not seem to be the shielding hitting the muffler.

 

I have looked at old past posts and the crack looks to be a common problem - the consensus seems to be just weld the crack up. However for the rattling, is it possible that a metal baffle inside the muffler has come loose or are these mufflers just packed with steel wool and the rattle is coming from somewhere else?

[Taber10]

Yes, after less than a year, and around 1200 miles, my exhaust cracked in the same place. I took it to a nearby local welding shop, and got some interesting stories, "...I used to race my Corvette against these things in the '60s....." and a $20 weld, that has held up since with no problems. I can't remember the rattle sound, but I don't think anything else was loose.

[athens7]

One possibility is the heat shield; it is attached to the muffler/cat by several straps. The welds on the heat shield strap retainers are small and will break easily. I had mine re-welded when I had the 4-1 crack fixed, and have had no problems since. I also highly recommend getting a front exhaust mount from Ben at Caterham USA. it mounts to the frame and the flange at the collector, providing much needed support to a very long exhaust assembly. Lastly, check the exhaust mount rubber bobbins at the rear- they are shite quality and fail frequently. My fix for these was a combination of shock absorber bushings and circle cut pieces of old Z rated tire side walls with a bolt, 2 fender washers, and a nut.

[Croc]

I checked the heat shield and it is tight - none of the fastenings are loose or broken - so no rattling from there. Rear mounts are solid - so not there.

 

I really like the idea of a front mount and was considering making something like that - I had no idea it was a Caterham part. I will give them a call today.

 

I am not surprised the weld gave way given NJ has the worst roads in the US. The vibrations are a killer.

[athens7]

Actually, I don't think it is a Caterham part. It's an assembly I got from Ben Wofford when he was with Rocky Mountain Sports Cars. I have had no further issues with the exhaust cracking since it was installed, and I think a recurrence of the weld failure is almost inevitable without some type of support due to the length of the unsupported section of exhaust and the vibration it undergoes.