Leaking V Band Clamp

Separate the flanges and see what's going on between them. The flanges are precision ground assemblies and seems odd that they would leak.

The outer clamp could be broken somewhere and allowed the flanges to warp possibly but either way a full disassembly would be required and everything examined to find the problem.

V-bands are all I use when I build exhaust systems for cars, they are expensive but worth it in my opinion. They are foolproof and reliable therefore, probably used in that position behind the turbo for that reason.

Some advise to save you and anyone else some headaches is to never touch a V-band assembly clamp with a 1/2" ratchet, they should be torqued properly (they are precision ground and just snugging them up has always worked for me) . I also use high temp anti-seize on the threads for trouble free reliable disassembly and reassembly.

 

New clamp. If your old one is still leaking after you tried snugging it up, then you need a new one.

I work mostly on Cummins, and I have never worked on one that has a gasket at that joint. Just check and be sure the flange is not bent, and maybe take a hand wire brush to it to knock off any crud. Don't use a whiz wheel; more is not better in this case.
When you put on the new one, once you have tension on it, if all you have is a half inch drive, just use one finger on the handle until you can't turn it anymore. If it still leaks, one-eighth turn at a time until it stops leaking.

Also be sure to get the correct replacement clamp. Use part numbers if possible; seemingly identical clamps can have slightly different profiles. Good luck!

 

If you find nothing wrong after disassembly you could use a stiff sanding block and go over the mating surfaces of the V-band flanges lightly and squarely after you color them in with some Dykem layout fluid or a sharpy marker. This will indicate if the flanges are warped if any color is left on the mating surfaces.

If there is color left you could keep sanding lightly and squarely until all the color is gone and that should true them up enough to seal.Careful about letting debris in the turbo side.

Don't use silicone!

I HATE exhaust leaks.

 

I tap the clamp with a hammer as in getting the bolt tight

 

I always get a rubber mallet or blow hammer and tape around the clamp as I snug it up. Gives it a better seal.

 

Any time I need to remove an exhaust pipe I try and use a new clamp if possible AND clean the two mating surfaces. Any debris or rust in between the 2 surfaces will keep it from sealing correctly.