It’s a question the SkillShack with Practical Classics team are often asked: when assembling a new exhaust, should you use an assembly paste or copper grease? Well, exhaust paste expands as it gets hot and dries out, thus guaranteeing no leaks even if the pipes are a poor fit. However, it makes the sections harder to disassemble at a later date. Copper grease makes for easy disassembly but won’t seal leaks. Decide which solution best suits your needs by trial-fitting the sections on the floor first. If they’re a snug fit, use grease.
Copper grease makes sense to E-Type owners or any Jag with an IRS (Independent Rear Suspension). The exhaust has to be removed allow removal of the IRS whilst not an every day job it needs to drop to replace the rear brake rotors and calipers. I know from experience!!
My retired auto technician dad advocates a silicon sealant. It actually works very well. I had to replace the middle section last weekend. About 3 years ago I had fitted a new rear section. Normally it is a real pain separating the two sections. All it took was a bit of flexing the joint to break the seal and the 2 parts separated surprisingly easily. Also there was very minimal corrosion along the area the pipes joined.
Cut the joints off and flange them both grease or paste are useless, sometimes you have no choice ie through chassis rails then tight joints with minimum paste cheers Steve
if you fit a exhaust with grease and it could leak maybe under the car ? and you may want to dismantle it at a later date ? if I has to come of I would assume it needs replacing If you fit with paste and no leaks job done ! if it has to come off at a later date by then it is U / S ?