Sacrificial zinc anodes, inside the exhaust where water collects. I actually found a patent application online for exactly this setup. I think it would work to significantly slow or halt rusting in the problem areas. It will not do very much where water does not collect, an electrolyte being necessary to close the electrochemical circuit.

That would extend the life of the exhaust.

The guys on Turbo Bricks just run a larger diameter (2.5-3")from the cat back.
If a turbo car it won't make much noise at all.

I'm doing this on my 740/940 next time I need an exhaust. I'm tired of the salt 2 year rot.

good luck

I agree with the 4 year max assessment. Unless you want to spend big bucks on stainless steel.

Had my 90 244DL for 10 years in N.E. Never had an aftermarket system last more than 3-4 years. Maybe paint would help. Never tried that. Think Volvo OEM will do best. Installed a Volvo OEM cat-back system about 3 years before I sold the car and it was still going strong at that point. Don't know if they are still available, but the entire cat-back system was about $160 from Boston Volvo. Not much more $ than the aftermarket systems. Might be worth checking out...

as I have mentioned before, I think an economic partial solution is to buy a large spray can of Rustoleum cold rich galvanizing compound and also a quart container. The rust chemical reaction will apparently work with zinc before it attacks steel. If the system can be treated before assembly it might be easier to coat inside the steel via pouring some of the rustoleum liquid in, and using the spray to go further. As an example, I had a 78 F150 PU that had the y pipe cut to make a dual exhaust - no cat. I purchased the cheapest exhaust system the discount muffler shop had and coated as above. Driving 10 minutes to work and NO long distance driving the system was still good the 8 years I had it. Some of the rubber hangers failed, however. The muffler shop couldn't understand how the system survived short trips in the rust belt. Of course, they were viewing the rustoleum as "silver paint", which it looks like but isn't. It does resist heat, but I don't know about engine parts. The hole in the low spot sounds good too but I would coat inside and out as much as possible. A breathing mask with any coating might be nice, also.

Drill a 1/16" diameter hole at the bottom of the end plate of the new muffler. When you start the car you will see water run out.

Greg

A few clarifications:

I'm not trying to extend the life of the current muffler; it can't be fixed. I got a Volvo replacement unit under my warranty.

But 4 years, and only 15k miles just did not seem that long, especially since I purchased a Volvo muffler. Ditto for the previous one which was installed by Volvo for the previous owner.

Yes, I do lots of short trips with most being 5 - 10 miles, and the car is only used from November - May when there is lots of salt on our NE roads.

From Art's second picture "That axle pipe is where they all seem to go first, always, right where it enters the rear muffler.".

This is not where mine are breaking. That connection was ok both times the rear muffler failed. It is failing at the weld of the small piece of pipe that is part of the rear muffler, the one that slips into the axle pipe. That is the weld to the left of the clamp in Art's second picture.

All the feedback is helpful.

Possibly my comments here will generate more feedback

Thanks to all.

I bought a NOS Bosal muffler and it had a small moisture drain hole drilled under the point were the axle pipe connects. With the car running you can fell a small bit of exhaust come out.

I'd try Art's method but use metal as a bandage with large hose clamps. Pop cans of today are a bit thin, but you get the idea.

There are also exhaust pipe connectors available.

I've also found that JB Weld epoxy putty sticks can handle heat and are good for sealing holes and cracks. Use water while smoothing. They're cheap, useful and easy to use.
--
1980 245 Canadian B21A with SU carb, M46 trans, 3:31 dif, in Brampton, Ont.

I know your desire.

That axle pipe is where they all seem to go first, always, right where it enters the rear muffler. My thinking is it makes a low spot for water on a short-tripper. I've been discounting the idea there's stress on the joint due to the swinging of the heavy rear muffler and tailpipe -- that just hastens the disconnect after it rusts. Old Volvos getting relegated to short trip duty makes us think the new cat-back systems are somehow less rust-resistant than the original stuff.

Just did one on my daughter's 330K 91. I looked to see when I did it last, and it was 6 years and 120K ago. Those are primary car miles, not 2nd car miles. Everything else in the cat-back system was ready to go, but the fail happens first at that axle pipe joint.

Rattle can paint didn't help. Understanding I might only delay the demise of the system by a year or two, I haven't yet made the effort to swab in some POR-15 before clamping up a replacement. Might make a nice long-term experiment. Or wrap the new joint with Muffler Bandage!





Road trip fix.



--
Art Benstein near Baltimore

What engineers say and what they mean by it:
"The software is being developed without excessive process overhead."
The documentation will be written in clear and lucid Chinese.

Properly installed, your system should not snap off - this should occur long after it is leaking.

There must be some stress in the installation.

I jack up the right side and rest the tires on a couple of old wheels - they never shift or collapse.

I check the new system on the ground beside the car - Volvo systems are generally a good fit,

I then draw a line around any pipe that slips into another, one inch and 2 inches from the end so that I can monitor how much each pipe has been inserted,

I then cut the old system up with a tail pipe cutter - this a pipe cutter with 4 cutting wheels and a screwdriver handle. It can cut a pipe with just over a 90 degree swing.

I hang the entire system with the clamps just snug - checking that each section is perpendicular or parallel to the ground as needed - I make sure that the pipe that kicks over the axle is spaced the same front and rear.

Look at it from a distance, side and rear - don't forget that the car is tilted.

Then tighten everything up, lifting sagging sections slightly - do not move the parts so that they are stressed after you are finished - that can cause breakage.

Inspect it once and a while by shaking the tail pipe for looseness and hold a rag firmly over the pipe to check for leaks.

I don't like welding exhaust pieces together. Use a Starla cat back kit, install it with the Volvo rubber mounts and clamps. Before cranking down on the clamps lower the car and make sure all the parts are as far away from the body and differential as possible.

Four years in the rust belt may be all you can expect.

Dan

You may want to research grounding the exhaust system at the connections to the car body using a durable braided stainless conductor.

Also, be certain the header pipe IS supported at the bracket, connected to the 4 and 5 O'clock bell-housing bolts (as you look from rear to front) as it both grounds and supports the header pipe and cat. converter weight at the front.

Also, check the rubber hangars. These things can fail; certainly if not Volvo OEM or an OEM quality part.

Sometimes people install the exhaust and tighten all up without checking alignment and proper hangar condition and installation. Some people, like crappy exhaust shops, will allow the rear axle to hang down and the exhaust shop won't raise (support) the rear axle so the exhaust system aligns and hangs properly before torquing.

Probably why you have the same failure at the rear pipe connection. The exhaust pieces are all hung and secured while forced to support the a low hanging, unsupported rear axle, so, when the car is down, you have the rear exhaust system pieces torqued yet not properly aligned.

Questions?

Cats?

Kitties?!?!?!?

Happy Friday Kitties!!!!!
--
Extra fuzzy kitties!!!!!
Super-fizzy kitties!!!!
Ultra funny and fuzzy kitties!!!!!

That joint isn't any "weaker" than any other part of the system. It fails first because it's farthest away from the motor. Overnight water condenses in the exhaust system; when you drive away the next morning the hot exhaust blow drys the system from front to back. If you make a lot of short trips, that bend that you've noticed failing first never gets dry. If you want that part of your exhaust to last longer, drive more. If you get the car good and hot every day, you might get 10 years out of it. If you make lots of short trips you might only get 2 or 3 years out of it.