Rusty exhaust replacement

      [Not actually finished yet; the story is slowly unfolding.
      Stay tuned for further developments!]


  This page comes after a significant time gap since any prior pages about the Prius.  It's early Spring in 2020, and I still have the same 2004 car.  It's been a heckuva journey and quite a rewarding experience, and this car doesn't owe me a dime.  After fifteen years, though, it is finally starting to show signs of age, or more properly of the abuse it has put up with from New England road salt.  That's what killed all my other cars, and that's what will ultimately kill this one too because other than the insidious creeping rot, the car is still rock-solid.  Original battery still going strong, engine sounds the same as ever, it's *not* burning oil, the VFD speedometer hasn't sprouted the blank-out problem, and all my mods and added stuff are still fully functional.  Its fourth set of tires is in decent condition, especially after getting remounted with the beads "gooped" to the rims to stop slow leaks.  While the Kona electric is a fine and fun vehicle, the Prius is still the "muscle memory" car, a long-time extension of my body, and has never been boring to drive.  I kept it as the long-haul and camping car, hoping it would be reasonable to keep on the road as long as possible before it would finally crumble into a heap of rust flakes.

Unfortunately that process had started, notably in the exhaust system.  I began noticing a different sound when starting up, and realized that I had an exhaust leak somewhere ahead of the final muffler and tailpipe.  Cold weather stood in the way of getting a close look at things under there, but with the Kona available I could more or less stash the Prius in the "back forty" and not think about it for a while.  With one of the mildest winters to date threatening to end on the early side in 2020, here I'm finally able to get the car in the air and evaluate the situation.

I'm not ready to write this car's epitaph yet.

Prius rear in the air, good view underneath High-tech redneck mode: a Prius up on blocks in the yard.  Well, sorta; the wheels are still on it.  With the little rear plastic spoilers or airflow tails behind the tires unpinned and removed, I could back it onto the ramps without even using the riser blocks ahead of them [unlike the front, which needs a 2 inch pre-lift to clear the aero stuff].

Things aren't great under here; a lot of rust on the suspension and brakes, and the "boot" well under the 12V battery is apparently starting to rot out.  The rear brakes make occasional grinding noises while rolling, because rust flakes fall in between the drum and back plate and have to either work themselves out or I have to pull the drums and scrape down the edges.  I've still never changed the rear shoes, though; never needed it.  [Kinda goes with my not needing shoes in general, I suppose]

Very rotten muffler hangar fittings So frankly, I have no idea what's still holding up this muffler against simply dropping out on the road.  These hangar fittings look like they've been under salt water for fifty years; there's maybe about a third of the actual metal left in there.  The pair of pegs at the front end of it are in similar condition.  The body-side pegs are both welded to the frame; my first hint that perhaps this is a job best left to the pros.

It is commonly said that exhaust system work is about the most thankless area of car maintenance, because it's *always* a rusty mess by the time it comes into the shop.  Fortunately, exhaust specialists are geared up to handle it.

Pipe joint, and where the leak is I have to run the engine and crawl back underneath to find the leak; it's actually hiding under the little integrated piece of heat-shield or whatever that is.

Every effort I've thrown at it has failed to budge either of the coupler bolts, however.  Penetrant, impact, brute force, all for naught -- the threads seem permanently bonded into place by corrosion.  Online advice mostly agrees that such things generally need to be simply cut apart when the time comes.

New OEM muffler ready to go in Knowing all this was coming, I had already bought a completely new OEM replacement muffler and tailpipe assembly, thinking it might be a relatively simple matter to just swap it in.  If the car was newer or driven in a different part of the country's climate, maybe, but the impediments relative to the tooling I have on hand are rapidly piling up.

I thought it was rather significant that the local dealer had these in stock and didn't have to order it.  Perhaps I'm not the only one hereabouts with this problem.  Actually, the far more common 2G Prius exhaust problem nowadays seems to be more toward the front -- I'm hoping that having the car conveniently in the air like this for a while isn't a wide-open invitation for catalytic thieves.

  On one hand, I could think about extra stuff to buy in an effort to tackle this ... a decent angle grinder and metal cutting wheels, an impact driver and sockets, a welding setup ... but for what, a one-off job on an elderly car that I hadn't needed any of that stuff for previously?  While I can dream of a heated outbuilding with a hoist, air compressor, and cabinets full of high-end tools, short-term practicality has to step in.  There's also a well-spoken-of exhaust shop right in town, so on the other hand maybe it's time to bring them some local business.

What's kind of baffling is how the front half of the exhaust system is made from stainless steel, and while it's got a little discoloration here and there it's still plenty solid. Why the back half has to be typical cheapass mild steel instead, I can't imagine.

There's the actual leak The pipe rot centers around the weld holding the little heat-shield on, leaving it quite cracked and easy to just break the rest of the way and pry the thing back and eventually off.  Obviously the pipe itself is on the way to severing completely, but it's not quite there yet and there's still enough structural metal through here.

Problem is, vehicle inspection is due in March and I don't know if I have time for the full fix quite yet.  Alternate strategies and options are pondered...

Fiberglass buffer layer over hole The conclusion is: the muffler hasn't actually fallen out yet and doesn't seem about to despite the condition of the hangars, and a quick and dirty patch can stop the leak [and its telltale inspection-flunking noise] and hold things together for a while longer.  I do have the parts, however halfassed, to do a reasonable job on it, especially this far to the rear of the system where things don't get quite as hot.

First step is a bit of fiberglass mat to impede pulses of exhaust gas trying to flow out the hole.

Aluminum tape bandage The whole thing gets a tight multi-layer bandage of aluminum flashing tape, which isn't the most robust solution one could effect but it doesn't have to last too long.  It's also aluminum against steel in the presence of moisture, a recipe generally doomed to eventual galvanic failure.

A thing to note in passing is that directly above here is where the big battery sits, and the passage of the exhaust pipe underneath is probably why the temperature sensor at one end of the pack registers generally warmer via OBD2 reporting than the one at the other end, after the car has run for a while.

Extra patch and clamp to hold things together As a little insurance against blow-out, a patch of thicker metal goes over where the hole was, curved to match and clamped down.  The piece appears to be the adhesive nameplate from the back of an old stepper motor or something; it was kicking around in the small sheet metal box in the hoard.  It will probably go back in there again when this comes apart.

Mild steel with an oxide layer, aluminum, more aluminum, and a stainless clamp band, all in close contact with a generous splash of chloride ions.  I think I've built a little battery right here.

  -->   To be continued ...

_H*   200311