On my way down to York in the C1 I pulled into the excellent Mainsgill Farm Shop for some provisions. As I made my way across the car park there was a rattle from the back. A quick visual inspection revealed the cause – the exhaust hanger on the back box had snapped and it was resting on the rear beam.
Whilst it was still attached when I left home, it had presumably managed some distance before I had noticed. It wasn’t dragging, and it wasn’t leaking so I figured it would make it the rest of the way to York.
Before heading home, TomB engineering fashioned me a temporary exhaust hanger that was more than adequate to get me back.
The culprit was pretty easy to identify – the hanger was heavily corroded and the 10 years of vibrations had caused it to neck to breaking point.
The following weekend I took a trip to TMS motor spares to pick up a new back box. Getting the old back box off proved somewhat challenging – first I had to cut off what was left of the old exhaust clamp as the bolts were more rust than metal. Then it came to separating the joint with the centre pipe.
This did not want to budge – despite persuasion with a full tang screwdriver and a mallet. As it had gone bad I had to cut it off.
However, I was expecting this to be a butt joint – as on the 2CV – but, once I’d finished cutting, I realised it had been a socket joint…
So, at this point I knew I was now going to need a new centre section even if I didn’t want to fully admit it to myself yet – especially given it was now Saturday afternoon meaning I wouldn’t be able to get a new pipe until Monday morning.
Still, I could still remove the old centre section in preparation. Fortunately the two spring loaded bolts that went into the cat exit flange weren’t too badly corroded and were only a two swear rating to free up. Being the same age as the rear section, the centre section was, unsurprisingly, similarly heavy with surface rust even if it wasn’t holed.
However, once it was off the car and I could have a good look at it I found that the front exhaust hanger was in much the same state as the rear – heavily necked and not far off failing.
So it turned out to be fortunate that I’d cut through the wrong bit as it now meant that I was going to be replacing it before it failed and whilst I had everything apart anyway. If it had failed in a few weeks time and I’d had to spend another weekend under the car swearing at the exhaust I would have blamed past me for not having done the job right in the first place.
There was still one major obstacle to overcome – getting the oxygen sensor out.
The Book of Lies™ says “The oxygen sensors are delicate and may not work if dropped or knocked, if the power supply is disrupted, or if any cleaning materials are used on them.” I translated that to mean: “Dose it in penetrating fluid, apply blow torch until cherry red, clamp with mole grips and beat with a hammer.”
The only alteration I made to that was to substitute the mole grips for a correctly sized 22m spanner. With the aid of +2 gloves of power and full application of my not inconsiderable body weight, after a few heat cycles it came free and I went backwards, fortunately my landing was cushioned by my not inconsiderable derrière. A four swear rating for this job.
Reassembly was the reverse of removal – but without a blowtorch and an angle grinder. Joking aside, everything went back together remarkably easily – the only point of note is there’s a gasket made of compressed wire wool in the joint between the cat and the centre section.
With the exhaust fitted and everything tightened up nicely I turned on the engine to check for leaks – all good!
I was concerned that I might have damaged the oxygen sensor when spraying Super Crack Ultra on the cherry red mounting but the ECU seemed happy.
After a short shakedown it was still holding together so I went for a longer run to get everything fully up to temperature – there were some funky hot metal smells which would have been worrying if I hadn’t just replaced the exhaust but everything held up fine.