Pre Cats

Recently on the emissions machine for the MOT the car passed the emissions test with flying colours. When I bought the car, the dealer told me that the pre cats had been removed. Now to be honest I was and still am dubious about anything a dealer tells me.

For those not in the know, the Chimaera, well mine at least has three catalytic converters, one in each manifold and one in the main exhaust. All of these are in the engine bay, so are unlikely to get damaged hitting the road or shocked with cold water or similar that ends up destroying the cats.

I was listening to the car running and I could hear a strange rattle, not in time with the engine revolutions, but more like something left lying about in the engine bay that was being rattled by movement, but I wasn’t moving. It is really difficult to hear it over the engine noise, but listen out for an unusual rattle from the inlet manifold.

Now you will have struggled to hear the noise, but I could clearly hear it in person. So I suspected that one of the pre cats had become loose. Obviously I had been told they were no longer there, so some further investigation was required before taking things apart for the sake of it.

With the help of a thermal camera, the main catalytic converter can be clearly seen hot and working.

The nearside pre cat was clearly doing something too.

And finally the driver side that I can hear the rattle from.

Yes that’s right, much cooler than the other two, so something was clearly going on.

A trip down to the workshop to get the exhaust system taken off and inspect the manifolds.

Sure enough once removed I realised that they had not only been left in, someone had clearly had a go at removing one, the drivers side one. It was all smashed up and banging against the oxygen sensor. Now I had stopped taking photos at this point because it was getting on and I had two pre cats to remove.

I tipped the smashed bits of cat out of the main catalytic converter as they were all sat on top and set about smashing the remains out of the manifold. If you have never done it before, it is tough stuff and hard to remove. Once I had it removed and blown the bits out of the now hollow manifold, I set to the other side which was still intact.

Both pre cats removed and putting everything back together, pleased with my work I realised that the exhaust silencer had also been opened and sleeved to improve the exhaust note. Happy days, back on the way home enjoying the additional burble removing the cats had created I couldn’t help but grin.