Hi folks,

Over the last wee while - maybe 2 or 3 weeks - there's been a 'rattle' from underneath the car. I only have one 'bay' in my garage, and the Defender's been hogging that, so I've been unable to get underneath for a good look or poke around.

It's only really audible from the outside, or from the inside with a window open and stopped alongside a wall or something (so the sound reflects back towards the driver). Engine runs sweet as a nut. It's been my daily driver now for the last 3 or 4 weeks at least, including some longer trips away with work. Oil good, coolant good, nothing showing on the gauges (though I haven't plugged in the nano.)

I thought it would be something like an exhaust clamp, or loose bit of heat-shielding, but with a very quick look underneath today there's nothing obvious. I've figured out how to post pics here, but a wee 18 second video I took earlier seems to be taking a long, long time to upload to imgur, and even if it did, I don't know if that would go up here.

It sounds 'light' and 'rattly', and it's there with the engine idling/car stationary.

If I can't post the video yet ( I need to go away for the weekend v. shortly) then I suppose what I'm really asking is: "What are the serious, terminal things it could be, with gearbox or engine?" - and what would they sound like.

I haven't been able to get under properly, so I haven't been able to check gearbox oil level, but like I say it runs really, really well. I can't really tell if the noise changes underway.

I realise this is a bit of a hopeless question - what's this noise, without being able to let you listen to the noise... but unless someone more web-savvy than me can help on that front I don't know what more I can do. I sometimes use an image compressor before posting pics on the web but that won't work on video files.

Any rough ideas though?

Ta.

Most likely is a rattle from the innards of one of the cats. If it is, you have two options, replace it, or the cheap option, clamp a lump of steel against the side of it so it squeezes it in and holds the internals in one place.

As for the video, it will depend on what settings you used when shooting it. If you've shot it in full 1080p HD, you'll get a big file so will take a long time to upload. If you change the settings to 720p the files will be much smaller. Or just upload to Youtube and link to it there.

Hi Gd,
That does sound 'about right' - that would be about the right place.

Also not just so inconvenient as I've been meaning to reinstate the middle silencer which the PO removed.

I'll try and get back underneath again and eliminate anything more obvious.

So, never having been in this position before what are the implications of running with a rattling cat? Is it a case of 'it'll last for ages' or get it changed ASAP?

I might even investigate the clamp option temporarily, but I think the car's worth a replacement given the amount of use and fun I'm getting out of it.

Brake dust shields are worth a look at if the noise is whilst moving.

The guts of the cat are ceramic so if they start to break up the bits get blown out so would normally end up inside the middle silencer box. As you don't have one, they are probably just laying in the delete pipe. OE cats are ridiculously expensive but aftermarket, which are much smaller but still work well enough to go through the emissions test at MoT time, are quite reasonable. You need to get the correct one as the boss for the lambda sensors is a different size between GEMS and Thor, so up to 98, you want ESR4095 but 99 onwards you want WCD105350. Only difficulty is getting the crossmember out to fit them.

I had a rattling cat on a Dodge Dakota I used to have. I removed the cats and gained a lot of power. The cats were very plugged. I think the large cats on our P38’s might not be as prone to plugging up.

Thanks again.

ChrIs - My first thoughts were something like the shields - heat shields or something rubbing against a moving part. Then it was clear the noise was present even sitting still.

On the point about large and small cats, is the conclusion that bigger is better or more long-lasting; cheaper = smaller and will clog up quicker? Maybe it doesn’t really matter. If the originals lasted 22 years, though I’m in no rush to get rid of the car I can’t see my still using it in that timescale. And I saw the genuine ones for £4000 - that certainly ain’t going to happen.

One of the members on here buys unloved P38s and depending on the condition, either refurbs them and sells them on or breaks them for spares (using some parts on the ones that need refurbing). One thing he always looks for on a breaker is whether it still has the original cats on it as he can weigh them in for £300 each. Cats don't normally clog up on a car that is running properly, it's only one that is running badly that will clog them.

Thanks again. I hadn't realised they had such potentially significant value - that's food for thought, and if I can get a decent fraction of that price above then it certainly makes any decision about replacement easier.

As I said, the Defender is hogging the garage at the moment - front axle refurb and transfer box/overdrive re-install. Realistically, looking at other commitments in the calendar it's going to be there for at least the next fortnight to three weeks.

Apart from the noise, if all else is running OK, is there any real/likely issue with using the RR over that period? Gives me time to order up replacements cats and centre silencer anyway. (And also take a better check this is the issue. Finally a use for the 'mechanics stethoscope' I bought on a whim about 2 years ago!)

No problem with using it, just use ear defenders if the rattle gets too much.....