Catalytic converter how do you know.

[The Pan Man]

Below is a copy of my post last Monday. The car I now fixed and better than it ever was so my questions are "How do you know when things start to go wrong with this bit of kit"

Since getting the car back it is smoother more responsive and doing a better MPG will confirm at next fill up. Could my Cat have been not working properly for over 30,000 miles? And would it have gone through 3 MOT's?

I will be more than interested in your replies.

Same Thing last Friday

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The same thing happened to me last Friday and caused me to break down the car going into limp mode and the engine management light coming on in lane 3 of the M5 South.
Breif history a few weeks ago on a 10 mile journey the car dropped into limp mode twice.
A couple of weeks ago as I was putting the car in the garage the wife says "When you put the car away there was a strange rattling by the rear nearside wheel" Next day get the car out of the garage and listen, no obvious noises. When we got to our destination I had another listen and there was a slight rattle. On the way to the motorway into limp mode twice and just prior to the first time I remarked "The car does not seem to be going very well" Got the all clear from the mobile mecanic "Just use a gentle throttle" The upshot is a £1700.00 bill and a E270 CDi which goes like stink. So the question here would be "How long has something been going on?" Not cheap but sorted. I was going to change it for a 280 or 320 sport but that will be on hold for a few months.
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[television]

When you have 4 CATs the lower ones start to rattle,,one thing that can cause this is driving on long wet grass, as this causes the the outer casing to cool before the ceramic CAT has cooled, and crushes it, and this happened to me when I reversed onto a grass island to let a tractor pass in a lane.

When the upper ones fail then these usually block the pipes as they are in the near vertical part of the system,,when this happens the performance falls away, as it did in your case

 

[zedmeister]

You know when you get the rattle! Mine started to rattle only when put into reverse or at certain revs. Then they just get worse.

 

[television]

You know when you get the rattle! Mine started to rattle only when put into reverse or at certain revs. Then they just get worse.

Mine always rattled in a busy town center where everyone looked on

 

[dragon]

I am not aware there are more than one catalyst. How can you tell?

 

[kth286]

I can see on V6 and V8 there will be two cats (one each outlet side of engine), but why 4 cats ?

Are you sure ????????

 

[dragon]

I am beginning to understand why there are more than one catalyst, if it double barrels.

 

[GEORGEROV]

Any cats in my garage and they get both barrels!.

 

[zedmeister]

I can see on V6 and V8 there will be two cats (one each outlet side of engine), but why 4 cats ?

Are you sure ????????

Absolutely sure - theres 4 CATs on my car, 2 pre CATs and 2 CATs. 2 are under the car and 2 are in the engine bay. On the pipe, there is 1 CAT on 1 section and 3 on the other section, so if the ones under the car are gone, you need to change 3.

 

[dragon]

Absolutely sure - theres 4 CATs on my car, 2 pre CATs and 2 CATs. 2 are under the car and 2 are in the engine bay. On the pipe, there is 1 CAT on 1 section and 3 on the other section, so if the ones under the car are gone, you need to change 3.

Are you sure it not silencers? Will have to check with russian website.

 

[kth286]

zedmeister

I think you will find the top ones nearer the engine are just insulated sections of pipe to ensure the hot engine gasses stay hot, so that the cats actually get up to temperature in the shortest possible time. I have these on mine too.

You have only got two actual cats (these being under the car) but albeit on the one pipe section as you say.

 

[dragon]

No wonder Merc cars emission is so low 0.01% CO

 

[zedmeister]

zedmeister

I think you will find the top ones nearer the engine are just insulated sections of pipe to ensure the hot engine gasses stay hot, so that the cats actually get up to temperature in the shortest possible time. I have these on mine too.

You have only got two actual cats (these being under the car) but albeit on the one pipe section as you say.

kth286,

I think you'll find that they are all 4 cats - if it were simply insulation, there is no point in insulating just a small part of the pipe in the middle! The nearside section with only 1 box is sold as a cat:

The offside section contains 3 cats:

The other point is that I had the 2 lower boxes cut open and removed - if the other 2 boxes were merely insulation, then it would not have passed the MOT.

 

[zedmeister]

Furthermore, you can read on this cat website: http://www.cats-direct-shop.co.uk/two-year-catalytic-converter.php?recordID=993

Where they are selling the nearside section which only contains the upper box and they state: "This cat is fitted with a standard ceramic monolith."