The 160/2002 ' A' Class exhaust system is made up of two major parts, the inlet manifold combined with the catalytic converter and the front & rear pipes combined with the silencer
Exhaust systems
A The exhaust manifold complete with Catalytic Converter. MB Part number KT 0126. A168/490/08/14 Cost June 04 £390 inclusive of VAT give or take a few pence.
B The main box complete with front and rear pipes. Part Number SN 0512. A168/491 0800. Cost June 04 £83.00 inclusive.
In addition to the above there is a manifold gasket & exhaust fixing kit which apparently contains brackets and rubber hangers, although this wasn't available, as none had been sold by my branch. When purchasing any part of a system from MB the vehicle chassis number will be required. Thank you Nigel, Parts Dept, for information MB Chichester West Sussex.
it is worth noting that there are no body panels under the engine area on the A160/2001
I must say I was some what alarmed to see that the Catalytic converter was in one piece with the exhaust manifold, although it has advantages in that there are less joints and therefore less potential leak spots I was concerned about the cost, I was somewhat relieved to hear that it was £389.00 as I felt sure it would cost more, it being a very sophisticated piece of equipment.
I suspect that removing the manifold complete with cat would be quite a challenge, gaining access to the nuts alone would be difficult task. A challenge I hope I do not meet.
The cat is well supported by a right angled bracket which is secured by two standard nuts on the cat and star drive bolts to the underside of the engine. 
it is interesting to note that this catalytic converter appears to only have one oxygen sensor port, almost certainly a pre-February 2001 EOBD 2 model, another reason for always providing your VIN Number when ordering spares on line or at MB parts.
If ordering from other outlets ensure you have the correct parts before committing, some outlets deduct considerable sums from you monies where goods are returned. Also take great care if purchasing from scrap yards /second hand parts outlets.
The CAT on cars produced since February 2001 (Face lift Models) has two monitoring connections, Lambda's (02 sensors) one near the gas inlet upstream part No. A00 154 09 417 and the other mid way along the back of the CAT casing, downstream of the gas flow. Part No.A002 540 01 17 These will not be supplied with the new catalytic converter and from Mercedes will cost £150.00+ each. plus VAT
However fellow owner Tony has provided information below that will greatly reduce your outlay on these items.
Tony many thanks for this valuable and money saving information. My discussion with the company today 9/6/09 has revealed that they are able to provide the correct sensors pre-fitted with the correct connector, for £69.95 inclusive of VAT.& £99.95 inclusive of VAT
The Upstream sensor on the end of the CAT being the more expensive @ £99.95 (11/06/09) inclusive less 5% if you follow the directions on this page, still a fantastic saving on the Mercedes prices, and by fitting the complete assembly you delete the possibility that the fault is in the connector.
Both of these lambda sensors are available from Gendan.Ltd
Gendan.co.uk
Tel: 01792 588002 Fax: 01792 588233
It may not be necessary to replace the sensors with the catalytic converter but if all components are the same age then at this greatly reduced price it would be worthwhile if you can go to the extra expense.
Discounted Purchase facility I have also arranged a 5% discount for my readers with this company on the oxygen sensors only, although Gendan Ltd can supply other products, visit their site to view the range. I would ask you not to abuse this facility and the offer is open to the individual owner and not the retailer or trade.
When placing your order, on reaching the check out enter the word in small case, aclassinfo in the comments box this will trigger the 5% discount, it will not show on the invoice/page but will show on the amount deducted from your credit/debit card.
I would like to thank the Management of 'Gendan Ltd' for their consideration in allowing this special discount to my readers.
Front sensor (Pre-CAT): Order front sensor (Lambda).part No. A00 154 09 417.
Rear sensor (Post-CAT) Order Rear sensor (Lambda) Part No.A002 540 01 17
I am not that familiar with the working of the cat but understand that the front sensor is responsible for the monitoring of the fuel flow, along with the mass air flow sensor(MAFS) which ensures the correct amount of air flow with the fuel for a clean burn .The second Lambda sensor monitors the condition of the catalytic converter and will warn you if for some reason this fails to do it is job.
When working under the car be aware that the converter reaches very high temperatures.
One warning that does stand out is the over filling of the engine with oil, the effects of the high oil level will damage the Catalytic converter so always ensure your oil level is level with or slightly below the max level mark.
Note also your car is fitted with electronic oil level indicator. If the letters HI show or appear in the instrument cluster this is the car telling you the oil level is too high, not the car being polite and saying hello! High oil levels with damage if not kill the CAT!
The second main portion of the system starts here at the flexible joint and continues on the main exhaust box and tail pipe. It is worth remembering that exhaust systems are attacked by heat from the gases on the inside as well as wet salty conditions on the outside. I am of the opinion that although I can do little about the inside of the system accept by cutting out short runs where the engine never really gets warmed up, I can look after the outside washing it off when washing the car and giving it the odd coat of paint thus keeping out some of the rust which will form and eventually cause deterioration and thinning of the metal.
When inspecting my system I found that when the car was ticking over, the flexible joint was dripping condensation through the joint, if this was allowed to continue the joint like a tap seating will be damaged and therefore I tightened the joint slightly to stop the leak. A star drive kit is essential for undertaking even small jobs on this car. The springs keep the joint between the exhaust inlet pipe and the Cat under tension and therefore gas tight.
The exhaust system is almost joint free, however there is a flexible joint between the catalytic converter/manifold section and the exhaust pipe silencer box section.
Owners may not be aware but there is a lead/gauze compression gasket/seal at the joint of these two sections. If like me you have a leak at that point which could in extreme cases fail your car on the MOT, you will need to replace that seal.
Part No MA 168 492 01 81 £6.31 plus VAT, 10/02/07 very easy to fit albeit a star Torx bit is required to undo the bolts.
Do not be tempted to over-tighten this joint or the benefits of the compression seal will be lost.
When changing this seal you will require a T40 Torx drive male bit, having released the clamp, carefully tap the old seal away from the flange on the neck of the catalytic converter A
DO NOT DAMAGE THE FLANGE, replace seal flat side towards the catalytic converter, refit bolts and springs, I sprayed the bolts to aid refitting.
The main box and pipes are supported on three rubber hangers one either side of the main box and one on the tail pipe these are easily replaced, cut off the old unit and using a small amount of washing up liquid to lubricate the new rubbers force them over the nose of the lugs of the brackets that give the support. The supports on the box are either side and inline with the securing band positioned around the box.
It appears that one weakness on this system is this metal band, apparently MB have had to replace main boxes where this band has failed. One way over this should yours fail is to use a Band-it fastener, the type of thing used by local authorities to fix signs to posts. Certainly worth the effort when the box cost £83.00 With the Band-it tool you may even get away without having to lower the box,
and you will be assured that the hangers are
in the correct position.
System showing signs of exterior damage by salt and other contamination.
The rear hanger showing the support rubber which is so essential in taking weight of the rear joint at the back of the exhaust box, without this support the system will fail in no time at all, so it is worth casting the odd glance when washing your car, alternatively give the tail pipe a wiggle you will instantly see if the supports are gone.
Having now checked the system for defects a lick of paint tidies it up, and we get a good look at the underside of the car in the bargain.
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