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Discussion Starter #1
My S430, MY02 has done approx 108K miles.
Its driving fine but I have not replaced any of the O2 sensors on it yet.

Should I replace them anyway or should I just keep a couple of the pre-CAT sensor ready to replace, if I get CEL on with the appropriate code ?

Should I replace post-CAT as well or are they not very critical ?
 

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My 2001 has over 338,000 miles and never had O2 Sensors replaced. Also, never had CEL for O2 sensors. My CEL has been MAF and frequent EGR.
 

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I wouldn't change out any O2 sensors if there is no CEL.

If you have money burning in your pocket, there is a lot of things that could/should be replaced with the mileage you currently have on your car.

Off the top of my head (if they haven't been done yet):

spark plugs, serpentine belt/tensioner/idler pulley, engine/transmission mounts if needed, any fluid change that wasn't done on schedule (like transmission, differential, brake, coolant etc), EGR hoses..............or just wait. These cars will suck the money out of your wallet sooner or later :smile
 

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On the other hand......

I change out O2 sensors at the very first sign of a CEL. Particularly the pre-cat sensors - to avoid the possibility of not having the right stoichiometry and running too rich - which will shorten the life of the expensive catalytic converter.
 

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On the other hand......

I change out O2 sensors at the very first sign of a CEL. Particularly the pre-cat sensors - to avoid the possibility of not having the right stoichiometry and running too rich - which will shorten the life of the expensive catalytic converter.
If you have DAS, you can monitor the performance of each O2 sensor, i.e. the voltage cycles. DAS will tell you the permissible range.

Wouldn't change one unless it is significantly out of range.
 

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I wouldn't change out any O2 sensors if there is no CEL.

If you have money burning in your pocket, there is a lot of things that could/should be replaced with the mileage you currently have on your car.

Off the top of my head (if they haven't been done yet):

spark plugs, serpentine belt/tensioner/idler pulley, engine/transmission mounts if needed, any fluid change that wasn't done on schedule (like transmission, differential, brake, coolant etc), EGR hoses..............or just wait. These cars will suck the money out of your wallet sooner or later :smile
^^ Well said. I would change one of the above before replacing the O2 sensors.
 

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Discussion Starter #7
Thanks Guys.
Based on your advice, I will leave O2 sensors alone.

I have changed the spark plug wires, valve covers, brake fluid, transmission connector due to leak, ( regular oil change of course), Airmatic pump. I thought about the transmission fluid but have not done it yet.

The serpentine belt looks good, but should I change that and the hydraulic tensioner anyway ?

What would be the order of priority for getting these items done, if that is important. Has anyone used the Yumling method( described in the W210 thread) on a W220 for exchanging the transmission fluid ?
 

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Thanks Guys.
Based on your advice, I will leave O2 sensors alone.

I have changed the spark plug wires, valve covers, brake fluid, transmission connector due to leak, ( regular oil change of course), Airmatic pump. I thought about the transmission fluid but have not done it yet.

The serpentine belt looks good, but should I change that and the hydraulic tensioner anyway ?


What would be the order of priority for getting these items done, if that is important. Has anyone used the Yumling method( described in the W210 thread) on a W220 for exchanging the transmission fluid ?
I would change the transmission fluid at your mileage too or simply freshen it up with a few drain and fills over time. That is what I did. There are many write-ups on how to do it. As to the belt tensioner and serpentine belt, those are potential fail parts for sure. See my writeup here.

Looks like you are doing the maintenance correctly.

Good luck,

Bob
 

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The tensioner is spring-loaded, not hydraulic. I check the tensioner and idler pulleys when I change the belt - if the bearings and the pulleys are perfectly smooth and quiet, with no signs of damage or wear, I leave them alone.
 

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X2 on the transmission service. Should be done every 39-40k miles.

If the serpentine belt/idler/tensioner are original, I would change them out. Does your tensioner pulley has a stud in the center, I would definitely replace it if it does.

Don't forget the differential, very often neglected. Don't think there is a service interval for this item. I like to do it every 50k miles along with fuel filter.
 

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x3 on transmission service. If it is original ATF, you either need to ensure that you continue to use 236.10 spec, or else do a complete fluid flush with 236.12 (or 236.14) with ATF brand endorsed from BEVO website.

ATF DIY http://www.benzworld.org/forums/w220-s-class/1631656-transmission-service-diy.html

BEVO Mercedes-Benz Specifications for Operating Fluids: Engine Oil, Gear Oil, ATF, Coolant, Brakefluid

As far as the belt, tensioner and idler pulley - failure of any of these can result in a very bad day - and chew up the radiator. IMHO best to replace them preemptively to avoid a breakdown at your mileage. For example, you cannot see the idler pulley cracking until it is disassembled. Some good name brands to consider for these include: Contech, Gates, Trucktec.
 

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I just changed the belt and idler pulley when the AC compressor seized and ate the belt and melted the plastic idler pulley. The Dayco idler was in stock at my local Advance Auto Parts for less than $14 - it looked good and felt good.
 

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Discussion Starter #13 (Edited)
My Tensioner does not have a bolt in the middle, but based on the good advice here , I plan to change the serpentine belt and parts next weekend. I looked at the belt kit that has a Contitech belt and Ina Tensioner and idler. However, I can see two idler pulleys, whereas the kits come with only one, except the one from fcpeuro as in the link :

https://www.fcpeuro.com/products/mercedes-drive-belt-kit-m273-m272-genuine-ina-272273beltkt1

Is this a good way to go ?

I have the Fuchs transmission fluid, filter ( 12 litres ) and gasket. I plan on lowering the transmission pan, changing the filter and gasket -- messy job by the looks of it. I have the Mercedes transmission dipstick I used on the E320 -- should work on this transmission as well ? I am thinking of changing the transmission fluid 2-3 times to get a good ration of the new fluid. Unfortunately, my assistants to turn the engine ON and OFF are not the worlds most cooperative !
 

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The tensioner kit you have in your post appears to be incorrect. There is only one idler pulley. Check this link for the I think the correct setup. (Double check before ordering of course.)

For your transmission fluid freshen up, you only have the drop the pan once to change out the filter and from there on just drain from the drain plug. That's what I did on my '01 but I only had 8 liters of Fuchs to freshen with. With your 12 Liters, you should be able to wind up with fairly clean fluid.

Good luck,

Bob

(Don't forget the Transmission adapter plug if not already changed out!)
 

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My Tensioner does not have a bolt in the middle, but based on the good advice here , I plan to change the serpentine belt and parts next weekend. I looked at the belt kit that has a Contitech belt and Ina Tensioner and idler. However, I can see two idler pulleys, whereas the kits come with only one, except the one from fcpeuro as in the link :

https://www.fcpeuro.com/products/mercedes-drive-belt-kit-m273-m272-genuine-ina-272273beltkt1

Is this a good way to go ?

I have the Fuchs transmission fluid, filter ( 12 litres ) and gasket. I plan on lowering the transmission pan, changing the filter and gasket -- messy job by the looks of it. I have the Mercedes transmission dipstick I used on the E320 -- should work on this transmission as well ? I am thinking of changing the transmission fluid 2-3 times to get a good ration of the new fluid. Unfortunately, my assistants to turn the engine ON and OFF are not the worlds most cooperative !
INA and Conti are good brands. However - this is not the kit for on your car.

If you are doing ATF work - you should also change the pilot bushing. $18 part.

For a full transmission flush, you will need just under 14 L - you don't want to be short handed or put old fluid back in. Drain and fill works when the same fluid is in play - mixing spec 236.10 ATF (Hard to get now) and 236.12 or 236.14 ATF Fuchs could give you some shift problems. The best way to approach this is to do a full flush. Fuchs is a good brand and on BEVO - I used it to flush out our 2002 S430 in post 35 of this link:

http://www.benzworld.org/forums/w220-s-class/1631656-transmission-service-diy-4.html

While the post from Pinkster is an excellent reference (I recently used it for my 07 S550) it is in the context of the next generation 722.9 (NAG 2) transmission - However, yours is the 722.6 (NAG 1) covered by the link that I provided above. The 'Yummling' flush from breaking the connection at the front of the car as described is easy - and you won't need an assistant for start / stops (the outfall is medium flow). (I take it your assistants don't yet drive :smile)

The dipstick tool works on all 722.6 platforms.

Keep everything surgically clean - no lint or debris that can clog a solenoid passage.

IMHO the installation of a new red lock on the ATF dipstick tube cap is a waste - I ran 3 cars for several 100,000's of miles and the caps always stayed in place.
 

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Discussion Starter #17
I took the good advice of my more experienced colleagues and changed the Serpentine belt, idler pulley and the Tensioner with Conti parts kit ( idler, Tensioner and belt). Once I took off the idler and the Tensioner and compared with the new parts, I could easily tell the difference in the free play and noise when rotated. It was good advice and needed to be done. The belt looked OK, but its so cheap that replacing with a new one is a "no brainer".

I did the complete job on the transmission oil change, with the new filter and new bolts etc. The complete flush took 14 liters. I did get quite a bit of the transmission fluid on the floor, but clean up was not too bad. The oil was dark but I am not sure it was degraded and ineffective. However, I changed it all out at 112K miles. I do not expect to keep the car for another 100K miles.
 

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Discussion Starter #19
Well. Wally, its definitely used -- not sure if its good !
Its only 14 years old and costs about $25, so I am not sure how to keep it preserved -- perhaps inside the spare wheel space or in a display cabinet ?
 

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I had a spare belt in my trunk for the last 46 years! Never needed it. If your belt comes off, usually its because of a BIGGER problem..............like a broken idler pulley or a tenstioner which just grenaded :(
 
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