W124 E220 estate - MOT fail - emissions

[adrianb]

My 1994 W124 E220 auto has just failed it's MOT on a few points, front bulbs wrong colour, rear brake pad below min thickness (1.5mm) and emissions, which is the one that is biggest worry:

Fast Idle test
CO 0.96%
HC 217ppm
Lamda 1.20

2nd Fast Idle test
CO 0.89%
HC 224ppm
Lamda 1.21

Natural Idle
CO 0.83%

The pass levels are:
Fast Idle
CO 0.3
HC 200
Lambda 0.97 - 1.03

Natural idle
CO 0.5

I changed the air filter before the test, and it had a bit of run up a dual carriageway, but it wasn't hammered. My dash temp gauge seems to read at around 60 when warmed up, which is about 25 degrees below what I'd expect as normal. I changed the thermostat, but that hasn't changed the dash reading. When the engine is warmed up, the heater certainly feels like the car is up to temp, which makes me think that maybe a temp sensor is duff. I've got a few questions:

Does the sensor for the dash temp guage also feed the engine management system? If so I'm guessing that if it's duff, changing it might improve the emission readings.

If the dash guage runs off a different sensor, is there any simple way of checking if the engine management sensor is working OK (and the oxygen sensor?)? I've got a multimeter.

The MOT lists the indicator bulbs as being the incorrect colour:
"Nearside front (white) Direction indicators incorrect colour [1.4.A.2d]"
The indicator lenses are both clear, and both have orange bulbs - are these illegal aftermarket lenses? I'm sure I've seen plenty of other cars with these style of lenses.

While I'm doing the rear pads (same fitting as the earlier 200 / 230 TE?), I've got an adisory on excessive play in the rear ns wheel bearing - are these adjustable?

Cheers.

 

[Bolide]

The Lambda is well out so there is a "proper" fault. Someone with more knowledge of gas readings will have to help

The indicator bulb MOT fail is normally caused by the orange paint flaking off the bulb. So fit two new bulbs

Pads will be easy but I'd advise using MB ones - aftermarket ones tend to squeal when you're reversing

The rear wheel bearings are not adjustable and replacing them is one of the nastiest jobs on these cars. If a rear bearing actually is worn I'd expect it to be noisy. I'd replace the entire hub - it's easier & normally cheaper than replacing the bearing. The last two I have had done were £450 each

Nick Froome
www.w124.co.uk

 

[Alex M Grieve]

As for Nick - 1994 was the year in which the front indicator lenses were changed from amber to clear. A good number of cars had clear lenses retrofitted, so amber bulbs then have to be used.

Yours may be such a car? I think the change was around April manufacture.

 

[television]

Odd the temp reading so low, is the fan coming on too soon or has the visco packed up I wonder, this alone could stop the car passing

 

[adrianb]

Thanks Nick/Alex/Malcolm

Nick, rear hub bearings @ £450 each fitted - or was that for complete hubs? The advisory says "slight play" so maybe that can wait. I noticed that the bearing repair kits are not too bad - but I guess the removal - re-fitting is hard work.

Alex, mine is showing as Feb 94 maybe it ought to have these.

Malcolm - thinking about it I've never seen the fan come on - but I'd put that down to a duff thermostat. Having put a new one in, I'm hoping it's not that. I'll try and get hold of thermometer.

 

[television]

Doing the rear wheel bearings not that bad, member turnipsock did it in his drive way, the details are all here, this is a link
http://www.peachparts.com/Wikka/W124RearWheelBearing

 

[Alex M Grieve]

Doing the rear wheel bearings not that bad, member turnipsock did it in his drive way, the details are all here, this is a link
http://www.peachparts.com/Wikka/W124RearWheelBearing

but we haven't heard much from him since!!

 

[television]

but we haven't heard much from him since!!

He fell in love, lives up in Scotland somewhere

 

[Number_Cruncher]

>>Doing the rear wheel bearings not that bad

Rear wheel bearings on W124s are absolutely NOT a DIY job.

What you can do as a DIY proposition, is to remove the hub from the car

Then, take the hub to a garage who can remove and replace the bearing using their press and tools. Even then, most garages will struggle a bit - access isn't great.

Then, as DIY, you can replace the hub after the garage have done their work, and then, depending upon which links you disturbed, get the suspension checked and if necessary re-aligned.

 

[television]

Well a few people have done the job and turnipsock here was no exception, sure you have the bearing pressed in, and easier to replace the brake back plate at the same time. care must be taken on parts as the estate is not the same as the saloon

 

[Alex Crow]

rear wheel bearings can be changed insitu if you have the kit, maybe an hours work and cheaper than £450!! without the correct flange puller this is pretty much impossible though, and you would need to follow the link malcolm posted.

emissions readings are odd, lambda readings suggest it is running very lean, but CO readings suggest the opposite. possibly the lambda probe has failed, and the cat may have failed too.

 

[television]

Have this complete thread, lots of info here

http://forums.mercedesclub.org.uk/showthread.php?t=37818


Thank goodness I can remember every one of my post

 

[whitenemesis]

Have this complete thread, lots of info here

http://forums.mercedesclub.org.uk/showthread.php?t=37818


Thank goodness I can remember every one of my post

A bold boast from someone with nearly 80,000 posts!

 

[television]

A bold boast from someone with nearly 80,000 posts!

Not a boast at all, it is a fact, I can remember most of my post

 

[whitenemesis]

Have this complete thread, lots of info here

http://forums.mercedesclub.org.uk/showthread.php?t=37818


Thank goodness I can remember every one of my post

Not a boast at all, it is a fact, I can remember most of my post

Ah, a climb down already!!

Sorry Malcolm, just teasing

 

[adrianb]

Thanks all for the replies

Hub
Malcolm - if replacing the bearings makes you fall in love and move to Scotland I think I'll leave that for now... and see what the play is like when I do the pads - easy to feel what is too much?

Emissions
Alex is there a simple way for me to work out the culprit? Will diagnostics on this car hold this kind of information or is it a question of "keep renewing bits 'till it's fixed"? I'm going to fit new plugs as a precaution, that's cheap and might improve things a bit.

 

[television]

I do not think that plugs will help,,, they only way I ever got my 300TE through the test at 2 years old was to lock it in second and drive it hard with the temp up to 90c for a few miles

I love your bearing comment

 

[Alex M Grieve]

Thanks all for the replies
Alex is there a simple way for me to work out the culprit? Will diagnostics on this car hold this kind of information or is it a question of "keep renewing bits 'till it's fixed"? I'm going to fit new plugs as a precaution, that's cheap and might improve things a bit.

Read this and thought "Crikey (or similar words) - what have I got myself into now"? :Oops:

Happily, it was the real Alex you were asking - the one who knows what he is doing!

 

[Alex Crow]

...Happily, it was the real Alex you were asking - the one who knows what he is doing!

but you are 'the funny one' - wish i was

i would check the output from the lambda sensor first, it is easy to get at on this car and you should have varying voltage between 0.1v and 0.8v at the black wire. if no volts then check power supply to it on grey wire (i think!).