SAMM

Hi there guys,

Ive just finished replacing the control arm bushings, ball joints, all springs, drag link, tie rods, steering damper.

Ive been trying to figure out why my car is spitting out so much unburnt fuel approx 25-30%. Poor acceleration and a slight hesitation.

I found the fuel air mixture was wrong and when it was corrected there was a MASSIVE hesitation. An independant mechanic who supposedly knows these 103 engines so WELL told me it was fuel related and most likely the fuel distributor or the fuel governor. Well ....

Now just by luck I thought that I had fitted the wrong spark plugs in the last service a few months ago. So I bought the correct ones from the dealer.

Came to change them and found that the plugs I had were the correct ones BUT.....

Covered in oil!!! Particualrly the first plug, so much oil that I could not see how the spark would happen to burn the fuel..

Now I am almost 100% percent certain that the valve STEM seals are to blame here. So I will be replacing the following:

VALVE GUIDES
VALVE STEM SEALS
HAED GASKET
CYLINDER BOLTS.

iF any of you guys had this job done on a 103 300E before, could you PLEASE let me know what else could be needed and any special TOOLS required?

Thank you kindly for all your help!!

overboostTSI

You can usually get away with just changing the valve stem seals. I had the same problem, changed the valve stem seals and haven't seen anything disturbing on the spark plugs since then (6 years ago).
These cars are known for having fuel system problems too like your mechanic said.

danholm

Timing chain

SAMM

whoa! Timing chain??

I thought they were really good on the 103 engines??

Anyone else have an idea about this?

Thank you kindly,
SAM

dan_c

Yes, timing chain!
while youre allready deep in the head, you might as well check that out... maibe a little play, check the tensioner and guide rail... many miles and brutal ups-downs in rpm get you there...
I'm also there, with white smoke and dirty spark plugs...
things to do: valve stems and guides, gaskets, distributor cap and rotor (coroded really hard), spark plugs and wire set...
did the perfect job on m102 (=m103-2cyl.), so it would work for another 200k miles...
Also check the air-fuel, that might be off, so check sensors to... and prey they're ok!

SAMM

OK we will definately be checking the Timing chain out and the tensioner as well! Thanks for the advice guys..

Ive had the rotors and all electricals replaced with proper Bosch items. Im probably gonna renew the water pump as well while Im disabling the car for this long period..

124-Fan

Checking the timing chain while you are at it won´t hurt, but even if the timing chain is beginning to stretch it won´t cause oil on your plugs. You can estiemate the chain´s condition by bringing the crankase to its tdc mark (rotating clockwise viewed from front with the tensioner installed) and see how much the camshaft is off its mark.
-But replacing the seals should cure your problem, unless your headgasket is really bad. And if the chain tensioner fails or gets stuck, it is always recognised by a light mechanical clonking sound, as the chain´s slack starts making noises..

The timing chain is usually good up to around 350 or 400 thousand km., although I´ve sometimes replaced it at an earlier point while doing a headgasket.

Cheers,

SAMM

Thanks a lot 124fan,

Yes I will be taking the head off hopefully this coming weekend. I have a close friend of mine (Merc trained as well) who will be with me throughout the work. We will first remove the head and then have a GOOD look at everything.

May even change the water pump and hoses if they seem a little worse for the wear. Will check the timing chain for play as you say, that is for sure.

I will keep you guys updated and if there are any more tips I'd be very grateful!

Thank you kindly,

myfirstbenz

If you are that deep in the motor, not changing inexpensive parts such as the timing chain, guide rails, and tensioner would be absurd. Also get that water pump changed out since it is not that fun and doing it at the same time as the head gasket makes a world of difference.

SAMM

myfirstbenz

what a beautiful 280sel...isnt that the one from the James Bond movie Octo*****? When it drives on the railway tracks? Very very cool

Yes we will be checking all these components out for sure when we take off the head. Its done 129k miles so usually the timing chain would be ok. But You just never know and I would like it to run properly for once. Since Ive had it it has been spitting out petrol, so sluggish acceleration and ridiculous fuel consumption have been ever-present. Basically drives badly. Luckily I have my Impreza WRX Prodrive and a Golf GT TDI so I can park up the Merc and work on it instead of having to use it while its not right.

rivcal4life

Lmao @ the word filter...

SAMM

HAHAHAHAHAHHHAHAHAAA

I didnt realise that!!!

SAMM

A little update guys,

A very experienced head mechainc at the Merc dealer told me how to avoid the massive job of taking the head off and doing all these replacements JUST because the Valve stem seals need replacing.

SO he lent me a special tool, I bought an air compressor, valve stem PLIERS, and a rocker remover.

i will be attemptimg to do it over the next few days with my friend who is a fully trained Merc tech and I will let you guys know everything, as Im sure some of you have this problem (very pop issue on m103)

SAMM

W124-FAN is the man!

Thank you for his perfect description on how to get it done. Did NOT need the air compressor at all.

spring compressor
valve stem pliers
magnetic tool with small precision point

of course all the other usual tools (sockets etc) that you would have already.

Much easier if you have a friend to help you as its a bit tricky trying to do some of the things just with 2 hands at once.

just get 1 and 6 pistons at TDC. Work on those.
then 2 and 5 at TDC. work on those.
then 3 and 4 at TDC work on those.

Like this there is no risk whatsoever of the valves dropping down that would require the head to be taken off.