HGF concern - Mercedes not immune

[mercrocker]

Had a bit of a misfire in the 190E recently.   Replacing the leads for new MB genuine ones not only relieved me of a month's beer money but cured the misfire (which was only apparent in damp weather).

 

However, the car still fluffs on initial start up (its also had new MB genuine dizzy cap and rotor arm) and I am concerned that the head gasket may be telling me it will soon be kettle time...

 

I know they suffer around 100,000 miles and that the 1.8s are especially prone (tick both these boxes in my case).

 

Rather than wait for the inevitable is there anything I can do to confirm my fears?

 

 

[filthyjohn]

Check for water in the oil, oil in the water, I'm sure you knew that already. The type of HGF to cause misfires could be the subtle early stages of water/oil getting into the combustion chambers (you'd see some smoke), or the most pernicious of all, combustion gases into the coolant or the oil.

To test for the escaping gases, you can do a compression test to see if one of the cylinders is lower than the others, or use a hydrocarbon 'sniff tester' which actually smells the coolant for escaped combustion. Most garages may check it out with the sniffer for free or nearly free.

[Bear]

M102 8V?

 

Check the breather systems first - the SLK (M111 supercharged, so more complex) was suffering all manner of issues all down to oil in the intake and clogged breathers. My experience of M102s is limited - the last misfiring one I had, it was down to the coil lead arcing.

 

It's not an especially complicated engine to work on though - if it's giving you the warnings, get the spanners out - do the head gasket and other gaskets/seals for the top end before it lets go properly, and then it should be good for another 100,000... Sort the timing chain tensioners/guides at the same time...

[dieselassist]

what state is the 'over voltage relay' in?? I had a similar misfire/ hard to start occasionally sympthoms - a new red 'two fuses' on top OV relay cured it... The originals are black, with one fuse uptop, and the red 2 fuse topped one is the 'upgrade'... these cars have a mixture of mechanical n ECU 'management' - all sorts of stepper motors n switches around the inlet/injection system, as well as vacuum lines as said above, which can perish n break down over time....

.

[gordonbennet]

Mercs usually start to discolour the coolant (dark ring around the tide mark?) before CHG lets go fully.

[mercrocker]

Thanks fellas.... Yes M102 8V...

 

 Currently no apparent or visible cross-contamination - oil clean, coolant still correct colour and level, temp normal in all conditions.  OVP relay tested previously (by substitution) in first round of misfires.   It only coughs a second or two before settling down to good idle and only then if its been sat for more than an hour.   "Feels" like leakage occurring when stationery - not enough to give a misfire at any other time, especially given all the new ignition parts.

 

I just remember my DOHC Granny doing this just before it grenaded the head in deepest Poitiers.     

 

I am not going to do this one myself as I already have a full schedule of winter fettling but I think I have got enough information now to risk putting it in for the job (I have used an MB specialist for the past 9 years and trust him to not have me over plus Mrs Rocker gets a free courtesy E Class for the duration).

She pays anyway!

 

I just don't want to let it get hot and do all sorts of other damage....