W124 Radiator Plastic Elbow Over Heating

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Oct 1, 2005
E320 Coupe
:) Hi, i wonder if anyone can give me a little help.

I've just bought a second W124 320 Coupe (1993K (uk)) Drove the vehicle home, 200 miles, all working fine and please with my purchase.
2 Days later i'm travelling down the motorway with the cruise on at about 75mph and the temp gauge started to rise quite rapidly with steam coming from the left front bonnet. i pulled off to the hard shoulder and opened the bonnet. the small elbow plastic connector - top left of the radiator to expansion tank and "blown" out and steam was coming out of the radiator. I waited for it to cool, pulled of the motorway and topped up the radiator (afer re inserting the plastic elbow connecting the top of the radiator to the expansion tank). Temperature went back to normal and vehicle was ok for the next 100 miles.
Following day the radaitor light came on bright on the dashboard (it had illuminated dim/on off the previous time). the temperature was ok. I pulled off to the services and waited a while then put about 1 litre of water in the radiator.

This is the second e320 w124 i've had, both have now had the same problem with the radiator / connection to the expansion tank.

when running, (like the other) all seems to be fine and it runs great. Good oil pressure, temp at between 8 and 9 oclock on the gauge (can remember the numbers, but its not at the top end of the scale).

Anybody got any ideas?
you could try replacing the elbow joint with a new part from the dealers, there's an "O" ring on there which holds the elbow joint in and with time that loses it's effectiveness and the elbow can fall out.


i had the same problem on my previous merc so i purchase a new plastic elbow from the stealers and used 2 rubber ''O'' rings. never had the same problem again.
must admit this is the second time for me. first was a 93L 320 coupe about a year ago, second was this one a couple of weeks ago. both cars run very very well. Just concered what causes it? Oil looks like Oil, water looks like water and spark plugs look fine if a little black. metal part thin layer of black carbon while ceramic was sandy.
Is it just that the little o ring seal get knackered with age?
car is a one owner, fsh, 80k Merc E320 coupe on a 92 K reg.

Just wish the V220CDI was as good :p, that said, car is OK - its just the dealers. Pity as i fancied a new CL
sjc123456789 said:
Is it just that the little o ring seal get knackered with age?


replacing them makes all the difference.


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