Tip & How-To about Mercedes-Benz 300-Class

Valve adjustment on a mercedes benz w123 240d 8v

So in starting this project your probably thinking to yourself,hmm i should have paid someone else to do this... but once you finish it on you own youll be thinking i bet i could get paid to do this...

so there are several specialty wrenches that are a must for this adjustment,ive heard of people doing it with home made versions but i can tell you that im not one of them. there are 2 perfecly bent 14mm wrenches and one oddly shaped wrench to hold the valve spring in place while making the minor adjustment.along with a set of feeler gauges that will measure .105 and up for intake and .305 and up for exhaust ., and a wrachet with a 22mm socket.
so first step would be removing the air filter assembly and other vaccum lines that run above the valve covers.there are 4 bolts that secure the throtle linkage to the valve covers along with 1 small e clip that holds the 2 parts togather.once the valve covers are clear of obstrctions there are only 4 nuts that bolt the covers to the top of the head, and will remove easily once the seal is broken(dont forget a new valve cover seal).
so for a second your going to see this pristine piece of work infront of you and feel fuzzy inside, then youve got to get your hands dirty. take your 22m socket and put it on your power steering pump pulley and turn it clockwise until the first cam lobe is pointed sraigt up, then take the feeler gauges to see if there is any space between(most overdue engines will have no space;remember that the intake valves should be at .105 and the exhaust at .305)then take the odd valve spring wrench and slide it into place on the top of the spring and double wrench the adjuster nut and lock nut. loosening the top nut and turning the bottom nut clockwise will avail for a larger gap, and counterclockwise a smaller gap. generaly said most valve nuts wont need to be moved more than 2 or 3 quarter turns of the wrench.once the exhust valve "feels" the .305 gauge go to the next size up to make sure that there isnt too much space in between, so say the next size up is .315(which is in mine) the .315 shouldnt fit but the .305 should.
the same needs to be done with the next 7,making sure to turn the cam lobes up with the power steering pulley, and measuring intake and exhaust valves closly.
once they are all adjusted everything can be reassyembled and put back togather.my steering linkage gave me some problems but nothing i couldnt get back togather...
so you did it, start it up, take it for a drive, see if you have any more power than you did before...have fun and safe motoring.

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