1988 420SEL W126 Water Pump Removal - PeachParts Mercedes-Benz Forum

zymurgist · #1 08-15-2004, 04:25 PM

I'm trying to replace the water pump on a 1988 420SEL, and I can't reach the bottom bolt holding the water pump in place. I have removed the 6 bolts holding the main pulley, and the pulley then came off fairly easily. According to the shop manual, I have to remove the main bolt to get the balancer off, but I have seen several threads here that say that removal of the big bolt is not necessary. Should the balancer come loose without taking out the 27mm bolt?

William · #2 08-15-2004, 04:56 PM

I just finished the same job on a 1986, 420 SEL, same arrangement as yours.

Trust me, you don't have to remove the large bolt. The harmonic balancer is fitted tightly to the crankshaft and it requires some persuasion to knock it loose. I used an old tire tool as a pry bar working from one side and then the other and it finally popped off. One word of advice is to put down some paint so you'll know precisely how the harmonic balancer remounts because one of the circle of bolts that you removed to remove the crankshaft pulley is "offset" and can only reassemble in one position.

Once you get the harmonic balancer off of its perch, I recommend that you put the balancer and the pulley together on the work bench so as to line up the holes as you peer down from the top and put down some more paint so you'll know the relative position when putting things back together.

On reassembly, I first lined up the harmonic balancer on the crankshaft and tightened down all of the bolts, which remounted the balancer. I then removed the bolts and proceeded to remount the pulley, using my paint marks as reference.

I hope this helps, William

zymurgist · #3 08-16-2004, 11:40 PM

I worked the balancer loose. It just took a bit of PB Blaster and some gentle persuasion with a prybar. Even though I'm not thrilled about having to remove the balancer to remove the water pump, I'm happy that I don't have to pull it off the crankshaft. Been there, done that many times with small block Chevys.

As for aligning it for reinstallation, I had already indexed the balancer at TDC. (This was after turning the engine over several times, because I had just installed timing rails, tensioner liner, and a new timing chain.) Not only that, there is a green paint spot on the pulley that lines up with the peg on the balancer, so that alignment is fairly easy. I think that I may want to use a stud in one of the holes to get it started when I put it back together.