OM617 W116 300SD Front Crank Seal Replacement--Can It Be Done With Radiator In Place?
 

The front crank seal in my 1980 W116 300SD is leaking. I'd like to replace it, but the OM617 engine manual says to remove the radiator. I really don't want to have to drain the coolant and deal with plugging the lines to the transmission and oil cooler. Removing the radiator is a pain anyway.

Obviously the fan shroud needs to come off, but it looks like there is enough room to get the crank pulley and harmonic balancer off with the radiator in place. Even if for some reason the bolt in the center of the puller tool is too long, I could cut it down or make a shorter bolt. I can get underneath the car to work on the seal and can put cardboard or something over the radiator to protect it.

Has anyone replaced the front crank seal with the radiator still in place? I am hoping I am able to do this. There is a good 5" between the face of the crank pulley and the radiator. The width of the pulleys is about 3", and they don't need a puller tool to remove them. That leaves the harmonic balancer, which itself is only about 2" wide. By this time I'd have about 8" or so of clearance between the harmonic balancer and the radiator, which should be plenty of room for the puller tool, especially if I cut down the center bolt. What say ye?

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If you remove the pulley from the balancing disk there is enough room to remove and re-install.

However, you will not have favorable conditions when realigning new pins and installing the balancing disk. It is highly suggested that you remove the radiator.

Drain the coolant into a very clean container and reuse it. It is worth the added effort in this case.

Thanks for confirming that there is enough room. I had thought about the difficulty of installing the dowels. I'm fairly flexible and think that I may be able to install it all with care, especially if I have a mirror taped up in a proper location.

Not only is draining the radiator a pain, but disconnecting the transmission and engine oil cooler hoses and not getting them to leak all over is a hassle. Just unbolting the radiator with oil cooler from the body is a nuisance. I'm hoping that since I'm agile and fairly dexterous that I can do the job while avoiding removing the radiator.

I suppose I can try it my way, and if it doesn't work, remove the radiator as plan B.

I think you can remove the radiator without removing the oil cooler.

I think it can be, except the long bolts that attach it to the radiator have to be removed toward the front of the car, and the air conditioning condenser is in the way. I think it makes it nearly impossible to do, but I'll have to look at it.

I did on an '83 300D. Probably not materially different than a W116. Round up a LONG breaker bar for the crankshaft bolt. An 18" version probably isn't going to cut it.

Sounds like someone put the clamps on backwards.

Perhaps a clue indicating that the engine might have been replaced at some time:)

I don't think the oil cooler bolts are reversed. All the ones I have seen slide from the front of the car toward the back, making removing the oil cooler by itself difficult. I don't think it's possible to slide the bolts in from the back to the front, and the nuts would never go on the condenser side. At least this is what I remember from my last 300SD and the others I have taken parts from. I've never been able to remove an oil cooler without removing the radiator with it, unless I bent the condenser out of the way.

I'm pretty sure I have removed the radiator without the oil cooler on a 115 body which is pretty similar to the 116.

I would not consider trying to replace the HB without removing the radiator. Getting in the lock pins without ruining the crank nose is difficult enough with the engine on a stand.

Many many of these engines have been ruined by folks buggering up the installation of the HB and its locating pins. I had an engine that was this way when i bought it....ran beautifully but the HB was wobbly. before it was all over I had bought a new (used) crank and gone through the motor at considerable cost. it was a lovely motor after all that but it was completely unneccessary because someone did not get the pins installed correctly.

Whatever time it costs you to remove the radiator you will more than save it on the HB and seal installation.

Yes I have done it
 

I had to replace a balancer hub on my friends '79 300SD (pulley bolts got loose somehow, and stripped out two bolt holes). I did not remove the radiator. The hardest part was getting enough leverage to loosen the crank bolt. Getting the dowel pins lined up was not as big a deal as I was led to believe it was going to be. The puller I had worked well, with plenty of room with the radiator in place. When you go to put the crank seal on, use a cone shaped plastic drink cup as a sleeve to slide it on over the crank sealing surface.

Would you do it that way again?

Absolutely.

I'm glad to know that it can be done with the radiator in place, though care would have to be taken to ensure the radiator does not get damaged.

I have never been able to get a radiator off of a W116 300SD without also pulling the oil cooler. I don't think the long bolts can go in from the engine side because the clips that hold on the fan shroud that the bolts go through don't have a square hole for the head side to fit through. Removing a radiator on one of these has always been a pain job that takes almost all day. I'm going to try to replace the seal with it in place, but if not, then I'll resort to removing it.

I will replace the spacer ring on the crank, probably sliding it partially onto the seal first, then pushing the seal and spacer onto the crank in unison, thus not needing the plastic cup sleeve.

I plan to bake the balancer at 250 F and then slide it on with oven mitts as others have said to (maybe with the crank end greased). I plan to have the dowels in the freezer overnight, then I can put grease on them and push them into place. Apparently, the engine manual states that the balancer goes on first, then the dowels are driven into place.

I would have a problem with baking the balancer (just the hub, and no rubber pieces) because of that much heat next to the seal once it is installed. I have done several with the dowel pins still in the crank, and installing the balancer hub cold. I also don't know how you are going to remove the old spacer ring with the crank still in the engine. Maybe it can be done, but I don't see how. I believe it is pressed on (otherwise it may turn on the crank). If you are able to remove the old one, you are a better man than I.

250F will be no problem at all.

The spacer doesn't rotate on the crankshaft because it's sandwiched behind the balancing disc, which is under the influence of a bolt tightened to a pretty high torque level. I pulled my spacer ring off with two flat screwdrivers, 180 degrees apart. Simultaneous, opposing force is the key.

Considering that the dowel recesses in the balancing disc do not extend fully through the disc, that's quite the trick.