Bad harmonic balancer - PeachParts Mercedes-Benz Forum

shiretmstr · #1 09-15-2009, 10:18 AM

I'm in the process of buying an '84 300D that had the harmonic balancer fail. It marred the end of the crank shaft and tapered the hole on the balancer itself. Beyond that the engine seems OK. My question is do I need to pull the crank and have it machined to adequately repair the damage or is it possible to do a minimal repair and use the engine as is? The car is in very good condition and I am purchasing it knowing I may have to do a swap with my '85 that runs perfectly but is dying of terminal cancer and other various ailments and afflictions (rotted floor, cracked windshield, electrical quirks, etc, etc). The engine in question has under 200,000, my '85 is approaching 260,000. I'd like to do the simple repair but want the job done correctly. Dale

kerry · #2 09-15-2009, 12:24 PM

Do a search on here for harmonic balancer repair. Some members have had excellent results with drilling new holes for the pins when the old holes got damaged. Other people have put on new balancers using the old holes. Pulling the crankshaft is a huge job and best avoided if possible.

junqueyardjim · #3 09-15-2009, 12:58 PM

Having messed with a car with that problem, I would highly recommend the only good repair. If the nose of the crank is messed up, fix it with a replacement engine.

#4 09-15-2009, 01:08 PM

Can you post a few pictures from different angles of the end of the crankshaft without the balancer in place?

shiretmstr · #5 09-15-2009, 01:58 PM

I'll be picking the car up later this week and will take pics at that point to post.

shiretmstr · #6 09-20-2009, 12:24 PM

Here are pics taken this AM. The end of the shaft seems to have chips broken out near the holes but otherwise seems relatively true. I'm leaning toward a bandaid approach first since this engine will have to be pulled and ultimately torn down to put it back to ideal. This will give me time to pull the '85 and replace crank seals, etc. while it's out. At best the repair holds and I'm home free. At worst I'm out the cost of renting a car dolly and gas to haul it home again I guess? Am I way out in left field? I've not had a balancer go bad so I'm in the dark as to what hidden issues might be involved.

shiretmstr · #7 09-20-2009, 12:54 PM

I've been looking through some of the posts on balancer problems. I'd love to hear feedback on what some of you think of the damage to this crank compared to what you've dealt with before I make any decisions. I don't rule out taking it to a shop either. I've got $800 in the car, it's got a few paint bubbles and a little cancer over the left rear wheel well but hasn't faded anywhere, and the interior is excellent. The passenger front seat and rear seats feel like they've never been used, driver's seat has a very minimal sag. I don't mind paying someone to rework the end if that's a good option.

junqueyardjim · #8 09-20-2009, 07:28 PM

Well, the damage to the nose of the crank is extensive. Now I think it could be repaired in a machine shop. But short of removing the engine and then removing the crank I don't see getting it repaired. You can spend time and money doing whatever repair you can think of while the assembly sits in the chassis, put it together, start it up and some real loads build up on that thing, and I think in short order you will be right back where you are now. It looks to me like the last time it was installed it was not lined up correctly. It will only go on one way and some people miss that point. The dowel holes are not 180 degrees apart, even though it looks like they are. So they forced it on, one dowel went in and the other got into the side of the hole. So now you have a large hole and the dowel will no longer fill it, plus you have displaced metal around the end of the crank. It will probably be extremely difficult to get a new balancer to slip over that crank.