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Harmonic Balancer Woes...
I have an 1983 300 D Turbo that I bought recently. It had such horrendous motor mounts that my kids and wife named it the Rattlemobile. Well, after changing the motor mounts and adding a hood pad, it doesn’t rattle anymore, but now there are more serious problems afoot.
While driving a car full of sleeping family home from grandma’s, the power steering went out, battery light came on, and the motor began to run hot. I had no choice and limped home, eyeing the temp gauge the whole time, and later discovered that the main pulley was not turning at all. My friend, and experienced Benz wrench, declared the following: It appears that the following is the most likely sequence of events on this failure*... motor mounts out, continued operation caused extreme vibration, crankshaft snout bolt backed out about a quarter to three eights of an inch (no locktite evidenced on the snout bolt and the vibration*also completely backed out and lost the alt pivot bolt), harmonic balancer backed*outward enough to clear the keyways, the*woodruff keys disintegrated under the increased extreme load, the balancer spun ....snout of the crank?* Questionable, I'm anxious to see what the new*woodruff keys will look like*since the recesses for them on the crank nose look ... well ... weird to me ... Any advice on how to proceed? I have searched the old threads, but some questions remain: Would photos of the crankshaft snout help? Since I don’t have the old woodruff keys, which should I get? Fastlane has several, all calibrated to different angles. How can I tell which ones to get? Anybody have any ideas on how to hold the crankshaft in place while we torque on it without the $167 tool? I am sure more anguished questions are to come, and thank you in advance for your kind replies RSCarey |
Sure, pictures would help. I just hope there's no damage to the crankshaft or balancer. What is this $167 tool you're talking about? The crankshaft should just bolt back in with a large deep socket. While it's out, I'd change the front seal. The hard part is holding back the engine while tightening. I believe there's someplace down by the balancer that a tool can be wedged according to the maintenance manual. If unsure, I would just get the woodruff key from the dealer. It can't be that expensive. Paul central FL
300CD 1984 290,000 |
photos WOULD help. Pulley can be held in place by a bolt or pipe inserted through balancer slot. Don't confuse offset woodruff keys for cam sprocket with keys for balancer - the latter are cylindrical.
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I 've had a crank pulley come adrift, but if the harmonic balancer wasn't installed correctly and came adrift you could be facing some bad news. Its held in place with 2 dowel pins and a large bolt into the crank snout. Good luck
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Bad to worse
OUCH!
My friend and I pulled off the HB & pulleys only to find that the crankshaft is toast. The inside of the HB had no keyways, only a worn-out ring inside, where they used to be. At this point I am weighing my options regarding the replacement of the crankshaft versus finding another motor. I'll post some photos later so that you can all share in my pain. Any thoughts on proper crankshaft replacement procedure? Assuming the crank is bad, what else would indicate a trashed bottom end? What else should I do to the bad boy one it's out, opened up, and lying on the operating table? Anyone know of a good source for motors in the southern California area? RSCarey |
I'd try to find a good used engine if you don't know the history of the lower end of the existing one. There is a 300D listed on here somewhere that has been rear ended. You may want to look into that.
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Awful dude! Look into another engine, it is probably far cheaper than putting another crank into yours.
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Woe is me!
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As promised, here are the painfull photos of the thrashed crank in question. Finding out how bad the crank is did raise some ethical questions for me:
Should I do a band-aid fix and sell the Rattlemobile to some sucker? Should I part it out? Should I attempt the fix on the crankshaft? Should I get out of the Benz business all together? What I decided: I couldn't foist it off on someone else in good conscience, and can't afford a $4000 rebuilt motor--or even $600 for a used mystery motor--at this time. I also had to admit to myself that I am hooked on MBZ. Since I found a pulley and HB assembly for $75 at a junkyard in San Diego, I am going to order up new dowel pins and put it back together. Meanwhile I am taking bets as to how many miles the thrashed crank will last with the new HB/pulley. I am thinking that the problem started when the crankshaft bolt worked its way loose, allowing the old HB to flop around, totally unsecured. Hopefully with some loctite and the correct torque applied, the band-aid fix will last at least until I save up some $$$ for a used motor from a reputable source. The question is--for how long??? Who will make the first prediction? RSCarey |
Thank you for the pictures
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First prediction = best guess: If the bottom groove that I can not see, is no worse than the top, the oil seal is replaced, and the bolt has Loctite® applied + proper torque. Two - five years or between fifty and one hundred thousand miles. |
or you could weld it permanent;)
The other option is to find another crank and replace it. Plan on replacing the brgs while you have it out. Is the engine still in the car?
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I had this happen to me - several times. I finally got another engine.
It might work for you, it's certainly worth a try!. Be sure and line up the dowels correctly. The are not 180° apart...more like 185 & 175 - eyeball it really close, and you will see what I mean. Good luck! |
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Replacing the what? I'll post an update when I have more 411. RSCarey |
Main and rod bearings.
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Success!
Gentlemen,
With your kind advice--especially Larry Bible and WHunter--my friend and I put the Rattlemobile back together yesterday. The two pins cost $1.21 each from the local MBZ dealer. The replacement harmonic balancer was $75 at a San Diego junkyard. We'll see how long the repair holds. Replaced all the belts, installed a new top radiator hose and thermostat, inspected the brakes, serviced the transmission, topped off the brake fluid, and adjusted tire pressure. Thanks to you all, the Rattlemobile rides again. RSCarey |
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