300TDT 281kmi
On Tuesday my harmonic balancer and pulley assembly nearly caused a catastrophic engine failure. I now know that it is rare but not un-heard-of for the six bolts holding the assembly to the crank shaft to work themselves loose.

It destroyed my radiator, cooling fan, and of course the h-balancer. I think I was rather fortunate considering I was at 65 mph when all hell broke loose under the hood.

I have never heard of or hand this happen to a car of any kind and I guess anything is possible but this is certainly preventable.

The only indication I had that something was wrong was a slight vibration when I started the car 6 miles earlier.

Get under there and give it a shake.

Take care,
Alec.

The harmonic balancer is held on by only one big bolt. The crank pulley is the one you are refering to that is held on by the six allen head bolts. In my recent 240D rebuild I used new bolts, torqued them to the proper spec and used removable lock tight on them.

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Jim

Sorry to read about your misfortune. I recall another thread talking about these hex bolts coming loose. Fortunately, that person caught the problem before any damage occurred.

According to the official M-B manual, the US model of the 300D has an aluminum vibration damper plate sandwiched between the belt pulley and the harmonic balancer (or balance plate as M-B calls it). The damper plate and belt pulley are connected to the harmonic balancer by 6, 8mm x 65mm hex head bolts. The 240D does not have the vibration damper plate. Engtawork is correct that the harmonic balancer for the 240D and the 300D is secured to the crankshaft by a single 18mm X 45 mm bolt torqued to 270- 330 Nm or 200-244 ft. lbs. Engtawork also makes a good suggestion in properly torquing the 6 bolts (35 Nm or 26 ft. lbs.) holding the pulley and vibration damper to the harmonic balancer (I did not use thread locker because the bolts have the spring-type lock washer, but that is up to the installer and a bit of insurance so long as it is not the permanent thread lock formula).

The M-B manual says the new vibration damper does not need to be balanced - so that simplifies that portion of the repair (mine has partial drill holes located in different places and different depths - which to me means the damper is balanced to the engine, but M-B says different).

Hope this helps!
Tom

__________________
America: Land of the Free!

1977 300D: 300,000+ miles

American Honda: Factory Trained Technician & Honor Grad.
Formerly:
Shop Foreman;
Technical Advisor to Am. Honda;
Supervisor of Maintenance largest tree care co. in US for offices in Tex.

Well Alec I am sorry to hear of your demise on your 300TD. Two weeks ago the Harmonic Balance let loose on my 240D. I am now in the process of gathering the parts to repair it.

I had had an oil leak from somewhere but I just could not figure out exactly where it was coming from.

My Harmonic Balance was still attached by about two threads of the crank bolt that was also broken in half. I caught it as I was going out of the driveway one morning and the power steering was not working and alternator light was on.

When I pulled it apart the oil seal was stuck on the HB , turning round and round with ever revolution of the engine(found the oil leak) and the HB grinding against the spacer ring . I guess I was lucky I was in my driveway when it went out.

My new Harmonic Balance is supposed to be in on Monday but I still have to get it balanced statically with the old one. On the 240D engine you have to do this to keep the correct engine balance.

I wish I had given mine a shake and a look see weeks earlier !
Keep me posted on your repair progress

Joe