I do not understand what you are saying Frank.

1. The crank sprocket is keyed to the crankshaft.
2. The harmonic balancer/pulley is bolted to the crank sproket.
3. The balancer is held to the sprocket by a pin and with friction due to the bolt torque.

It seems like the balancer can shear the pin and spin, while the sprocket is still in the proper position relative to the crankshaft. No damage should happen to the valves if this is the case.

What am I missing?

If the 3.5L is like the 3.0L, then the cam sprockets are turned through the belt that is driven off the crank sprocket. If the crank keeps turning without the sprocket affixed, the the cams don't turn - causing the valves to become motionless - while the crank is still turning and the pistons moving up and down going bang, bang against at least some of the valves, unless there's a spot on the cams where all valves are recessed - and the odds of that are slim. I don't think the engine would run with a slipping crank sprocket.

Frank

Frank,

I think he's saying the balancer pulley is spinning, not the timing belt sprocket. The broken pin is the one that aligns the balancer pulley to the timing belt sprocket, not the timing belt sprocket/crankshaft keyway.

Tommy

OK, Tommy - I see what you're saying and you must be right. I read it the other way 'round. He's spun the balancer - not the sprocket. <img src="/forums/images/graemlins/confused.gif" alt="" />

Who's on first?

Frank

I see this problem alot and this is the case. Toyota trucks with V6 suffer from this plague as do VW 1.9 TD I have seen many. The crank bolt is remove to service the timing belt and not properly torqued when reinstalled. In the VW case the bolt should not be removed just the pulley but many technicians assume it does. As Frank pointed out, the customer will often drive the vehicle until it doesn't run then you have to inform them that they have done extensive damage. I have repaired or replaced damaged components and I install thread lock on all, most get a new bolt. Even if I know I will be servicing it again in 100,000km. The biggest problem in retorquing the nut is stopping the engine from rotating and locking the flywheel/ring gear works for me. Good luck <img src="/forums/images/graemlins/cheers.gif" alt="" />

Hello Gentlemen,

Just to calrify, the crank sprocket remained securely keyed to the crankshaft and thus kept on rotating and driving the cambelt as intended, while the crank pulley was halted by the resistance of the driven accesories.

Depending on your frame of reference the situation can be described as the crank sprocket spinning relative to the crank pulley or the other way around (Was it Einstein that said everything is relative?). The important thing is that nothing spun relative to the crankshaft.

pcc, I am very relieved that the crank sprocket key held up. The car was only driven a very short distance after the failure occurred.

Thanks for all the contributions.

Regards

Gerrit

P.S. Correct crank center bolt part number for 3.5 DOHC, anyone?

MD172725 is the number I come up with. If I find the package that the one I bought earlier this week came in I will verify that for you. <img src="/forums/images/graemlins/cheers.gif" alt="" />

I've spent quite a bit of time in South Africa, but I don't believe (while there) I ever discussed the automotive definition of "spin" or "spun", so I can't say if I would have had trouble with that terminology in a country that (for the most part) speaks the same language. While we here in America are known for speaking "American English", I should tell you that we often refer to the word "spun" as having the meaning of a rotating object having become detached from that which it is normally mated. An example would be to "spin" a tire - yes that has two meanings - one when jacked up and the other from excessive torque.... both have the tire operating outside the normal conditions. Another example would be when a bearing is "spun"... also 2 meanings with similar differential logic. Just to clarify, when a piece that is normally affixed to a rotating shaft is said to have "spun" in the context that something unwanted has occurred, the generally accepted understanding here is that the part that is said to have "spun" has broken free of normal containment. Otherwise, it's just "turning" - or as you first said in your last post.... "rotating".



Actually, the crankshaft pulley "spun" relative to the crankshaft - or at least relative to the pulley hub..... even though the outer belt groove stopped moving. <img src="/forums/images/graemlins/wink.gif" alt="" />



He did have some theoretical knowlege..... <img src="/forums/images/graemlins/zombie.gif" alt="" />

Anyway, I'm glad we know what stayed in place and what let go... but wait... does "staying in place" mean that it turns with the crankshaft.... or not? <img src="/forums/images/graemlins/lol.gif" alt="" />

Good luck,
Frank

Thanks for the number, Doug. That is one of the the numbers mentioned in the recall notice on the 3.0 V6.

The bolt that I got from the dealer is numbered MN155081. It has the necked down section in between the bolt head and the clamping flange, but is not gold coloured (cadmium plated?), but rather is a sort of shiny grey colour. Now I am wondering whether I should be worried <img src="/forums/images/graemlins/scared.gif" alt="" />... I would appreciate it very much if you could check the number on your bolt's packet.

Regards

Gerrit

Hi Frank,

I would have to be the first to admit that my English language skills are not the best in the world (not my mother tongue), so thanks for enlightening me...(OK my other language skills are also suspect <img src="/forums/images/graemlins/wink.gif" alt="" />)

And yes, it would have been much better if the crank pulley had not rotated relative to the crankshaft either <img src="/forums/images/graemlins/smile.gif" alt="" />.

Regards

Gerrit