Cam Belt Failure

As additional folks come into the fold, old issues are new. Searching threads is fine but sometimes you just want to hear it fresh............

 

They have date codes. We organize them on the rack chronologically. I presume all the parts suppliers rotate FIFO, as we do.

 

Thanks Daniel. That's what I thought. How old are the belts that typically go out to customers?

 

I know this is an old debate- but it's just one of those questions you have to personally answer... That's not a cop-out... it just is. My car was well looked after but ended up going 10 years without change. Of course it only went 6k miles so the owner didn't lose sleep over it. He also didn't mind the original P-Zeros which would spin just letting the clutch out with no foot on the throttle pedal! Perfect tread depth and pretty with tire dressing and those beautiful yellow "P ZERO" markings but rock HARD and dangerous!

I could only imagine the cam belts. So within 100 miles of getting the car (and no sleep during that time) I got it done. I figured it was the time value of $1k of labor (so figure $60/yr) vs. the risk of catastrophic failure. So what are the odds? They made ~440 GTM cars in 5 years, and I'm sure at least one has failed in the 11 years they've been making them- so let's just say conservatively that my $60/yr is protecting a $25-30k repair with 1:440 odds meaning I'm about dead-evenly leveraged (i.e. $25-30k/440 is about equal to TVM of the labor).

I'm probably looking at it wrong financially, but it helped me sleep knowing I was reasonably spending $, avoiding a huge liability, and feeling more confident in the car.

But only you can answer this for yourself.

BTW- To Brian's point... I've attached photos of my old worn out belts and bearings. In reality you had to know which was old vs. the brand new ones because visual differntiation was virtually impossible. But again, to me it's still a great way to spend $60/yr.
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Jim,
This is really pointless, and threads like this have been started countless times on this forum over the years. You may wish to review those threads first, before proceeding further. Assuming 5 or 6 people jump up and say they went 10 or 15 years and 25k miles....what does that tell you? You think anyone that went that long and had a failure is going to post here and take the drubbing that is likely to happen? There is one person here that I am not certain is "public" about his experience, but he went 7 years (less than 30k miles) on his F355 and was scheduled for the major service when one of his belts failed and sheared a few teeth. I believe he talked about it on the FerrariList, but don't recall him talking about it on this forum.

 

I recall a guy (may be the same one, Dave) called me about belt service on an F355 from down south. Never heard back, so I assumed he went elsewhere to have the belts done.
12-18 moths later the same guy was posting on here about losing a belt and bending valves.
Lesson learned, I'm sure.

 

If you have not already read the previous 300 threads covering exactly the same ground they are still "Fresh".

What people come here and read they take away as truth. If the misinformation or stupidity is not answered in a more believeable presentation they will go away satisfied they know what they need to know. The result of that all too often is a broken car, an emptied bank account and another owner forever soured on the make and in all probability a wife who will never let him do that again. The cars and the owners mean more to me than that and I all to often am the one that gets to deliver the bad news. I am tired of it and I am tired of the constant new threads on the same old tired subject.

 

Usually 12 months or less. High volume stuff like 355/360 is usually within a 6 month period. For us, timing belts are a serial-number controlled item. We have a log book of when we purchased them (on which PO, from which supplier, etc) and when we shipped them out to a customer.

I'm quite anal about belts. Normally, when I pack a service kit myself, I'll "inside box" the belts in addition to our sealed bags. I worry that something heavy inside a box might inadvertently crimp/kink a belt in transit, or worse, an overzealous customer will run a box cutter right into the belt while opening the box.

 

Jim, I am glad that you mentioned that you are an ME. That puts the exact purpose of your question into better view. You need to research SAE (Society of Automotive Engineers) standard J2432. The answer you seek will not be found on this forum. You would need to see J2432 test data on various Dayco belts to determine what factors of safety are typically engineered into their timing belts.

Alternately, maybe you invest some time with the Ferrari service manual and a Dayco belt to do your own DFMEA and root cause analysis. Back into the answer by defining all the failure modes. Best of luck if you decide to pursue this further.

 

I think somewhere in the middle of this thread Daniel is right. I don't necessarily think the belt is the thing that fails, but rather other stuff. My bearings looked good, but I have read of ones that didn't, so I think that could be a failure mode. Also I think the fence broke off Daniel's car and ripped up the belt? My fences were super tight so I didn't mess with them, if they had been loose I would have welded them. Also some of the eariler cars had problems with the jack shaft bearings - mine seemed tight and F of Atl. stated my car was post the problematic date. All in all checking stuff is the biggest reason for taking the engine out. I haven't got mine back in yet, but it really isn't hard at all if you have a lift. My wife was making fun of me this evening buying a car that needs the engine out of it every 5 years while we run the heck out of her 06 5 series without doing anything but changing fluids. It is more of a hobby I guess, I'm an ME (Virgina Tech) too, so this is kind of a learning hobby. If I keep the car a long time I'll probably pull it again in 5 years just to go through all the stuff that could fail again...

 

I am not a mechanic, but I believe you are making a mistake. I'm not sure how the condition of the backside fence can be accurately determined without taking the gear off. And once the gear is off, the simply act of re-torqing that ringnut during installation **may** be a catalyst of fence failure.

My suggestion would be to remove the gear, drop a few blobs of TIG on the fences, then reinstall properly.

Others may have alternate advice, and I'd enjoy hearing their comments..

 

Preposterous, where do you come up with these thoughts Daniel? The fact that Ferrari finally figured it out on the 360's after 25 years of watching fences breaking off the gears YET chose to go cheap and still leave large areas unsecured? Let's not let facts get in the way of perfectly good "What if" conversations. One would be led to think you "Paid your dues" to have goofy ideas such as this.

I tried to refrain from getting involved in yet another thread of debate on how far one can let maintenance go as I could see no upside to being involved in this foolishness. I would have thought an engineer would have looked at the question with eyes open and understood that Ferrari handed us a wonderful design in the modular removable package where Everything could be serviced and maintained at a very high level. Brian is correct, folks read this nonsense and then make decisions that over time cost them a great deal in deferred maintenance costs yet it still seems to pop up a few times a year. It took about 8 years of us harping about cam timing before there was even a slight trend towards that being done correctly... why should this be any different? Why would anyone want to maintain a lowly Ferrari to a high degree?

I choose 3 welds on each fence as a minimum to reduce the unsecured fence area..... just cause. The fences are only tight... until they arent. I also choose to experiment with various methods of plating in an attempt to reduce the rust on the gears that is causing the highest amount of wear on the belt. Belts wear out for crying out loud. Daniel, if you ever stumble across the picture I sent you a few years back of the tooth wear on a 5 year old belt... post it up again and it will put an end to these foolish discussions.
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I'm not looking to join the debate, but all I find in the WSM is
to check the belt every 10,000km and replace at 60,000 km
on page B53. No reference to 3 or 5 years. Can someone tell
me where its documented.

 

Jim, Dave Monk:

If you read the comments from Daniel & David Helms, then plug them into a mental FMEA where the failure mode = belt breaks and the failure effect = valves contact pistons, the Severity Rating would be a 10, the Occurrence Rating would probably be low, like a 2 (since this may not happen very often within the total population of vehicles) and the Detection Rating could be high, like an 8, because the failure of the factory spot weld on the pulley fence is hard to detect during normal operation.

This produces a theoretical RPN of 160 out of 1000. (10x2x8 = 160)

You could come up with a higher RPN if you deem any of these values (especially the Occurrence Rating) to be higher than my mental guestimates.

Keep in mind this disclaimer: I have no first hand experience in any of these repairs, I'm just taking what has been written in various past postings and putting them into a risk occurrence model that engineers are used to seeing.

 

But that's the problem. The original pulleys are not welded at all -- they are simply pressed onto the gear. The blobs of weld are a critical improvement I think.

I know it sucks to "un do" a just completed belt and go through the hassle of installation again. But, my most honest suggestion would be to pull the gear and blob it. If you have all the right tools and you're careful with the ring nut, you shouldn't need any new parts or expense.

(Fair statement, Dave?)



Original appearance:
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Older version 132909 for comparison. Still, no weld.
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The governing documents in current effect are TSB 1003/A dated May 2008 and TSB 1215 dated May 2004.

These supercede prior documents of which there were many.

 

Are there any harmonic or balance concerns with these welds, or is the rotational mass and velocity small enough to not have any relevant impact?

 

Here you go...
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It happens far more often than you hear of Greg. These cars are aging and due to pressure to do Major's cheaper and faster.... many important things are getting ignored.

That's a tough call Daniel. IF everything is perfect the belt will never contact the fence at all. Set one component in place with a spec of Flyshlt under it and the belt will not center itself as intended and will touch the fence. If it is touching it will loosen the rolled edge in no time. I dont expect the welds to retain the fence under pressure from a non tracking belt. I am happy to just have the debris held in place while getting a warning like the baseball card in the wheel spokes of a bike.

It all boils down to how well one is assmebled, if its tracking exactly proper upon assembly and if every part stays the same condition as when it was assembled throughout the belt life. If yes to all the above, life is good. If not...... you have been there.

Just TIGing it without replating is an unknown. The welding will bubble the old flash CAD plating and that must then be bead blasted. I am on the 6th version of the plating process and think we are there. Not quite as simple as it appears, that thin fence getting welded to the gear is rather tricky without distortion.

 

thanks for that info Acemaster.

 

Dave, I absolutely believe you are right, and that might also explain why it took so long for the factory to implement a correction. Let's say they followed a conventional FMEA analysis like I outlined above, and they thought the occurrence rate was low. The Risk Priority Number (RPN) given to this issue would also come out low just like my earlier post. Someone looks at that RPN and says, "Oh, that's only a 160 so it's not really an issue that requires a corrective action." Then, over time the number of occurrences increases and finally the RPN score is elevated to the point where someone important starts to notice.

I used to work for a Detroit Tier 1 manufacturer that supplied anti-lock brake systems to Chrysler. These rigid analysis models were used all the time because it takes a lot of the subjective judgment and emotion out of the decision making process.

 

Things are 'a little' different with the Supercar manufacturers. Ferrari, being the front line player in the Supercar market, was a target for the Feds in many ways. They are a clever bunch, winning some but in the long run, loosing some. Think any Detroit manufacturer could get away with "Opps, sorry about that, we will fix it next year"? Look at the 355 and 360's, both models first year cars were Hot Rods and made front page in all the publications. Quitely they recieved a potato in the tail pipe the next model year. Coinsidence? Not hardly, the magazines already had printed the fluff articals, had everyone talking and dealers taking orders. Mission accomplished, next.

When the TR's were new, Ferrari had to contend with the "Annual Cost of Service Index" in N. America. Belt change intervals were set at 5 years here while in Europe they were officially at 3 years, even back in the late 80's/early 90's. Politics and Risk/Benifit ratio's had far more influance here than most realize, its a different mindset, Ferrari has nothing to do with transportation, its passion driven. A few years after a new models release no one looked at the ACSI, cars were out of warranty and it was clear sailing. Ferrari, by the very nature of the product, played on the ragged edge of technology, performance and politics to stay out front. Few factor that in when reading Factory recommended Service Interval's on these cars. Even fewer listen to their mechanics recommending a direction as they are obviously just pushing service work. The answers to the question are far more complex once you factor in the politics and mindset that came up with the original recommendations. Turn over enough rocks and you will see there are two sets of books in play. And with this folks want to push it further yet? Plug that into the calculator!