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Discussion Starter · #1 ·
Apologies if this has been answered before but I couldn't find it. But does anyone know the technical reasons for the VVT intake & exhaust solenoids failure? I'm wondering because I've noticed an uptick of hard downshifting postings here and on FB the last several months. TIA

GM 12646783 Intake Solenoid
GM 12646784 Exhaust Solenoid
Cylinder Font Auto part Tool Engineering
 

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oil pressure and how often that thing is working.

You have to remember that the piston inside that thing has to push against the oil pressure. That's pretty substantial for something a small as that thing is. The other thing is from the time you start the engine until the time you shut it down that solenoid is moving non stop.
 

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All the failures I have seen are electrical. They look perfect but fail the resistance test. Unless there is an issue with oil contamination, the electrical components are thermal cycling which may contribute to premature failure.
 

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I doubt it's premature. It probably hat the components were built so they would fail after 14 or so years. Has nothing to do with use or mileage. Just like the timing chain guide and tensioner failures. planned obsolescence. Too many of them failing within a really short period of time to be a coincidence, they are designed to fail at a very specific age.
 

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All the failures I have seen are electrical. They look perfect but fail the resistance test. Unless there is an issue with oil contamination, the electrical components are thermal cycling which may contribute to premature failure.
You have probably dealt with more of them than anyone else. Have you paid attention to mileage at failure? The contamination failures I have seen seem to be high mileage, and I wonder if maybe the electrical failures are lower mileage.
 

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I doubt it's premature. It probably hat the components were built so they would fail after 14 or so years. Has nothing to do with use or mileage. Just like the timing chain guide and tensioner failures. planned obsolescence. Too many of them failing within a really short period of time to be a coincidence, they are designed to fail at a very specific age.
LOL
While what you say may be true, every engineering effort I have been involved with design to a life span, not a failure plan. more life generally equals more money and raises the price. In the car industry they will generally target a multiple of the warrantee period or a specific span of time that equates to the customers perception of a "quality" product.

In earlier times, before aero and MPG drove design, cars looked very different from each other and the companies drove the replacement cycle through styling. Changing the style every two or three years drove many consumers to go buy a new cr so they are not "out of style" with what is current. Smooth, fins, no fins, chrome, no chrome.. . But when MPG became a driver, the physics problem tended to make every car look very much like every other car.

I believe that one of the design criteria for our cars was use off the shelf parts that wold last beyond the 100k mile warrantee. And they generally achieved that goal I believe.

They chose materials based on what was available that was called out in their design guidance documents. Testing was done on application and life, number of cycles etc before the materials made it into the design criteria documents. A chain guide is made of this material and will last at least this long under normal operating conditions.

No engineer I ever worked with considered designing a product to fail. Everything fails eventually. Well maybe not a magnet. But you design for life with cost as a major driver. You dont design for failure.
 

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Most of them have been prett low mileage cars. In the 30 to 40k range
Interesting. I have seen solenoid coils in industrial valves overheat and fail when they get stuck, so i wonder if that is what is happening with the electrical failures. The car sits, the valve sticks, and when actuated it overheats and eventually fails sooner than normal.

I fully agree that parts are not designed to fail, certainly not based on calendar life. It would actually require exceptionally precise engineering to design in a failure just after the warranty period, and based on what i have read in these forums no one seems to think that GM engineers are that good in any case.
 

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LOL Well said

Most of the "engineering" going on at car shops is based on using what the tool is preloaded to allow. need a fastener? enter the location and materials and the design tool tells you what size fastener to use. In my experience, very few production engineers are actually designing new hardware from scratch.
 

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Discussion Starter · #11 ·
I thought one of the main parameters of engineering a vehicle part was price point? The lower the cost, the lower the quality of materials & labor to produce said part. In other words, low-bid wins the contract. I understand a bidder has to meet the specifications set out by the manufacture, but I also understand that its human nature to cut corners in order to win and keep a contract.
 

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An engineer will design for ultimate performance but the cost constraints must be considered. I frequently have customers ask "is this possible?" and I respond with "anything is possible as long as cost and timing aren't factors."

Frequently a design FMEA is used - "failure mode and effect analysis." In this case the failure mode is "electrical failure" and the effect is "poor engine performance". Each failure mode is ranked by likelihood that the failure would occur, severity of the effect of the failure and the effectiveness that a design control or feature to off set the first two. The 3 ratings are multiplied to create a Risk Priority Number. The failure modes with the highest RPN rating are addressed first as they would be most likely to occur, most severe effects, and little design control in place to prevent the failure.

Then there is always the "safety factor" that is taken into account with any engineering performance specifications. If you're designing something to withstand 100 psi of air pressure, for instance, you may use a safety factor of 25 or 50% to assure the design will safely and repeatedly exceed requirements. If it's a safety critical application such as an air brake system, that safety factor may be increase to 100% or more.
 

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I thought one of the main parameters of engineering a vehicle part was price point? The lower the cost, the lower the quality of materials & labor to produce said part. In other words, low-bid wins the contract. I understand a bidder has to meet the specifications set out by the manufacture, but I also understand that its human nature to cut corners in order to win and keep a contract.
But there is a risk in being the "low cost" supplier. If it's a safety critical item you could end up in court. If it's just poor performance you'll lose the work and risk future work. If the price point is unreasonable in my experience, I'll walk away from the work.

I just had a situation where a customer asked us to co-develop a door handle release system that their customer had already proto-typed in China. They asked me if we could compress our delivery and we developed a plan. The plan included switching plastic resin from the originally spec'd material as it was only made in Asia. Orders were place and we began building tooling and a color-house developing colorants to meet the OEM's requirements.

The resin maker then informed me that we would have to purchase truck load quantities of the material which would be about 5 years worth. I was able to find yet another alternative resin in a few days BUT the color match had to be re-started because of the resin change, pushing our delivery out another 4 weeks. My customer had to expedited more prototypes from China to meet pilot builds and wanted my employer to foot the bill because we were "late".

I wrote an e-mail and sent it the next morning stating that we are requesting them to find another source for their plastic molding requirements. We simply could not see a business case for maintaining a relationship where we would be financially punished for the shortcomings of a resin supplier (fortune 500) that are beyond our control. I also explained that a large part of the reason we were in this situation was our willingness to work every angle possible to help them achieve their delivery requirements.

In other words, shame on me for trying to help you.

They haven't pulled any work from us - it's been just over 2 months now.

;)
 

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FWIW, I recently posted photos of my VVT solenoids at over 100K miles. (Post #62, Investigating some metal in oil and filter @ 47k miles).

Essentially no problems with them, no plugged screens, no deposits, a little oil staining from age and no codes. This Monday after Thanksgiving they would have been in the car 16 years. I only changed them because I've been doing a little 100K perceived maintenance, but I do drive my car. Looking at all fluid changes (trans, diff, coolant), full brake replacement (rotors , calipers, pads, lines) and the third set of plugs (at slightly over 50K miles per set). Etc.

Monitoring mileage more closely, seems it's fallen off some since the VVT replacements. Car runs fine...knocking on wood!

Maybe I just got a good car. So far it seems happy. 🙏 :)

Richard
 

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a risk analysis generally includes probability of occurrence and consequences. A hi hi will be addressed. A hi lo not so much. A lo hi can be tricky
 

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FWIW, I recently posted photos of my VVT solenoids at over 100K miles. (Post #62, Investigating some metal in oil and filter @ 47k miles).

Essentially no problems with them, no plugged screens, no deposits, a little oil staining from age and no codes. This Monday after Thanksgiving they would have been in the car 16 years. I only changed them because I've been doing a little 100K perceived maintenance, but I do drive my car. Looking at all fluid changes (trans, diff, coolant), full brake replacement (rotors , calipers, pads, lines) and the third set of plugs (at slightly over 50K miles per set). Etc.

Monitoring mileage more closely, seems it's fallen off some since the VVT replacements. Car runs fine...knocking on wood!

Maybe I just got a good car. So far it seems happy. 🙏 :)

Richard
Lucky you.
 

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Just getting back to this...luck has nothing to do with it. The machine was well built and I maintain it as its needs arise. Often times being preemptive to a fault, economically, but I'm hardly alone in that approach. There may indeed be some "luck" involved being that I am the third owner. So, yes, perhaps some luck for both me and the machine. Could be worse...but were I bitter and unhappy with this car I would not be here.

Richard
 

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I thought one of the main parameters of engineering a vehicle part was price point? The lower the cost, the lower the quality of materials & labor to produce said part. In other words, low-bid wins the contract. I understand a bidder has to meet the specifications set out by the manufacture, but I also understand that its human nature to cut corners in order to win and keep a contract.
Price, delivery, and quality are the things that determine whether a contract is won and kept, and failure to meet any of the three can cause you to lose it. Price, in my automotive supplier experience, is the least important of the three, since failure to meet the other two can cause your customer to lose a significant amount of money due to warranty claims or the inability to produce the final product.
 

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An engineer will design for ultimate performance but the cost constraints must be considered. I frequently have customers ask "is this possible?" and I respond with "anything is possible as long as cost and timing aren't factors."

Frequently a design FMEA is used - "failure mode and effect analysis." In this case the failure mode is "electrical failure" and the effect is "poor engine performance". Each failure mode is ranked by likelihood that the failure would occur, severity of the effect of the failure and the effectiveness that a design control or feature to off set the first two. The 3 ratings are multiplied to create a Risk Priority Number. The failure modes with the highest RPN rating are addressed first as they would be most likely to occur, most severe effects, and little design control in place to prevent the failure.

Then there is always the "safety factor" that is taken into account with any engineering performance specifications. If you're designing something to withstand 100 psi of air pressure, for instance, you may use a safety factor of 25 or 50% to assure the design will safely and repeatedly exceed requirements. If it's a safety critical application such as an air brake system, that safety factor may be increase to 100% or more.
A very good description, but your safety factors are a bit off. Basic compressed air systems in factories, for example, are required by OSHA to be designed for a minimum of four times their working pressure (ie: 400%). Brake systems, that typically operate at 600 psi, are required by NHTSA to be tested at 7,000 psi, which is more than ten times their working pressure (ie: 1000%).
 

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Yes - I didn't mean to imply those were the factors in use, just as examples. Components we make in such things as air brakes are all designed by our customers so I haven't needed to understand the exact spec's.
 
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