Author Topic: What to do about a wrist pin  (Read 16206 times)

Offline VileZambonie

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Re: What to do about a wrist pin
« Reply #30 on: March 10, 2017, 05:18:01 AM »
If you are trying to isolate a noise association with a particular cylinder then a a power balance test will certainly help you do just that. You generally want to bring the engine RPM to where you can hear the noise steadily. Short one cylinder at a time to find the culprit.

I would suggest you disconnect the torque converter from the flexplate and see what happens and follow bd's suggestions.

I have lots of "best mechanic" stories I can tell where they've overlooked the obvious time and time again.
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Offline Irish_Alley

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Re: What to do about a wrist pin
« Reply #31 on: March 10, 2017, 07:24:36 AM »
Quote
When you have eliminated the impossible, whatever remains, however improbable, must be the truth ~Sherlock Holmes

its in my Signature


your mechanic maybe very right but imo theres more dishonest ones or ones that just guess at your expense then good ones. my mom took her van to a shop that had been in business for a while. the old man past a few years before and the daughter took over. she was aways there when he was around and i think she was a good person but with no one honest in the shop to keep the guys straight they were doing some shady stuff.

moms van had a misfire on one of the cylinders, the van only has two coils so i swapped the coils thinking if the misfire followed it was a bad coil. well it didnt follow, she then took it to the shop they "tested" the coil the misfire was on and it "tested" bad. so they replaced it and it didnt fix the issue (spark plug boot had loosened up and arced the plug to the point it couldnt make good contact). there was also an issue with the EGR passages they said they cleaned. but when i found the messed up spark plug and boot i also found they never took the throttle body off to clean the EGR port. got the guy to admit that he cleaned it and when i asked how did you do it without taking the throttle body off he said he has a special tool that can do a 90° turn and clean out carbon. i then pointed out the fact if this tool did exist he just knocked carbon down into the valves. he got this dumb look on his face and turned around and walked out.

sorry for the story but it was to make a point, a shop can be nice and charge a good price on a timing belt but a bigger job like changing the engine they can make more money off you especially if its a crack flex plate or something simple.
If you can’t tell yourself the truth, who can you tell it to?~Irish_Alley

When you have eliminated the impossible, whatever remains, however improbable, must be the truth ~Sherlock Holmes

Online bd

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Re: What to do about a wrist pin
« Reply #32 on: March 10, 2017, 09:15:42 AM »
Look.  There isn't a technician out there who hasn't identified the wrong cause of a symptom.  We've all done it more than once.  Anyone who claims otherwise is lying.  Honest professionals will dust themselves off and learn from the experience, refocus and persist to find the problem, or direct you to someone who can.  Those who only claim to be professional will continue to live the lie. 

I do not imply that your mechanic is "taking you for a ride."  But, neither am I, or any of us, convinced he has sufficiently pursued the diagnosis to arrive to the correct conclusion with any degree of reliable certainty.  More likely, he's reaching for an answer, because he simply has run out of options... or willingness.  He said it himself, he thinks it's a wrist pin, but has no way to confirm it.  So, essentially, he's guessing.  That in itself doesn't make him right or wrong.  His diagnosis simply is incomplete.

If you trust this particular mechanic, I'm certain you have good reason based on the routine services he's provided in the past.  But, some of the assurances you claim he's made are in question when faced with extensive training and experience.  Candidly, I think he's at the edge of his comfort zone.  A power balance test is a tried and true method of diagnosis that works hand-in-hand with other diagnostic procedures and direct observation to come to a viable conclusion. 

Although wrist pin failures are uncommon, they do occur.  However, there are other failures that can easily be confused, sharing similar (not identical) symptoms.  Since none of us are there, we also are guessing based on what you've written.  But, our guessing is more to the point that the diagnosis is inconclusive.  At this point the best approach is to be methodical and start with the basics in a new unit of time, making no assumptions and "leaving no stone unturned" so to speak.
Rich
It's difficult to know just how much you don't know until you know it.
In other words... if people learn by making mistakes, by now I should know just about everything!!!
87 R10 Silverado Fleetside 355 MPFI 700R4 3.42 Locker (aka Rusty, aka Mater)

Offline 82silverado

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Re: What to do about a wrist pin
« Reply #33 on: March 10, 2017, 02:40:23 PM »
the same mechanic who says you need a new wrist pin?

My thoughts exactly.
82 Silverado 454/700R4
86 Buick GN
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Offline 82silverado

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Re: What to do about a wrist pin
« Reply #34 on: March 10, 2017, 03:31:43 PM »
Although I am relatively new to the board I can tell there are quite a few people on here that know a lot about what they are talking about. I am no expert but, I have been doing this kind of thing since I was 16. I am 52. Consider the years of experience in this one thread alone. We are only trying to help and we are all basically on the same page with our thoughts and comments. Consider our advice.
82 Silverado 454/700R4
86 Buick GN
02 WS6

Offline Irish_Alley

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Re: What to do about a wrist pin
« Reply #35 on: March 10, 2017, 11:47:52 PM »
righty tighty lefty loosey
If you can’t tell yourself the truth, who can you tell it to?~Irish_Alley

When you have eliminated the impossible, whatever remains, however improbable, must be the truth ~Sherlock Holmes

Offline Monkey Uncle

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Re: What to do about a wrist pin
« Reply #36 on: March 11, 2017, 05:54:13 AM »
Thanks very much for all your thoughtful input, guys.  I really appreciate your willingness to help out a newbie.  And your willingness to stick with a thread that doesn't seem to have any prospects for a clear resolution.  Maybe someday I'll know enough to help out someone else here. 

I hear what you're saying about the possibility that my mechanic is merely guessing.  Unfortunately I'm not any better at guessing than he is.  About the only tool I have left in my arsenal at this point is checking out the flex plate and torque converter myself.  Two questions on that:

(1)  Unbolting the torque converter and sliding it backward - does that involve dropping or partially dropping the transmission?  Or is there enough space to just slide it back?

(2)  Would I need to use a torque wrench when re-attaching the torque converter?  Loc-tite also?

I guess the other tool I have in my arsenal is taking it to another mechanic for a second opinion.  That might be interesting.

Your thoughts on the power balance test inspired me to do some more googling.  I'd never heard that name applied to the test, so using it in the search dug up some stuff I hadn't seen before.  This explanation in relation to engine noises suggests that piston and wrist pin noises actually can increase (or stay the same, but not decrease) during a power balance test:

http://www.autozone.com/repairinfo/common/repairInfoMain.jsp?targetPage=productsHowToInspect&leftNavPage=productsHowTo&pageId=%090996b43f80a011e8&subtitle=inspect

Quote
There are several different types of piston noise resulting from cracked pistons, piston slap, excess piston pin clearance, and other causes.
•Retarding the spark timing will generally reduce the intensity of piston noise.
•Grounding out the plug during the power balance test can increase a piston noise. This is the opposite result from the way a bad connecting rod reacts to ignition grounding.

Quote
Piston Pin Noise
•Noise from excessive piston pin clearance makes a "double click" sound at idle or fast idle.
•Pin noise often becomes more intense after the installation of new piston rings. The noise will gradually become less as the rings wear.
•With the engine running at the speed where the most noise occurs, grounding the plug wire will sometimes increase the noise even more. The noise level might not increase, but it will not become less. Piston inertia causes the noise, which is why the noise does not go away when the the spark plug is shorted out.
•The noise usually becomes less or goes away when the engine warms up.

That description seems consistent with my experience.  But again, more guessing.

Offline 82silverado

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Re: What to do about a wrist pin
« Reply #37 on: March 11, 2017, 06:49:16 AM »
righty tighty lefty loosey


 ;) ;)

Excellent advice!!!
82 Silverado 454/700R4
86 Buick GN
02 WS6

Offline 82silverado

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Re: What to do about a wrist pin
« Reply #38 on: March 11, 2017, 06:58:22 AM »
As to your question on the flexplate/torque converter.......just drop the dust cover and unbolt the flexplate from the torque converter. Nothing to do with dropping the transmission at all. There is space enough to slide it rearward so it is away from the flexplate. There is a torque for every fastener. Personally I don't know what the torque for the t/c bolts off the top of my head. Also I do use loctite on torque converter bolts but, not everyone does. I am not sure what the service manual calls for but both of those questions can be answered by looking it up in the service manual. There are some to look at here on this site in PDF format. I would download the one for yours and do some reading.

82 Silverado 454/700R4
86 Buick GN
02 WS6

Offline Monkey Uncle

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Re: What to do about a wrist pin
« Reply #39 on: March 11, 2017, 07:29:56 AM »
As to your question on the flexplate/torque converter.......just drop the dust cover and unbolt the flexplate from the torque converter. Nothing to do with dropping the transmission at all. There is space enough to slide it rearward so it is away from the flexplate. There is a torque for every fastener. Personally I don't know what the torque for the t/c bolts off the top of my head. Also I do use loctite on torque converter bolts but, not everyone does. I am not sure what the service manual calls for but both of those questions can be answered by looking it up in the service manual. There are some to look at here on this site in PDF format. I would download the one for yours and do some reading.

Thanks.

Offline Stewart G Griffin

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Re: What to do about a wrist pin
« Reply #40 on: March 11, 2017, 07:48:20 AM »
Also can you make a video of the engine running and post it?

Offline 82silverado

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Re: What to do about a wrist pin
« Reply #41 on: March 11, 2017, 09:42:44 AM »
I would like to hear it also.

You are quite welcome Monkey uncle.
82 Silverado 454/700R4
86 Buick GN
02 WS6

Offline Monkey Uncle

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Re: What to do about a wrist pin
« Reply #42 on: March 11, 2017, 11:30:54 AM »
O.K., haven't posted video before, so this might be a little clunky.

This is underneath when the engine is cold.

https://youtu.be/gamzysJv11E

Offline Monkey Uncle

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Re: What to do about a wrist pin
« Reply #43 on: March 11, 2017, 12:13:50 PM »
That seems to have worked, so let's try a few more:

cold engine from above
https://youtu.be/9OB5iDZqhww

cold engine from inside cab, trans in park
https://youtu.be/yqBAR7nILok

cold engine from inside cab, trans in reverse (sitting still)
https://youtu.be/Vq_5-FRSNzc

warm engine from inside cab, trans in park then shifting to reverse
https://www.youtube.com/watch?v=IX0-8YyEUsg

warm engine from underneath
https://youtu.be/VySNsYp9Cac

warm engine from above
https://youtu.be/ApCATqp3gsQ

Offline Stewart G Griffin

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Re: What to do about a wrist pin
« Reply #44 on: March 13, 2017, 08:25:42 PM »
links don't work........