What to do about a wrist pin

[Monkey Uncle]

Well, now I'm thoroughly confused.   

Took it for a drive today, out on the highway to test the odometer (another issue that I won't drag into this thread).  Drove it a few miles at 60+ mph and then around town for a bit.  Noise decreased in intensity as the engine warmed.  After it was thoroughly warmed up, I made a couple of stops and noticed that I could not hear the noise at all from inside the cab when I was sitting still with the transmission in D or R.  When I shifted to P, I could immediately hear it again, although not as loud as when the engine was cold.  This behavior continued consistently until I got home and put it in the garage.

I know no one is going to definitively diagnose anything from what I'm writing here.  But I can't help but wonder whether a major internal engine problem would behave like that.  I really don't want to sink a couple grand into an engine swap or re-build if I don't have to.

[SkinnyG]

Could be worn pistons, which often are noisy when cold.

Maybe start socking money away, and if and when it blows up, throw in a rebuilt motor. 

It will probably last for years, still making the same noise like that.

[bd]

Without hearing the "knock" it's pretty hard to do anything but confuse the issue.  Measure the crankshaft end-play; should be 0.002" - 0.006".  Carefully recheck the flexplate for cracks.  You may need to unbolt the torque converter and slide it rearward then bar the engine over with a flywheel spanner and look for rust tracks using a bright flashlight.  Look closely across the entire face of the flexplate. 

[VileZambonie]

^ This

[Stewart G Griffin]

Do you have AAA?

No.  Are you suggesting just continuing to drive it until it blows?

Pretty much.  But make sure you have a back-up engine....or definitive plans/budget to get another engine.   Or have a back-up car.

i mean, you said you didn't want to sink a couple grand into a new engine......   This may be the most economical way.

i kind of concur with what Skinny G said.

[Monkey Uncle]

Thanks for all your thoughts, guys.  I talked to Mr. Mechanic again yesterday, and he says he's pretty sure it is a wrist pin.  Says he inspected the flex plate and torque converter closely and didn't see any issues there.  I'm going to talk to another guy today who supposedly does re-builds and see what my options are there.

Still thinking about the just-keep-driving-it approach.  It's not my primary transportation and I don't put many miles on it, so although having to tow it from it's death site would be inconvenient and an added expense, I'm not too worried about it being out of commission for a while.  The big thing that worries me about driving it til it blows is the potential for additional damage.  If it goes catastrophic, I probably lose the block, which means an extra few hundred on the replacement engine due to not having a core to trade in.  Also, I'm thinking the forces generated by a catastrophic failure could destroy other parts of the drive train, or even present a safety hazard due to flying parts.

[Stewart G Griffin]

That was my reason for asking if the engine was smoking, or losing oil/coolant?   If not, then that is another reason, in my opinion, to just keep driving until the engine quits.

While it isn't good to lose a block, a lot of the gm replacement engines---like the crate 350 don't have a core charge.

As far as the engine exploding and causing a safety hazard.  In my opinion, not likely.  Unless the crank comes out of the engine----which is unlikely.

[Engineer]

This is free and you can do it yourself:

Take your valve covers off and tighten all 16 of your rocker arm nuts 1/4 turn. This will determine if you have a loose lifter or any other valve train issue. This does not sound like a wrist pin or rod bearing to me.

[Monkey Uncle]

This is free and you can do it yourself:

Take your valve covers off and tighten all 16 of your rocker arm nuts 1/4 turn. This will determine if you have a loose lifter or any other valve train issue. This does not sound like a wrist pin or rod bearing to me.

Thanks for the suggestion.  If I remove the valve covers, do I automatically have to replace the gaskets?

[Engineer]

This is free and you can do it yourself:

Take your valve covers off and tighten all 16 of your rocker arm nuts 1/4 turn. This will determine if you have a loose lifter or any other valve train issue. This does not sound like a wrist pin or rod bearing to me.

Thanks for the suggestion.  If I remove the valve covers, do I automatically have to replace the gaskets?

No, but the odds are better than not that they will leak afterward. You can use RTV to reseal the valve covers, but that is the Bubba way. If you buy new gaskets then you will have peace of mind. Just don't over torque the valve covers. It's a mistake that is easily made on the perimeter bolt type.

[Jerr-conn]

I agree with ENGINEER all the way, especially the valve covers, which also could be causing the
Oil leak on rear of engine. You could try some 20/50 wt oil. Thicker oil may make a diff.

[Irish_Alley]

just getting in but did you eliminate the flex plate like vile and BD suggested? did you unbolt the torque converter and push it back away from the flexplate then start the engine? did you make sure your bolts were tight?

[Monkey Uncle]

just getting in but did you eliminate the flex plate like vile and BD suggested? did you unbolt the torque converter and push it back away from the flexplate then start the engine? did you make sure your bolts were tight?

I did not do that personally, but the mechanic who looked at it assured me that he thoroughly inspected the flex plate and torque converter and eliminated those as possibilities.

[VileZambonie]

the same mechanic who says you need a new wrist pin?

[Monkey Uncle]

the same mechanic who says you need a new wrist pin?

Yup.  Believe me, that thought has crossed my mind.

I don't think he'd take me for a ride, given past experiences with him.  He once did an exhaust system patch to fix a doughnut gasket leak on my last truck, when he could have easily told me that I needed a new manifold.  He also did a very reasonably priced timing belt and water pump replacement on my son's car.  But I guess you never know.

Says he listened with a stethoscope on the block and could tell that the noise was coming from the driver's side, but he couldn't localize it to a particular cylinder.  When I told him about my spark plug wire test, he said you can't really tell anything from that because the parts are still moving up and down regardless of cutting the power to the cylinder.  IDK; like I said, I know the basic anatomy, but I don't really have the experience to second guess his diagnosis.