420A 420a Rod Knock...Piston Slap... What the heck is Knocking...?

[Morris95talon]

Hello dsmtuners! I first want to thank everyone for the fast response in my last challenge. Got me back on the road for a good year! Until recently I had a tensioner bracket break due to a failed plunger style tensioner. So yeah cylinder head valve damages occured. After changing the head seals and gaskets new, everything ran better then before and best of all No blue smoke. I noticed a knocking developed at start up and RPMs super low but when the car corrected it's idle the knock would go away. Then when approaching a stop the knock would come back but if I kept my foot between 1000-2000rpm No knock. I just changed all Connecting Rod bearings and oil pump and when reassembling the engine and turning by hand right before TDC it felt as if every little tug I would hear a slight knock and something dragging I stopped at this point before I do anymore damages. Not sure if it's rod knock piston slap or or something simple like low blinker fluid. Thank you again for everything everyone does and thank you for everyone's Hard work!!

 

[97egl]

When rotating by hand if the noise happened at TDC when the piston is changing from going up to going down you could have a piston with a loose wrist pin bore. Unsure of what the dragging could be or if it could be related

 

[BLACK'98DSM]

Do you have a video of the noise? Any idea of the general area it's coming from? Does hot vs cold make a difference?

 

[DSMPT]

I noticed a knocking developed at start up and RPMs super low but when the car corrected it's idle the knock would go away. Then when approaching a stop the knock would come back but if I kept my foot between 1000-2000rpm No knock.

This doesn't sound good. Could be spun bearings.

I just changed all Connecting Rod bearings and oil pump

Why did you change the rod bearings and the oil pump? What happened before?

when reassembling the engine and turning by hand right before TDC it felt as if every little tug I would hear a slight knock and something dragging

I can't be so sure since it's hard to know the situation without seeing but the first thing came up in my mind is you may have an assembly error. Maybe you didn't recondition the rods or/and the bearing clearance was improperly set. Something like this sometimes happens when you spun the rod bearings really badly before and just replace the rod bearings. The rod caps could be deformed by spinning bearings.

 

[motomattx]

My wag is going to be a rod issue, possibly a bent rod.

 

[Morris95talon]

This doesn't sound good. Could be spun bearings.

Why did you change the rod bearings and the oil pump? What happened before?

I can't be so sure since it's hard to know the situation without seeing but the first thing came up in my mind is you may have an assembly error. Maybe you didn't recondition the rods or/and the bearing clearance was improperly set. Something like this sometimes happens when you spun the rod bearings really badly before and just replace the rod bearings. The rod caps could be deformed by spinning bearing

This doesn't sound good. Could be spun bearings.

Why did you change the rod bearings and the oil pump? What happened before?

I can't be so sure since it's hard to know the situation without seeing but the first thing came up in my mind is you may have an assembly error. Maybe you didn't recondition the rods or/and the bearing clearance was improperly set. Something like this sometimes happens when you spun the rod bearings really badly before and just replace the rod bearings. The rod caps could be deformed by spinning bearings.

The knocking developed slowly a couple months after the rebuilt cylinder head. I tried almost everything fluid wise like engine treatment which seemed to help I used rislone seemed to help then finally I decided to try to fix the issue so I thought let me check the rod bearings and they were all damaged except 1( cylinder 3) 4 seemed to be the worst let me add photo of the the bearings. Thinking it's rod knock reassembling checking clearances. Reassembled fired up then still same knocking. Checked bearings all were fine. So I ordered new oil pump..and here I am... Thank you for your help

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[Morris95talon]

As it's reaching tdc it knocks. I tried to post vid but it won't allow

 

[DSMPT]

The knocking developed slowly a couple months after the rebuilt cylinder head. I tried almost everything fluid wise like engine treatment which seemed to help I used rislone seemed to help then finally I decided to try to fix the issue so I thought let me check the rod bearings and they were all damaged except 1( cylinder 3) 4 seemed to be the worst let me add photo of the the bearings. Thinking it's rod knock reassembling checking clearances. Reassembled fired up then still same knocking. Checked bearings all were fine. So I ordered new oil pump..and here I am... Thank you for your help

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Judging by the pic, IMO a new oil pump and new bearings probably wouldn't fix the issue. Would be just a band-aid, the same thing would probably happen sooner or later. Obviously something is out of spec, and probably journals are damaged, too. Especially cylinder #4, it looks the bearing tang is gone.
If I were you, I would disassemble the engine and inspect all parts roundness, straightness, flatness etc and repair/replace, instead of trying another new parts. And would rebuild the engine properly. If you don't have proper tools for that, should ask a machine shop to do that.

 

[Morris95talon]

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[Morris95talon]

Okay I found this behind the starter

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[BLACK'98DSM]

Is the head broke off the flex plate bolt? Or is it just loose?

There's a dust cover at the bottom of the transmission that gives you better access to the bolts. You can do whatever needs to be done through there.

 

[97egl]

Even with the bolt fixed the damage to the #4 bearing indicates the rod journal on the crank has some damage. If you polished the crank it would give it a longer lifespan but without having it turned at a machine shop it'll probably develop another knock in short order. (I hope it lasts for quite a while, but reality is that it's not a long term fix)

 

[Morris95talon]

Thanks to all your tips again!!! Everyone Your truely what makes this community work in unity!!!. Well this is absolutely causing the freaking knocking and tugging. So just to update. Thank you I made sure to polish before bearings installed and now going to attack the flexplate/flywheel. I am just going to replace it due to those bolt holes being stretched out.

 

[DSMPT]

Okay I found this behind the starter

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Yeah the video's sound is from this. Not internally occurred.
But just keep in mind that what I said above means you probably have another issue internally. You should inspect all parts, and fix/replace if necessary, and rebuild the engine properly at once. I strongly reccomend it. Otherwise it would still be a time bomb.

 

[Morris95talon]

Yeah the video's sound is from this. Not internally occurred.
But just keep in mind that what I said above means you probably have another issue internally. You should inspect all parts, and fix/replace if necessary, and rebuild the engine properly at once. I strongly reccomend it. Otherwise it would still be a time bomb.

Absolutely thank you!! I'm currently in search for a short block to rebuild with the cylinder head I have....any suggestions?

 

[BLACK'98DSM]

Absolutely thank you!! I'm currently in search for a short block to rebuild with the cylinder head I have....any suggestions?

Just be patient and wait for a low mileage engine. Less than 100k miles would require the least amount of machine work but I once bought a 420a with 130k miles and almost everything was still within spec. No matter how many miles are on the engine you purchase, you still need to take it apart and check the condition of all parts and check your clearances. You're just less likely to do a 100% overhaul on a lower mileage engine.

It's probably going to be tough to find one in decent shape. Remember that Eclipses, Talons, and Avengers used the same longblock assembly. Some Neons used the same shortblock assembly. Don't be afraid to get your hands dirty at the junkyard. Occasionally a car with super low mileage will end up at the yard because it got t-boned or rolled multiple times or what not. The engine is usually salvageable. The other option if you have no junkyards nearby is wait for a partout near you. This will probably take some time.

 

[Morris95talon]

Thank you so much that's what I needed to know I appreciate the tips! I'll be back with updates

 

[97egl]

It's probably going to be tough to find one in decent shape. Remember that Eclipses, Talons, and Avengers used the same longblock assembly. Some Neons used the same shortblock assembly.

Just to add to this chrysler sebrings from 95-00 also use the same longblock assembly and tend to be less beat on since its the only car that came with a 420a that was not a "Sportscar".

The neon DOHC engines use the same shortblock. The SOHC neons the shortblock is almost the same but the pistons are different and will give you a lower compression ratio so you'd want to change to 420a pistons. On SOHC neons 01 and newer there may be a few other differences as well.

 

[Morris95talon]

Yes!!! Thank you!! i was at the junk yard today peeking around and noticed the convertable sebrings but wasnt sure. And now that i picked up my new flexplate im excited to get her back on the road. So just to help confirm this challenge was the Flexplate. The bolts backed out and when the engine rotated the bolts were tapping the shield but it literally sounds like the rod hittng the upper cylinder but upon closer look when rotating the engine the torque converter is rocking back and forth and when it knocks it echoes.. So crazy would have never thought.
Thanks again DSMTuners! Your the Best I will keep updates