LNF bad piston/ring. What should I do next?
I think I have a bad piston ringland or ring in my LNF. I want to fix the engine but i'm not sure what I need.
This last weak I've observed more and more misfires either upon deceleration or cruise, but none under acceleration. The car felt OK but my scan gauge said otherwise. I did a dry compression test with the engine cold, I got ~162psi on all cylinders except 83psi on #2. Then i did a wet compression test on #2 and got 158psi, then repeated the test an hour later and got 131psi. I did a compression test about 3,000 miles ago - all cylinders were within 4psi. I looked at the #2 piston with my $15 smartphone borescope camera, didn't see any obvious problems. My cobalt has 100k miles on her, I've owned it since 65k, and I've had it bolted and tuned since 75k. My goal is to keep it running reliably as is with the stock turbo and custom tune. Should I just order some new stock pistons and rings and slap them up into the bottom of the motor? Do I need to spend a bunch on money on Wiseco pistons? I'll check but I'm hoping my cylinder walls are not scored. Do I need to start thinking about replacing my valve train or timing chain or anything else? As far as I know the engine is all original. |
LDK
/thread |
yupp LDK, contact Jeff Reiland. He offers a brand new complete LDK for $2,700 shipped.
|
Originally Posted by leemanfor
(Post 7673225)
LDK
/thread |
this wont be cheap. you cant just slap forged pistons in an engine without doing work to it. and forged pistons will not last as long as OEM ones.
|
You could source a single good LNF piston, pull the rod out and hone it with a drill hone then get some new rings. gap them and see what happens.
I wouldn't do that. but you could |
It kinda depends on how bad the damage is. You could pull the piston out, then inspect; but I really doubt you wouldn't need at least a hone. It also depends on if you're able to do the work yourself. It sounds like you're comfortable doing it yourself so that is helpful.
|
if the ringland cracked and broke, and you cant find the pieces. I'd be worried. I'd pull my oil pan off and check to see if anything ended up in there.
|
..
Also there is no way in hell a piston is going up thru the bottom. Aint happening. Head has to come off and down thru the top. They make 86MM ring compressor rings that work perfect for install. If you do go that route, and I see a few have, I would wad up a bunch of clean rags and shove them down the bore to minimize debris circulating thru the engine. Also mask of all the top of engine except the bore like a surgeon. Once done, wipe the bore a zillion times with automatic transmission fluid or a clean towel. Keep repeating till its clean. The ATF will grab and hold the dirt from hone job. Lots of labor, but it could be done for $500 or so and a good bit of time. Change the timing chain while your in there too
|
So i could start by removing the oil pan and looking for metal, but it sounds like i'll end up pulling the head and pistons soon anyways. It's temping to spend $2,700 on a new LDK but freight shipping to Alaska will probably take three times the cost and time. So assuming the cylinders are OK with just honing, I could nearly have a new LNF for under $1,000. ZZPerformance sells a set of 4 "take out" LNF pistons and rods for only $300 and new head with valves/springs for only $300. Timing chain is only $100 plus gaskets and fluids etc...
|
At least you have some options. If you are keeping the car till it rusts to the ground I would go with the ldk setup. If your head is ok (you could go with a takeoff new head), you could always just throw in a ldk shortblock. Block is a lot better and you wouldn't have to worry about pourus block later.
|
Originally Posted by Natomic
(Post 7673239)
So i could start by removing the oil pan and looking for metal, but it sounds like i'll end up pulling the head and pistons soon anyways. It's temping to spend $2,700 on a new LDK but freight shipping to Alaska will probably take three times the cost and time. So assuming the cylinders are OK with just honing, I could nearly have a new LNF for under $1,000. ZZPerformance sells a set of 4 "take out" LNF pistons and rods for only $300 and new head with valves/springs for only $300. Timing chain is only $100 plus gaskets and fluids etc...
|
Originally Posted by royce777
(Post 7673229)
yupp LDK, contact Jeff Reiland. He offers a brand new complete LDK for $2,700 shipped.
Originally Posted by HGT
Top ring land bits can't get past the piston. There in you cat now.
|
He lives outside Pittsburg Pa
|
Originally Posted by Natomic
(Post 7673403)
What cat? haha no state inspections where i'm at. But really I wouldn't think piston pieces broke off because last time I ran the car it was ok, just sounded a little off at idle and showed lots of misfires but none under acceleration. But who knows without taking it apart. I'll check for pieces in my muffler haha
|
I was in your shoes about a month ago. Looked into rebuilding but decided it wasn't worth it. I am in the midst of swapping in an LHU from a rearended Buick Regal.
|
Nobody here has mentioned a leakdown test.... yet. Everybody wants to put all kinds of work in w/o proper diagnosis. May be simple as a bad valve or head gasket... We will never know without a leakdown test...C'mon. Baby steps here...
|
He did a pretty definitive wet compression test, so...
|
So..... what? Where is the PSO (pressure squirting out)? Through the cyl. bore? Through the head gasket? Through a valve (can you hear air coming from the intake or exhaust)? Where? THAT tells you what to fix. Not a "wet test".
|
And btw... chances are if he detonated it via tune, bad gas etc... he knows this but is not sharing that info--- just straight to a new piston.
|
you do a wet test to see if the issue is ring seal. if it's valves or head gasket, the number wouldn't change. if i'm wrong, please explain how it's possible that a wet compression test would change if the valve seals are faulty.
|
Originally Posted by exninja
(Post 7673806)
you do a wet test to see if the issue is ring seal. if it's valves or head gasket, the number wouldn't change. if i'm wrong, please explain how it's possible that a wet compression test would change if the valve seals are faulty.
|
Holy butthurt batman
|
Originally Posted by double clutch
(Post 7673809)
Holy butthurt batman
Originally Posted by nickate
(Post 7673807)
I don't give a s@#$ about the "valve seals". And I am helping the op PROPERLY diagnose his issue. Step by step. Not saying you are wrong... or disagreeing with you. Pull the motor down. I'm outta here..
|
Guess that was uncalled for (it was meant to be sarcasm)....as it was probably a typo.... sorry. And exninja you are almost surely correct but this IS the innernet and proper diagnosis is always a good thing.... (maybe the valves could use a freshen as long as the head's off, ect...) --- unless he's going through the bottom.... (more sarcasm)....
POW!?!@%$ Trying to help... not offend. |
why fuck with it?
you do a compression test. you either got cracked ringland or valvetrain issues. Either way, the head has to come off. these cars aren't known for headgasket issues. a smart person would take the head off, inspect it to see if anything is broken. then go for a piston. |
Originally Posted by leemanfor
(Post 7673829)
why fuck with it?
you do a compression test. you either got cracked ringland or valvetrain issues. Either way, the head has to come off. these cars aren't known for headgasket issues. a smart person would take the head off, inspect it to see if anything is broken. then go for a piston. |
Originally Posted by ECaulk
(Post 7673847)
Or just replaced the motor because the cost to get to a new piston is approaching a new motor all things considered. He's not high mileage but hell he'd get an additional 100k miles from a new motor.
|
Originally Posted by exninja
(Post 7673857)
His quote for the LDK shipped to AK is still cheaper than what mine cost including shipping.
|
from ZZP. they since knocked off $500 from the price.
|
yeah, why even mess with it.
LDK it |
Also don't need the turbo from the LDK. Save 500 bones there.
Could also try negotiating the shipping cost. An extra $960 seems steep considering they do free shipping to lower 48. |
Originally Posted by nickate
(Post 7673805)
And btw... chances are if he detonated it via tune, bad gas etc... he knows this but is not sharing that info--- just straight to a new piston.
I'm getting a shipping quote for barging a new LDK from Washington to Alaska to see about a better shipping option. Hopefully ZZP will work with me a little. I'll consider doing a leak down test. I'm borrowing a better endoscope to peak around the engine with before taking the time to take the engine apart. Meanwhile I have my old Dodge work truck to drive everywhere. |
wait....where did you live before Alaska? Did you ever get a retune?
|
|
|
The LDK happened! Thanks everybody. The whole swap with new turbo and shipping ended up costing me about $3,000 from ZZP.
https://cimg9.ibsrv.net/gimg/www.cob...5aa7ec1e3d.jpg https://cimg3.ibsrv.net/gimg/www.cob...5bc8200f90.jpg https://cimg7.ibsrv.net/gimg/www.cob...46cd651225.jpg https://cimg0.ibsrv.net/gimg/www.cob...935a0b8277.jpg https://cimg4.ibsrv.net/gimg/www.cob...2e72aae8bd.jpg |
:cssNET:
|
Nice!
|
Anyway, I put 11 miles on the car doing a break-in procedure. No problems! Then I checked for leaks yesterday morning and saw my hydraulic clutch elbow is leaking. I thought I could get away with not replacing it because I put in all new clutch parts 15k miles ago. Not a big deal, just one more thing i have to order from ZZP. I've not been super impressed with ZZP's customer service. They could have made more money off me if they offered me some things I would need like exhaust gaskets, flywheel bolts, etc.
Also if you order a new engine from ZZP to be shipped 5,000 miles, all they do is set it on a pallet with some cracked 2x6's screwed around the oil pan. The forklift driver at the shipping company was nervous to even load it onto my truck. https://cimg2.ibsrv.net/gimg/www.cob...c481ac326d.jpg |
All times are GMT -4. The time now is 09:58 PM. |
© 2024 MH Sub I, LLC dba Internet Brands