Engine piston good to go or done with??? Expert advice or not!
03-30-2010, 08:35 AM
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Engine piston good to go or done with??? Expert advice or not!
Alright guys recently my 4runner had no compression in cylinder 6 and was low on others. So, I tore into it and realized there were 4 burnt valves. Well I got the heads back from the machine shop and have been preparing my block for the head when I noticed this on cylinder 6. It looks like there are little scars on top of the piston and on the bottom a lttle chip or somthng alike. Will I have problems with this if I slap it back together? The cylinder walls look fine there is nothing scared or dug into the walls. I tryed getting the best pictures I could, let me know what you think.
-Oh-yeah and I have been taking pictures of everything along the way. As soon as I am done putting this back together I will share them with everyone.
-Nick
-Oh-yeah and I have been taking pictures of everything along the way. As soon as I am done putting this back together I will share them with everyone.
-Nick
03-30-2010, 08:58 AM
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It looks like your motor inhaled something metallic, or something inside broke off. Either way, that piston bounced something around for a while. The question is: where did that piece end up?
And no, I wouldn't ever run a piston that looks like that. The high spots (if any) can cause pre-ignition, and the damaged surface will give carbon a spot to start building up.
You say the cylinder wall looks fine. Even if it is, do you know what condition the rings are in? I'm betting you really wish you would have seen this before you sent the heads out.
Basically, if you only need it to run for a week or so, go ahead and slap it back together. It will probably last that long or longer. But if you want to know it will be good for a long time, I would rebuild the bottom end.
And no, I wouldn't ever run a piston that looks like that. The high spots (if any) can cause pre-ignition, and the damaged surface will give carbon a spot to start building up.
You say the cylinder wall looks fine. Even if it is, do you know what condition the rings are in? I'm betting you really wish you would have seen this before you sent the heads out.
Basically, if you only need it to run for a week or so, go ahead and slap it back together. It will probably last that long or longer. But if you want to know it will be good for a long time, I would rebuild the bottom end.
03-30-2010, 09:19 AM
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Hmmm... well other facts the car was not smoking before I tore it down only at start up and then it would go away. The cylinder walls def. look good. I already have $800 invested in this basically changing out everything belts waterpump every gasket etc. besides the bottom end, and dont want to drop anymore money into the thing. Besides that I do not have any more money. Do you really think it would not run good from that little chip. If the walls were messed up I would be more skeptical, but since they look good I am tempted to put it back together and pray, lol. Let me know any other opinions.
03-30-2010, 10:00 AM
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This is a tough call. You might be ok to just run it as is. I can certainly understand not having the money to rebuild everything the way we want to.
Back when I was wrenching on motorcycles, I could not ever put a motor back together with something like that. There's also more of a safety factor with motorcycles. If this motor goes, you'll likely just be stranded, but safe.
Like I said in my first post. Something got in there that wasn't supposed to be there. That something was definately metal. Foreign metal objects in the motor are a very bad thing.
My guess (exactly that, nothing but a guess) is that the piece of that piston that is missing broke off while driving, bounced around a bit, and (hopefully) found it's way out through the exhaust.
If that's the case, these questions come to mind:
1. Why did that piece of piston come off? Was it just a faulty part, or is there too much clearance, allowing the piston to rock, and chip off that corner? Unfortunately, we as humans are not precise enough to determine piston to cylinder clearance by wobbling it back and forth by hand. We're talking thousands of an inch here. Even 10 thousandths excess clearance could cause problems.
2. Where did that piece end up? Did it get ground up and distributed through the motor (probably not), or did the whole piece make it's way out through the exhaust?
3. Are there any high spots left where that piece gouged the piston? If so, those would have to be filed down before attempting to run again. If you file them, you have to be VERY careful to get ALL of the filings out of the cylinder before closing it back up.
4. If ran with current parts, will the piston do it again? Will another piece break off from a different section, causing this to happen all over again?
In summary: To do it right, means more money and time, but then you will know that the motor is good to go for who knows how many more hundreds of thousands of miles.
If you just run it as is, who knows what might happen. There is a chance that if this or anything else happens in the future, it might damage the head work that you recently paid for, and the bottom end would still need to be rebuilt.
I know, this news sucks. I'm sorry for that. Just remember: I DON'T know it all, and I'm very conservative. I don't like taking chances, but you might. I hope some others weigh in on this.
Back when I was wrenching on motorcycles, I could not ever put a motor back together with something like that. There's also more of a safety factor with motorcycles. If this motor goes, you'll likely just be stranded, but safe.
Like I said in my first post. Something got in there that wasn't supposed to be there. That something was definately metal. Foreign metal objects in the motor are a very bad thing.
My guess (exactly that, nothing but a guess) is that the piece of that piston that is missing broke off while driving, bounced around a bit, and (hopefully) found it's way out through the exhaust.
If that's the case, these questions come to mind:
1. Why did that piece of piston come off? Was it just a faulty part, or is there too much clearance, allowing the piston to rock, and chip off that corner? Unfortunately, we as humans are not precise enough to determine piston to cylinder clearance by wobbling it back and forth by hand. We're talking thousands of an inch here. Even 10 thousandths excess clearance could cause problems.
2. Where did that piece end up? Did it get ground up and distributed through the motor (probably not), or did the whole piece make it's way out through the exhaust?
3. Are there any high spots left where that piece gouged the piston? If so, those would have to be filed down before attempting to run again. If you file them, you have to be VERY careful to get ALL of the filings out of the cylinder before closing it back up.
4. If ran with current parts, will the piston do it again? Will another piece break off from a different section, causing this to happen all over again?
In summary: To do it right, means more money and time, but then you will know that the motor is good to go for who knows how many more hundreds of thousands of miles.
If you just run it as is, who knows what might happen. There is a chance that if this or anything else happens in the future, it might damage the head work that you recently paid for, and the bottom end would still need to be rebuilt.
I know, this news sucks. I'm sorry for that. Just remember: I DON'T know it all, and I'm very conservative. I don't like taking chances, but you might. I hope some others weigh in on this.
03-30-2010, 10:12 AM
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So could I get away with just pulling this piston out and replacing it. On this motor can you drop the pan and do this job with the motor in the car? I have never replaced a piston on a motor, but have heard there is really not much to it. I am reading on it already.
Im thinking drop pan, unbolt that rod from crank, and pull piston out, can they come out from top? Replace rings and drop piston in, bolt back up and be good to go. I honestly would love to do the whole thing but I am thinking just replacing that piston would be better than doing nothing. Any advice or tips on this would be appreciated. I am going to go start reading the fsm and other stuff to figure out how I can do this. Thanks for the reply and keep them coming.
Im thinking drop pan, unbolt that rod from crank, and pull piston out, can they come out from top? Replace rings and drop piston in, bolt back up and be good to go. I honestly would love to do the whole thing but I am thinking just replacing that piston would be better than doing nothing. Any advice or tips on this would be appreciated. I am going to go start reading the fsm and other stuff to figure out how I can do this. Thanks for the reply and keep them coming.
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03-30-2010, 10:36 AM
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I think I would even run it before changing out only that piston. That sounds like too much work for only one piston. You would still have to measure clearances to make sure they are correct.
I can't comment on whether or not you can unbolt that rod with the oil pan removed. If you can, yes, it will come out the top. If you decide to do this, pay extra attention when you go to remove the rod bolts, and then when you re-torque the rod onto the crank. If you don't support the rod properly, you can force a flat spot on the plain bearing when applying that much torque.
Personally, I wouldn't do this. Just my opinion.
I can't comment on whether or not you can unbolt that rod with the oil pan removed. If you can, yes, it will come out the top. If you decide to do this, pay extra attention when you go to remove the rod bolts, and then when you re-torque the rod onto the crank. If you don't support the rod properly, you can force a flat spot on the plain bearing when applying that much torque.
Personally, I wouldn't do this. Just my opinion.
03-30-2010, 11:28 AM
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Correct me if I am wrong but does not seem like too much work to me.
Unbolt oil pan- sure some bolts will break b/c of the rust. That will be somewhat of a pain.
Remove oil strainer and baffle plate.
Unbolt Rod end cap on #6 cylinder, put some kind of small hose over stud ends off rod to prevent damaging the crank.
Now how do you get the piston out, do you just push the rod with somthing screwdriver or alike from bottom and push the piston out? lol
Take rings off with expander.
Push pin out, does anyone know a way of doing this without the toyota sst?
Put new piston on old rod.
Compress new rings.
Drop piston in.
Reconnect at bottom with alternating and corrct tourque.
Reassemble everything you took off.
Well I guess it is alot of work for only one piston and that does not include measuring everything which honestly I probably will end up not doing.
I probably will only be driving this car for a year or two until I start working and get somthing new.
Alright YotaTech lets make a poll drop the piston, or just put it back together how it is. I want this to last atleast a year or two. If I can get that out of it I will be happy.
Unbolt oil pan- sure some bolts will break b/c of the rust. That will be somewhat of a pain.
Remove oil strainer and baffle plate.
Unbolt Rod end cap on #6 cylinder, put some kind of small hose over stud ends off rod to prevent damaging the crank.
Now how do you get the piston out, do you just push the rod with somthing screwdriver or alike from bottom and push the piston out? lol
Take rings off with expander.
Push pin out, does anyone know a way of doing this without the toyota sst?
Put new piston on old rod.
Compress new rings.
Drop piston in.
Reconnect at bottom with alternating and corrct tourque.
Reassemble everything you took off.
Well I guess it is alot of work for only one piston and that does not include measuring everything which honestly I probably will end up not doing.
I probably will only be driving this car for a year or two until I start working and get somthing new.
Alright YotaTech lets make a poll drop the piston, or just put it back together how it is. I want this to last atleast a year or two. If I can get that out of it I will be happy.
03-30-2010, 12:26 PM
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There's actually a few steps more to it than that. You'd want to run a hone throught the cylinder to break up the glaze on the cylinder wall for the rings to seat right. This of course mean cleaning up any metal debri. You'd also want to plastigauge the rod bearings to be sure they have the right tolerance. You don't want a spun rod bearing.. then you'd be looking at a new crank as well. I honestly think you'd be better off if you found a way to do the whole bottom end but I also tend to be more cautious and don't want to end up stranded.
If you did do the bottom end it would give you a chance to deck the block and do all the machine work. With the problems the 3.0's have with head gaskets you want to check the block anyways. Ask the folks who do your heads how much they took off to make them square.
I know it kinda sucks but i sure wouldn't want to tear it down a few thousand miles later..
If you did do the bottom end it would give you a chance to deck the block and do all the machine work. With the problems the 3.0's have with head gaskets you want to check the block anyways. Ask the folks who do your heads how much they took off to make them square.
I know it kinda sucks but i sure wouldn't want to tear it down a few thousand miles later..
03-30-2010, 01:00 PM
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one time, one of the nuts holding my air cleaner on fell inside my intake and dinged up the piston worse than that. after i removed the nut that was stuck in the top of my piston, it ran great and i never had a problem. though i cant guarantee that you wont.
like said above, it would be best to rebuild the bottom end. but i would run it.
like said above, it would be best to rebuild the bottom end. but i would run it.
03-30-2010, 02:56 PM
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Well, if I have to vote between replacing just that piston or running it... I vote to rebuild the bottom end. 
Just kidding. I realize that is a rather large added expense. Even as cautious as I am, I would have to vote to just run it.
Possible outcome #1: It runs fine for another year or two without you shelling out anymore money. Yay!
Possible outcome #2: It craps out at some point, who knows when. It could be a month or two from now, or a month or two before you're ready to be done with that vehicle. You would still be looking at a full rebuild if it does crap out.
So, you can take the chance of running it as is. Worst case scenario: you have to rebuild the motor anyway.
Have I been indecisive enough? Sorry. I have a hard time telling somebody to just run something. I don't want anybody mad at me for giving bad advice. But if you promise to not get mad, I say just run 'er!
Just kidding. I realize that is a rather large added expense. Even as cautious as I am, I would have to vote to just run it.Possible outcome #1: It runs fine for another year or two without you shelling out anymore money. Yay!
Possible outcome #2: It craps out at some point, who knows when. It could be a month or two from now, or a month or two before you're ready to be done with that vehicle. You would still be looking at a full rebuild if it does crap out.
So, you can take the chance of running it as is. Worst case scenario: you have to rebuild the motor anyway.
Have I been indecisive enough? Sorry. I have a hard time telling somebody to just run something. I don't want anybody mad at me for giving bad advice. But if you promise to not get mad, I say just run 'er!
03-30-2010, 06:45 PM
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It has somthing to do with the lighting and my camera.
I'm really thinking about putting this back together as is. In person the chip on the piston does not look as bad and really looks like it will work. For everyone that has put input into this I thank you.
I'm still asking for input on this. And either way I will be letting everyone know how this goes in the long run.
-Nick
I'm really thinking about putting this back together as is. In person the chip on the piston does not look as bad and really looks like it will work. For everyone that has put input into this I thank you.
I'm still asking for input on this. And either way I will be letting everyone know how this goes in the long run.
-Nick
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