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  #1  
Old August 28th, 2018, 22:28
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Head off, replace rings while exposed?

Suggestions on (what I assume) to be shot rings on #3 piston...

Situation: Picked up a '98 4.0l 180k with a blown head gasket. I have the head off and it's out getting cleaned, but found the #3 cylinder drained all the 2-cycle oil I poured on the pistons to cover/coat it while cleaning the surface for the soon-to-be cleaned head and new gasket. I have to assume this means the rings are shot. Would you agree? Anything else I should be looking for? The others appear to be holding the oil back well.

I had a shop drop the oil pan and they said the rod bearings looked good; they didn't say they found any parts in the pan.

So, thoughts on replacing just one piston's rings? Should I replace them all since there? Should I be concerned or looking for anything else? Etc....
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  #2  
Old August 28th, 2018, 22:49
RCP Phx RCP Phx is offline
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Re: Head off, replace rings while exposed?

Well, your facts make no sense. There's no way to detect bearing damage from removing the oil pan. If you need ring's, you probably need the cylinders honed?
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Old August 28th, 2018, 23:58
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Re: Head off, replace rings while exposed?

I'm not a mechanic, but all I've read is the bearing can be checked (and replaced) when the pan removed.

My non-expert eyes like how the cylinder walls appear. Do they need to be honed if the ring(s) are just worn?
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Old August 29th, 2018, 06:07
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Re: Head off, replace rings while exposed?

The honing needs to happen so the rings can break in properly.

Given what you have described, if the head is off and the pan is off, I would say you have nothing to lose.

A cylinder hone on a drill should be adequate.

Since the 4.0L doesn't have shared journals it should be no problem to keep things clean below and confirm they are clean afterwards.

I would recommend getting the help of someone with some experience for the reinstalling of the piston with the new rings on it. There are a number of details to screw up in that process, and if you are not a mechanic it may be easy to find more than one pitfall.
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  #5  
Old August 29th, 2018, 16:10
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Re: Head off, replace rings while exposed?

Well, the pan was put back on. So, do you think it is worth pulling again to hone the cylinders?

To confirm, am I correct in my assumption the rings are worn since it did not hold back the oil poured in?
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  #6  
Old August 30th, 2018, 04:03
sflier sflier is offline
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Re: Head off, replace rings while exposed?

You would be replacing the rings from the bottom. I'd recommend putting it together and do a proper compression test. Oil draining past the rings on a cold engine doesn't necessarily mean bad or broken rings. As stated above, there are many things that could go wrong with the ring replacement so why risk it if you're not sure you have an issue.
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Old August 30th, 2018, 04:12
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Re: Head off, replace rings while exposed?

Quote:
Originally Posted by sflier View Post
You would be replacing the rings from the bottom. I'd recommend putting it together and do a proper compression test. Oil draining past the rings on a cold engine doesn't necessarily mean bad or broken rings. As stated above, there are many things that could go wrong with the ring replacement so why risk it if you're not sure you have an issue.
Forum is not letting me edit my post. You would be replacing the ring from the top, but I'd still recommend putting the head back on and perform a compression test first.
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Old August 30th, 2018, 16:22
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Re: Head off, replace rings while exposed?

That is an interesting thought... you think it better to put it all back together, test it to see what/if I have noticeable compression loss?
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Old August 30th, 2018, 16:39
RCP Phx RCP Phx is offline
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Re: Head off, replace rings while exposed?

Your taking a pretty big chance on something you have no background on and died from a over-heating problem! But if your that close?
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  #10  
Old August 30th, 2018, 16:42
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Re: Head off, replace rings while exposed?

I'm more interested in doing what's right while I have it open then creating more work.

Are you thinking re-ringing it is not worth the hassle at this point?
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Old August 30th, 2018, 16:44
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Re: Head off, replace rings while exposed?

At this point it would be most cost effective to replace all 6 sets of rings. The pan isn't rocket science to remove (if not already done). And the head already being off makes the effort almost negligible. In for a penny, in for a pound.

As for necessary...without disassembly and inspection by a knowledgeable repair person, its anyone's guess. A couple rules of thumb:

Deep scratches in an updown direction are not a good sign.
Keep pistons, rod caps, and rod bearings together and oriented so as to be reinstalled in the same bore, direction, and position.
Take lots of pictures before and during disassembly.
Rent (or invest in) a good piston ring compressor!
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Last edited by four_shot; August 30th, 2018 at 16:50.
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  #12  
Old August 30th, 2018, 16:57
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Re: Head off, replace rings while exposed?

As mentioned earlier.

Quote:
Originally Posted by sflier View Post
Oil draining past the rings on a cold engine doesn't necessarily mean bad or broken rings.


I'm thinking that time and budget are the more deciding factors.
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  #13  
Old August 31st, 2018, 10:35
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Re: Head off, replace rings while exposed?

Quote:
Originally Posted by four_shot View Post
As mentioned earlier.





I'm thinking that time and budget are the more deciding factors.
Yes, though time over money on this senerio. The last think I want is to put it all back together only to find the compression is out of spec.

To confirm, I can re-ring without having to pull the block?
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  #14  
Old August 31st, 2018, 10:51
RCP Phx RCP Phx is offline
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Re: Head off, replace rings while exposed?

Not properly, you should have the block completely checked over before proceeding on anything. The includes align bore, cylinder bores, and the deck surface. Same would apply the crank and rods, pistons you won't know about until they check the block!
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  #15  
Old August 31st, 2018, 11:05
RCP Phx RCP Phx is offline
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Re: Head off, replace rings while exposed?

What have you done to inspect the head?
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