Technical How do you replace pistong rings without removing engine?

[Momanatorz]

I just replaced my valve stem seals and the engine still burns oil at operating temperature. :bang:
Only thing it can be i believe is piston ring... as it was #2 cylinder only that had alot of oil in it, the inlet and exhaust.
but i will change all of em of course, if i can...

 

[RB2009]

hi, you can do it without removing the engine.. but generally seeming as you have to strip most of the engine anyway its easier just to pull the engine out. Because by the time you have taken the head off, and the sump off your in a situation where its litterally an engine mounting and maybe 5-6 bolts connecting the block to the gearbox... if that some engines only have 4.


you would have to completely remove the head, and the sump... then lay underneath, undo the caps on the conrods ensuring they are kept in order.

then push the pistons out through the top of the block. as they usually only come out 1 way, and if they do come out from underneath... you still cant do it because the crankshaft is in the way..and to remove that would be imposible with the gearbox attached.

Usually though when doing this.. for what its worth people usually do the crank bearings as well, they are relatively cheap and do wear over time.

Also, beware just changing piston rings, its good practice to get the bores checked for wear as they maybe too worn to just use new rings and may require boring out to the next oversize, at the very least honed to break the glaze to help the oil control ring seal properly.

This is important because if the bore has gone oval shaped the rings would of worn to fit this shape.. then a new round ring wont seal properly and you could end up in a worse situation than you are now.

 

[B3NNETT]

remove head, remove sump, undo rod bearing caps and knock out

 

[Momanatorz]

remove head, remove sump, undo rod bearing caps and knock out

simple enough, cheers !

 

[B3NNETT]

simple enough, cheers !

but like rb2009 says replace all bearing shells will save hassle later on and is just better practice.

(hint thats what the thanks buttons for )

 

[Momanatorz]

hi, you can do it without removing the engine.. but generally seeming as you have to strip most of the engine anyway its easier just to pull the engine out. Because by the time you have taken the head off, and the sump off your in a situation where its litterally an engine mounting and maybe 5-6 bolts connecting the block to the gearbox... if that some engines only have 4.

Thanks very much for your reply, very helpful. but i read in another thread that the bearings will be fine as it's better to leave them or fit new ones in incorrectly?

 

[B3NNETT]

Thanks very much for your reply, very helpful. but i read in another thread that the bearings will be fine as it's better to leave them or fit new ones in incorrectly?

even better fit new ones correctly, there not exactly hard to fit so will be worth it

 

[Momanatorz]

even better fit new ones correctly, there not exactly hard to fit so will be worth it

cool, ite then! as they're cheap! i'll order rings and bearings together.

 

[RB2009]

Hi, dont order anything until you have removed the old shells, and had the bores checked for wear.

as some engines dont use standard bearings, some are undersize. Most manufacturers did this to salvage incorrectly ground cranks in the factory. Very rare, but if yours is undersize it will save you ordering the wrong ones.
You will know when you remove the shells which you require as it will be stamped on the shell, so you cannot go wrong once you have the correct ones, lubricate them with oil, ensure there is no dirt or grit on them.. they need to be clean. then install the bearing cap and rotate the crank.. do 1 at a time to ensure everything is good and not tight/siezed as previously said they are really easy to do anyway.. and because you have to remove them anyway when removing pistons so its well worth doing. Because once done it will give the engine a better oil pressure, and if you dont and they fail in the future its a nuisance pulling the sump off again.

Also with the piston rings.. installing new standard piston rings in worn bores will make things worse as the bore could be out of shape. So don't order these until you have had the bores checked for wear. If it is ok to take new standard size rings a bore hone/deglaze will ensure a good seal with the new rings and can be done relatively cheaply.

 

[Momanatorz]

Hi, dont order anything until you have removed the old shells, and had the bores checked for wear.

as some engines dont use standard bearings, some are undersize. You will know when you remove the shells which you require as it will be stamped on the shell.

How do i check them for wear?
the ring had gone soon after the head gasket change. the car had not actually traveled any distance for 2 weeks, instead it was run stationary as i was checking as much as i could that all was well, and the piston ring went during the 2 weeks. so the bores should be fine? i checked them with my finger, they are smooth as hell all round.

ok i'll check the stamp on the bearing shell, its a number of course, right?

 

[RB2009]

most engine bores with wear are smooth.. but it is a mistake most people make to assume smooth is good.

When new, and rebored/honed the bores are actually cross hatched.
like, which is why even if the bore is in good condition, honing is good practice, because it breaks the smooth glaze and brings back the cross hatching which ensures a good seal.

Checking for wear, look for things like how much of a wear ridge there is around the top of the bore.. normally you get a ring around the top which is a few mm deep.

to properly check though would need to go to a specialist.
they measure accross 2 axis of the bore.


<-- -->

and


/ \
|
|
\ /

if both measurements are equal then the bore is round.. but if


/ \
|
|
\ /

is geater than the bore has gone oval shaped.. hard to measure accurately though without the proper measuring device as your talking measurements of less than a quarter of a mm and thats the problem, the old ring would of worn to the shape of the bore and would of itself become oval shaped. But because with a round piston ring, if the bore is oval shaped and the ring is round you have a gap on 2 edges as it would be a different shape to the bore.. so the compression inside the cylinder will be less than before you started.

In regards to the bearing shells.. yep its stamped on as a number, or STD for standard.

 

[Momanatorz]

most engine bores with wear are smooth.. but it is a mistake most people make to assume smooth is good.

to properly check though would need to go to a specialist.
they measure accross 2 axis of the bore.

lol really? i would assume smooth would be a tighter fit :/
i'll get my gf to check the shape of them, she works in a garage
Thanks alot for your help and hopefully this will cure my engine problem. :worship:

 

[RB2009]

yep lol, more info here
http://www.aa1car.com/library/honing98.htm

yep, definitely get them checked extreme case scenario you may find your bores are worn too much for standard rings.. which would be highlighted by a check.

once you remove the head.. before removing the sump.. have a look and see how much more work would be required to remove the block.. usually just 4 bolts on the gearbox and the engine mount.

Reason I say this is because,

1) makes things easier, when doing the bearing shells, and re-inserting the pistons.

2) you can use it as an opportunity to check the clutch condition.

3) a chance to replace any gaskets or oil seals that are starting to go.

lol, this kind of job.. really does need doing properly. Alot of work alone is involved in removing the head and pistons, practically stripped the engine almost anyway by the time your finished and it would be a shame to do all the work and find somethings still not right, or a few months time something else goes wrong or the engine develops an oil leak and you have to pull it apart again.

If not though, bare minimum check the bores before putting new rings in, if everythings good get the bores honed, and new shells. then the bottom end will be almost as good as new then.

 

[D4nny8oy]

Before you go further, are you sure the oil you're burning isn't just what's left in the exhaust, and is only burning once the engine (and exhaust) is hot?

Just a thought.

 

[Momanatorz]

Usually though when doing this.. for what its worth people usually do the crank bearings as well, they are relatively cheap and do wear over time.

So what bearings can i actually replace without taking the crankshaft out? as i'm not removing the engine
isn't there 2 parts to make 1 bearing? so if i replace the crank bearing only 1 half will be replaced and prob wont be good :/

 

[Momanatorz]

Before you go further, are you sure the oil you're burning isn't just what's left in the exhaust, and is only burning once the engine (and exhaust) is hot?

Just a thought.

I'm still not 100% sure, it smokes from the moment it starts. plugs are wet with oil and carbon it seems. they are new aswell...
smokes alot more at higher temps

 

[RB2009]

you can replace the big end bearings which are located in the lower end of the conrods these are what can be seen once you remove the bearing caps.

Its the main bearings you cannot do. as this needs the crankshaft to come out.

 

[Momanatorz]

I looked up a bit about it and if i replace the bearings, clearances may be out? i'm thinkin to keep the originals at this moment

 

[RB2009]

no they wont be out, the clearances should actually decrease, because the bearing shells will be new.

as long as you get the correct bearing shells its fine.. it will say which bearing shells you need on the old 1s its stamped on it.

bearing shells are quite important to oil pressure, when they wear too much you loose your oil pressure... which is why most people change them while the bearing caps or off, just means its 1 less thing to worry about in the future, and with a better oil pressure less internal wear.

only time you dont change bearing shells is if the crank is all scored up.. but this would be quite a serious problem if bad enough and would require a crank regrind, and the old bearings wouldnt help things.

 

[rallycinq]

So what bearings can i actually replace without taking the crankshaft out? as i'm not removing the engine
isn't there 2 parts to make 1 bearing? so if i replace the crank bearing only 1 half will be replaced and prob wont be good :/

Dare I suggst that asking the above question indicates that the job might be beyond your capabilities.

Its all very well coming to the forum for advice, but thats a wee bit basic.

Cheers

SPD