Engine wear ?

[stevemac 0]

As some of you already know, I'm currently playing around with my engine - ohh err...lol

Many things have come to my attention and I'm very glad that I've uncovered a few misdemena's done by the previous owner.

 

Anyway, the current point in hand is the condition of the cylinder walls. I was a little shocked when I took the cylinder head off. The engine had been rebuilt using a paper type head gasket :roll: I initially thought that there was a substantial amount of bore wear - due to a large lip at the top of each cylinder. After speaking to a couple of engine re-builders/engineers today, it appears that this is just a fairly thick coating of carbon !!

 

The watermarks are caused by my forgetting to completely empty the cooling system before removing the head.. :roll:

[Scruffythefirst 0]

That looks very odd. The thick layer of carbon is fairly normal and should scrape off. You should also have a slight lip at the top of each cylinder but it shouldnt be very big.

 

What do the other cyls look like? Do they have the white band as well? Looks almost like you've had a ring sieze in the block. TBH, at this stage i'd be going for a rebore / hone, new rings and bottom end shells as a minimum but if your going to take the whole thing out you might as well do a full re-build, its a car your most likely to keep for a while so best to save yourself future agro.

[stevemac 0]

Scruffythefirst, The white rings are just watermarks - they were not present when I took the head off. These marks have now been cleaned off.

 

My concern was that the carbon build-up is more than I've seen before. I'm not used to stripping engines that are 13 years old !! What should I use to clean the tops of the pistons ?

 

Your comment about the slight lip answers a question that had also concerned me. Do all PG engines have a slight lip at the top of each cylinder ? All the engines (Mercedes) that I've ever stripped have had a constant bore all the way down, with no lip.

My first thought was bore wear but the hatch markings are visible too high up the cylinder for that. All the cylinders show exactly the same carbon build up & clearly visible hatch markings.

[Scruffythefirst 0]

What should I use to clean the tops of the pistons ?

 

Petrol and a toothbrush. Depending on how much of a rebore you need you may have to get new pistons.

 

Do all PG engines have a slight lip at the top of each cylinder ?

 

All engines should - the piston rings are set a little way down the piston, at the top of the stroke the piston ring wont quite reach the exact top of the bore and as the rings wear the bore they wont wear the little bit at the top, forming a ridge. This will come out with a light hone and if the bores are ok (wipe them with engine oil on a rag to stop them going rusty) and if the lip isnt too big then you should get away with the same pistons

[potatonet 0]

you look like you blew an oil ring, are the edges of your pistons clean? if so your oil rings are smoked. also use brake cleaner does wonders =-)

[Mike Edwards 0]

Maybe a gas-axe would be more appropriate?

[stevemac 0]

Maybe a gas-axe would be more appropriate?

Cheers for your input Mike.. .. :lol:

[Scruffythefirst 0]

If your not going to have it honed and re-rung then dont even take the pistons out and dont try and clean them. It'll just make things a lot worse. Why did you take it all apart in the first place?

[stevemac 0]

Why did you take it all apart in the first place?

New top end. :wink:

 

Running out of spare cash so I'm gonna leave the bottom end as it is. I've already changed the B/E bearings.

I'll only be doing approx 5k before next winter when I'll be taking the whole engine out for a rebore, new pistons, main bearings, etc.

[Henny 0]

I can't believe you're not gonna rehone the block Steve! Standard rings from your place are only a few quid per cylinder and the loan of a honeing tool is gonna cost you less than a couple of pints... :roll:

 

A complete rebuild of the top end which you then mate back onto an unknown bottom end is gonna result in an engine which WILL pass oil past the rings 'cos the increased seals in the valve guides will cause the vacuum in the cylinders to draw oil past the old, tired rings and therefore burn oil even faster than it was before....... that turns into an ever decreasing circle with a complete failure (and a large bill!) in the center... :|

 

For the cost of the rings and the use of the honing tool, why not do it?!? :? Hell, gimme a call and I'll pop down with my mates honing tool and do it myself! :lol: ;) (at least that'd sort the carbon deposits anyway! ;) :lol: )

 

Don't forget that you've already had a muppet install a paper head gasket on that engine... God knows what else they've done to the bottom end in the past... :? :|

[Andi 2,147,483,647]

I dunno if I like the sound of one Mod sorting out another Mod's bottom end.

 

People might get the wrong idea about this site....

[Henny 0]

Andi, down boy! You know I'm not like that :lol: :roll: (and neither's Steve...)

[stevemac 0]

Henny, I would appreciate some help - if you have time ?

 

I'm a kind of "bottom end virgin"..lol

I've done head work before & big end bearings too. I'm a little out of my depth with honing crankcases & changing piston rings. I was going to leave the bottom end until after the summer & strip it completely in the autumn.

 

I assume I'd need to remove the crankshaft & take the pistons out from underneath ? Or could I scrape the coke off & remove the pistons from the top ?

What "oversized" piston rings will I need to get ?

[Scruffythefirst 0]

Pistons come out the top of the engine after you've undone the big end bolts. You really ought to strip everything else off the block and have it properly cleaned as and stray metal particles will cause havok. If you need to borrow and engine stand and ring compressors etc then send me a pm.

 

I've done head work before & big end bearings too. I'm a little out of my depth with honing crankcases & changing piston rings.

 

 

If you've changed big end bearings then you can change mains as well. personaly I'd take the block to a reputable engeneering place and get them to hone it for you. Shouldn't be more than £40 including having the block tanked. Then all you have to do is put the oil/ water pump etc back in and new rings on the pistons and you've got a brand new engine.