Petrol engine help - seized?

[hxk494]

I picked up a complete 2286 petrol engine with a view to changing my s3 back to original engine type, currently 2.5nad as original block was cracked and 12j was available at the time. However it appears to be seized solid.

Plugs looked OK, so I put release oil in bores for a week or so, still nothing. Took head off yesterday and there is a bit of rust in no 4 but not loads. No sign of water in oil so I'm assuming bottom end is OK, could it just be rings stuck in bore holding it? If I strip out crank should I knock pistons down or up to get them out of block, I'm thinking down?

Photos to follow once I manage to reduce file size.

Cheers, Martin

[hxk494]

Photo

Edited December 3, 2016 by hxk494
Photo added

[hxk494]

Is this enough to completely sieze it? Other bores look OK

[Soren Frimodt]

Since you've got the head off you could try heating the circumference of the piston with a torch to get the rings to let go. Otherwise there's only the BFH. However if that engine is going to be any good it'll need a re-bore, because that line of corrosion will not allow the rings to seal and it'll smoke and use oil + have excessive blowby. 

[Daan]

The pistons will only come out out from the top. You probably have something stuck in the gap between the piston and the bore. Is it stuck in bottom dead centre? If not, I would probably try pressing it down first to see if any debris shows up. Probably disconnect all 4 connecting rods to make sure you are dealing with one piston at the time. Maybe take out the crank also, so you can press them down from the bottom in a straight line.

 

Daan

 

 

[hxk494]

two aren't tdc, so the other two won't be quite bdc. I've tried a bit of gentle knocking with a hammer and wooden block and nothing budged, will give it another shot and then I guess it's sump and crank off. 

I realise we're in re-bore territory but there never seems to be anything completed or even near complete and running in this neck of the woods. Hopefully a bit of further investigation will yield whether even a rebore/rebuild is going to be a goer.

Cheers,
M.

[Les Henson]

If the crank is out, then they can be knocked downwards (I prefer this way as there's not the carbon ring in the way at the top of the bore|). Even if there is water free oil in the sump does not mean the crank isn't seized, and if it is, then expensive repairs might be required, such as a new crank. Rust pitting means that new pistons and a re-bore are required, so they are essentially scrap anyway. I would drop the sump, remove the crank, big and main  bearings, then knock the pistons down with a suitable lump of wood and a mallet. The problem with corrosion pitting is that it's very difficult to determine what oversize pistons you will need as one pit might be deeper than the rest. Usually the bores are machined to match a piston, but rust pitting changes everything. You would have to get it bored out until there's no pitting left, then buy the next oversize piston up and then get it bored again to match the new pistons. If you have standard pistons now, then it might be wise to just bore it out to maximum size to match maximum size pistons available - How many more miles do you expect to get out of what will essentially be a new engine?

 

 

Les.

[hxk494]

thanks for all the suggestions. I'll not have time to do anything else until the weekend but will report back after that, hopefully with pistons out.

There are a few more photos I took during the strip down so far here: http://s1235.photobucket.com/user/martinduncan/library/Series petrol engine

There is evidence of moisture around the valves/head of cylinders 3 & 4. 

Would a piston at DTC be level with the top of the block or sit slightly below it as shown with 2 & 3?

I've not cleaned the piston tops up but there does appear to be some markings on them - you can just about see it in one picture U-030 (?). Would this indicate a previous re-bore to 30thou? Reading my haynes manual suggests 40thou is the max oversize permsissible?

Cheers,
Martin.

[Les Henson]

That looks a bit grim  Looks like head gasket failure between at least 2 cylinders. It also looks like valve contact to one of the pistons. The valve corrosion could be due to the head gasket failure and perhaps water ingress if the engine was left outside and some of the valves were open. It looks like you have a lot of work to do there  If I remember right, TDC is level with the top of the bore on the old series engines

 

 

Les

[Tal]

I can see vertical scoring on the cylinder so it looks to me like an overheat may be the cause of the seize. if there has been a large water leak somewhere along the way along with the head gasket leaking it would have sucked steam into the head during the overheat causing the corrosion. You might be able to clean the head out with a rotary wire brush but do it before you remove the valves, they'll need reseating anyway but you don't want all the crud and extra hassle of cleaning bits of wire brush and corroded junk out of  your valve seats and cylider head before you polish them.