Slight Cylinder Score
08-02-2011, 10:41 AM
#16
Rennlist Member
Thread Starter
08-02-2011, 11:09 AM
#17
Team Owner
maybe the valves have damaged guides and were leaking oil check the backs of the valves for this cylinder,
If you can find a piston from tolerance group 1 then it should be a drop in deal , no boring needed or honing for that matter, re ring the rest of the pistons, use simple green and a tooth brush to clean the carbon off dont use any other type of abrasive on the pistons as you can neatly clean off the chrome coating. it wuill look dull green when its clean and there will be some wear on the piston skirts
IE it will look more like polished aluminum, instead of dull green, this should be OK
you should be able to pull the block out without putting the heads back on ,
remove the radiator first
If you can find a piston from tolerance group 1 then it should be a drop in deal , no boring needed or honing for that matter, re ring the rest of the pistons, use simple green and a tooth brush to clean the carbon off dont use any other type of abrasive on the pistons as you can neatly clean off the chrome coating. it wuill look dull green when its clean and there will be some wear on the piston skirts
IE it will look more like polished aluminum, instead of dull green, this should be OK
you should be able to pull the block out without putting the heads back on ,
remove the radiator first
08-02-2011, 11:41 AM
#18
Rennlist Member
Thread Starter
maybe the valves have damaged guides and were leaking oil check the backs of the valves for this cylinder,
If you can find a piston from tolerance group 1 then it should be a drop in deal , no boring needed or honing for that matter, re ring the rest of the pistons, use simple green and a tooth brush to clean the carbon off dont use any other type of abrasive on the pistons as you can neatly clean off the chrome coating. it wuill look dull green when its clean and there will be some wear on the piston skirts
IE it will look more like polished aluminum, instead of dull green, this should be OK
you should be able to pull the block out without putting the heads back on ,
remove the radiator first
If you can find a piston from tolerance group 1 then it should be a drop in deal , no boring needed or honing for that matter, re ring the rest of the pistons, use simple green and a tooth brush to clean the carbon off dont use any other type of abrasive on the pistons as you can neatly clean off the chrome coating. it wuill look dull green when its clean and there will be some wear on the piston skirts
IE it will look more like polished aluminum, instead of dull green, this should be OK
you should be able to pull the block out without putting the heads back on ,
remove the radiator first
The valves on that cylinder have carbon on them as well. Rest are clean.
08-02-2011, 11:42 AM
#19
Rennlist Member
Thread Starter
Radiator is out. Basically I have a block attached to trans and oil lines with an a/c compressor attached.
08-02-2011, 11:51 AM
#20
Nordschleife Master
Well, I used sea foam and a plastic brush and scotch brite on the tops of the pistons to get the carbon off. I still have the engine in so I haven't touched the rest of the piston surface. Also scrubbed the cylinder wall lightly to see what the dealio is on the grooves. Very light scuffs, not too deep.
The valves on that cylinder have carbon on them as well. Rest are clean.
The valves on that cylinder have carbon on them as well. Rest are clean.
08-02-2011, 11:58 AM
#21
Rennlist Member
Thread Starter
How does that sound for a plan?
08-02-2011, 12:08 PM
#23
Rennlist Member
Thread Starter
I'll have to look that up in the WSM. Never done that before. Then again, I have never torn an engine down and it really isn't that bad. Part A goes in Part B, torque, repeat. Guess I'll have to get a spring compressor to do this.
08-02-2011, 03:58 PM
#24
Former Sponsor
Engine is still in the car. How big a deal is it now to pull the engine block and replace that piston? Just put the heads back on and lift out. Pistons are stamped with a number 1 on them. do I need to bore that out or just put in new piston and rings and call it good? I am assuming this 90 S4 has 100mm pistons.
If I am gonna do that, I might as well do the silicone pan gasket and stud kit.
Waiting for your reply
If I am gonna do that, I might as well do the silicone pan gasket and stud kit.
Waiting for your reply
Why was there water in the engine? Haven't seen the pictures of what caused that.
The heads should just be sent off to a really good machine shop...I've use one of the best I've ever found....if you can't find one, in your area.
At the very least, I'd guess that the heads will need a whole set of exhaust guides, a valve grind, and a resurface.
08-02-2011, 05:18 PM
#25
Team Owner
Warning only use simple green and a tooth brush to clean off the carbon from anything in the block or pistons . hide the scotchbrite pads as they will neatly remove the chrome finish .
dont use any scotch on the block
Also microscopic particles will be left behind from the pads ,
soaking the pistons for a day then scrubbing will do the trick ,
wash everything 3 times in very hot water.
If you decide to have the crank polished then it should also have the crank plugs drilled out and all of the journals cleaned out, polishing will leave behind large deposits of grind material so if you dont get it all out,
your new engine will run for about 5 mins before it seizes or starts knocking
dont use any scotch on the block
Also microscopic particles will be left behind from the pads ,
soaking the pistons for a day then scrubbing will do the trick ,
wash everything 3 times in very hot water.
If you decide to have the crank polished then it should also have the crank plugs drilled out and all of the journals cleaned out, polishing will leave behind large deposits of grind material so if you dont get it all out,
your new engine will run for about 5 mins before it seizes or starts knocking
08-03-2011, 07:23 AM
#26
Three Wheelin'
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The tolerance group of 1 is the most common. You can pull the one piston out of the engine while it is in the car. The car probably needs new motor mounts too.
For a quick fix I would use the cherry picker to suspend the engine in the car. Remove the rack and fix the right side seal which is probably also leaking. With the engine suspended you can pull the pan and have access to the rods. You can then pull the piston out of the engine from the top. Some will say to replace the rod bearings - which are cheap. But if the bearing is good I would use it. In fact, the contion of the bearing will tell you a lot about what damaged the piston.
The Porsche rings are good and last the life of the engine. If you get a 1 tolerance piston from another engine you can simply install it - use new nuts and torque it to spec. If the rest of the pistons are good you should be good to go for another 100K miles
The piston runs on the silicon embedded in the block. If you compare the block with the rest of the engine you will see the engine block has a different texture than the rest of the engine. This because of the silicon in the block. If you bore out the piston then you need to polish the cylinder to expose the silicon. This is probably rarely worth doing. But if you leave the surfaces alone there is no problem.
As far as the head send them to the machine shop. They will replace the valve guides and seals and seat the valves. Machine shops that have done 944 or other german work will do a fine job on the heads. Locally I was quoted $350 a head plus parts on S4 heads.
To pull the engine put a head bolt in each end of the engine and then use a chain over the head of the bolt. This will allow you to suspend the engine or even pull it.
For a quick fix I would use the cherry picker to suspend the engine in the car. Remove the rack and fix the right side seal which is probably also leaking. With the engine suspended you can pull the pan and have access to the rods. You can then pull the piston out of the engine from the top. Some will say to replace the rod bearings - which are cheap. But if the bearing is good I would use it. In fact, the contion of the bearing will tell you a lot about what damaged the piston.
The Porsche rings are good and last the life of the engine. If you get a 1 tolerance piston from another engine you can simply install it - use new nuts and torque it to spec. If the rest of the pistons are good you should be good to go for another 100K miles
The piston runs on the silicon embedded in the block. If you compare the block with the rest of the engine you will see the engine block has a different texture than the rest of the engine. This because of the silicon in the block. If you bore out the piston then you need to polish the cylinder to expose the silicon. This is probably rarely worth doing. But if you leave the surfaces alone there is no problem.
As far as the head send them to the machine shop. They will replace the valve guides and seals and seat the valves. Machine shops that have done 944 or other german work will do a fine job on the heads. Locally I was quoted $350 a head plus parts on S4 heads.
To pull the engine put a head bolt in each end of the engine and then use a chain over the head of the bolt. This will allow you to suspend the engine or even pull it.
08-04-2011, 03:00 PM
#30
Rennlist Member
just put it back together and run it! 
that cylinder looks pretty sad. probably ok if you are not expecting peak performance. not worth pulling the engine, unless you want to do a full rebuild. im sure the other cylinders are not that great either. any idea what the compression was on each of the cylinders?
get those heads to be cleaned up by someone good. get a nice surface by taking a few thou off it, and slap the thing back together again.
by scrubing those piston tops you could create more problems than the trouble is worth. chpping off the big stuff is warrante, but to go crazy is not advised as a lot of junk could be falling down the sides of the piston tops. lurking to make even deeper scratches.
have fun!
Mark
that cylinder looks pretty sad. probably ok if you are not expecting peak performance. not worth pulling the engine, unless you want to do a full rebuild. im sure the other cylinders are not that great either. any idea what the compression was on each of the cylinders?get those heads to be cleaned up by someone good. get a nice surface by taking a few thou off it, and slap the thing back together again.
by scrubing those piston tops you could create more problems than the trouble is worth. chpping off the big stuff is warrante, but to go crazy is not advised as a lot of junk could be falling down the sides of the piston tops. lurking to make even deeper scratches.
have fun!
Mark