Chris Lockhart

I've gotten the heads off and I'm in the inspect/clean phase with the short block. Does anyone have some good tips or advice on what products/procedures worked for them to clean everything effectively? I have cleaning supplies/chemicals, but I'd like to know if there are some "gotta have it" products that make it easier. Or a "what ever you do, don't....." warning, etc... Thanks in advance.

Chris "Big-un" Lockhart
'89 S4 5spd Supermodel
'89 GT s/n 1210 (My Former Baby)

dr bob

Chris, whatever you do...

-- DON'T try to clean the bores with anything coarser than a terry towel. The silicon in the metal is what the pistons ride on. Any mechanical or common abrasive cleaning method will knock those silicon molecules down, so the silicon surface is no longer proud of the supporting aluminum. Pistons rubbing on the aluminum will quickly scuff and seize.

-- RESIST the urge to try to mechanically de-carbonize the piston tops unless you are dead sure that you'll be able to a) get every single bit of carbon out of there that you loosen, and b) you are dead sure that whatever method you use there's absolutely no chance of a tool slipping and touching/damaging the bore.

There's no downside to leaving the normal thin layer of carbon on the pistons, considering that whatever you scrape off will quickly be replaced by fresh new carbon after you start the engine again. Obviously loose chunks are OK to pull out, so long as you are able to follow the above rules. I good Italian tune-up will do a lot more for you than any amount of scraping and scrubbing, with none of the downsides of those activities.

RFJ

I know some of you will curse me for how i did it. I would bring a piston to the top of its bore,cover all else take my trusty drill with a wire brush in it. I would proceed to clean the tops of the pistons then flip the motor over(in the engine stand take low pressure air and blow around the piston tops then turn the crank and bring up the next piston and go back check the bore of the last and wipe it out take a high intensity light and look around the top of the piston to make sure there is nothing in the bore around the piston top works well. Sorry Dr bob but how else can you get the hard carbon out of there unless there is some chemical that will dissolve it.

BRB-83-911SC

A toothbrush, carb cleaner, and lots of time got me the following results. I worked with the piston at the top of the bore and the engine turned upside down such that the runoff ended up in a drip pan below. I did nothing to the bores other than wipe the carbon lip off with a soft cloth and carb cleaner. Not sure if this is an approved method, but it worked for me.

Livio928

Using Gasket cleaner on the carbon also gets the job done. Again, if possible let it drip down and not into the cylinder bore if possible Try a little area and see if it works for you before going full bore (pardon the pun).

Daniel5691

From a minimalist approach, has anyone used painter's/ woodworker's "tack cloth" for gently lifting out particles, etc ?

Just a thought...
probably a bad one.....

RFJ

Well I gotta say that looks great so you win. But i am always in a hurry(I hope Greg is not listening ) well i won't be in a hurry when i do that rethreading job anyway. One side took about 20 minutes. best,Ray

Imo000

You should listen to Livio. Permatex Gasket Remover will get the carbon off the pitons in less than 10 minutes. I came across this method by accident when I was working on my 996 engine. Since then others have used it on a 928 with amazing results. It will look as good as the toothbrush and lots of time method. As Livio stated, have the engine rotated so the bores are pointing downwards. This way the gasket cleaner (smells and stings just like furniture stripped) will leak out of the bores, as opposed to leak down to the rings. You will be amazed how fast and we'll this works. One can is more than enough.

Chris Lockhart

Thanks. I appreciate the feedback.

Roy928tt

What is it with you people ?

I've been a mechanic for over 30 years and there is no good reason to go removing the light layer of carbon on the piston or bore, leave the bloody thing well alone!

Chris Lockhart

A light layer I would probably leave alone. Large chunks is another story.

Brian, I forgot to mention that your before/after pic looks amazing.

Doc, I will definitely be careful. The hardest thing I used so far was a plastic scraper. Thanks all for the tips.

Imo000

Here is how well the gasket remover works. https://rennlist.com/forums/rennlist...f-these-8.html

mark kibort

i wouldnt go too crazy with the chemicals and cleaning. any little pieces of grit that escape and go down to the first compression ring, is there for good and will just scratch the heck out of the cylinder walls.

I would tape off the edges and get most of it off with a rag and some chemicals. again, as someone said, is it worth it.. the carbon just grows back in no time!

Speedtoys

I'm not sure what problem's being solved.

Unless it's gonna be house art.

The Forgotten On

If it is a thick layer of carbon that can form and raise compression enough to cause the engine to knock (like many a GTS )clean it off.

If it is a thin layer that is just there and not affecting anything. Leave it, you are just risking the possibility of damaging your nice smooth factory bores.