Piston Top Cleaning

[Mr Project]

Ok, I popped a head gasket on Saturday (at least that was when I noticed oil in the coolant res.), and Monday I got the head off and into the machine shop. Still waiting for them to get to that and let me know what the prognosis is, but until then I'm cleaning and painting things in anticipation of reassembly. (Yay! I'll have a nice-looking engine compartment at last!) :D


On that note, I'd like to get the 181,000 miles of carbon build-up off of the piston tops and the upper edges of the cylinders. What is the recommended method? I've wiped with ATF on a rag, carb cleaner on a rag, and scrubbed gently on #1 with a plastic brush and carb cleaner. It is sortof working, but it's really slow, and I won't be able to scrub down on 2-5 in the bore.

Also, I need to clean off the gasket material remnants on the block surface. Method and materials there? Is a gasket scraper and scotchbrite safe on that surface?

I have my long Q-tips for the bolt holes, and a nice air compressor, so I think I'm ok on the bolt holes.

Thoughts, tips for a HG-N00b?

[Martin in Bellevue]

I wiped the piston tops with a rag & gasoline for a long time. You can hold the chain up & rotate the crank to clean the other pistons. Just find TDC before the head goes back. I tried to keep oil on the rings to reduce junk falling between the pistons & cylinder walls.

Bill recommended a smooth mill file for the top of the block. Put the pistons down when doing that.

[Anton CH.]

I saved this link:
http://www.bimmernut.com/wwwboard/e34/messages/90138.html

[Mr Project]

Thanks, guys.

Martin, what is a 'smooth mill file'? Can you elaborate? I have a couple of hand metal files, but that makes me nervous for obvious reasons! Shavings in the motor, my unskilled hand making things uneven, etc.

[gale]

I have a carbon scraper that I bought many decades ago that works pretty good for removing carbon without scarring the piston tops:

http://www.nmia.com/~dgnrg/scraper.jpg

You can also use a wire wheel in a drill.

[Bill R.]

pictured here is a fine finishing file as opposed to a flat bastard which is much coarser of a cut. Here is a mill smooth (http://www.jlindustrial.com/catalog/product.jsp?id=NIC-08799C&origin=froogle)
You can pick one up at any Sears or ace hardware.








Thanks, guys.

Martin, what is a 'smooth mill file'? Can you elaborate? I have a couple of hand metal files, but that makes me nervous for obvious reasons! Shavings in the motor, my unskilled hand making things uneven, etc.

[George Davis]

Back in the good olde days, decarbonizing was normal practice for British cars. The procedure was to get a piston almost to the top of the bore, then pack grease around the edge of the piston, then move the piston the rest of the way to TDC. The grease is there to trap crud. Clean the top of the piston any way you want (scraper, soft wire brush, or maybe one of those plastic bristle abrasive brushes?). When done, move the piston a little ways down, the grease sticks in place and holds the crud there, too. Wipe off the grease, do next piston.

I've used very fine sandpaper, like 600 grit, on a flat wooden block to clean the gasket surfaces after scraping off the big pieces. Spray WD-40 on liberally first to lubricate it. Use only as much force as necessary. Seemed to work well, and the sandpaper is too fine to remove any significant amount of metal. Work around the pistons that are down in the bore, and stuff a rag in each one to keep stuff out of the rings. Can't help but get a bunch of stuff in the passages this way, so an oil change either before firing up, or after a few minutes of running, is recommended.

A good idea I recently heard was to fill the engine with plain water for the initial firing up. That way if you have leaks or other problems, you don't get anti-freeze all over and don't waste it, either. After making sure all is well, flush and fill with a/f mix.

Hope some of that is useful.

[632 Regal]

The procedure was to get a piston almost to the top of the bore, then pack grease around the edge of the piston, then move the piston the rest of the way to TDC. The grease is there to trap crud. Clean the top of the piston any way you want (scraper, soft wire brush, or maybe one of those plastic bristle abrasive brushes?). When done, move the piston a little ways down, the grease sticks in place and holds the crud there, too. Wipe off the grease, do next piston.

A good idea I recently heard was to fill the engine with plain water for the initial firing up. That way if you have leaks or other problems, you don't get anti-freeze all over and don't waste it, either. After making sure all is well, flush and fill with a/f mix.

Hope some of that is useful.

[Hector]

First, paint-brushed the top of each piston with chemi-clean solution sold at kragen, pepboys... Let it soaked for a day or 2. Was careful not to allow this stuff run down the cylinder walls. I used a combination of a green scouring pad and a tool similar to the one Don showed - a scraper with blunt edges so that when you are scraping, the scraper doesn't bind in the piston top. The scoring pad was used pretty aggressively until I can see the metal that was underneath the carbon, then I backed off on the aggressivenes. Like I said in the intro, I used oil (somewhat messy) to catch the debris set on the rings. I cleaned all this with a combination of a wet/dry shop vac and compressed air. Applied and bit more of oil in an attempt to do debris lift-off and again vacuum and used compressed air. I did this cycle 3 times and check with a magnifying glass and a flashlight to make sure most of the debris was gone. All this took some time and might've been an overkill but at least don't have to worry about metal filings on the rings.