This is a question for someone who builds engines. Here's what has happened: I pulled the heads off of my engine. I was having trouble getting one of the heads off. What happened was that I had loosened the head just enough so that some coolant leaked into two of the cylinders. The motor sat that way for about 10 days before I was able to get the head off. Now there is a visable stain on the cylinder wall from where the the coolant was. I can actually feel a difference in the surface of the wall. It's like the glaze of the wall has been changed. Does this mean that I'm hosed? Can I run it like this, or do I have to completely rebuild the engine? It has 145K miles on it, but there is essentially no ridge from ring wear at the top of the stroke.

Ouch...If you've already cranked it over since this showed up, then I'd say the damage is done already. If not, you MAY be able to use some really light (like 3000-4000 grit) wet sandpaper with some oil on it, but then you'd have to make certain that all the bits of metal/rust/sand are out before cranking the engine over. Maybe clean it and blow it out with compressed air. Could follow that up with a magnet wrapped in cloth to pick up the little remainders. Worst case scenario, I think you'd fry the rings in that cylinder. Whatever you do...do not clean the area using an Up-&-down motion; try to go around the inner circumference of the cylinder wall.

I've tried cleaning the stain with solvent. I did rotate the the crank by hand so the rings have gone through the area a few times, but I don't think that's a big deal. The damage to the wall is very slight, but like I said I can feel it. It's not like the is any material build-up or missing. It just feels different. It's like the glaze has been broken.

This is actually very common and most pople dont think twice about it.

Take a good abrasive scotch brite pad like the kind they sell in the paint stores and run around the cylinders in question. Dont go all out with the pad just enough to suff the distortion out so the rings wont catch.

Here's a photo of the stain.

Ahhh...doesn't look as bad as I saw in my head. I think it may be cool.

DO NOT USE A SCOTCH BRITE PAD! Big no no. Go out and by a cylinder honer from autozone for $20. Get the very fine one and just slap it on your drill and give it a whirl in that cylinder. A scotch brite pad has many uses but does not belong near engine internals.

How could he stroke the hone properly without taking the piston out?

I had assumed it was out of the car =/.

I still wouldn't use the scotch brite pad. I would use a piece of oiled up emery paper or crocus cloth.

the surface conditioning disks or "cookies" are what a lot of people used in the past to clean gasket surfaces, they are made from the same stuff the scotch brite pads are made from,... lots of bearings were killed because of those disks in short order, like in 1500 miles or less.

like paskey said, use oiled emery paper or crocus cloth.
after your done with the sanding, wipe it out with a clean rag with some brake clean on it & then spray the cylinder with the brake clean & then right away before the brake clean dries blow it out with compressed air, be sure to get down around the edge of the piston at the cylinder wall. afterwards, oil it down to prevent rust.

The engine is still in the car, so it will be almost impossible to get all the way down to the bottom of the stroke with any type of abrasive. (The engine coolant pooled on top of the piston...) I think that uising something very fine grit with some oil as a lubricant is a good idea. I'll givethat a try.

Thanks for the advice everyone.

One more thing: Should I try to work the surface all the way around the cylinder equally, or just work on the damaged area and blend out the edges? I'm just wondering if the rings will react differently to a new surface as opposed to the old glazed surface.... Won't the rings essentially have to re-seat?

My thoughts are that you're going to lose at least a small amount of compression across that region, but hopfully not any amount that you'd notice. With this in mind, I BELIEVE you'd only want to polish the affected area, but I'll wait for someone who's had to do this to chime in. I haven't personally run into this.

A good grade scotch brite will not leave deposits in the engine, It doesent have to be applied with enough force to rip the pad apart. Emery paper/cloth will leave deposits, get oil on it and it will fall apart.

I've never tried oiled emery paper. My thoughts were to use some extremely fine oiled sandpaper followed by a meticulous cleanup.

I'd use a paper towel with brake fluid, followed by transmission fluid. And then not worry about it any more.

Amen. Don't be using abrasives w/ the piston still in the hole.

Explain GM's reasoning for sending out a bulletin about not using scotch brite pads on any internal engine components. . Im sure they did it to knock scotch brite out of the market...

Sure

Theres a big difference between a scotch brite pad and a roloc disk.

Techs would go balls out with the Roloc disks and the crap including metal shavings would fall down into the pan. Good tech articals on Roloc abuse floating around. Theres a new product similiar to it being used now that isnt as bad I havent used it yet.

I use scotch brite pads cut in strips all the time for internal engine work, nothing polishes a crank better.

GM specifically stated scotch brite and the same materials are present. I'll see if I can find the link.

<B>Gasket Surfaces - Use of Surface Conditioning Discs

File In Section: 06 - Engine/Propulsion System

Bulletin No.: 00-06-01-012

Date: May, 2000

INFORMATION

Subject:
Use of "Surface Conditioning Disks"

Models:
2000 and Prior Passenger Cars and Trucks</B>

This bulletin is being revised to change the model years and the status of molded bristle disks. Please discard Corporate Bulletin Number 87-61-24 (Section 6 - Engine).

<B>The Use of "Surface Conditioning Disks"</B>

When cleaning engine gasket sealing surfaces, and/or cleaning parts from an engine which are to be reused; surface conditioning disks (typically constructed of woven fiber or molded bristles) which contain abrasives, such as a high amount of Aluminum Oxide, are NOT recommended.

The use of such surface conditioning discs dislodges Aluminum Oxide (from the disk) and metal particles, which can lead to premature engine bearing failure. The presence of Aluminum Oxide in engine oil has been shown to cause premature engine bearing failure. In some cases, this failure occurs in as little as 1,000 miles (2,200 km) or less after the repair has been made.

Surface conditioning discs may grind the component material and imbed it into the disc. This can result when more aggressive grinding of the gasket surface takes place.

Notice: Do not use abrasive pad/bristle devices to clean the gasket surfaces of engine components. Abrasive pads should not be used for the following reasons:

<LI>Abrasive pads will produce fine grit that the oil filter will not be able to remove from the oil. THIS GRIT IS ABRASIVE AND HAS BEEN KNOWN TO CAUSE INTERNAL ENGINE DAMAGE. Abrasive pads can easily remove enough material to round cylinder head surfaces. This has been known to affect the gasket's ability to seal, especially in the narrow seal areas between the combustion chambers and coolant jackets.

<LI>Abrasive pads can also remove enough metal to affect cylinder head, block, oil pan rail, and intake manifold runner flatness, which can cause coolant and oil leaks. It takes about 15 seconds to remove 0.203 mm (0.008 in) of metal with an abrasive pad.


<B>Recommended Cleaning Procedure</B>

General Motors recommends the use of a razor blade or plastic gasket scraper to clean the gasket surface on engine components that are to be reused. When cleaning gasket surfaces, please note the following:

<LI>When using a razor blade type gasket scraper, use a new razor blade for each cylinder head and corresponding block surface. Hold the blade as parallel to the gasket surface as possible. This will ensure that the razor blade does not gouge or scratch the gasket surfaces.

<LI>Do not gouge or scrape the combustion chamber surfaces.

<LI>Do not gouge or scratch any engine-sealing surface during the cleaning process.

Important: The appearance of the gasket surface is not critical - the feel is. There will be indentations from the gasket left in the cylinder head after all the gasket material is removed. The new gasket will fill these small indentations when it is installed

i think thats what im going to do on my motor in the cylinders but for the gasket surfaces i guess i'll need to use a fine grit sand paper because its real rusty and use air to blow out the metal fileings. what gasket sealent should i use what putting it back together?

For that, you can use Scotchbrite or sandpaper or whatever; just duct tape some newspaper or something over the cyls, to keep debris out.

I prefer to use nothing whatsoever on the head gaskets, wxcept for a thin smear of silicone around the water ports. Use Loctite Automotive "Hi-Temp" Thread Sealer with Teflon on the head bolt threads. Chase them with a tap before putting the heads on. Make certain that the deck surface of the block and the heads is as clean as possible, if not cleaner, with lacquer thinner and a lint-free towel, right before putting them together.