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how do I clean the block ready for a new head gasket


Ian Barrett

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I'm sorry if this has been asked a thousand times, but I can't find it if thats the case.

I've had the head off and am happy the engine is in good nick so its time to start putting it back together again.

I have a new Elring gasket and new head bolts and had the injectors tested and they are absolutely to spec.

I've been told to clean the head and block with something very flat to get the old gasket and gunk off and to use some emery of about 1500

I can lay my hands on the emery but what the hell is something very flat - what do you guys use that I might have kicking around or can get at a local store?

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Use a scotch-brite or other plastic pad, but not metal, and if you use a scraper, use something like a DIY decorating scraper with the corners filed round to avoid scratching the block's deck. Don't use sharp tools, metal scourers or abrasive papers, other than fine papers fixed to a sanding block.

Remember to plug the various holes first!

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Fill in the gap between block and pistons with clean grease, then if any bits go on it you can turn the engine over a tad and wipe it off. Its important not to get debris in, think open heart surgery. I like the stanley blade too, not brand new ideally.

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I use the long edge of an engineer's steel rule, run along the block face from end to end; with this you'll feel it snag on any bits of gasket or other grot that may still be adhering to the block-face.

Then *immediately* before fitting the head-gasket I give both the block- and head-faces a good going-over with Acetone on a kitchen-towel to make sure they're free of any oil or grease that would get in the way of the chemical impregnant in the head-gasket making a good seal.

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You can get a scraper that takes a razor blade, after this some wet and dry, as long as your not stupid 240 will be fine. We use brake and parts cleaner and a wipe with a clean rag after blowing the pots/orifices out with an airline. FFS if you do stuff things in the holes remember to take them out.

Will.

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Looking at the above this doesn't seem popular but I've always used a brass (real brass not brass plated) brush in a drill which is sold for this purpose. I've never had a problem in quite a few head gaskets so I'm sticking by it. Afterwards I've always wiped down with white spirit.

I like the grease suggestion and will be using that in the future.

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Don't you have in your workshop a flat sharpening stone ? course grit on one side, fine on the other ? Most of us do just to sharpen the occasional wood chisel, anyway if you don't have one, buy one about 8" long x 3" wide and you will find this ideal for cleaning off the head surface.

"Plug" the camshaft follower holes with pieces of lint free material so that no grit enters them that cannot be easily removed.

Go back and forth over the block surface with the wetted honing stone in a figure of 8 motion, Once the block is with compressed air clean out any remaining debris from all the cylinder head bolt holes and ensure that the threads are clean - DO NOT RE-TAPP these threads, simply remove any debris and oil so that the treads are clear.

Wipe out any grit from the cylinder bores - a dab of engine oil to follow.

Fit the new cylinder head gasket & head and happy days.

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Don't you have in your workshop a flat sharpening stone ? course grit on one side, fine on the other ? Most of us do just to sharpen the occasional wood chisel, anyway if you don't have one, buy one about 8" long x 3" wide and you will find this ideal for cleaning off the head surface.

I have a sharpener but its the diamond stone variety and I don't think its that fine.

Somewhere I also have an engineers square and a couple of smaller engineers steel rules. I say SOMEWHERE because we moved house last year and I still can't find a bloody thing in my garage.

It doesn't help that I still have so many bits - including my compressor - in the garage at the other house, which I'm fortunate to have kept hold of.

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I wouldn't be putting a sharpening stone anywhere near my oilways or bores, there's no way you would get it all out, and you'd likely end up with it going round and wrecking all sorts of things in short order. Nor would I be using W&D paper that would be leaving abrasive bits all around.

A Stanley knife/blade/scraper is all an excellent way to get rid of it, and introduces no foreign matter to the engine, I have an old sharpened putty knife that I use on steel blocks, but for aluminium I use brown scotchbrite or a nice fine whirly wheel I have in a drill.

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Block is cast iron, so almost as tough as MR Mmgemini :) The deck will be stained by the previous head gasket, which can only be removed perhaps unnecessarily by skimming, which not only requires total dismantling of the engine, but is also most likely unnecessary. Having the deck skimmed then will most likely require measurement of piston protrusion and the complications associated with that. Don't use anything that will be abrasive enough to remove cast iron, as you may well make things worse, so no sandpaper, wet and dry, angle grinder, or whatever. Wire brush in an angle grinder or drill is fine on the deck, as is a stanley blade or single edge razor blade. Tip of your finger is by far the best way to detect imperfections on the deck face, so feel the surface. TDi heads are not known for distorting, but because they are alloy, care has to be taken in cleaning old gasket off them. You can have what is known as a light skim, which removes the same stains as there are on the deck. if you want to check the flatness of the head, then an engineers/printers steel ruler laid in various positions - lengthwise, widthwise, diagonally across each valve pair, will tell you how flat the head face is, I did a 200 TDI gasket yesterday, and only used a stanley blade to clean up and reassemble, so not as worrying as you might expect :)

Les

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