Date: Wed, 1 Oct 1997 13:11:32 -0700 From: Mike West Subject: Making a gasket >Hello all: >I removed the clutch housing from my transmission this evening to replace >the rear drive shaft seal. In the process, the paper gasket >between the tranny and the clutch housing shredded. Knowing my >chances of ever finding another one of these gaskets is slim to none, >I'm wondering if there would be any problems sealing the clutch >housing to the tranny with some RTV. Or maybe I should use that >Permatex 3H stuff I used between the engine case halves. > Any thoughts? bobw@execpc.com (Bob Whitby) I thought I had covered this subject but maybe not. This is one of those that is easy to do but tedious to explain or even listen to. . . . There we were, 50 miles off the coast of China and the #3 fuel pump was ready for reassembly. . . Needless to say this is not in the order of size that your VW fuel pump is. It's about 2 foot square on the base and stands about 7 foot high. I have a 2 foot square housing with a 1/2" flange all the way 'round. What to do about a gasket? No FLAPS for thousands of miles. Well obviously we made one. A quick run up to the chart-house and stroke the Navigator a little and we have a map of some obscure harbor in the world that will never be missed. . . . :-) Strap that puppy over the flat half of the housing and trace the outline of the flange. . Cut it out. . Put it back on the flange and hold it there while you cut out the inner edge of the flange and the bolt holes with a razor knife. Tap out the bolt holes first and tie the paper down with thread thru the bolt holes. then with it held in place, cut the inner surface. There you have it, we're lost but the #3 pump is sealed with no leaks. :-) The map paper by the way has a very high rag content and is exactly .004" thick. (0.1mm) That particular gasket is not stuck to either side of the flange due to the need to hold that .004" in the scheme of things. The other requirement is that it be easy to disassemble next time. On a car etc., I would stick it down with the #3 H on one surface and then cut or tap it out with a ball-peen hammer. This holds it in place while I do my forming. Notice how the ball-peen is just right for tapping out those bolt holes. . . . and all those radii ? This buying of pre-formed gaskets is really a relatively new thing. Back in the "Old Days" . . . . we didn't have "Formagasket" or "RTV". Had to walk to the flaps, uphill both ways . . in the winter it'd be slick. . . no shoes . . wrap your feet with barbed wire so you could get traction. . . :-) You can still walk into any decent FLAPS and ask for gasket material and they sell it by the sheet. Various thicknesses. Looking at the "clutch housing" that started all this, you could put it up with RTV and still get it off without too much trouble next time. RTV has a very weak bond to anything but itself. Handles temps up to about 500F I think. If all you had was the "3H", I'd want a paper gasket over the 3H to keep it from sticking to the other flange. The deal here, is many parts cannot be beaten and pried at to get them apart. It will ruin the part. "How thick a gasket?" : That is realative to how flat your two parts are with relation to each other and how deep the tool marks or pitting are. The thinnest gasket that will do the job is the rule. I generally lap the two surfaces with each other and some medium grinding compound before I assemble them. Example: the oil strainer flange on the bottom of the case. I could very likely put that together on my cases without a gasket. I put a paper gasket in just to be sure. That is also a good example of why you don't seal them with the 3H on both sides. If sealed so, you have to pry that sucker off. This warps the cover and now it doesn't seal so good. Types of gasket material: although there are literally hundreds and perhaps thousands of types, for the most part you are going to see three. "Oil and gas", "hi-temp oil and gas" and "Water/steam". Oil and Gas: this can be any thing with a high rag content or any other long fiber material. The stuff in the VW gasket kit looks like rags, thats the red gaskets, the stuff at your flaps in sheets, looks and feels like vegetable fiber and is brown. It does the job but will not take much pressure. Pressure is one of the reasons for the "thinnest is best" rule. Hi-temp Oil and Gas: This is generally a fiber-glass fabric with a grey binder. Used to be asbestos. This is the stuff you use on your manifolds and usually don't last. It's just cheap, you can get better but . . . . Water and steam: a low pressure product, high pressure will have a steel support. This is usually a fiber-glass with a rubber binder. Also grey in color. You'd use this on your water cooled rigs relative to the cooling system. So you go to your flaps and he only has two kinds, grey and brown. Just pretend you know no better and use the grey for hi-temp and the brown for low temp. I can't help you. :-) Thicker gaskets will require retorquing from time to time also. Computer paper is a high rag paper, .003" thick, should work well for those oil applications. Newspaper: It sucks and is short grained wood fiber but it will do the job where the purpose was to keep one surface from sticking to the other. Used to be a gasket shellac you could coat it with and get better service out of it. Runs .002" to .003" thick. Magazines with color printing, the slick ones, are generally a high rag content. You want a thicker gasket but are 3000 miles from a flaps? Laminate 2 or more layers with shellac or gasket sealer like 3H. Brown grocery bags: good fiber content of some kind. They do good! About .008" thick. How about those plastic grocery bags? I have never been in the need yet, but I expect I could work out something. They're only half a mil thick tho and what would I put my clothes in then? :-) west Making a gasket