My install of the Crown/MOPAR 4295875AC transmission gasket (nylon over steel with molded-in double silicone sealing bead) failed. It was leaking in multiple places around the pan. Started as being wet, then dripping, and finally flowing when I turned the engine over. I took the pan off to inspect.
When I last installed the pan, I'd modified the pan. To add a drain hole, I'd drilled a hole through one of the bumps at a low point in the bottom of the pan, and welded a nut there on the inside (leaving a sliver between the nut and the pan unwelded to let fluid at the bottom out, instead of having to be at or above the height of the nut). Then I could use a drain bolt with a shallow head and a small magnet on the threaded end, instead of the usual undo the pan bolts and let the trans fluid leak out all around. This worked fine, and I found a collection of extremely fine particles, almost a grease, sticking to that magnet. Same for the flat donut magnet I left stuck to the bottom of the pan. After that mod, I painted the outside of the pan with an aluminum paint to protect against rust. And to protect the outer bit of the flange that the gasket sat on, I'd painted that too.
When I took the pan off, I discovered that the bottom of the pan and the lip of the flange were rust free. I could also see where the fluid had been leaking past the gasket in several places, on its top & bottom, where the gasket's silicone sealing bead had adhered to the paint on the flange, then that paint lifted from the flange, negating the seal. (I don't understand how the top of the gasket had some of the aluminum paint on its bead in a few places, as I don't recall painting the gasket contact surface of the transmission, which looks entirely paint free.)
The paint appeared nicely adhered to the pan flange, but the bead had adhered & lifted paint in more places than it hadn't. So I'm not going to play with degreasing and more paint. Count it as a fail and move on.
I cleaned up the pan (and magnets), scrubbed the remaining paint off of the flange gasket seat with steel-wool (looks like inadequate surface prep before painting). Another quick wash in dish soap, rinse & dry, then a light coat of fresh transmission fluid to the inside of the pan and flange to protect against any rust before I get to installing the pan.
Then I used some acetone on paper towel to carefully & quickly remove the paint from the gasket's silicone bead, then quickly washed the gasket in dish soap to remove any residue. Looks good for a second use (gasket should be good to use 5 or 6 times).
Since the pan is off, it will get a new transmission filter, just because.
Later today I'll get it back on and do the 150 inch pound torque, with the special fun getting those bolts in behind the exhaust pipe...
Topic: Composite gasket INSTALL failure (Read 3113 times)