Discussion
Hi Guys. I have a David Brown tractor with a new set of pistons to put in. It had a warped head which blew the head gasket allowing water into the combustion chamber, which pressured the piston on number two and broke the skirt off. Pistons and cylinders are relatively new having only done 500 hours, so there is no wear ring on the top of cylinders. Pistons in 1,2 and 3 came out easily through the top of block after unbolting caps. Number 4 jams solid when the piston comes 5/8 inch above block top and won't budge. It's solid. Hitting it with a 4 pound hammer bounces back. It runs perfectly up and down bore but wont come out top. Wonder if the skirt is deformed due to water in combustion chamber when head gasket leaked. Thinking of using a 6 ton jack and a 1 inch rod to force it out, maybe forcing cylinder out too. Any thoughts.
John
John
Thanks guys for the thoughts. It may be possible to see the bottom of the piston skirt from below. I do have the sump off obviously to remove caps. The conrod is moving freely at point where the piston sticks, so I don't think its deformed being a diesel its very strong. There is some carbon around the top of the bore, so I will clean it off and oil it before trying again. I don't want to take the block out as I would have to take the tractor in half. Damage to the bore is less of an issue as the cylinder is a replaceable sleeve. Thanks guys
Thanks for the thoughts. The piston is to be replaced anyway so it doesn't matter about destroying it. One suggestion is to smash the piston to get it out. The bore may be out of whack, but the piston does come up 15 mm above the block before jamming. To remove the crank I would have to remove the flywheel, clutch and gearbox, pulling tractor in half. I will try cleaning the bore top of carbon and use oil to lubricate. I will use 6 ton jack and heavy rod to push it up. Hope it doesn't crack block. Cylinder is not too expensive to replace, but block is a hassle to remove as described, if I crack it. The joys of having motors!!!
Does anyone know how the cylinder liner comes out? I have taken out a wet liner with an o ring in bottom but not a dry liner. Do they press in? By the way, the liner looks ok from the top, apart from the usual carbon buildup. There is no rim on it from wear. I''l have a go tomorrow and let you know. Thanks
I did check the conrod to make sure it wasn't jamming but I'll recheck it. Good point about the top of the bore having an obstruction. It does seem to be catching on the top compression ring. I'll measure it after I clean the carbon and see if one of the other pistons will go down the bore upside down when the stuck piston is at the bottom of the stroke. It may have been bumped putting the head on a while back and have a burr on it from damage. I'll try the piston trick from the top and do some filing with a round file to remove any burring on the top lip. Top compression ring doesn't reach the rim when its operating so small file marks won't do any noticeable bad effects. Thanks
Hi Guys. Interesting discussion on whether a piston can come out the bottom of the block. Most I have seen won't. This one may do so, as it looked like a bit of space between crankshaft bearing abutments, but I wasn't going to pull the block out to see. I cleaned the coke off the bore and filed around the top of the bore where the top ring was jamming, oiled it and bingo, out it came. New piston in, caps on, head replaced torqued down to 100lbs, and rockers on, ready to connect diesel injector lines, hoses and exhausts. Thanks for your comments and keep up the discussions.....John
Gassing Station | Home Mechanics | Top of Page | What's New | My Stuff