AC 720 Oil Leak

[WickedAC 0]

Hey all. Just found this site a couple weeks ago after I bought my first Allis Chalmers. Great site and all kinds of info. I am hoping that someone may be able to provide some insight on an oil leak I have on this Allis Chalmers 720. The tractor is in great shape and only has 1100 hours on it. After running for about an hour or so to cut the grass I get some oil laying on top of the engine. The 20hp Onan has been rebuilt and I have checked the crankcase breather, and replaced the valve cover gaskets. The breather is clean and functioning well. Any thoughts would be much appreciated.

[JP 0]

WELCOME! I'd look at 3 places. The bearing plate gasket (BE SURE if you replace it to use the SAME thickness of gasket(s)). The Oil seal on that plate and then the gasket between the points box & block (possibly the points plunger seal too..). Let us know what you find!!! JP

[D-17_Dave 12]

If it's pooling around the top of the engine, look at the 2 gaskets on both sides of the spacer for the fuel pump also. And welcome.

[WickedAC 0]

Thanks. WIll do. I am hoping that the crank case pressure is not too high and the result being oil leaking out of multiple places. I am getting some oil leaking from the filler neck (very little) and hope that it is not a result of a bad piston ring or something where I would be getting oil blowing by. Might be that it needs a new gasket under the cap. Checked the Compression and it is 105 on both cylinders, which seemed pretty good. No obscure engine noises either.

[WickedAC 0]

Great. I thought it might have been seeping from under the fuel pump but thought that was strange. Thanks again. You all are a wealth of knowledge. Thanks.

[D-17_Dave 12]

TJ, one thing to remeber is that these older mech. fuel pumps are a sorce for problems on these ONAN's. It's also possible the diapram in the fuel pump has a pinhole in it and it's passing oil. This is a blessing of sorts as they usually bust and pour gas into the crakcase. I'd spend plenty of time carefully looking it over while I was into it or just replace it w/ an electric pump and do away with all the possible associated problems.