Is a cracked block reparable?

[Michael L]

I have been getting water in the oil, and have checked waterpump, exhaust system, and behind valve cover plate and have seen nothing. Today I preasurized the block to 20psi, with air, and lost all of it in less than 1 minute. There is an audible hiss at the rear of the block, below the valve cover I think, and I have to assume that this is a crack (although I thought I did a good enough job winterizing it). If it is a crack, is there a fix? Do I need a new block?

[Don Moyer]

Michael,

There's a good chance you'll find that a 1/4" pipe plug may be leaking in the back wall of your valve chamber. Before doing anything else, I'd remove the valve cover and repeat the pressure test while checking the very center of the casting behind the valve springs for an air leak.

Don

[Michael L]

Did as you said, and detect no leak, in fact I was surprised how good it looked in there. The leak sounds as if it is coming from a lower location than is visible through the valve cover, and at the transmission end. If I pull the block, flip it over and remove the oil pan, am I going to be able to see anything? Thanks in advance.

[Don Moyer]

Michael,

Yes. After removing the oil pan, you should be able to see any of the usual places where cracks or other flaws have appeared in cooling jackets, including pin hole leaks in the lower part of cylinder bores.

Don