I just finished replacing the heads on my '84 1.9l.  It started up ok and idled fine, then the oil pressure light started to flicker.  I checked the dipstick and found signs of water in the oil.

I assume that I disturbed one or more of the o-rings at the bottom of the cylinders, but I'd like to hear about anything else that could cause this.

Is there any way to figure out which side the problem is on, so I don't have to take both sides apart?

Can I slide new o-rings on over the cylinders, or do I have to remove the cylinders to fix this?  Argh, it's not fun putting the cylinders back on with the engine in the van!

Thanks for any ideas you have.

Bill