1999 Ford F-150 compression

We aren't a repair shop. We just dispense the best advice and answers as possible.

You need to include a lot more detail. How do you know cylinder number two is misfiring? Are you sure it's water you're seeing? Are you losing coolant? Does your engine have an EGR valve? What has led you to want to do a compression test?

You can have a leaking cylinder head gasket or any of a number of other problems and the compression will be fine. In fact, oil and water don't compress, so if either is leaking into the cylinder, that will make the compression readings higher than normal. Fluids will seal leaking piston rings too and make compression readings go higher.

The best test to verify this type of leak in a head gasket is to add a small bottle of dark purple dye to the coolant, then check a day later with a black light. The dye will show up as a bright yellow stain that you can follow back to the source. If a head gasket is leaking you'll find the dye inside the tail pipe.

How long you wait depends on the severity of the leak. Real bad leaks usually result in pretty obvious symptoms and observations that are easy to diagnose. It's the slower leaks, including those where the leakage dries up and evaporates before you get to see it where this dye is the most useful.

If it takes, lets say, a thousand miles for you to lose a quart of coolant, you may need to drive 50 to 100 miles to have enough time for the dye to work its way to where it can be seen. If you lose a quart of coolant in a day, perhaps 50 miles of driving or less, you can probably drive just five miles, then check for the yellow stain. If you can't find any indication after a hundred miles, just keep checking at regular intervals until it shows up.

Auto parts stores will have the dye for the fluid you're leak-checking, and those that rent or borrow tools should have the black light.