2003 Honda Jazz L15A - Water in oil

My daughter has a 2003 Honda Jazz with the L15A VTEC engine. It has done a little over 200000km and recently started miss firing. There is definitely water in the oil which can be seen by the milky emulsion on the underside of the oil fill cap. I was thinking a head gasket issue but after testing compression on all cylinders (range from 200 - 215 PSI) I thought maybe something else? Checked the radiator which was empty so I began refilling it and after several jugs of water in finally reached the top. Thought I would also check colour of the oil in the sump so removed dipstick - clean water poured out of the dipstick tube and level went down in the radiator - clearly there is an easy path for water to flow from the radiator and into the oil sump - any thoughts on cause here??

Its strange that the compression test is OK. Maybe do the compression test with the radiator cap off.

It sounds like you have a blown head gasket or cracked engine.

Yes, I agree. I also just drained all of the fluid out of the sump - a nice light brown/rust colored oil/water mix and a lot of it. I suspect most of the contents of the radiator was in there- this may also have contributed to the apparent good compression as the fluid level in the sump was very high? I also suspect a cracked block or sizable hole between the cooling water and oil sides of the block? With the sump plug out and all the fluid drained, I just tried pouring water into the top of the radiator and, as I suspected it would, the water flowed directly out of the sump plug hole at the same rate I was pouring it in! That means a big flow path - just wanting to know if there may be something less terminal going on or if anyone has seen something like this before?

I've seen this on Mazda alloy head engines (80's laser and Mazda 323). In both cases it was an alloy plug in the head coming loose (like a welsh plug, but a pressed in alloy plug). This separated the water gallery in the head from the camshaft area, allowing the water and oil to mix. As this path has nothing to do with the combustion chamber, the compression will test OK (and in fact will be fine)

Whip the tappet cover off and have a look around for a dislodged / missing plug (it will probably just be pushed partially out of the hole - not enough to pop it out completely). If that is the case, then it is an easy fix. Rip the head off and get the plug welded back in place. It could also be something similar in the block, and judging by the fact that the water is pouring straight out of the sump when you pour it into the radiator, I'm thinking it's more likely in the block as it seems to be close to the bottom radiator hose. Maybe something to do with the water pump? If it's a block related issue, then you'll probably be best to lift the engine out to investigate. A bit of a pain, but not an impossible job.

Either way, it's either corrosion, a crack, or a dislodged plug. Haven't personally seen this on a Honda, so can't offer anything more definite.

Thanks Hondarally, good info and encouraging to hear that there may be something a little less problematic than just a cracked block! I also suspect something low down in the engine rather than the head given the ready flow path from the radiator. Time will tell I guess. Not in a big hurry to pull the engine out -will need to dwell on that one for a bit!

Book and complete a leak down test and a reputable mechanic.

This is will confirm the presence of a leak , and the area where it is coming from.