Darn, I have a problem with one of my 2004 Merc 525"s. I'm finding cream colored foam on the oil fill cap. I figure I'm getting water in the oil. I have not noticed any change in the coolant tank level but I'm not sure how much of a leak it would take to make the engine oil begin to foam. I am going to pressure check the oil cooler this week. I am hoping big time that it is a blown cooler. I did notice this week that at 50MPH I have 50 PSI of oil pressure and 55-60 PSI of water pressure. With the pressure differance, water being higher, I'm guessing water could get into the oil. If the cooler is not the cause I'm not sure what to check next. Does anyone have any advice as to where to look next? Has anyone else had this problem? It is not just condinsation because the other engine doesn't have foam and this engine has never had foam before. Both engines, according to the gauges, are the same.

Im going through this right now, on a 496HO, I tested my cooler and it was good, and i would probably bet money its not the cooler, mine was a exhaust related issue, i would do some research on here, there has been alot of lost 525's in the last few years, alot do to the Exhaust, some cracked, some not sealing properly.. it would be good to pressure test them and check for cracks, i bet you find a problem, last case would be a head gasket thats about ready to let go.. do a pressure test on your coolant tank!

My bet is the exhaust , seems like they are good for 200-250 hours, then they leak.

Pressure test the coolant tank?? Are you saying to remove the fill cap and pressurize the tank and see if fliud level drops?

Also I have heard of some exhaust issues on the 525's. If they are leaking wouldn't the water steam and go out when the exhaust valve is open or liquid lock the cylinder. How can the water get to the oil?

Water pressure should not be that high. Confirm that it really is and find the reason. Maybe blocked oil cooler or heat exchanger. Still the only way it would get into the oil is the cooler or header leak.

The water pressure is that high...both engines match and the Fountain test sheet has those numbers as well.

Yeah, they run high pressure. We had a header fail in Key West and the only symptom was water entering the oil, ran great, no overheat, no smoke, no hydro lock. Apparently it was a small trickle that would seep past the rings as the boat sat.

Pressure check your headers.

Reversion: happened to me, I caught it in time. Oil pressure went south and oil temp went north one day because the water caused the oil filter to collapse and bypass the oil cooler. If left unchecked, the pressure will blow out a main seal or the oil pan gasket (an expensive fix for a 40 dollar part) If left really unchecked...............you'll be writing a big one!

That's raw water in your engine, not coolant. And yes, the pressures are supposed to be that high as the gauge reads the raw water and not the coolant pressure. If you're head gasket was letting go, you would probably see oil in the coolant tank since there is more oil pressure than coolant pressure. The 525 head gaskets are caulked around the coolant and oil passages to prevent that from happening.

Get you some fresh headers and send these back to CMI to see if they're fixable. If they are, keep them as spares. If you run salt water, flush with salt away every time and drain the water out of them.

Well, looks like you guys are right. I pressure checked the oil cooler last night. I put 100PSI to the oil side, pluged one end of the coolers water passage and poured water into the other end....no bubbles after 15 minutes. I them drained the cooler and re-did the test using boiling hot water to expanded everything and still no bubbels. Conclusion: darn cooler is fine...must be the headers. I did pull the plugs. They are very white...very lean looking...all but 2. I'm guessing from the water entering the cylinders. I cranked the engine over and no water came out but the engine has sat for two days...maybe it evaporated. Guess I will remove the headers and try to find a way to pressure check them. Any ideas as to how? I did get a leak down test kit but have not done the test yet. I think you guys are right about the head gaskets being ok because the coolant tank is still full. Darn the luck. It's very sad that Merc and CMI can produce such junk. I believe I am done with Merc...next time it will be Ilmors for me.