Cummins Generator Core Cooler Leakage

Leak may not be in the cooler but in the heads. Bad head gasket can have oil forced under pressure of compression through it. That maybe the oil you see in the coolant. Pressure test on the cooling system would also fail it the gasket leak is bad enough as coolant would run into cylinder.

does the engine have wet liners ?

they suffer from cavitation damage which makes the liners porous.

also possibly head gasket damage

some specs

http://openpdf.com/ebook/cummins-qsx15-g8-pdf.html

http://www.techcom.com/cutaways/gallery/qsx15-3.htm

Might Help

http://www.diesel-service-parts.com/cummins-codes.html

http://www.everytime.cummins.com/every/applications/construction_tier_3_stage_iiia/qsx_const_tier3.page

http://www.pdfgeni.com/book/cummins-troubleshooting-isx-fault-codes-pdf.html

http://www.justanswer.com/tags/UK-Car/diesel?r=ppc|ga|5|Cars+%2D+CYN|Diesel&JCRN=Diesel+Mechanics&JPKW=a%20diesel%20engine&JPDC=C&JPST=www.pdfgeni.com&JPAD=4567730988&JPAF=txt&JPCD=20100309&JPRC=1&ShowExperts=1&JCLT=Diesel&gclid=CKnupOfr9aECFYNs4wodAQtKFQ

Cummins engines have a history of leakage just put in sealer in the coolant it will work. I used a liquid type so as not to block radiator and have had years of trouble free service .

The above answers are probably right on. I would like to mention one thing and that is about the coolant.

It is very critical to keep the proper amount of chemicals in the coolant to keep the electrolosis/cavitation from happening. I think the mechanics checked it every time they changed the oil and usually added some to keep it up to proper concentrations.

30 years ago, I had a similar problem at about 20 degrees below zero. I started the engine and pulled the radiator cap. It blew cold, black oil all over my blond wife's hair and face as she stood about 10 feet in front of it.

Lesson learned: Don't laugh...because that causes the temperature back inside the house to stay at about -40 for a couple of days.

As already mentioned, Cavitation of the liners could be possible.

If there is a Turbo Charger and an after cooler (for the intake air), check also the After cooler for leakages: this will draw air into the cooling water when at rest or eve while working, resulting in depletion of the chemicals active ingredient (anti-oxydants) in the water, then the hottest place being the base of the liners, Oxygen in the water will attack the liner and make it porous.

At least this was my experience with such systems...

All prior possibilities are true, but the Guest has stated that the Oil Cooler tests bad every six months, I can only then assume that when the cooler is replaced the problem is sorted until the core fails once more. This said it is not necessary to be looking at cylinder heads, liners, etc...

Do a destructive test on the failed cooler core. Carefully cut coupons as close as possible to the actual failed point in the core. By doing this you should be able to determine rather this is pitting, stress due to improper assembly, failed solder joints or what? Depending upon your location, you may be receiving sub-standard cooler cores as replacements, or even used cores that have not been repaired to manufacturers specifications.

I would tend to agree with taking a very close look at your coolant properties. If memory serves me, Cummins recommends a Fleet-guard pre-mix. Get this right as these engines produce enormous amounts of heat (i.e. Kw) as compared to there size and construction.

The Cummins QSX15 has an inherant problem with the oil coolers. Copper units have been leaking coolant into the oil. Cummins have now installed a stainless steel oil cooler but these units are not as efficient as the copper units and cannot cool at engine load factors above 60%. Cummins have yet to come up with a real fix for this. They are mumbling now about an extra cooler or remote cooler.