Originally Posted by Jake Raby

Possibly MOF#12, a cracked cylinder head... Check the oil for coolant intrusion.

The cracked head MOF is becoming more frequent as the water pumps in these engines get more time on them and are not being changed as they should due to high time and age.

How does the water pump crack the head?? well, first off the engine (as a whole) never totally overheats when this occurs, the gauge never shows an elevated temp, all of a sudden you are missing coolant and then you notice coolant in the oil. Here is why:

You'll be reading this info first here before anywhere else, I haven't even added it to my site yet and have never shared this before.

For the past 4-5 years we've been seeing engines fail with cracked heads that had symptoms of overheating, but the engine never overheated. As we developed proper and extensive repairs for these cracks and milled away the area of the head where the crack originated prior to welding it we found small pieces of plastic inside the tiny orifices of the head. These small pieces of plastic were finding their way to the smallest passages in the cylinder head cooling jackets, then lodging there sideways thus shutting off the flow of coolant to one small area of the head. This creates a hot spot and then a crack.

Guess where that plastic comes from?? The POS plastic water pump impeller! Small pieces of the plastic chip off and enter the coolant, meanwhile no one knows the water pump is bad, because it doesn't make noise and the engine runs cool on the gauge.

I have 40,000 dollars worth of repairs in my facility right now that is directly attributed to these cracks that were positively created by the water pump impeller breakage.

This has happened to cars with as little as 38K miles on them. If you water pump has 50K, I'd change it this weekend. Its cheap and fairly easy to do. We now HAVE to finish the steel billet water pump impellers to kill this issue, it could even happen to one of our engines.

cracked heads don't have to leak into chambers/ cylinders.. they can leak into the cam cover area. Drain the oil and look for even the slightest coolant intrusion.

Originally Posted by blue2000s

I've been watching for evidence of the UV dye from the coolant in the oil, I'm not finding anything yet, but I'll be keeping my eye on it.

Originally Posted by Tranlm

By the way, how exactly did you add in the florescence additive to your coolant?

I ask because I'm thinking, wouldn't it just sit in the reserve tank if you added it there?

Originally Posted by blue2000s

If you open the bleed valve and let the car run, or drive around for more than 15 minutes, it gets circulated throughout the car.

You're right, without the bleed valve, it does just sit in the tank.