Oil in coolant

[Field6.5]

Recently bought a 98 6.5. I knew it had engine issues and plan on fixing it, previous owner said it was losing coolant and bringing up the oil levels so he parked it. I got it running and checked things out, the oil was very thick but I drained it off and flushed it, the engine runs and sounds good, good oil pressure, no overheating or white smoke, is there any way I can tell if it is a head gasket issue or a cracked block other than taking it apart? Hope to pull the heads soon. Thanks.

[trbankii]

It would be difficult to determine that without a visual inspection.

[Field6.5]

It would be difficult to determine that without a visual inspection.

Ok thank you

[DmaxMaverick]

If you have oil in the coolant, it's a fair bet you also have coolant in the oil. Fluids will take the path of least resistance (as will almost anything), and the two systems are pressurized at differential periods of operation. Engine running, the oil pressure is +, and engine off the coolant pressure is +. It's difficult to know anything without getting eyes on the internals, but you can pressure test the coolant system and hope you see something obvious. Next, remove the radiator and have it tested (more common suspect).

In any case, don't run or drive it any more than absolutely necessary. Oil in the coolant is no real big deal, in regards to furthering damage, but coolant in the oil can destroy the engine pretty quick.

[Robyn]

A leak that's not causing cooling system issues is likely coming from the bottom end.
The 6.5 can and do crack in the main bearing areas and can see a crack run from a main web up into the lower end of a cylinder ...water jacket.

The best way to find whats going on is to get the engine out of the rig and on a stand.

Rip it apart.

Head gasket issues on cylinders 1 and 2 are common with high miles.

#8 cylinder cracks about 3/4" down from the top near the rear of the block have occured on the later 6.5 (1998/1999)

This issue cause coolant pressure issues.

The Early 506 blocks (Large outer main bolts) with the large oil squirt passages in the main saddles were prone to carcked main saddles that would see the crack propagate up the cylinder wall.

I have seen the later 6.5 squirt blocks do the same thing....

Way too many stress risers in the bottom end of these engines (Sharp corners and drilled holes that have not been chamfer'd

Get it out and carefully tear it down.

Having sat for a period with Glycol in the oil will have taken a toll on the bearings and the hydraulic lifters.

Before you tear it apart...Drain the oil, add a fresh filter and fill the engine with ATF (Full oil fill) and let it idle for a few minutes and keep an eye on the oil pressure.

This will really clean out the crap.

Drain it, then yank it out.

[ronniejoe]

Do you know if the water pump has been replaced? Several opportunities to mingle oil and coolant if that was done improperly.

Other than that, it's probably cracked.