My brother's 96 12v is having a problem with the coolant. He replaced the radiator several months ago when he tabbed his kdp and did the front main seal.
All of a sudden, his coolant is discolored/clear and smells very strange like a solvent or something, but not quite like diesel.

Is this a cracked head or blown head gasket, or something else entirely? The coolant really smells bad and is no longer green even though it was replaced recently. The oil seems to be fine, it's just the coolant that is contaminated.

 

There shouldn't be any way for fuel to get into coolant. It's most likely oil.
Milky color and thick consistency are the symptoms. Sources of a leak could be the engine oil cooler that mounts to the block behind the oil filter, or if it's an automatic transmission there's a transmission oil heat exchanger attached to the block below the turbo.

 

Thanks for the response.
We couldn't think of any way for fuel to get in there either. If something related to the injection system was leaking, it could only get into the oil, right?

It's so strange because it doesn't look like oil contamination. The coolant isn't milky. It's just a lot more clear colored than the original green, it doesn't smell at all like coolant, and there's already a bunch of rust and stuff floating up. It also doesn't seem to be loosing any coolant, but the overflow container looks nasty. He used the same coolant that he uses in the fleet he maintains at work, they get it in big drums.

We'll check the oil cooler and transmission heat exchanger.

We were thinking it might be some kind of chemical reaction, but to what?
Could it be that there was an air gap in the system that released a bunch of stagnant old junk that had leached stuff from the metal and made it smell like some kind of solvent?

 

Maybe someone accidentally filled the coolant overflow bottle with windshield washer fluid.
I've seen it happen more times than I can count.

 

Ok, we found the problem and I figured I'd post in case it happens to somebody else. There were bad electrical grounds on his truck that caused an electrolysis process in the radiator, basically turning the coolant into an acid.

We did figure it was some type of chemical reaction, just couldn't come up with what exactly caused it at first.

Bad grounds really do cause a ton of problems, this is a new one on my list though.