Fuel in the coolant? What the.....?!?

[Cheaper Jeeper]

I've got a really odd cooling system issues for you all. I noticed the other day that my coolant was looking dirty (cloudy) so I decided I was going to do a flush-n-fill to get nice clean coolant.

Well, I decided to get a little jump on the flush-n-fill job & drained the radiator last night. Refilled it with clear water, started 'er up (to circulate the coolant between the engine and radiator) and drained it again. Repeated this process several times until the coolant at the radiator fill cap was almost completely clear - just a hint of cloudiness left. Figured I'd get some antifreeze on my way home tonight, drain a 2-3 gallons of water out and replace it with the antifreeze.

Drove 20 miles to work today and noticed that the engine wasn't getting as warm as usual (by looking at the gauge) so I decided I better check the radiator. Pulled the cap off and was greeted by a STRONG smell of diesel! Looked in the radiator and there was a definite layer of diesel floating on top of the water! At least a couple of teaspoons worth, maybe even as much as an ounce - pretty hard to tell. But it is DEFINITELY diesel. What's more, the water under the diesel is looking pretty cloudy again - indicating that there might be even more fuel mixed into the water!

So it kinda looks like the cloudiness may have been due to fuel getting into the coolant (somehow) all along! My question is; How the HECK does fuel get into the cooling system?!? The oil has NO signs of water in it. No signs of fuel in the oil either. Just the slightest hint of diesel smell to the oil (normal) - otherwise it just smells like used motor oil.

The cooling system is not developing any pressure, and the engine is running great - no signs of any "missing" on any of the cylinders. tail pipe is dry - nice layer of BONE dry soot in it. So given all that it seems unlikely to me that it is a cracked head or a head gasket leaking. In order to leak that much fuel from the cylinders into a water jacket, it would have to be loosing significant amounts of compression - certainly enough to make it miss on at least one cylinder and to overpressure the cooling system. Right?

I'm really at a loss here as to how my coolant is getting contminated with fuel. Any help here would be appreciated.....

 

[spencnaz]

Leaking head gasket would be my first guess. But that would be showing bubbles in the coolant and your truck would have a miss in it.

 

[Cheaper Jeeper]

Leaking head gasket would be my first guess. But that would be showing bubbles in the coolant and your truck would have a miss in it.

Pretty much my thoughts (fears?) exactly - which is why I mentioned that it isn't missing or over-pressurizing the radiator. It isn't ATF either. My ATF isn't the red stuff - its nearly clear with a slight brown tint (a little dirty) and has almost no smell at all. What's showing up in the radiator is kind of yellowish-green - pretty much the color of diesel. It has a little different smell than diesel - almost a slightly gasoline smell, but that may be due to it being mixed with antifreeze.....

I don't know *** is going on with it.....

 

[argve]

are you sure it's not oil... because oil when mixed with water or coolant will get a milky color to it...

 

[spencnaz]

Yeah, good point. Oil mixed with coolant will look like runny mayonasse.

 

[Gr8ride]

Sounds like the ATF cooler in the radiator is leaking.
I had this happen on a car one time, not good for the trans

 

[Cheaper Jeeper]

Well, the ATF cooler leaking into the radiator core seems to be a logical possibility. But the stuff in the radiator sure doesn't look or smell like the ATF in my tranny - or any other ATF that I've ever seen or smelled. It is greenish-yellow and has a strong smell of fuel - with maybe a little bit of a solvent smell to it. I dipped the twisted up end of a paper towel into the neck of the radiator and it wicked it up just as if it were straight fuel.

I'm not saying it isn't ATF - just that it doesn't look or smell like it. On the other hand, I can't say exactly what a small amount of ATF thoroughly mixed with a larger quantitiy of water and antifreeze would look or smell like either. The coolant isn't exactly milky - it is more the color and appearance of weak coffee with creamer in it. Kind of a cloudy tan color.

Tonight I picked up one of those flush & fill kits on the way home. Installed the adapter in the heater hose, hooked up the garden hose and flushed the whole system for about a half hour. The engine was still warmed up and I kept it running during the entire flush. Ran clean water into it until the water coming out of the radiator neck was crystal clear.

We'll have to wait and see what the fluid in the radiator looks like tomorrow morning when I get to work - and more importantly, what it looks like tomorrow night after driving to AND from work......

BTW, if it does turn out to be the radiator, do I have to get one for a diesel? Or will one from a gasser work?

 

[yARIC008]

Not to scare you... but when i had cavitation problems i didn't notice any pressurizing of the coolant system. I just had a layer of oil at the top of the radiator, i'd flush the hell out of it and get pure clear water running through it and let the engine run for a few and then it'd be all cloudy again.

As for your engine not getting warm, I'm guessing the pure water may have seized the thermostat open, that's what happened to me when i did pure water.

About the rad, i'm pretty sure there is a difference in the diesel and gasser radiators. The diesel one is bigger and obviously more expensive, make sure you get the one with the tranny cooler in it too, i think some don't have them.

 

[Agnem]

Can you put some kind of dye in your diesel fuel? Mabye get some of the off-road stuff and try it? I dunno if you can see it in the rad that way or not, but it seems to me your first problem is to identify the contaminant with 100% certanty.

 

[Dsl_Dog_Treat]

Can you put some kind of dye in your diesel fuel?

Hows about the UV dye additive? That might do the trick.

 

[argve]

Hows about the UV dye additive? That might do the trick.

yep - the auto parts store should have it - just get a blacklight to view it... the black light makes it stand out something fierece...

but I still think it's oil for what it's worth...

 

[94f450sd]

i had one do this.dont know what it was,never tore the engine apart to find out.just replaced it.it ran perfect no over heating or anything,just dumping fuel into the cooling system.

 

[Cheaper Jeeper]

Well, I checked my tranny fluid this morning just to make sure it wasn't getting low (indicating leaking into the radiator). It wasn't quite down to the ADD mark. So, its a little low, but since I haven't checked it recently I can't say for sure that its loosing any. I can say that there is NO sign of any water in the ATF - which is a very good thing. Guess I'll have to top it up and watch it to see if it stays full....

......I picked up one of those flush & fill kits on the way home. Installed the adapter in the heater hose, hooked up the garden hose and flushed the whole system for about a half hour. The engine was still warmed up and I kept it running during the entire flush. Ran clean water into it until the water coming out of the radiator neck was crystal clear.

We'll have to wait and see what the fluid in the radiator looks like tomorrow morning when I get to work......

Well, this morning the radiator was full of gunk again (sigh). I'm going to try flushing it one more time before I come to the conclusion that it isn't going to go away. When I did the flush last night the temp was staying low and the upper hose wasn't getting very warm. That makes me think that the t-stat may not have been opening up, so there's at least a chance that there may still have been some "gunk" trapped in the engine that got circulated to the radiator this morning when it warmed up enough to open the t-stat. I know it doesn't take much to make the coolant look really bad. I'm going to block the airflow to the radiator and run the garden hose at a much lower flow when I flush it tonight to make SURE the t-stat stays open and the block is getting flushed out too. I'm not holding out much hope of that making it go away, but I guess I have to try.

If that doesn't do it, then I think pressurizing the tranny cooler with air will be the next thing I try - to see if I get bubbles in the radiator. Though I'm not too hopeful that doing that is going to reveal the source of the problem either. The **** in the radiator this morning looks and smells exactly the same, even though there's really very little antifreeze left in the system. And it still doesn't look like ATF. Still looks and smells more like fuel.

I'm really stumped on this one guys.....

 

[Cheaper Jeeper]

Not to scare you... but when i had cavitation problems i didn't notice any pressurizing of the coolant system. I just had a layer of oil at the top of the radiator, i'd flush the hell out of it and get pure clear water running through it and let the engine run for a few and then it'd be all cloudy again......

Did you have anything floating on top of the water in the neck of the radiator? If so, what color was it? What color was the cloudiness? Any smell?

I would think that if it was from engine oil you'd have been seeing droplets of oil on the water, that the droplets would be black, the cloudiness would be kind of milky white, and there wouldn't be much of a smell. Is that what you saw?

What I'm seeing is droplets of very thin greenish-yellow oily stuff floating on top of the water, the cloudiness in the water is more the color of tea with a little creamer in it, and it has a strong fuel/solvent smell......

 

[Cheaper Jeeper]

Hows about the UV dye additive? That might do the trick.

Dye is a pretty good idea. Is the UV dye additive oil compatible - or is it water-based?

I could always dump a gallon or so of Marvel Mystery Oil into the tank. That should be enough to dye the fuel BRIGHT red - and it should burn just fine. Might even be good for the fuel system. The pump & injectors would sure get lubed up good!