Any way to tell between red diesel and ATF in the bilge?

I've been chasing the source of this red fluid, my boat has a diesely smell especially after it's been run... but is there any definitive way to tell if it's diesel or ATF?
The fluid in the velvet drives is red.

Nopistn said:

I've been chasing the source of this red fluid, my boat has a diesely smell especially after it's been run... but is there any definitive way to tell if it's diesel or ATF?
The fluid in the velvet drives is red.

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1- smell. soak up a little on a clean paper towel and sniff.
2- location. Put white oil sorbent sheets under the engine and transmission and check for drip spots.
3- drops. Using a white paper towel or oil sorbent sheet, carefully wipe the underside of every hose and corners of metal looking for drops of red fluid then follow the trail uphill to the leak.

They smell entirely different. So as High Wire said, soak it up with a paper towel. Then get off the boat and smell it. If the boat has a pronounced diesel smell you may have to stick it in a sealed glass jar and take a sniff after you are away from the boat for a bit. I know for me that after I get a nose full of diesel fumes, that is all I can smell for a long time.

You could put some UV dye in the velvet drives, first one, then after a run and check with black light, dye the other and repeat. If no sign of glow under black light you can assume it’s the Diesel.

Smell and felling between your fingers, try to rub a drop of tranny oil between your fingers and do the same with diesel, you will feel it.

L

What color is your coolant? It would have it's own stench and taste also.

Captain Ralph said:

What color is your coolant? It would have it's own stench and taste also.

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Not coolant, I know that taste and it's green.

Island Cessna said:

You could put some UV dye in the velvet drives, first one, then after a run and check with black light, dye the other and repeat. If no sign of glow under black light you can assume it’s the Diesel.

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I like this idea. Is it ok to use the same bye for AC systems? If not what kind of dye?

dhays said:

They smell entirely different. So as High Wire said, soak it up with a paper towel. Then get off the boat and smell it. If the boat has a pronounced diesel smell you may have to stick it in a sealed glass jar and take a sniff after you are away from the boat for a bit. I know for me that after I get a nose full of diesel fumes, that is all I can smell for a long time.

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This is also a good idea. Need to get it off the boat

Your boat probably has a ton of diesel, and the ATF would be measured in quarts.

Is the fluid level in the tranny dropping?

If not its more likely diesel.

Tear or cut 1 inch wide ribbons of paper towel and tie one on every fitting and joint , operate for a few days, you will eventually find the leak.


Some leaks happen when not operating , so check for the red flag when boarding.

I had same issue. No fuel on underside of transmission or engine. Had a bad gasket on the injector pump. Fuel would drip directly to the pan.

Have you seen diesel in the water? Have you seen hydraulic fluid in the water. Two completely different initial oil sheens. Put a couple drops of this in a bucket of water. If it’s completely iridescent and shimmering it’s ATF hydraulic fluid. If it’s just a homogenous sheen it’s diesel fuel. (Not fool proof). But I’ve seen enough to know that there is a difference.

Nopistn said:

Not coolant, I know that taste and it's green.

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Good you know, the antifreeze in my Caterpillar C12's is reddish.

If it's the drive you want to get on that ASAP. I had a gas boat last season grenade it's starboard v-drive due to a line failing (fitting snapped off). Puked ATF out lickety-split and ate the box. It was spendy to fix, made more so by doing cutlass bearings, prop rebalancing and strut realignments. Ran like a top afterward... just in time to have the wife decide to sell it.