dirty cooling loop

[h2opolo]

Last time we went out I noticed alot of build up in the coolant reservoir. Does anyone know where this substance could be coming from?

[NautiqueJeff]

Any chance some of the wrong coolant has been mixed in?

[h2opolo]

Any chance some of the wrong coolant has been mixed in?

The boat was a demo boat before I owned it. I think they knew the correct coolant to put in. When we bought the boat from the dealership this summer, they gave us some additional coolant to add in case there was some air left over in the lines from a valve job they did. Heres what they gave us.

The manual says ethylene glycol so I think thats the right stuff. I have heard of people adding the green stuff to this and it basically all turns to sludge.

[h2opolo]

Also the stuff on my finger isnt just from dipping it in the coolant, it's what I wiped off the inside wall of the reservoir.

[ffmedic74]

If it's a different coolant from the GM product, would highly suggest getting some professional assistance as mixing will gunk up the cooling system.

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[h2opolo]

It says its for GM motors that use DEX-COOL.

[jonsquatch]

If you are not getting water in the oil there is a good chance its just the coolant starting to fail.

I have had a fair number of vehicles with dex-cool in it and no matter how well I maintained the coolant some of them eventually gummed up and looked like that, and eventually they all get flushed and replaced with normal coolant. I have heard that it could be air, or some contaminate such as normal antifreeze or oil or sealant or something in tap water that got in the coolant and is causing it to degrade and start to sludge up.

Since it looks like a good system flush is in order if it were my boat I wouldn't refill it with dex-cool. If it were warm enough I would drain and flush the system and then run distilled water in it for a while and drain then refill with a normal coolant that claims to be compatible with dex-cool for the first refill and then keep an eye on it for a while.

[h2opolo]

I think thats the issue as well. More than likely at one point there was some bad coolant in there. When the coolant was replaced I don't think it was cleaned out properly. When you say normal coolant, what kind are you talking about? I did think about draining the coolant then just taking it out a couple times with just water to flush it out. Will this remove the scum buiildup though? Maybe there is an additive or detergent you can add to bond with the substance to remove it?

[jonsquatch]

There are plenty of brands of coolant, I usually use Prestone, and I like the plain old 50/50 premix that is advertised as compatible with any coolant. I still flush everything well before hand, typically I drain and recover whats in there, then run water through everything. There are cleaning and flush products you can buy, but it makes another 2 gallons of liquid I have to recover and bring to the recycling center so I guess it depends on how bad it is.

[h2opolo]

I think I am going to empty the cooling system, use a flushing agent, then run it with distilled water a couple times to make sure it is all decontaminated. If that works I think I will just go with the stuff pcm suggests.

Is it ok to take the boat out on the water for a day if there is just water in the cooling system? I think that would be fine if I kept an eye on the temperature.

[AirTool]

I think I am going to empty the cooling system, use a flushing agent, then run it with distilled water a couple times to make sure it is all decontaminated. If that works I think I will just go with the stuff pcm suggests.

Is it ok to take the boat out on the water for a day if there is just water in the cooling system? I think that would be fine if I kept an eye on the temperature.

Should be but remember the boiling point is now much lower....but still should be above your operating point. High temps would hit the boiling point causing a "boil over". Check where your cap vents and make sure if boiling water blows out no harm is caused.

Also take a gallon with you in case you boil your level down you can add to it AFTER IT COOLS OFF (SO YOU DON'T MAME YOURSELF).

Finally, once you decide your done,...just drain out that distilled water. Don't put any city water in there as it will bring a fresh load of minerals and chlorides.

[Zach@n3]

What he said^^^. Also remember the boiling point of water is lower than with the antifreeze(but higher than normal water being a closed loop pressurized system). Regular old open loop engines live very long lives on fresh non pressurized water so you should be good to go. Basically if you take it out just to be safe run it like normal don't go hammer down for extended periods and you should be ok. Or take it back to the dealer and ask why the coolant looks like seaweed after they did a valve job. And why did they do a valve job? Manufacturer defect?