coolant overflow bottles

[Paul45c]

I'm about to flush out & refill my freshwater side on my 6v92's, and figured it would be a good time to upgrade my coolant bottles. My boat didn't originally even have any, and I added ones from an auto parts store. My mechanic told me they're undersized significantly, but said the bad news is that the standard DD ones are stupid expensive for what they are. It hasn't been an urgency, and I've been keeping my eyes open (i.e. NAPA, etc., but no luck) for something reasonable.

Anybody have a source of reasonably priced ones? Or perhaps know of jugs for another use that would be sturdy enough to adapt and use for this application?

 

[Genesis]

CarQuest near here had "heavy duty" diesel ones made for trucks. They were considerably larger and work fine.

With that said, I'd install them but consider not "using them" actively. What I mean by that is to keep those bottles DRY and fill the expansion tank / heat exchanger only to 1" BELOW the neck.

Why below the neck? To leave an air space for expansion. This keeps the system SEALED, which is tremendously to your advantage in terms of coolant quality and longevity. This way when the coolant expands it does not get pushed out into the bottle, but instead compresses the airspace you left.

 

[Paul45c]

Thanks a bunch, Karl.

 

[Nonchalant1]

That's what I do on 8V71TIs. It's 1.5 inches below the cap and it never overflows and I never have to add coolant, plus it's not going in and out of a bottle. If I ever see any in the bottles, then I'm going to worry about it. We've been running a lot for the last month and my coolant use is zero.

 

[REBrueckner]

Why would I NOT want to use the bottles for overflow since millions of cars and trucks do so?

I've been using RV overflow bottles for several years and have them set up so that when the engines are hot, the bottles are full. When cold, the bottles are almost empty..coolant level is low in them. It's so easy to see thru the bottles to check antifreeze levels and clarity. I use a car size bottle for my Onan diesel genny.

My experience is that Detroit Diesel heat exchanger cores begin to come out of the expansion tank coolant level pretty quickly so I have always figured it was best to keep that full and have a bit of spare in case a leak develops when underway.

 

[Genesis]

If you got a leak it ain't gonna help.

Here's the thing - yes, the new cars do all have those bottles. Guess what - they're SEALED! That is, the "cap" on the system is on the bottle!

Ever look in one of those overflow/expansion bottles that is NOT sealed? Pretty cruddy eh? So you want to flush clean coolant in and out of there, picking that up and putting it in the engine?

Not me!

 

[Top Shelf]

Sen-Dure has them in their catalog....Thx.

 

[REBrueckner]

Genesis, how does crud get in a overflow bottle if not from the engine coolant??

Any crud from the engine in the coolant IS likely to overflow and be visible in an overflow bottle. Isn't that what you want? Say a bit of oil...comes out and floats in the bottle so you see a potential problem. In any case, my overflow bottles for my 8V71TI's have been clean and the coolant clear for three or four years. I removed them once a removed tiny amounts of sediment from the bottles, but they have been clean and clear ever since...as they should be.
In addition, when a bottle shows a lower coolant level, I know to look for a slow leak. In one case I found a hose clamp loose and a bit of coolant dripping out...But the coolant in the bottle DOES replace any lost from the engine. Of course the volume of coolant in a bottle is minimal compared with that in the engine, but the ability to see clear coolant and the coolant level wigthout having to remove expansion tank caps is a real nice feature on my set up.

Is there some negative that I don't understand yet??

 

[Paul45c]

Hey Top Shelf -- any idea how large that coolant bottle is? I can't tell from the picture, and when I checked on Karl's tip for CarQuest, I found they're just the small automotive size -- like 2 qts. Not enough, sez the mechanic. He's looking for as close to 1 gal as I can get. Thanks for the lead, though -- they're right around the corner here in Ft. Lauderdale.

 

[Genesis]

Oxidation. In a closed system there's no oxygen - its consumed and then that's that. In an open system the oxygen is continually replaced.

The reason automakers (and others) went to closed systems was primarily this - it keeps the system cleaner.

If you're changing coolant every couple of years the differences aren't big, but they're there. I personally don't like the bottles because they give a false indication as often as not - if there is an airleak in the system or the cap's suction-return valve is screwed up the level will not drop even though coolant is being lost in the system. You will believe all is ok when it really is not.

I pull the caps and dip 'em during cold checks. (Yes, I realize that some engine setups make this difficult; its all a trade-off.)

 

[Trojan]

I have overflow containers on my 6-71s. I got them at Napa for about $8. bucks each. The only time they receive fluid is when I crank up the rpm. I like them.


BILL

 

[SKYCHENEY]

I put the small automotive bottles on last year. They seem big enough. I have never had them overflow or run dry so they must be adequate. I did find a plugged overflow line when I was installing the bottles. It was a copper line which I replaced with clear plastic. Now I know that it's not clogged since I can see it.

 

[REBrueckner]

Genesis..Oxidation.....without bottles, I guess the system IS effectively closed....good point...thanks for ther tip.

Also, regarding antifreeze replacement/replenishment. This is not be "by the book", but periodically you can empty (syphon out) the overflow bottle coolant when the engine is hot and they are full. Then refill them with a 50/50 fresh mix. If the coolant bottles show dirt/corrosion/cloudy appearance, definitely drain and flush the entire system. This replenishes the additives with minimum of mess/fuss. I also added drain cocks to the engines so I can drain out a gallon or so and replenish periodically. Test strips confirm antifreeze is still good.