Small amount of coolant in bilge on my 12v71 650hp.

[Aussie Mike]

greetings all from Australia,

I have recently noticed a small amount of green coolant in the bilge in the ER of one of my 12v71's.
I checked all the petcocks and seems to be okay. I wet n dry vacuumed up about 3-4 litres

any suggestions?

thanks, Mike

 

[Captain Ralph]

Is this a new issue?

Do you use a coolant recovery system?
Any work recently preformed?
The last you added coolant (water)?

 

[cww]

Do you have overflow tanks? If not and the water temperature is high and/or your engines are running warm, they will dump coolant out the overflow tubes into the bilge. It makes a mess so a lot of us have added coolant recovery bottles. But if your boat doesn't have them, then yeah, the design of the engine is that the tube just goes straight into the bilge, that's what happens. Get some recovery bottles.

 

[SEVEN]

After checking the above items make sure to re-tighten all hose clamps. They do loosen over time.

 

[dottieshusband]

Run your hand under the crossover pipe behind the coolant tank at the hose connections, under the thermostat housings, and at the bottom on the coolant pump to oil cooler pipe.. those are all likely spots for leaks.

 

[Aussie Mike]

Run your hand under the crossover pipe behind the coolant tank at the hose connections, under the thermostat housings, and at the bottom on the coolant pump to oil cooler pipe.. those are all likely spots for leaks.

Thanks for the replies all.
No, there is no coolant overflow tanks. I would like to see how these are set up with some photos if possible please.

There has been no work done recently on the motor other than replace the engine anodes.

I replenish the coolant to a level about 2 inches below the cap to allow for expansion when hot.. Is that about right?

I will check all the hose clamps and other suggestions.

 

[SEVEN]

Here’s the overflow drain on my 8V71 TI. One thing that was not mentioned was how hot your engines are running. Mine are a steady 170 and I never get any overflow. You can put a small bucket underneath that drain to see if that’s where it’s dripping.

 

[Boatsb]

Get a cooling system pressure tester. That's the best way to locate or confirm idnthere is or isn't a leak.

 

[Captain Ralph]

Unlike a standard "open" radiator cap, A closed or recovery coolant system used a double sealed cap. easily identified by a second rubber gasket under the cap top, to seal the very top of the HE fill neck to the top of the cap. On a factory spec, these closed caps are rated around 7psi.

The overflow line, usually 1/4" clear water tubing/hose will pass from the H/E neck, just under the cap, to a remote bottle bottom fed. I install these bottles outboard of the engine and try to match the mid of the bottle level with the top of the cap.
This does not work every time and other locations are used that require some extra effort but any where close to this is preferred (IMO).

It is normal for a radiator or Heat exchanger to release some air or coolant as the engine warms up. This closed recovery method allows for any expansion air and coolant to expand and pass pass the cap. Now the recovery bottle catches any coolant lost.
As engine temperature and coolant pressure rinses, the cap closes.
Now the magic; When the engine is shut down and cools, coolant from the recovery bottle is drawn back in as the engine coolant contracts.
Eventuality, all the air is purged from the engines coolant system and you just maintain a level in the recovery bottle.
When all is working, never open that cap again.

There is an universal bottle that Cat & Cummins uses. About 2 gallons in vertical shape. I find them on e-bay.

So, after you run the engines, the bottle looks full. The next morning, it looks low. As long as that bottle never goes empty, all is good.

 

[Aussie Mike]

Unlike a standard "open" radiator cap, A closed or recovery coolant system used a double sealed cap. easily identified by a second rubber gasket under the cap top, to seal the very top of the HE fill neck to the top of the cap. On a factory spec, these closed caps are rated around 7psi.

The overflow line, usually 1/4" clear water tubing/hose will pass from the H/E neck, just under the cap, to a remote bottle bottom fed. I install these bottles outboard of the engine and try to match the mid of the bottle level with the top of the cap.
This does not work every time and other locations are used that require some extra effort but any where close to this is preferred (IMO).

It is normal for a radiator or Heat exchanger to release some air or coolant as the engine warms up. This closed recovery method allows for any expansion air and coolant to expand and pass pass the cap. Now the recovery bottle catches any coolant lost.
As engine temperature and coolant pressure rinses, the cap closes.
Now the magic; When the engine is shut down and cools, coolant from the recovery bottle is drawn back in as the engine coolant contracts.
Eventuality, all the air is purged from the engines coolant system and you just maintain a level in the recovery bottle.
When all is working, never open that cap again.

There is an universal bottle that Cat & Cummins uses. About 2 gallons in vertical shape. I find them on e-bay.

So, after you run the engines, the bottle looks full. The next morning, it looks low. As long as that bottle never goes empty, all is good.

Thanks very much Capt Ralph ! An excellent explanation.
I think I have the next project now

My engines run at 160-170 after warming up.