An annoying problem that I just can't solve :(

[Frank Langer]

Hi,
The coolant accumulator tank on our boat has a small 3/8 inch overflow hose coming off a nipple just below the radiator cap on the tank (not on the manifold). The nipple is so close to the top of the tank that I can't slide a hose clamp between the nipple and the tank, and so it leaks just a bit of coolant when the engine is running and the cooling system is under pressure. I have replaced the hose with the tightest fitting 3/8 inch hose that I can slide/work over the nipple. I have added a small zip tie, tightened as much as I can, still no help. I have placed a small wire around the hose and tightened it as much as I can with pliers, still leaks. I have applied Seal All sealant around the hose, as it's supposed to seal leaks including gas, diesel and coolant, and it's worked well in other applications, but it didn't work here for some reason.

I have also tried lowering the coolant level in the tank, but it refills from the plastic overflow tank that the small hose runs to. I think that if I kept the overflow tank empty and reduced the accumulator tank level, then it might not reach the overflow hose and wouldn't leak, but I'm hesitant to do that because I don't think that's how the system was designed to operate.

I am out of ideas to try next and would appreciate any suggestions.

Thanks,
Frank

 

[Prairie Schooner]

Hi,
The coolant accumulator tank on our boat has a small 3/8 inch overflow hose coming off a nipple just below the radiator cap on the tank (not on the manifold). The nipple is so close to the top of the tank that I can't slide a hose clamp between the nipple and the tank, and so it leaks just a bit of coolant when the engine is running and the cooling system is under pressure. I have replaced the hose with the tightest fitting 3/8 inch hose that I can slide/work over the nipple. I have added a small zip tie, tightened as much as I can, still no help. I have placed a small wire around the hose and tightened it as much as I can with pliers, still leaks. I have applied Seal All sealant around the hose, as it's supposed to seal leaks including gas, diesel and coolant, and it's worked well in other applications, but it didn't work here for some reason.

I have also tried lowering the coolant level in the tank, but it refills from the plastic overflow tank that the small hose runs to. I think that if I kept the overflow tank empty and reduced the accumulator tank level, then it might not reach the overflow hose and wouldn't leak, but I'm hesitant to do that because I don't think that's how the system was designed to operate.

I am out of ideas to try next and would appreciate any suggestions.

Thanks,
Frank

Is the tank nipple metal? If so, do you know what kind?

 

[JSM]

I have also tried lowering the coolant level in the tank, but it refills from the plastic overflow tank that the small hose runs to. I think that if I kept the overflow tank empty and reduced the accumulator tank level, then it might not reach the overflow hose and wouldn't leak, but I'm hesitant to do that because I don't think that's how the system was designed to operate.

I don't have an accumulator tank but I have been running with my overflow tank empty for the last five years with no problems. My thinking is that the overflow tanks only mission is to give coolant somewhere to go other than the bilge in the event of an overheating event.
Maybe try running with the overflow tank empty and watch your temp gauge.

 

[Captain Pete]

What about trying one of those ring clamps like you see on fuel lines on outboards? They may fit better and seem to sink into the hose material a bit.

Something like in this line: https://www.rotorclip.com/hose-clamps/

 

[Frank Langer]

Is the tank nipple metal? If so, do you know what kind?

Yes, I am almost certain it's brass.
Frank

 

[Frank Langer]

What about trying one of those ring clamps like you see on fuel lines on outboards? They may fit better and seem to sink into the hose material a bit.

Something like in this line: https://www.rotorclip.com/hose-clamps/

Captain Pete,
I will look into these a bit further, but the additional factor that I didn't mention is that not only is there almost no space between the nipple and tank, the rad cap on the accumulator tank sits right above the nipple. I need to be able to remove that cap to fill the tank, so any clamp can't have any protruding end sticking up.
I think I'll visit our local Hose and Fittings shop again to see if they have anything like what you suggest.
Thanks for your suggestion!
Fan

 

[Frank Langer]

JSM,
Yes, if nothing else works, I'll try running the overflow empty with reduced coolant in the accumulator tank. What I don't know is that if the whole cooling system is under pressure when hot, does coolant splash around in the accumulator tank as the coolant moves, which would cause the leak even if the level was lower. But it's worth a try if nothing else works.
Thanks for your reply!
Frank

 

[Loren Beach]

Is it possible to (even slightly) move that tank to make it more accessible?
I ask because EY put the plastic overflow tank for our Universal diesel in an adjacent compartment under a seat hatch in the cockpit. I changed it to a new tank mounted on the bulkhead inside the engine compartment. There is a picture of it in my engine-change blog.
Since you refer to a tank with a radiator (pressure) cap, your installation might be different, so my advice might be worthless, upon reflection. (?)

BTW, your thread title is ironically funny, if considered from our spouse's occasional view of the whole relationship!

 

[Frank Langer]

Is it possible to (even slightly) move that tank to make it more accessible?
I ask because EY put the plastic overflow tank for our Universal diesel in an adjacent compartment under a seat hatch in the cockpit. I changed it to a new tank mounted on the bulkhead inside the engine compartment. There is a picture of it in my engine-change blog.
Since you refer to a tank with a radiator (pressure) cap, your installation might be different, so my advice might be worthless, upon reflection. (?)

BTW, your thread title is ironically funny, if considered from our spouse's occasional view of the whole relationship!

Loren,
The issue isn't access to the tank, but rather the lack of any space between the tank top, overflow hose nipple and rad cap, making it impossible to use even the thinnest hose clamp. I can barely slide the smallest size zip tie around the nipple, but it still leaked.

 

[Loren Beach]

The issue isn't access to the tank, but rather the lack of any space between the tank top, overflow hose nipple and rad cap, making it impossible to use even the thinnest hose clamp. I can barely slide the smallest size zip tie around the nipple, but it still leaked.

Hmmm... perhaps time to consider a different tank or a modification to this one??

 

[AK67]

Can you post a photo?

 

[Captain Pete]

Captain Pete,
I will look into these a bit further, but the additional factor that I didn't mention is that not only is there almost no space between the nipple and tank, the rad cap on the accumulator tank sits right above the nipple. I need to be able to remove that cap to fill the tank, so any clamp can't have any protruding end sticking up.
I think I'll visit our local Hose and Fittings shop again to see if they have anything like what you suggest.
Thanks for your suggestion!
Fan

Gotcha. Maybe also consider a thinner radiator cap if such a thing exists to give you more room to work. Not sure I would be confortable running with a lower coolant level.

 

[Prairie Schooner]

Loren,
The issue isn't access to the tank, but rather the lack of any space between the tank top, overflow hose nipple and rad cap, making it impossible to use even the thinnest hose clamp. I can barely slide the smallest size zip tie around the nipple, but it still leaked.

Could you solder a brass extension tube to the nipple? Or have a radiator shop do it?
+1 to Adrian, a picture would be helpful.

 

[peaman]

Given how many ways you have thoughtfully considered how to leak-proof the hose connection, I wonder if maybe the leak could be at the joint of the small tube and the filler neck? If you can put some air pressure on the system through the filler cap, you should be able to block that pressure with a finger tip over the small brass nipple and then watch for soap bubbles at the joint.

JSM,
Yes, if nothing else works, I'll try running the overflow empty with reduced coolant in the accumulator tank. What I don't know is that if the whole cooling system is under pressure when hot, does coolant splash around in the accumulator tank as the coolant moves, which would cause the leak even if the level was lower. But it's worth a try if nothing else works.
Thanks for your reply!
Frank

Also, if your tank is high and of small diameter as mine is, keeping the coolant level a couple of inches below the top should be safe and generally splash-free. But remember to open the cap now and then, since you won't be able to count on the overflow tank to inform you of adequate coolant level.

 

[Frank Langer]

Could you solder a brass extension tube to the nipple? Or have a radiator shop do it?
+1 to Adrian, a picture would be helpful.

Interesting idea to solder an extension to the nipple.
I won't be at the boat until tomorrow, but will try to post a pic then.
Frank

 

[peaman]

Interesting idea to solder an extension to the nipple.

And if a shop does that for you, they will certainly pressure test it for leaks.

 

[Kenneth K]

I have placed a small wire around the hose and tightened it as much as I can with pliers, still leaks.

I'd try seizing wire twisted on with specialized wire-twist pliers (also another good tool to have in the arsenal). This from Harbor Freight:

Maybe a pair of seizing wires around the hose--with the twisted ends facing opposite directions.

 

[JSM]

What I don't know is that if the whole cooling system is under pressure when hot

I don't believe the cooling system is under any real pressure (until it overheats). I've run my engine for hours on end at standard operating temp with no coolant moving from the engine to the overflow.
I decided to leave my overflow tank empty after removing the cap on the engine coolant tank one day to check the level and ended up with coolant gushing out due to the fact that the overflow tank is mounted higher than the engine in the lazarette.
I have worked on older boats where there is no overflow tank just a hose running down to the bilge.

 

[peaman]

I have worked on older boats where there is no overflow tank just a hose running down to the bilge.

I'm pretty sure that is the reason the tank is there. Water and coolant expands with heating. That expansion will manifest in increased pressure in the cooling system. Too much pressure can result in blown seals and worse issues, so pressure relief caps are used at fill openings. But dumping coolant chemicals into the bilge and then into sensitive biological habitats creates other problems. So use of a more sophisticated relief cap which can relieve into a zero-pressure overflow tank which will then be emptied by vacuum back into the engine cooling system as the engine cools down after shutdown addresses all of those issues. Responsible boat owners should strive to keep our systems in good order according to best available practices, even as they add complexity to our attempts at recreation.

 

[Frank Langer]

I'd try seizing wire twisted on with specialized wire-twist pliers (also another good tool to have in the arsenal). This from Harbor Freight:
View attachment 53987
Maybe a pair of seizing wires around the hose--with the twisted ends facing opposite directions.

Thanks, Kenneth
I have added seizing wire around the hose, tightening it with needle nose pliers, but I can only do one side as the tank is screwed into the bulkhead, so no access on the back side. It still leaks a bit, so I've been tightening to the point where the wire could snap if I tighten further, but I've been risking it in the last few days. I'm also concerned the wire will cut the hose if I tighten further.
Frank