The Mystery of the Disappearing Coolant
 

I keep refilling the coolant overflow bottle on my RX3, but it never stays full. How is the coolant disappearing? :wtf:

All motorcycle engines with water cooling have an small hole near the water pump which will ooze coolant if the water seal fails. I have repeatedly examined this inspection hole on the RX3 water pump, and it is not leaking coolant. Therefore, I must believe the water seal is in good condition.

I have also checked all the hoses and connections between the engine and the radiators. I have not discovered any leaks.

How is the coolant disappearing? I certainly think any air voids in the coolant system should have been filled by now. I have recorded over 8,000 miles on the odometer of my RX3 motorcycle. :shrug:

8000 miles ... you are my hero :clap:

As to the coolant ... could it be leaking inside the engine somehow? How's the oil level, smell and color?

How much and how often are you needing to add coolant? Is the overflow bottle vented, could it be evaporation that could happen very quickly with the heated coolant. Is it possible to temporarily block off the overflow bottle so you have a completely sealed system. Then ride for a week as usual and see if you lose any coolant. Just an idea, don't know if it will work.


/

The oil level remains constant. At every oil change the used oil is in excellent condition. :tup:

The coolant disappears slowly, so I don't suspect faulty gaskets. At first, I thought the left radiator had an air void from the factory, which needed to be refilled. However, after refilling the coolant overflow bottle many times, I now suspect Adjuster is correct. ;)

If it's evaporating ... is your coolant getting more concentrated? or do you think the coolant evaporates along with the water?

The coolant overflow bottle is rather small, and I only need to add a small amount of coolant every two weeks. The coolant overflow bottle is not vented, but the cap does not tighten securely as it does on my Honda CRF250X. Therefore, I suspect you are correct, and the heated coolant is slowly evaporating over a span of several weeks. ;)

I could plug the tube to the coolant overflow bottle, but I don't think that's a good idea. ;) The cooling system is working superbly, and my engine never overheats. Every time I remove the radiator cap, the coolant level is full to the top of the radiator. :) Therefore, I suspect evaporation is the problem. ;)

I am willing to accept slow evaporation from the coolant overflow bottle as a minor quirk of the Zongshen RX3. ;)

I haven't studied this issue, but I suspect a 50/50 mix of ethylene glycol maintains the same concentration as it evaporates. :shrug:

http://www.researchgate.net/publicat...liquid_mixture

Also, the suspected evaporation occurs very slowly, over a span of several weeks. Therefore, I don't think the coolant in the overflow bottle is becoming concentrated. ;)

According to the following thread, if the coolant overflow bottle does not hold pressure, the coolant will evaporate. ;)

http://www.bobistheoilguy.com/forums...Number=1600370

I seriously doubt the coolant overflow bottle of my RX3 motorcycle can retain pressure. If I tighten the cap too much, it releases. :wtf: Did I get a bad coolant overflow bottle? Does the cap tighten securely for others?

The following threads also support the theory that an unpressurized, coolant overflow bottle will allow coolant to evaporate. Is my coolant overflow bottle defective, or do all the RX3 bottle caps refuse to tighten securely?

http://www.jk-forum.com/forums/stock...normal-137010/
http://forums.nasioc.com/forums/show....php?t=1467927
http://honda-tech.com/tech-misc-15/n...-tank-2880706/
http://www.subaruoutback.org/forums/...ed-normal.html

I thought overflow caps weren't supposed to seal well. They need to vent air in and out as the overflow level rises and falls with engine temperature. However, the radiator cap must seal to force expansion into the overflow bottle and suck fluid back in. And the overflow level must stay above the fill tube to prevent air from being sucked in from there.

Any white smoke at idle?

I also noticed my coolant bottle was low a week or so ago, and filled it to the "top" mark, and it also seems to be gradually dropping. Like Spud I am beginning to wonder where the coolant is going. I don't accept the "evaporation" theory, since none of my other bikes (or cars) with non-pressurized expansion bottles loose coolant at anything like this rate.

I am not seeing (or smelling) any sign of a bad hose connection or other "outside" leak.

One possibility is that there is a head gasket leak allowing coolant to enter the cylinder, but this sometimes results in hard starting and other running problems, which I am not experiencing.

My plan is to let the coolant drop in the bottle, and then to start checking the radiator cap (engine cold of course) to see if the coolant level there also begins to drop. If it does, further diagnosis may be in order.

My bike also experiences a small amount of coolant loss over time.
I suspect an inherent design and not a problem because there appears to be a few bikes with this going on.

I filled my radiator and overflow during my valve adjustment a couple of weeks ago. But when I looked just now, it was empty. Filled it and we'll see if it drops again.

Leaking coolant is usually pretty easy to smell. And you would definitely see it if it was going into the oil. Remove your oil fill cap and examine the cap for small droplets of condensated water. You would of course also see this water in the crankcase vent tube.

Have you checked the water pump for leakage?

No, non whatsoever. The bike runs great, and the cooling system operates wonderfully. :tup:

The cap on the coolant overflow bottle for my Honda CRF250X seals very well. ;) As stated in the threads to which I linked in post #9, some coolant overflow bottles are pressurized, and others are not. It appears the non-pressurized, coolant overflow bottles are prone to evaporation.

The threads to which I linked in post #9 support the evaporation theory. :shrug: Also, I always remove the radiator cap and check the coolant level in the radiator before I refill the coolant overflow bottle. The first few times I checked, the coolant level in the radiator was down a little. However, the coolant level in the radiator has now stabilized at full level, while the coolant overflow bottle continues to require a periodic refill. However, the slowly dropping level of coolant in the overflow bottle does seem to support the evaporation theory. ;)

Yes, I did. As I stated in post #1, all motorcycle engines with water cooling have an small hole near the water pump which will ooze coolant if the water seal fails. I have repeatedly examined this inspection hole on the RX3 water pump, and it is not leaking coolant. Therefore, I must believe the water seal is in good condition. :)

I don't have any coolant leaks. The cooling system works superbly. The used engine oil is always in good condition, without any contaminants. I am not collecting any contaminants in the dump tube from my crankcase vent.

I believe the left radiator probably had a small air pocket when I received the bike. I also believe the coolant overflow bottle has now completely filled both radiators with coolant. The coolant level in the radiators has stabilized at the full level. However, the coolant overflow bottle continues to lose coolant, but at a much reduced rate. Therefore, at this point, I am inclined to believe the evaporation theory. ;)

Will others please report if the cap on your coolant overflow bottle is somewhat loose, and will not tighten fully?

I suspect you have a small air bubble in the left radiator. Keep filling the coolant overflow bottle. The air void will disappear, and the coolant level in the radiator should stabilize. After that point the coolant level in the overflow bottle should begin to drop at a much slower rate. ;)

Please remember, I have now recorded about 8,250 miles on the odometer of my RX3. Therefore, I had ridden enough miles to fill the coolant in the left radiator. The coolant level in my radiators has now stabilized at full. Nevertheless, the coolant level in the overflow bottle continues to fall, but at a much reduced rate. ;)

To me it seems counterintuitive to fill up your over flow bottle.
I'm not convinced that it can "top up" the coolant system.

If the bike were to over heat and blow, I want super hot coolant in the bottle not on me :)
so I leave mine empty so there's plenty of room

But that's just me :hmm:

Excellent. Any evidence of milkshake on the underside of the oil filler cap?

I just changed the engine oil several days ago, when I passed 8,000 miles on the odometer. No, I did not notice any 'milkshake' on the underside of the oil filler cap. The bike runs cool, the engine runs great, the used engine oil looks wonderful, et cetera. I can't find any coolant leaks, and I don't believe the engine is consuming any coolant. :)

You have an interesting perspective on this matter. As always, thanks for your input, Kat. :)

I do know the overflow bottle will top off the radiators on my Honda CRF250X. If the overflow bottle can't top off the radiators, why do the manufacturers always tell you to fill the overflow bottle with a certain amount of coolant? :hmm:

Kat,

Does the cap on your coolant overflow bottle snug securely, or does it open when you 'overtighten' it?

Just went out and checked mine, and it seems to seal good, and tight (I didn't "Try" to over tighten it, but what I felt was good amount of torque for a plastic bottle) so maybe yours is bad Spud...

Spud, the cap on my bottle tightens normally, it doesn't skip threads. I actually loosen the left side radiator so I can unhook the bottle and unscrew it, leaving the cap in place. I had no problems last week when I did this to bring the coolant up to the "full" mark on the bottle. It screwed back on correctly to a normal "tight" feel.

I think it's likely yours was overtightened at the factory and stripped. I'd try a new cap and bottle from CSC.

BTW my coolant level (in the bottle) seems to have stabilized at about half-full.

Only one place for fluid to go when you overfill an overflow bottle "hence the name". More than likely, as the fluid expands from heat "while running", the excess is being forced out the drain tube. The overflow bottle should never be more than 1/4 to 1/3 full. You have to allow for fluid expansion due to heat transfer. Stop filling the bottle, and you'll be fine, so will your bike.

I got tired of removing the plastic covers when I put in coolant so I put this funnel extension gizmo together. Now to add coolant ,I just reach in and pop the top of the overflow bottle hose off the radiator end with some pliers to remove the hose clamp and put the white end of the funnel extension into the overflow hose and add coolant. Don't have to take any thing off that way or remove the overflow bottle cap.
Spud my RX3 has 4500 miles on it and the coolant has gone down a little when out on long rides. I carry a bottle of coolant with me but now I am confident its not needed as the coolant takes a lot of miles before it gets very far down in the overflow bottle. I'll try it out this coming week at the Sound Rider Rally in the Gorge .rj

it sounds like all systems are go. Enjoy your bike.

If you don't have any coolant in the overflow bottle, you risk drawing in air when the system cools. Think of how you keep a hose in a bottle of brake fluid while bleeding brakes.

You don't need much fluid; just enough to keep the hose end immersed. Is there a min/max indication?

While on this subject, has anyone measured the full capacity of that little bottle? It's not very big and looks to be thick walled.

I'm guessing less than a cup (8oz) total. So about twice my bladder capacity.:ohno:

Spud, sorry I missed your water pump comment in your first post. I checked my cap for tightness and it's fine. I would not leave the overflow tank dry, as it needs a prime to function properly, however, as long as one regularly checks the fluid level in the radiator, the overflow tank is superfluous.

Hey Spud, my cap has been an issue since the beginning. It pops off easily when tightened. I get it snug, not too tight, and then I find it popped later. I assumed my periodic coolant loss was due to spillage. The last time I was refilling I did notice a tiny vent hole in the cap, so even if the cap is fully sealed the system should be able to vent through the hole. My cap threads appear to be fine when I look at them, so I have been suspecting the bottle threads are "bad". I just haven't had the time to pursue it further. I switched from filling the "overflow" bottle through its cap to filling through the radiator cap. If you have the bike on the side stand and fill it slowly with a funnel, it overflows into the bottle just before it would overflow out of the radiator (I picked up that technique somewhere from another RX3 owner). I can unscrew the radiator cap without removing any panels, so that seems to work better for me.

Thank you, gentlemen. I will make the call to CSC tomorrow, and request a new coolant overflow bottle, with cap. :)

Thanks for posting the good information, George. :) Based upon the replies of Huck and NoVa, I'm pretty sure my coolant overflow bottle and cap are damaged. I'm hoping a new cap and bottle will fix the problem. :tup:

Yes, the bottle has min/max markings. ;)

:lmao:

I'm thinking we are about the same age, Jay. ;)

:lol: