# CK25 Cooling System issue



## VicV

I've owned my CK25 HST for 10 years with few problems. Lately though, I have noticed a bubbling sound when I shut the engine off after it's fully warmed up. The Low Coolant light has also come on twice, and I've had to replenish the recovery tank. A closer look shows that while the motor is running after warm-up there is a steady stream of bubbles coming into the recovery tank through the bottom tube that goes to the radiator cap base. It's become obvious that somehow radiator pressure is leaking through the suction valve in the cap, which I believe should only allow coolant in the recovery tank to flow back into the radiator when the engine cools down. The bubbling continues for a while after shutting the engine off, and eventually stops. I tried adding an additional layer of gasket on top of the existing rubber ring that forms the seat for the suction valve, but this did not work - still lots of bubbling. I have ordered a replacement cap, but I thought I'd post the problem for anyone who'd care to comment. Thanks


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## pogobill

Welcome to the forum VicV. Where would the bubbles come from, I wonder. They are not smokey bubbles, are they? Does the tractor overheat along with this problem?


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## Groo

Could just need a new cap. Could be much worse. How is your oil?


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## marc_hanna

A couple thoughts:
1. Airlock somewhere in the system 
2. Improper concentration of antifreeze
3. Some crud in the system somewhere preventing proper circulation
4. A leak somewhere in the system


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## marc_hanna

Groo said:


> Could just need a new cap. Could be much worse. How is your oil?


Agreed, check your fluids to see if there is any contamination.


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## VicV

Thanks for replying pogobill,
No, not smokey or diesel-fume smelly, if that is what you meant. The temp gauge did go above normal the last time the recovery tank went empty before I had to add coolant to it, but it does not overheat otherwise. I flushed the cooling system yesterday with the Prestone product and put new coolant @ 50-50 mix. I'm pretty convinced that positive cooling system pressure is somehow getting through the radiator cap to the recovery tank tube, & I'm hopeful that the new cap will fix the problem. BTW, do you know what is the typical pressure that cooling system is at when fully warmed up?


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## VicV

When I drained, coolant was clean-looking. The only crud was in the recovery tank, which I think is typical. Oil on dipstick looked clean - no water droplets. How can I check for airlock?


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## pogobill

The pressure may be indicated on your cap. The part number E6200-72631 indicates 4 psi.


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## marc_hanna

I would try burping the hoses, that’s the most common area for an airlock. 

But generally speaking, it sounds like you have a circulation problem. Here’s what indicates this to me:
You are losing coolant with no apparent leaks and you’re hearing bubbling. This tells me that your coolant is actually boiling at some point in the system but not at the temperature sensor. Why would this happen? Coolant is not circulating properly. 

The next question is, what causes coolant not to circulate properly?
1) bad radiator cap/overflow/siphon
2) plugged coolant system
3) bad water pump
4) bad thermostat
5) airlock


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## DK35vince

Bubbles in the coolant can also be a sign of a head gasket problem.


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## VicV

Thanks, new radiator cap coming in a few days, will see if problem goes away when I install it. Fingers crossed.


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## ck3510hb

Is it possible you were adding polypropylene based A/F to glycol based A/F? They don't mix. Since you have drained and changed that may solve the problem, good luck


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## John Liebermann

Radiator cap has nothing to do with it. The question is where does the air come from. It cannot be from an airlock as that after a while would dissipate.

I don't know anything about mixing incompatible solutions as ck35 points out so possibly that could produce vapor somehow. If that is not the case then you have combustion gas getting into the cooling system and coolant loss to combustion chamber at shutdown.

Keep Forum posted, I am very interested in solution.

Oops another edit, the water pump is sucking air then leaking when not running.


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## ck3510hb

of all the mechanical problems if I were him I would hope for the water pump which sounds possible.


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## VicV

I think I found the problem: In my original post, I incorrectly wrote that the bubbling in the recovery tank happens only after full warmup. I bought a replacement radiator cap, and it made no difference, but then I noticed that when I start the cold engine, the pulsating pressure coming through the recovery tank tube happens IMMEDIATELY! To me, that is a sure sign that the head gasket has a slight leak somewhere, and some cylinder pressure is finding its way to the cooling jacket. I have also noticed that when the engine first fires up, it runs rough, as if one of the cylinders isn't doing any work. That condition soon disappears, and then the engine sounds & feels normal. This did not happen before the problem showed up. Gonna call Kioti in NC to ask if there's a head gasket kit that needs to be bought to replace the head gasket. Any thoughts out there?


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## DK35vince

Call Michigan Iron.
A great place to get Kioti parts.
https://www.michiganironandequip.com/


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## Groo

I wouldn't blow more money on it before seeing exactly what you need.

open it up first and see what you see. you might find a failed head gasket. you might find you need something more than that.

I'd start with draining to oil and see of any coolant comes out.


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