Boiling over... what?

dcstrom

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#1
Yesterday was a first in 140,000-odd miles on this bike... riding moderately fast on a warm day up a mountain road, and when I stopped shut off the engine I could hear a gurgling noise coming from the radiator... hmm that's never happened before. Turned the ignition back on, fan started immediately and temp is 223, which is high but not higher than the normal top end of the range when the fan kicks in. Then I noticed a wet patch under the bike. Looked like the coolant tank had burped. Tank seemed empty so topped it up with tap water.

Kept an eye on the temp gauge after that, didn't seem to be anything going on out of the ordinary.

I know it's overdue for a coolant change, could it be that that's the only problem? Coolant is 3 years old...
 
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#2
I can't comment on how effective 3 year old traditional coolant is. I usually flush my water cooled bikes once a season. OTOH, my Evans waterless coolant has been in my Beta for over 4 years.

Maybe do a vinegar flush? With a 140,000 miles it might be a good idea to check the impeller, hoses, and whole cooling system.
 

Jlq1969

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#5
Let's start with the cheapest. With 3 years the coolant may have lost some ability not to boil at 100 degrees. Change it. Check that there are no external obstructions in the radiator (bugs, mud) ... the radiator cap may be failing and is opening before the correct pressure (more pressure = more temperature to boil) .... the most expensive, obstruction internal radiator (only some pipes) by sludge produced by the degradation of the coolant, or incrustations of salts by incorrect water, but loses refrigeration capacity, thermostat that does not open at 100%, but is rare
 
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Sierra1

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#6
Funny that you should post this. Last night, turned the car off, heard gurgling. A little fluid in the engine bay, and a little on the ground; below minimum in the reservoir. Radiator cap completely dry. Heat gauge exactly in the same "normal" spot. Last time this happened to me, it was a bad thermostat seal. It didn't leak when it was hot, everything swelled with the heat. It leaked when it stopped running. This car is 10 years old, but only has 67K miles. My money is on another seal, or a failed hose. Heat is hell on that kind of stuff.
 

Checkswrecks

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#7
Trevor -
I've had it happen twice, having it overheat and then finding the overflow cap off. There were some weeks in between. Both times refilled the radiator (cool) and the coolant tank and motored on. My guess is like the others, that the rad cap leaked. Never did replace the gasket although I should have. Just kept a closer eye on it and still do.
 

steve68steve

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#8
I killed my rad fan in a left-side drop and didn't know it until I shut the bike off and could hear the coolant boiling. The pressure increase had blown the rubber cap off the reservoir and I lost about 16oz of coolant.

I rode it around for a week or two (daily driver) without a fan and judicious use of the kill switch at red lights. New fan, new coolant, and 25k miles later, no problems.

You either got hot and pressure blew the cap off, or the cap worked lose from vibration or shock and you lost enough coolant to reduce the cooling efficiency, leading to the hot running. Chicken vs. egg.

EDIT: reading that back, I assumed "burped" meant the reservoir cap was off. If the rad cap burped, you probably need a new rad cap or new coolant, so change both.
 

Squibb

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#9
Hoses, rad cap, failed fan/sensor are all possibilities, as it a jammed thermostat. 3 Y/O coolant shouldn't be an issue, unless contaminated. - remember you need coolant in the system, not water (OK in an emergency), to keep things flowing/lubricated.

There are usually witness marks on the bike when coolant blows onto hot engines/exhausts, which should give a clue. Worst case scenario is the head gasket, but let's hope it's something simple at this stage.
 

Fennellg

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#10
It may be a good ideal to change the coolant. But I don’t think it is causing the problem. Something is cracked or plugged up. Only a couple other possibilities, Water pump, Or head gasket. Not sure about the last one with our bikes but it’s true for cars. Take your time look things over slowly and calmly the answer will come.
 

EricV

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#11
I agree with simple things first. Radiator caps lose their ability to seal and hold pressure, allowing the coolant to boil earlier. If you don't see any damage to hoses, I'd look to the thermostat next. Some auto repair shops can test nearly any radiator cap for you to see if it's holding pressure. In the States it's free, but I don't know where you are now.
 

dcstrom

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#12
Thanks all - no further issues 400 miles later, but I'm doing an oil change in Bulgaria so will do a coolant change at the same time, and inspect hoses and whatever else I can. Heading to Bucharest, Romania from there so maybe pick up a radiator cap there if it seems like it could be the problem. Without checking part numbers, I'm guessing rad caps are pretty universal across Yamahas, and probably other bikes too. There should be a decent Yamaha dealer in Bucharest.

Steve68steve - when I say "burped" I'm not sure what I mean! There was a biggish puddle of liquid under the coolant tank, but the cap was still on the tank, so I'm not sure where the liquid came from. If there was any on the bike to give a clue, it had dried up. But the tank was pretty much empty so I have to assume it came from there...
 

steve68steve

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#13
Steve68steve - when I say "burped" I'm not sure what I mean! There was a biggish puddle of liquid under the coolant tank, but the cap was still on the tank, so I'm not sure where the liquid came from. If there was any on the bike to give a clue, it had dried up. But the tank was pretty much empty so I have to assume it came from there...
The reservoir tank has an overflow hose which drains ground. I assume this is to prevent a pressure build up... which would blow the lid off.

Low coolant, or old coolant would get hotter fresh, full, coolant. A tired spring in the radiator cap would let coolant to the reservoir tank prematurely. I assume this would lower your coolant volume which would lead to hotter running. Obviously a leak anywhere in the system will ultimately lead to reduced coolant volume, which means hotter bike, which means more chance the radiator cap bypasses some pressure to the recovery tank... which itself has that drain to ground.

All that said, if you have fresh coolant and a full tank I'd maybe just watch it for a while. Maybe you just had a perfect storm of operating conditions and coolant level/ quality. If you have DO have a steady leak somewhere, you'll smell it... and over time your coolant volume will drop. If you pull the radiator cap off the COLD bike and there's coolant right up to the top, you're fine. If you smell coolant when the bike is hot, check that level every now and then. Fixing the source of the leak is ideal long-term, but just keeping the coolant level topped up will keep you rolling.
 

dcstrom

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#14
So this happened again today, twice. I didn't see the "burp" happen, just the wet patch on the ground. It's as if she waits till my back is turned before she takes a leak :D Wierd thing is, the rubber cap is still solidly on the coolant tank, and there is no sign of any moisture underneath the bike below the tank. It couldn't have been more than a couple of minutes between the burp and me checking for the source, I doubt enough time for it to dry without a trace. But I guess it must be coming from the tank somehow, there's not really anywhere else in that location.

Coolant change and system check tomorrow...


IMG_20190705_115958667_HDR.jpg IMG_20190705_120046623_HDR.jpg
 

steve68steve

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#15
Look at the rubber cap to your coolant recovery tank. It has two hoses thru it. One comes from the radiator. The other end is open and hangs near the ground. It's an over-pressure drain hose.

I bet you a million internet bucks that the coolant you see on the ground is coming from that drain hose. Your skid plate may be interfering with the hose draining.

Check your radiator cap when the bike is cold - make sure you can see coolant in there up close to the filler neck.

No offense intended, just trying to assume nothing: the radiator has a metal cap and sits behind the plastic shrouds on the left side of the bike. You can't see the radiator or rad cap with the plastic body panels installed.

The coolant recovery tank (I sometimes called it "reservoir tank") has a black rubber-ish cap with two flexible black hoses thru it. The coolant recovery tank is translucent plastic and sits behind the engine / on top of the swingarm/ in front of the rear shock. You can see easily see it and pull the cap off from the left side of the bike.
 

Cycledude

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#16
On my bike the overflow hose is routed from the cap on the overflow bottle over to the right side and comes out near the rear shock absorber on the right side sort of behind the brake pedal. Right above where the wet spot is in your picture. If you put your finger on the tip of that hose and it’s wet you can be pretty sure that where the liquid came from. As others have said changing the antifreeze and the radiator cap would be a good place to start. Hopefully it doesn’t need a new thermostat. steve68steve has given you some very good advice, I bet your radiator is not full.
 
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jrusell

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#17
There are two lines into the overflow tank. The one in the middle is from the rad cap. The one that comes out at 90 degrees goes to ground.
You should do as stated previously. Cold bike, remove screws to left side plastic and remove rad cap. If it is not full, fill it completely. Then fill the overflow tank to the full-cold mark and replace the overflow tank cap.

Any more riding without making sure the rad is full is risking a blown head gasket.

If you look at the overflow tank cap you will see the hose come out at 90 degrees and then loop over the top and to the other side of the bike.
Over flow is located near the right side centerstand mount. Yours is draining onto the skid plate and then dripping off the back of the plate. That is why it is in straight line exactly lined up with the back of the skid plate. See pic below.

IMG_0040.JPG
 
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dcstrom

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#20
Checked the radiator, full to the brim. Put about 300ml of distilled water in the coolant tank. Let's see how we go today... Change fluid tomorrow.
 
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