Bubbles in coolant overflow tank - Coolant overflows

Although my bike rarely ever gets above 3 bars, if it sits long enough at 3-4 bars such as in long periods of stop and go on hot days, the bike will overflow coolant out the overflow reservoir. While this is happening, there is a rapid flow of bubbles/air entering from the bottom of the overflow tank.

- This has happened multiple times since I did the valve adjustment. When I replaced the coolant after the adjustment, I did use the bleeder valve and filled it up until fluid came out the bleeder screw on the top of the engine.

- Coolant level is good, I usually keep it midway between high and low. I have to add coolant to get it to the proper level after this happens - a LOT of coolant comes out when I park the bike and it is hot. Probably 1-2 cups.

- I have made sure the main radiator cap is tight. I could try replacing it to start.

My main question are my symptoms the result of a leak in the system causing the coolant to boil? - the coolant level rises quickly up the overflow tank when the bike stays in 3-4 bars. I am using Halvoline 'good for all makes all models' pre-mixed coolant - just the basic stuff you find at Walmart and I think many here use similar stuff.

Thanks in advance.

I believe......flow of coolant or vapor into the overflow is an indicator that the coolant is boiling in the system and escaping past the spring pressure of the cap...and working as designed.

If it's happening regularly I suppose it could be because of trapped air that's working out, however it it keeps happening....it may because of a stuck thermostat that's not opening when it should. Or it could be a weak spring on the cap, but I'd suspect it less than a thermostat.

If after it cools down it sucks back into the system....also working as designed.

*Until somebody that know cooling system better than I comes along shortly.

 

Edit: I like Bobblehead's rationale about hoses as plausible.

Bleeder valve on top of the engine? Don't mess with what ain't broke! Never even heard of that thing or anyone ever messing with it. Where is it?

Something is obviously wrong.

Your problem sounds very similar to what happened to me once when a delaer messed it up. They switched the two hoses that attach near the radiator cap or inlet. One is outside the pressurized system and goes to the resevoir, and the other is within the pressurized system and goes to the thermostat housing - I imagine it is a self-purging part of the system. (As in you don't have to bleed your FJR's coolant!) Might be worth a look.

When the two hoses were switched my FJR would not overheat or run hot, but would puke coolant out the resevoir after every shutdown.

Damn boy, what the hell have you done to that poor FJR of yours? Oil burning, coolant puking, fuel-pump non-whirring POS. Your making the rest of us Gen I guys look bad!

My advice to you is ride more, wrench less!

Ya know back at CFO Matt (carlson_mn) did say he might go the Car Tire route, after taking Elenore out fer a spin....

Meybe that's all he needs to do to finish the old whore off...

haha fun points made. The bleeder screw is easy to get to after putting the valve cover back post valve adjustment. It allows all the air to get out of the system and allows the coolant to completely fill up. It's at the very top of the coolant system and is a little 8mm bolt that you back out.

The bike is for sale but honestly it runs great, I had to let it sit for 5 minutes idling in my driveway after rush hour traffic to get it to spit coolant. I will double check the routing of the two coolant lines near the reservoir cap - but I don't know where each one should go compared to the other. - so if ya know, let me know! thanks guys

And Skoot - yes I did confirm that my bike does not always spin the fuel pump - maybe it depends on the kill switch? It has always started right away. In fact I've never had a driveability issue with my Gen1!

The oil burning... not sure, I think it might be a fluke thing when the bike is run 'hard' all day (I know most bike's don't do it). Don't notice any oil loss normally, but running higher rpm's and lots of engine braking does tend to show off anything that may be wrong. I've talked to two dealers about checking it out for possible valve guide wear and they think I'm crazy and don't seem too friendly about it, and want $$$ to start diagnosing anything. One listened to it and said no not a ticker - like you said.

I've got my eye on two '08 models for sale locally though.... might put my bike up for sale.

One more thing to try, with engine cold, remove rad cap and let engine warm up until thermostat opens. Then blip the throttle, and air will purge out the rad fill area. Repeat a couple of times. Then shut down, refill slowly, put cap back on. I'm kinda with Iggy on this one.... and have the rad cap tested or get a new one.

Re oil burning... revving high and backing off as in engine braking causes big vacuum, oil can get sucked past the valve seals. Now there's a fun job to replace those.... guides are probably OK, as they are not an oil tight fit, the seals on top are supposed to be. Probably just worn out or old... There are two ways to replace, either remove the head and do all the work, or get a pressure fitting tool that fits in the spark plug hole, cams are out so all valves are closed, pressurize to hold the valves closed while you disassemble.. This is a PITA but it can be done if you really don't want to pull the head. Don't drop any of the valve spring keepers or anything else, very careful!!

Time for a new cap most likely anyways if for nothing other than preventive care. They say it's best to replace them every 5 years to be safe. Sounds like a good burp and re-fill and I'll be on my way again.

Bubbling into the overflow tank is boiling.

The pressure cap holds a certain amount of pressure in the cooling system. As the coolant heats, it expands. When it expands, it goes through the cap's spring-loaded seal into the recovery tank. As the system cools, the cooling media reduces in volume as it "un-expands," and as the system creates vacuum, it sucks the overflow back out of the recovery tank into the radiator.

If bubbles are flowing into the tank instead of liquid, then the coolant is boiling in the pressurized side of the system.

Boiling at a temperature it shouldn't is indicative of not being able to build pressure. Boiling temperature at atmospheric pressure is 212 degrees, as every school-kid knows (or should!)

Engine coolant runs at a higher temperature so it can carry more heat out of the engine. To keep from boiling, it gets pressurized. At higher than atmospheric presssure, the boiling point is elevated. (Yes, it's elevated slightly by the anti-freeze coolant mix, but it's elevated more by pressure.)

No pressure build-up = boilover.

Replace the pressure cap first, see how it goes.

Beyond that, there would have to be a leak in the system somewhere, which should be visible as a coolant leak, water spraying under pressure, or even just dripping down after it's seeped out somewhere.

If it's leaking, and not visibly . . . . Well, that's something you don't want to think about.

Mine 'boiled' as it dumped coolant when the hoses were reversed.

It was definitely boiling you're right, causing the level to rise up and out the overflow tube.

Will check the routing of the two hoses that attach just below the radiator cap, hopefully the service manual has a picture of the routing. If that doesn't work I'll order up a new cap. No leaks anywhere else, everything is tight and dry. Thanks for the pointers.

I'm sure there would be other issues if the thermostat was bad... bike runs at normal temps, 2 bars most all the time, sometimes 3 when the going gets slow.

Here's an update - ran the bike and let her warm up with the cap off. As the coolant rose up near cap level I could see some bubbles coming up. I blipped the throttle as it warmed up some more and a huge belch came out like a volcano erupting, spewing coolant all over. I let the coolant level settle down, then I added coolant to the proper levels and so far it seems to be working ok. Coolant still rises and falls a lot through the overflow tank just before and after the fan comes on, but I presume that is normal operation.

So from my observation, looks like I was able to get a good bubble out of the system, not sure how those guys get in there.

I'm having the same issue as well. Did you ever find the tube routing? My book doesn't show the routing. My bike started overheating when I replaced the outlet tube. Interestingly I replaced the thermostat while in there. I've also replaced the cap when this started to happen.

I had the same problem a couple of years ago. I had to add a few ounces of coolant every day to get home from a trip west. A radiator cap solved the problem.

Corvine63 said:

I'm having the same issue as well. Did you ever find the tube routing? My book doesn't show the routing. My bike started overheating when I replaced the outlet tube. Interestingly I replaced the thermostat while in there. I've also replaced the cap when this started to happen.

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Make sure the outlet tube isn't kinked and that it goes to the bottom of the overflow reservoir. Rubber cap snug and secure on the bottle.
Make sure that the radiator cap is fully screwed on!! If not, coolant will boil.
Run the engine a couple of minutes, top up the radiator, screw the rad cover on all the way, fill the overflow reservoir 2/3 of the way.
Run it until the engine it is fully warmed up. Bubbles due to air in the system will exit via the reservoir.
Shut it down and let it cool - it should suck coolant from the reservoir back into the radiator. Top up the reservoir again and repeat.
Bubbles are usually due to air in the system (or a loose/defective radiator cap). Air is expelled as the engine heats up and (if the overflow tube exit is properly submerged in the reservoir) coolant will get sucked back as it cools. May take a few cycles to get rid of all the air.