Overheating

[mi wii]

My 2006 GV250 with 28K miles is overheating.
What I am finding is that I am loosing coolant.
All is well until about 40 minutes and 25 or so miles.

What I am finding is that the coolant reservoir tank (the plastic one accessible from the front cover), is over filling and coolant is being dumped out via the overflow tube. When I start out I have it filled to the mid point as viewed through the gap in the dash area when I end the ride overheating, the reservoir tank is full.

I have been trying to fix this for a bit of time now and can' make any sense of it.
I have checked hoses and replaced hose clamps making sure there are no leaks.
I tested the radiator caps pressure and it is good. Couldn't test the systems pressure as the testers cap wouldn't fully lock on.
Tested the thermostat and it is good. The thermo switch seemed questionable (fan worked sometimes, but when really hot it wouldn't come on.) It also measured as a closed switch when fan was on but other times wouldn't close when engine was into four and 5 segments on the dash. I took it out and measured it in boiling water and it measured in the meg ohms. I ended up bypassing it with a switch and run the fan manually.

Also, I can let the machine run at idle for an hour and and it doesn't overheat (that was when I knew the fan sensor was working properly.)

Any help/ideas?

[Bill G]

Normally, overheating is caused by some sort of leak in the cooling system causing it not to be water-tight.  Here is something to consider, although it may not be your problem, I am just offering this because it happened to me once.

I measured the oil level once while the bike was on the kickstand rather than the stand that holds the bike level.  (Big mistake)  Since the bike was not level, it appeared to me that the oil was low.  I added a bunch of oil to get it to show full.  In reality, had I checked it with the bike on the level stand, it would have shown that I very much over-filled it with oil.

It would not overheat while idling, but did overheat and boil over when I went out riding, similar to your experience.

So, I am just offering this for what it's worth.  If that is not the case, then good luck because I know from working on cars that cooling system leaks are sometimes hard to find!

[mi wii]

Thank you for your reply.
I can understand a leak causing the overheating, but why is the overflow tank "overfilling" and draining, or are you suggesting that the cooling system is over filled?

[Bill G]

Thank you for your reply.
I can understand a leak causing the overheating, but why is the overflow tank "overfilling" and draining, or are you suggesting that the cooling system is over filled?

No.  I was only saying that over-filling the oil can cause overheating,  I made it a point to say this might not be your case.

[mi wii]

I understand. Thanks

[BettinANDlosing]

I understand. Thanks

I had this issue with my 250 when I first got it. Turned out to be a warped head. Had the head milled down slightly and replaced head and base gaskets. Make sure you correctly fill and bleed the cooling system after. Mine was doing the exact Dane problem.

[mi wii]

Were you finding coolant in the oil?

[MaryK]

The radiator cap may be bad and allowing coolant to flow into the overflow bottle.

[BettinANDlosing]

Were you finding coolant in the oil?

Surprisingly I never had coolant in the oil or oil in the coolant. The head was warped in a way that allowed the compression to leak by and force air in the cooling system and then force coolant out the overflow. Im pretty sure once the head is overheated once, it's done for and should be machined and gaskets replaced. Are you getting coolant in the oil?

[mi wii]

No. No oil in coolant or coolant in oil. And no coolant smoke out the tail pipe.
I took the radiator in to the radiator shop for them to give it the treatment.
I'll look into the head if the radiator clean out doesn't do the fix.

[mrbios]

My 2006 GV250 with 28K miles is overheating.
What I am finding is that I am loosing coolant.
....
Any help/ideas?

How long have you owned the scooter?

Did it ever run correctly?

Have you or someone else flushed the coolant?

I bought my 2005 GV250 4 years ago with 2600 mi.  Now I have 18K.  Two years ago at 10K miles I had a issue like you are describing is after draining and refilling the coolant.  The problem is the GV is designed with tiny coolant lines that feed the engine.  After I drained and refilled the coolant I ran the scoot for 15 min without the radiator cap to get rid of trapped air.  Scoot ran fine UNTIL I got on the highway.  After about 10 min all 5 temp bars were lit and blinking and I was loosing coolant out the reservoir.  I then added coolant and tilted side to side almost letting the scoot tough the ground at least 4 separate times as my local dealer recommended.  Not one cooling problem since and the most I have ever seen is 3 / 5 bars lit on the highway at 90+ degrees. 

[mi wii]

Thanks for the reply.
When you filled with coolant and did the side-to-side tipping, are you filling into the radiator only, not the expansion tank;
and also are capping the radiator when doing the side-to-side tipping and rechecking fluid level after the tips?

[mrbios]

I can't remember exactly how I did cuz it was a few years ago.  I put the antifreeze into the coolant expansion bottle. Running a vehicle with the radiator cap off helps get rid of trapped air. Regarding tilting at side to side I probably put the cap back on. You could probably do more research about tilting a scooter to expel air in Google.

Also as a side note - I used regular automotive antifreeze but the downside to that is the green is much lighter so it's hard to see in the reservoir bottle window. If you use something intended for a motorcycle it will be a dark dark green so it's easy to see.

[BettinANDlosing]

You want to fill the radiator, the overflow bottle does nothing except store coolant when the system pressurizes and expands. I usually try and burp the system by the right size funnel that fits in the smaller hole of the fill spot, that way if it bubbles up a little it has room to go up and not overflow. Regarding regular green antifreeze, try and find one that says silicate free, the seal design on these engines don't like silicate I the coolant it will shorten the life of those seals. While burping the cooling system you can also take the bleed hose off the thermostat to release trapped air, it's the small hose on the thermostat, just take it of for a few seconds until you get solid coolant with no air bubbles (careful it'll be hot) and make sure to do this with the radiator cap off.

[Charlie P]

Is it showing high temp via the gauge or light or is it just pushing out coolant from the overflow tank after riding a while?  Usually the level in the overflow tank will not change at idle but can fill up if you have been riding a while and especially if it is hot outside.  Once the scooter is off and cooled off for a while, the coolant level in the overflow tank will go back down to the cold mark or so.

From what I have read from your post and the symptoms, it looks like there is just too much coolant in the overflow tank unless I misread something.  I can't remember from my Grand Vista if there is a cold and hot marking on the reservoir tank.   Coolant level when cold shouldn't be above the cold mark otherwise it "could" spew out the excess coolant once the engine gets above idle speeds and especially at higher speeds.