Dumping coolant again

[Bowdog]

I'm getting worried - I took my Gen 2 (08) out for a 5km ride to get lunch before going to work. Temp got up to about half way as normal after a couple of km uphill, and sat there as expected. Never went over 80kph, didn't rev over 5k (probably not over 4) and outside temp was about mid-20s. At the 5km mark I stopped and put the bike on the sidestand. 10-20 secs later it started dripping coolant from out of the bottom of the fairings. A lot of coolant - 4-5 drops per second - nearly trickling out. I took it straight to the mechanic 2km down the street (temp stayed at a normal 50%), who reported that:

1) The plastic reserviour was empty, but had no leaks
2) hoses were fine - no obvious leaks
3) The radiator was half full, and scorching hot.
4) He believed there was pressure in the system

This is not the first time it has happened. About 8 months ago (10,000km) it was playing up,and after much burping, fiddling and scratching of heads, it was discovered that the radiator core was corroded and buggered, so a new one was fitted and all was good- until now.
I have a Radguard fitted, so chance of a stone through the grill seems inlikely. I haven't bottomed out on anything.

Any ideas? I want my bike back :(

Thanks

Bowdog

[Hayabusabike]

[mozzie26]

Last week I did a track day at Lakeside on my GSXR750K5 and the guy next to me had the same model K4. His bike did the 8 laps in the 15 min sessions ok until he came back into the pits then after about 3 mins sitting there shut down the coolant in the expansion tank would start to boil and spew out the over flow hose. Did the same thing the next two sessions too. When the bike came into the pits the display read 97 degC when switched off but the temp would rise after shut down and spew coolant back out over flow. He was a bit worried because he had only just had the engine rebuilt.
We pulled the fairing off to top the coolant back up. He said he had replaced the radiator a few month ago but to me it looked like it was second hand. The cap locking tabs looked a bit damaged and suspect as well. I recon he had a blocked radiator core that was not cooling enough.
I run my track bike with the rad fan removed and have no problems.

[Vulgr]

? radiator cap not holding the pressure


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[Buzz]

Do a pressure test. Use waterless performance coolant. Check cap is holding pressure.

[Batfink]

I had that happen once on my 99 after replacing headers, and of course removing the radiator. Only rode about 3 klm to servo to fill up. I topped up the overflow bottle then kept on riding...

My issue was that I had an air blockage in the system that when got hot expanded and pushed out the coolant. Once I ran bike for a while (always with eye on temp and checking overflow bottle) I then returned home and topped up radiator. It never did it again and showed me how a little air in coolant system can have dramatic consequences LOL

[Bowdog]

[kozzo]

Definitely the thermostat!

[Bowdog]

UPDATE:
The bike is back. The mechanics found a gel-like whiteish substance between the water pump and the radiator inlet. Testing showed that there was 0.8V between the coolant fluid and earth. Somehow, there is a current leak that is corroding the radiator. The guys have put an earth strap to the radiator to stop the corrosion, and given it a flush.

I am guessing there is a coolant temp sensor that is causing the problem. I don't think there is anything touching the radiator, and rubber grommets holding the radiator are reported to be perfect.

At least it is back :(