Cooling system, bad hose???

[goldylocks303]

Had an interesting ride to the mountains this weekend, complete with a seriously overheating engine.  Left Foster City and headed east only to find a steadily increasing temp gauge.  There were some freeway speeds, and some slow lane splitting but even at a descent clip with the radiator fan on the temp still climbed.  

So I pulled into a gas station and pulled the radiator cap off.  Damn thing was hell of low.    A little back story:  I regularly flush and change coolant and I fill the radiator full and the reservoir half full (to where the line is).  A couple months ago I was riding back from the mountains through some high heat in the valley.  When I stopped, one of my coolant drain tubes was draining a bit of coolant on the ground.  When I got home I checked and the reservoir was completely full.  No problem, the thing was hot, pushed too much fluid back to the reservoir and some drained out.  I figured once it cooled down it would suck the necessary fluid from the reservoir back to the radiator.  

I'm at this gas station on Friday, and the reservoir is still completely full.  I added about a quart of water to my radiator, ran it, added a tiny bit more and got back to riding.  The rest of the weekend the temp stayed about where I'd expect it.  I added a bit more water on Sunday (reservoir still full) and came home.  Drain hose continued to drain a bit of coolant the whole way home.  

I've read a lot on here about how cooling systems work.  There's a hose from the radiator to the top of the coolant that vents fluid when the radiator is too hot and a line from the bottom of the reservoir that feeds fluid to the radiator when cools down and needs it again.  Right?  I'm thinking the line from the bottom of the reservoir back to the radiator must be clogged or pinched or something.  

Does that sound right?  Is there something I'm missing here?  

Ed

[bomber]

check the radiator cap -- when they go south, they can produce symptoms exactly like what you describe.

[goldylocks303]

Really?  I just replaced it last year.  These things can't go bad that fast.  

Andrew, I forgot you were so close now.  I'll get the cap off and give you a jingle.  

eD

[veefer800canuck]

Fill the cooling system to normal levels, run the bike up to FULL operating temp in your garage, then squeeze one of the rad hoses.

At 16 PSI, the rad hose should be solid. If it's sqooshy, your rad cap is not holding pressure.

PS: wear gloves

[bomber]

Really?  I just replaced it last year.  These things can't go bad that fast.  

Andrew, I forgot you were so close now.  I'll get the cap off and give you a jingle.  

eD

sure can . . . .  mine went bad in about 2 years -- the rubber ring that created the seal between the cap and the radiator top had hardened and cracked . . . . ..

checking it is easy, and replacing it is cheap.

+1 on checking the hoses.

+ many on wearing gloves.

[deagle10]

+1 on the radiator cap.  I found out the hard way after trying about everything else.  I had changed the fluid and my overflow was boiling over.  Finally someone on this site said to check the cap.  I of little knowledge didn't know how to check it and just bought a new one (under $15 from Honda).  Never acted up again (knock on wood).

[MadHattr059]

+1 on the cap as well. When they fail, it's usually they pop at too low a pressure.
That let's all of the coolant bleed off instead of circulating through the block/radiator.

Hope that helps, Ern

[Kootenanny]

Yeah, and if your rad cap isn't sealing properly, it won't generate the suction as it cools down to draw coolant from the reservoir back into the radiator.

[goldylocks303]

Andrew checked the cap for me and it's fine.  (thanks Andrew)  So we're going to look into a few more things.  Andrew also gave me some ideas on where to look.  I'm guessing I'll have time this joyish three day weekend.  If all else fails I'll replace the cap anyway.  It is, after all, the easy $10 fix.  

eD