2004 Honda 599; 1660 Miles; Bought it a couple of months back with about 800 miles on it;

I've a bit of a situation. Since I'm still at the stage where I'm exploring the bike, the other day I decided to check out the coolant level etc. I noticed that the coolant level in the reservoir tank (under the seat) was really low. So I decided to open the radiator (remove the cap) and see how it looked. The level of coolant looked alright… the edges where the radiator-cap goes looked like it had some rusty liquid (I’m assuming the cap corrodes a little easier) .. nothing alarming. Anyway, I go ahead and put the cap back on and tighten the little screw to secure the cap.

Now, I’m not sure if I tightened the screw a tad more than I should’ve. But the next day I see a few drops of coolant on the side of the engine. I figured that the coolant level is low and so the pressure is higher due to the heating, thus forcing out a few drops of coolant near the radiator-cap (not sure how accurate that assumption is).

I make a note to refill the reserve tank the same evening. Evening comes and goes, and I’m not able to find time to do the needful.

Next day, I’m riding back from work and I see coolant coming out near the front edge of the radiator-cap and almost streaming down the radiator… more on traffic signals when I’m idling. I’m terrified .. and stop over to buy the coolant.

Get home and the first thing I do is fill the reserve tank (after letting the bike cool for some time). I check the cap of the radiator to make sure I don’t tighten the screw too tight. Start the bike and let it idle for some time. I check the temperature gauge to see the temperature rising…. in fact, the temperature is now higher than what it usually is while riding.. no leakage…!! I rev the engine some (I don’t think I went beyond 2500rpm) and not a drop of coolant comes out! I’m happy and looking forward to the ride to work this morning!

This morning – I start the bike.. let it idle for a few minutes and start for work. I’ve barely gone a couple of hundred yard and notice the coolant is coming out near the radiator cap, a steady stream of drops! So basically I turn back.. sulk a ton.. get in my car and drive to work! Now I’m lost about what to do next!

What could be wrong:
1. Tightened the screw too tight to deform the neck where the radiator cap goes thus creating a gap for the coolant to leak out from?
2. Should have also topped the radiator when I filled the reserve tank?
3. Over-reacting when the solution is really simple and I’ve no clue of it?

Folks… really appreciate any help!

1. Tightened the screw too tight to deform the neck where the radiator cap goes thus creating a gap for the coolant to leak out from?
2. Should have also topped the radiator when I filled the reserve tank?
3. Over-reacting when the solution is really simple and I’ve no clue of it?

First, I have never touched mine....ever. But had all sorts of issues with my old bike. I'd say #1 is probably closest (it has a screw to lock the cap? never seen that before and will look at it in a minute) However check the cap and the gasket inside and make sure there isn't any crud or that the gasket isn't damaged or not in properly...

Bump. (...if someone can help, speak up)

Thanks Alex.. I found some info about the radiator fan being the probable cause (http://www.honda599.com/phpBB2/viewtopic.php?t=366). Will go check it out... will look forward to hearing about any similar experiences though.. Thanks again!

Did you push and twist the cap? It's kinda like a bottle of pills with a safety device so that if you open it when hot it won't splash in your face. Try pushing down hard then twisting.

The system is presurized and that pressure raises the boiling point (that's why if you open the cap when hot it will instantly boil and hit you in the face!). If there's even a small air leak it will cause the liquid to turn into gas (boiling) and this will form pockets of air in your system. Steam doesn't transfer heat nearly as well as liquid, so you'll overheat.

Folks.. thanks a lot for everybody’s help and comments… the problem is fixed now! It was actually a very easy fix.
What had happened is that after I’d taken the radiator cap out for the first time (to check for coolant level and to fool around in general), when I put it back on - in my enthusiasm to put it back on real tight n snug, I pressed it down too hard on one side. That led to the metal ring under the rubber seal (right around the inner edge of the radiator cap) to get bent in. That created a sort of gap which made the coolant gush out as the temperature went up while riding. I went over to the local dealership to order a new cap and was about to order one (it comes for $30!) when I bumped into this mechanic who I’ve spoken to a couple of times in the past, and he was nice enough to give me one for free (he’d a spare lying around)!! So, not only is the problem fixed… but also for free!! :)

PS: I live in the suburbs of Fort Lauderdale and if any of you do need, I can pass along the contact info for this mechanic…really nice guy and very reasonable!!