Coolant overflow drip

[JOEY11]

I noticed today after riding there was a few drips of coolant from the overflow line. It doesn’t have the overflow bottle so it’s just the line routed next to the rear m/cylinder. I checked my coolant level after it cooled down and it was right at the top. Why would it do it all of the sudden? It ran fine and wasn’t burning coolant so I doubt it’s the head gasket but I didn’t check for bubbles with the cap off while idling. I put a new 15psi cap on and rode again and it still drips.

[JOEY11]

I checked the rad while idling and there’s no bubbles whatsoever and when I rev it up the coolant sucks down as it should. The cap that was on it said 1.1 and it looks old and I believe it’s the oem cap. The cap I had in my parts dept at work is a 1.0 cap so maybe the original cap was bad and the new one is too low pressure? I think 1.1 is about 16psi and 1.0 is 14 or 15psi. The only way it can get past the cap is pressure building past the caps limit and going out the overflow tube.

[2ndmoto]

If it's dripping, it's leaking. It's overflowing because of pressure. The extra pressure is from heat or pressure is being introduced into the system. Could be getting hot because of jetting, radiator issues, head gasket issues, water pump issues and/or the coolant itself.

Do you have a way to check the coolant temp? An inline temp gauge would be helpful.

Check the radiator to see if the fins are nice and straight and is clean between the fins. Also check the shrouds, they should fit tight against the radiator. Is the water pump leaking? Have you done a leak down test? Lots of people are running larger radiators, and is recommended for big bore motors. Wouldn't hurt to flush the radiator also.

I don't run a reservoir, but I run the overflow tube down so it would drip onto the pipe, so of it does start to overflow I could see it steam and also smell it

I have heard of people running a higher pressure cap, but to me it is masking the real issue. Obviously if you lose coolant you are in more danger than if the coolant is running hot, but ultimately we want the coolant to be within temp range.


Hopefully this helps.

[JOEY11]

Thanks for the tips. I don’t have a way to check the temp. There’s no leaks at the water pump or anywhere else and I just flushed and put new rad hoses in it a month ago and today was the first time it’s dropped from the overflow hose. It’s jetted a bit rich so I don’t think it’s jetting causing it. It’s only got a few hours on the new top end so I hope it’s not the head gasket. I’ll check the fins tomorrow and I’ll check the hoses while running and squeeze the hoses to check that water is flowing.

[JOEY11]

I bought a new 16lb cap and torqued the head and base nuts and I was able to turn the head nuts a quarter turn to 18ft lbs so maybe that was causing the air leak. Also checked the intake and reed cage since I just installed new gaskets a couple weeks ago and they were also took a quarter turn to tighten. Took it out for a ride and it didn’t drip from the overflow hose when I shut it off. I did check the coolant with cap off and when I rev it up it does have like one or two bubbles but nothing while idling.

[The norm]

As per the Honda manual, you can torque the head nuts from 17-21 ftlbs. I always torque to the max number. Air bubbles in the radiator can always be a sign of a leaking hose. I have seen coolant systems lose coolant and have bubbles because of a bad hose. Just something to ponder on.
Loren

[JOEY11]

I just replaced all the hoses with a kit from ebay a few weeks ago and checked the clamps today and snugged them up again. I always thought if a hose was bad there’d be an external leak and I don’t have any. How would a bad hose create bubbles in the radiator and how can I tell if a hose is bad? I haven’t had to add any coolant to it and it’s still full from when I changed the coolant when I replaced the hoses.

[The norm]

The suction side of the pump could possibly pull air. I have not seen this on a 250r, but have many times on vehicles and equipment at work.

[2ndmoto]

You can do a leak down test on the cooking system. Basically it's a modified radiator cap with a gauge and pump.


When the level drops at rev, is it dropping low enough that you can see the rad tubes?

[JOEY11]

I don’t have the cooling system tester but I think advance auto loans them so I’ll check with one of my employees since he works there part time so maybe he can get it for me.

Yes, when I rev it up the coolant level drops slightly. At idle it doesn’t bubble at all and when I shut it off the coolant level rises back up. I took a video of it but i can’t post it here. I posted to YouTube link but not sure the link works
https://youtube.com/shorts/0CFIf9SKtHE?feature=share

[2ndmoto]

Hard to tell from the video, but it looks like it's coming from that top tube. Level drops and air entered the tube. Level rises and air gets pushed out.

Definitely pressure test it.

[JOEY11]

Yeah I’ll have to test it to be sure. The coolant doesn’t smell like exhaust and there’s no black sediment in the coolant. I’m hoping just re-torquing the nuts took care of it but testing it will tell me for sure. There’s no external leaks so that’s a good sign. The plug is also dry so it’s not getting into the cylinder.

[JOEY11]

I rode it today and no coolant dripping from the overflow so it must have been the loose head nuts or the cap

[The norm]

Glad to hear!