Help Needed Finding Coolant Leak

I have leak that I can’t find. Smells like its coming from underneath throttle bodies. I replaced all the hoses and clamps and inspected the thermostat housing for cracks. Still leaking about an ounce every 200 miles. No coolant residue anywhere that I can find. Any ideas or tricks to find a slow evaporating leak?

Sounds like you need to get a radiator pressure tester and hook that up to the stationary bike for a few hours, then look for puddles.

When the level drops so you need to top up, is it low in the coolant expansion tank or in the radiator? That might point out where in the system (which side of the radiator cap) the leak is. My ST1100 had a perished expansion hose where that hose joins at the radiator cap, so the expansion tank stayed normal but the radiator fluid level dropped.

My VFR had a slow coolant leak from one of the short hoses between the thermostat and engine block, it wasn't really obvious but I could occasionally see dried off coolant on the rear header pipes, and when I washed water through under the throttle bodies I got a lot of green coolant dye washing out.

I think the 99 is similar to the 4G, Mine developed a leak at the cross-over tube in between the V.

I noticed the reservoir level dropping but never saw any leak. It was pooling up a little in the V, and then drying out.

I replaced the o-rings on both sides of the cross-over tube, and then all the gaskets on that part of the coolant system that is accessible under the tank.

Some gaskets were completely flattened out and were in obvious need of replacement.

Good Luck.

Paul in SoCal

Fluid level is dropping in the radiator. I've run it with the side fairings removed expansion tank hung to the side so able to see all hoses and under the throttle bodies, and have never seen a drop of fluid, can only smell it.

I'm having a similar issue. I can smell it after a ride but can't find any sign of a leak. Mine is low in the overflow tank.

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Another option is to use fluorescent dye. You will need a dark garage and a black light for this.

Works very good, i used this method to find an oil leak on my car.

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gig

Fluid level is dropping in the radiator. I've run it with the side fairings removed expansion tank hung to the side so able to see all hoses and under the throttle bodies, and have never seen a drop of fluid, can only smell it.

I would first suspect the hose connections between the radiator cap neck and the expansion tank. And then I'd replace the radiator cap.

Good luck!

replaced cap and all hoses including expansion tank hose, thinking because its not pulling from tank it could be that. it seems to be getting worse, and feel its under the throttle bodies but i can see most connections from the side and can't run the bike with then off??

Thanks Miguel!! Good to be back!

So then the next step is to follow Terry's suggestion (in the second post) and get a radiator pressure tester and hold that pressure for a few hours. That should help point at the leak.

18 hours ago, gig

replaced cap and all hoses including expansion tank hose, thinking because its not pulling from tank it could be that. it seems to be getting worse, and feel its under the throttle bodies but i can see most connections from the side and can't run the bike with then off??

Thanks Miguel!! Good to be back!

The expansion tank will only fill/drain if the radiator pressurises when hot and the radiator cap lets the excess liquid escape, and then opens as it cools and the liquid contracts and pulls a vacuum . If the radiator and hoses aren't well sealed, these pressure differentials won't occur so nothing would happen in the expansion tank because the radiator cap wouldn't come into play. 

The idea of using a fluorescent dye is a very good one. Hand held black lights are dirt cheap.

1 hour ago, Terry

The expansion tank will only fill/drain if the radiator pressurises when hot and the radiator cap lets the excess liquid escape, and then opens as it cools and the liquid contracts and pulls a vacuum . If the radiator and hoses aren't well sealed, these pressure differentials won't occur so nothing would happen in the expansion tank because the radiator cap wouldn't come into play. 

The idea of using a fluorescent dye is a very good one. Hand held black lights are dirt cheap.

thanks for the feedback, i think dye is my last option, i cant find anything else, and tired of pulling throttle bodies with no evidence of residue anywhere...

Well, Did U find the source of the leak ?

replaced the hoses and clamps under the throttle bodies again and found some pitting in the thermostat housing that i dremalled smooth, seems to have taken care of the issue 

Thx

gig, 4/18/2016 at 1:06 PM

I have leak that I can’t find. Smells like its coming from underneath throttle bodies. I replaced all the hoses and clamps and inspected the thermostat housing for cracks. Still leaking about an ounce every 200 miles. No coolant residue anywhere that I can find. Any ideas or tricks to find a slow evaporating leak?

Even though you can't see it, you may have a crack in the thermostat housing. If you can, I would replace it and put a new thermostat in at the same time.

Make sure all surfaces seal well before you put it back together.