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Coolant leak mystery


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I've had my bike (89 VR) in the shop twice for this. Both times they couldn't find a leak.

 

The latest was after the bike sat for a month. When I put it on the side stand I got a little puddle. I could see about 1/4 cup collected in the bottom cowling. The mechanic couldn't find a source. He ran it up hot, rode it hard, let it sit, researched the web. Nothing. No trace. Fluid was low, though.

 

Anyone have any clues, or experience with this mystery?

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Sounds like a common issue.

The o-ring on the drain valve goes bad with age.

It only leaks when cold or very cold.

The good news is it is a very easy fix.

 

one screw, pullout the valve, keep an eye open for the spring and ball.

Clean out the bore, install a new o-ring and reassemble.

Skydoc_17 has a kit with the o-ring and a new stainless socket head screw.

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I went out to ride and there was another puddle. I got photos this time. Looks like the drain is suspect, but also where the lower radiator hose connects toward the pump.

 

I cleaned it up and let it sit without starting it. I'm wondering if I will see anything incriminating after a few hours.

Edited by tz89
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I went out to ride and there was another puddle. I got photos this time. Looks like the drain is suspect, but also where the lower radiator hose connects toward the pump.

 

The o-ring that goes into the thermostat housing is leaking, assuming bike was on side stand. The fluid path is downhill to drain valve. There is fluid in 2nd pic on t-stat housing.

 

Could also be seal between plastic t-stat top & aluminum housing. These have been known to warp.

 

If you have to remove thermostat housing, the bolt heads are easy to strip.

 

Gary

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That joint is the highest place I could spot fresh coolant. After it sits, I'll inspect, then run it up hot and inspect. I'll report back here. I'll do both jobs, plus any other recommendations.

 

Will the exhaust pipes have to come off? I'm thinking about the starter upgrade.

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  • 1 month later...

I installed my drain valve O ring today that I received from Skydoc. Simple install, hopefully no more cold morning leaks. Earl's directions tell you to be careful not to lose the small steel ball, that's no joke. When pulling on my valve it was resistant then came out all at once. I couldn't find the ball anywhere. Then I shook my coat and it fell on the floor. I would recommend putting a rag or duct tape around the valve when removing it so you don't lose the ball.

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  • 2 weeks later...

Just a quick update on this thread. I decided to take the bike to my mechanic to have him tear into it and hopefully when I get it back that will be the end of this topic. It's still raining in Oregon so while I have missed a couple of nice riding days I'm glad to be getting the bike ready for riding season. I'm hoping to get a few longer rides this year as part of travel for work.

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I looked again at the pictures you posted and noticed something else. In the 2nd picture there looks to be evidence of leakage running down the rubber hose that attaches to the thermostat cover. Maybe this is leaking higher up.

 

Also looks like green fluid visible between the thermostat plastic cover and the aluminum body.

 

Gary

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Thanks. And yes, my mechanic knows about the forum and working on old bikes. This is not a Yamaha dealership. My instructions were to re-do it all as long as he's in there. So he's tracking down parts. But just to be safe, I'll go in for a visitation and talk about the upper hose. I noticed that hose too, but when I was in there taking photos it didn't seem like the leak was really coming from higher. I need a real shop not a carport.

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  • 3 weeks later...

Dont see a o-ring listed on the crossover pipe going into the base of the thermostat housing...is there a listing for this somewhere. I've rebuilt water pump. The draincock. Now going after the T-housing and crossover. Do I need to remove exhaust pipe and do a gasket there as well? Thanks Dave

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  • 2 weeks later...

This project is done.

 

The mechanic said the housing in the photo above was warped. They replaced that and the o-rings, and while the pipes were off I had them upgrade the starter.

 

There were a couple moments of angst. After the first ride there was a puddle. But I reasoned they had topped things off and it was overflow. The next ride there was some spotting. After that nothing - so I'm good.

 

The second angst was when I realized that they hadn't replaced all the hoses and do all the rest while they were in there. I guess I should have made sure that request made it to the work order but I didn't and it didn't.

 

It's been good riding weather in Oregon this week so I'm up a few hundred miles already this year.

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Mine has leaked over the winter for the past I don't know how many years. The first few rides in the spring I would always bring fluid with me to top it off. It never seemed to leak much over the riding season. This year I am replacing all the o rings. Kind of wish I had ordered a new thermostat to throw in there while I have it apart.

 

Is there one out there at say a napa store that will work or do I have to order it from Yamaha.

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Mine has leaked over the winter for the past I don't know how many years. The first few rides in the spring I would always bring fluid with me to top it off. It never seemed to leak much over the riding season. This year I am replacing all the o rings. Kind of wish I had ordered a new thermostat to throw in there while I have it apart.

 

Is there one out there at say a napa store that will work or do I have to order it from Yamaha.

 

Stant #13758 Thermostat

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