Coolant leak

I just noticed that coolant has been dripping from the right radiator shroud and making a mess in the garage. Without taking anything off, there's no obvious damage to the radiators. Where should I look first? If it turns out it is the radiator, any suggestions for replacement?


Bike is a 2003 WR450. 

I would check first to be certain the radiator fill cap is on tight, then check all the hoses, including the small puke tank hose which comes off right below the radiator cap to see if maybe one of them is leaking. If not you will have to try and trace it back to it's origin.

A buddy once hit a bird at mach three coming down a big long sand wash and it stick into his left radiator. Forced its way past the plastic radiator stone deflector! Everything was fine till he pulled it off from the front of the radiator. When he did he pulled the beak out from a small hole it had punched in one of the radiator down tubes! Needless to say his day was over. Was funny watching him trying to stick that bird beak back in there to plug the hole!

Edited by ThumpMe

If there is no obvious same to the radiator and that is where the leak is coming from, you could remove it and take it to a radiator shop. They can probably fix it pretty cheap. Check the hoses and radiator cap first.

The cap is on tight. 


I realized looking over it that the expansion tank setup is different than stock. There's a very small bottle behind one of the radiators and the larger tank on the subframe isn't there. Luckily the previous owner gave me the tank with some other spares, so it shouldn't be too hard to put it back on. 


Based on what radiator work costs, it would almost certainly be cheaper to buy a set of China radiators off ebay... but I don't know if they're any good. Hopefully it's something other than the radiators themselves. 


Looking at the hoses a new set wouldn't be a bad idea, any brand suggestions? I don't need them to color match, just to work well. 

If the new bottle is pretty small there is a possibility that it might have just overflowed the new bottle once it got real warm and full. Where does it overflow to? Could be you are just seeing the remnants of that?

Years back I crushed my stock right radiator so I sent it off to Myler's Radiators in Utah. He straightened it out, fixed the leak it had and sent it back for WAY less than the price of a replacement...I think it was like 55 bucks or so back then.....might be more now....and it only took him about a week and half to get it back to me!

I also had a stick get flipped up once and it jacked the front end skyward as it ripped the left lower hose connection clean off the lower tank. I patched that one with epoxy to make it back to the trucks as we were about 15 miles back in the woods. It did leak some of the Tang mixture I used to refill it as that is what I had in my camelback, but it did make it back to the truck under its own power. I was glad I had started carrying a couple small packs of epoxy with me after I trashed the first radiator when this incident happened! I ALWAYS carry a couple small packs of epoxy with me now...on EVERY ride!

Myler's also fixed that radiator for me!

I then started watching e-bay and picked up a spare for both sides from bikes getting parted out for about 50-75 bucks each. I figure having a spare is real good insurance.

Most of those Chinese ones look good (in pictures anyway) but are thicker than stock so you loose room which I need since I added a cooling fan. Never do think I would trust them all that much either as Chinese aluminum is not near the quality of US and Japanese my experience anyway. So for me I want to stay with genuine Yamaha radiators.

I'll take a look at that plug. It felt like coolant to me but it didn't dry up in the same way I'm used to. 

I just took a quick look at it and found what I think is the plug. No signs of oil on it or anywhere else on the engine.

I just took a quick look at it and found what I think is the plug. No signs of oil on it or anywhere else on the engine. Makes me pretty sure it's coolant. 

Look closely at the radiator cap, I've seen guys tearing down engines cause the cap had a damaged seal. If the coolant is dripping off the radiator and no signs of leakage until it heats up to operating temp, replace the cap. It's only $ 10.0 and worth a try.

It's leaking when the bike is sitting in the garage. Of course, that may just be coolant that accumulated somewhere earlier. 


I suppose this weekend I'll pull some plastics off, plumb the factory coolant tank, make sure grey wire is done, and put that headlight you sold me on. Have some work to do on the SV1000 too, should be a busy weekend. 

Turns out I entirely misdiagnosed the leak... or at least the front brake fluid reservoir is empty. I didn't think it felt/tasted quite right for antifreeze but didn't know what he'd used. 


Hopefully I manage to fix it without too much effort, at least I have a spare master if I need it. 

Du-OH! Been there done that! (Misdiagnosed problems!)


Much easier to fix a leaky master cylinder than a radiator though! So you think it was the seal leaking or banjo bolt? Good thing you found it before you had no stopping power.


 I just had my SV650 rear M/cyl go out last week. It just quit. No leaks or anything. I went though it and there was this real weird deposit all over everything. Looked like a calcium deposit.White and crusty.No moisture in it anywhere that I could find though. It was even all over the spring in the m'cyl. I did not even replace anything as I took it apart before the rebuild kit/parts arrived. Cleaned everything out  re-assembled and all is fine again. Weird though. Bike only has 8K on it. Been garaged its whole life I think. Guess it just wanted MORE attention paid to it?


 Oh and THANKS grayracer513 for that link to the decompression plug. Had never heard about that.....need to check that out as if it came out way out the sticks THAT would suck.

Not positive but I think it's the hose from the reservoir to the master. It's a Brembo 16x18. 


It had some weird chunky residue in the reservoir when I flushed the fluid, which I pulled out as well as I could. The master is still a tiny bit sticky, I think it may be the pivot as there's evidence of a little rust there but I'm not sure how to pull the pivot pin... it has a strange clip on the bottom. 


I had the rear master on my 2004 KTM 625SMC stop working well. I think it had under 10k on it at the time. If I bled it it would work ok but then it would get soft again quickly. I think I replaced the master, not sure... it was 5+ years ago. 

 I am not familar with Brembo's but imagine it is some sort of cir clip.


Not sure why some brakes have issues.Liquid clutches sometimes as well. I know those KTM slave cylinder o-rings can give you fits too.Probably due inpart to all the heat and use they see.


 A couple riding buds are ALWAYS getting their rear brakes hot enough to boil and quit till they cool down. They also seem to have LOTS of issues with condensation. I guess as the brakes cool after boiling they are more susceptible to condensation? They are always having to flush out their brakes with new fluid.


 This weird crusty white deposit is a new one on me. Maybe due to the weird brake/clutch fluid that comes stock in Japanese bikes?  As long as it is ONLY the rears!

The leaky reservoir is remote, sportbike style. I think it's leaking where it fits on the barb on the master, you can see that but not the reservoir here: 




It isn't a circlip, I'll have to take a picture when I'm home. Think of a folded sheet with a slot cut in it. it, I'm not sure what that's called. 


The residue was in the front reservoir on this bike. None of the front brake components on it are OEM - Brembo master, braided line, Braking 4pot caliper, Braking 320mm rotor. Who knows what the previous owners put in though. 


edit: oh, and strangely enough, brake fluid doesn't seem to screw up dirtbike plastics. I had expected it to, it sure does on paint. 

Edited by toten

 What a cheesy way to "seal" off a hose!


I would just put a real small hose clamp on there. They can be hard to find locally though. I know McMaster Carr carries a whole bunch of real narrow band small hose clamps. I use them for lots of bike and truck stuff.Maybe if you have a high pressure hose maker close by they might have some as that is the only place I ever found them around my town.


Those wire ones like in your photo are what used to come with fuel filters (for trucks and cars) and are known to leak and give up. You would think Brmebo would have a little more class than that! Maybe it ws done by PO? I have seen shots of similar Brembo's and all they have there is a little short piece of Tygon tubing with maybe a teaspoon of extra brake fluid in there. Not what I would want for sure. I like having a little more just in case something does start to leak.


 That clip is pretty weird as well. Reminds me of how the key lock cylinders are held in on the doors on my 1963 International Harvester Pickup!  SERIOUSLY, it is the same thing only made out of steel. Measure the diameter and width of the groove when you do take it off. You might be able to substitute a REAL circlip for it.

I just bought the bike a few weeks ago, it wasn't me. I'm thinking of going to an auto parts store and seeing if they have any of the spring clamps that're used for low pressure fuel lines and the like, that should do the trick. I might still have a little of the clear hose around, I'll have to take a look. The reservoir is Brembo but that doesn't mean the hose is. 

That is true and it could just be the hose is getting old. It looks like standard  fuel line hose but not sure how well that stands up to brake fluid.


 I just had to replace the fuel line on my '99 as it was starting to leak just a little bit. Knew something was leaking a little as I could smell it when I first went into the garage for about a week or so. Took me that long to figure out which bike and where the leak was. Same thing  too, Cheap-o spring clamp (standard WR issue) and old, original I think, fuel line!

The hose has been on for a significant amount of time is my best guess, I wouldn't be surprised if it's been there for a few years. 


What's the best place to order some hose to use as brake reservoir hose? Where can I get clear fuel lines and clamps too?

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