All 2st Coolant Leak Is Driving Me Nuts

My WR300 has been plauged with a persistant coolant leak since day one, and I can't seem to fix it. It's at the discharge of the water pump where the big "Y" hose connects to it. It started dripping there the day I was heat cycling the motor when brand new. I tried tightening the hose clamp, but that seemed to cut through the inner wall of the hose because then it started seeping out through the fibers at the end of the hose. Two different Husky dealership wrenches told me to start over with a new hose, and put Perma-Tex Ultra Blue on the outlet nipple of the pump. So I did that, and I thought I'd done a fine job of it too, several test spins around the block yielded no sign of a leak.
Well I got back home from a big 3 day ride down at Hatfield/McCoy in WV with my PA buddies, and other than the forks being harsh the bike was flawless. I washed the bike thoroughly, blow dried it with my leaf blower and put it in my shop. Yesterday I got it out to service it up for the weekend, and there's a puddle of coolant laying in my Motosportz skid plate. I thought, "It can't possibly be the hose connection this time,...it's gotta be the water pump cover." So I checked the pump cover bolts, and I couldn't budge them at all with an 8mm T-handle,...they were tight.
I dried everything with a paper towel and dusted the whole area with baby powder and put it back to bed. When it seeps out this time I should be able to pinpoint exactly where it's coming from. But if it's the hose/pump connection again I'm gonna pull my hair out.
Will those silicone hoses from Eurocorsa seal up any better? If not, what then? I'm getting pretty tired of this. I've already bought one new OEM hose for it, and I have to remove my skid plate just to get in there to work on it, not to mention the coolant I'm wasting by having to dump it to work on it.

Anyone else ever struggled with this? Any suggestions?

I had the same issue. The root cause of the leak is a mismatch in the casting of the water pump cover which creates a ridged seam line axially all the way down the hose nipple. At first I tried a new hose and silcone, which held for a few rides but was not permanent.

To solve the problem I removed the cover (be careful not to lose the O-ring) and filed the ridges down till I had a completely smooth sealing surface. You can achieve an almost mirror finish on the nipple if you take some fine emory cloth and sand the surface after filing away the ridges.

I've had ZERO leaks since doing this and it's been several months and about 20 hours worth of riding.

Great tip! Should stick this.

Whatta guy! Thanks Krieg. I knew yours leaked initially, but I never knew all that. Gerald was one of the wrenches that told me to use the Perma-Tex. At the time, he was under the impression that it had stopped your leak.
Let me just get the details straight: 1) The ridges that need filed are on the hose nipple, and not on the pump cover mating surface, right? You only removed the pump cover to gain better access to the backside of the nipple, right?
2) Did you use the Perma-Tex on the final fix or not? If so,...just on the hose nipple, or on the pump cover mating surface as well?
3) Should I use another new hose?

I saw a strange looking sort of off-set protrusion right out on the very tip end of the hose nipple which I thought may have cut the inner wall of my original hose. I filed on it a bit only to remove any sharpness, without ever taking the pump cover off. Thinking back on it, that must've been due to the casting mismatch.

Thanks Krieg, ...you may have just saved my sanity. I tend to get frustrated and run short of patients when a little niggling thing like this just won't go away.

Rusty, the ridges I filed and sanded/polished were only on the nipple sealing surface. I did touch up the sharp ridges on the lip of the nipple because, like you, I thought they were cutting into inner surface of the hose and creating a leak path for the coolant to soak into the hose reinforcing fibers.

I would advise taking the cover off simply because you can manipulate the file and emory cloth more easily and you can also see the entire nipple without having to contort yourself under the bike. It made the job a lot easier IMO. Just be careful with the O-ring!

I did use a new hose because my original hose was leaking through the fibers ends already and I just wanted to make sure I was starting completely from "scratch".

I had thought about using silicone on the sealing surface after filing/polishing, but I wanted to see if it would seal without the silicone. If you do the polishing stage correctly, with a fine grit, you can get a VERY smooth surface. I ended up NOT using the silicone and it was fine... and still is to this day!

EDIT: ONE MORE TIP... As you probably already know from filing the lip a bit, this casting is made of a soft metal so you need to file very gently with a fine metal file. If you go nuts on it with a rough cut file, you'll damage the part.

Got it,...good deal!

I'm considering ordering a new pump cover & O-ring too, when I order the new hose, just on the chance that it may be cast better than mine.
Maybe if they have one in stock at Upstate or Hall's, they'll look at it for me and see if it's good and smooth. I hope it's not ridiculously expensive.

Okay, I'll start "Round 2" with this thing,...and see what I can do.

Thanks so much again Krieg!

Well that pump cover is 77 bucks and some change, and nobody has one on hand to look at. So on the one hand it's kind of an expensive gamble that it'll be any better, but on the other hand Jeff at Hall's said he'd never heard of anyone having this problem before in all the years of the WR250. So maybe there was just a bad few of them here lately, and possibly I could get lucky and get one from older stock,...I dunno.
I'll see what I can do with mine first I guess.

I'm inclined to believe it was a limited "batch" of bad castings made for the '09 bikes.

I'd tend to go along with that too. I don't know if I'd ever mentioned this or not, but my pipe had several pin-hole leaks in the fat expansion chamber part of it right off the show room floor too. I had them tack-welded up at a local shop and it's fine now,...but who'd ever heard of such a thing as that either?

I've seen the cast seems on the hose nipples on a few KTM's over the years, too. Gotta polish them smooth or they have a continual slow leak.

It's not just limited to the 09's, so I wouldn't waste your money trying to find a older part. My 02, 04, & 07 WR-250's all leaked there. As mentioned, a casting flaw is the problem. Some leak worse than others. On my 02, I had to take a file to the hose nipple. On the other two it is/was a slight weep, so I didn't worry about it.

Well how 'bout that?....Alright then, thanks!

My 07 doesn't leak, but it does "sweat" a little around the drain screw

Fil it dude. It's easy. Finish it up with fine sandpaper, then Scotchbright, just lik you buy at the grocery store. Mirror finish and it will work fine.

Any photo's of before and after

my 96 wxc does have the same drip, I thought I fixed it from reading here, two days ago, but This morning its got a wet spot, but not leaking as bad. My guess now is the hose is leaking through the fiber. Im going to try and seal that before I buy another hose with some 3m 5200.

Mike

What I found on my 300 was the initial leak did cause an inner puncture into fiber. I had to replace the hose to totally get rid of the leak. The hose was pretty cheap as I recall.

This is similar to the fix George did on kickstands. People complained the bolts were weak and broke. He took a grinder to the area under where the kickstand mounts and ground it smooth. The bolts became stronger after that....and decided not to break.