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Big coolant leak on left side of engine behind stator cover

jtalics

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Need help on an FZ1 2006 to diagnose a coolant leak.

Engine continues to run great. I changed the oil and there is zero antifreeze/water/coolant in the oil. (Whew.)

Leak started during a 100 mile highway ride; overheats when I come to idle at a stop. Since then, I have observed... it drips as I ride, but the leak becomes a solid stream of cooolant when I turn off the engine, dropping about 1/2 cup of coolant. If I refill the coolant, it just leaks out the same... very reproducable.

Position of the leak is shown below. (Ignore scratches, those are very old.) The leak is on the left side of the FZ1. The leak is coming out of the gasket at the bolt indicated in the picture. (Bolt fastens the stator cover, I think it is called.) There is no other leak detectable anywhere (cap, hoses, etc.)

I've got the shop manual and I am trying to figure what could be wrong before diving in. On p. 2-35, I see the water pump is lower than the leak, so it is probably not the water pump. Directly above the leak is completely dry. The leak is almost certainly coming from inside the stator cover.

I am very grateful for any ideas!
fz1-coolant-leak.webp
 

I know nothing about Gen 2s, linked fishe shows gasket, Item #10. Don't know if coolant should be behind that cover but I suspect it should or you would have oil leaking
 
Your link (thanks) shows that the gasket is for a cover that is not supposed to seal any oil or coolant. It just covers a cavity that is getting filled with coolant from a separate leak inside the cavity.
 
Still sounds like that cover will have to come off to see what's leaking.

Edit: Can it be leaking from above and tracking down to that point without coming from inside that cover?
 
Last edited:
Still sounds like that cover will have to come off to see what's leaking.

Edit: Can it be leaking from above and tracking down to that point without coming from inside that cover?
Yeah, I think you are right. It doesn't make sense that that the coolant would stream so hard all at once if it had to squeeze thru that gasket. So I got in there up close and, yes, there is a channel that could deliver the stream from the top where the thermostat is that could be leaking. I am in the process of removing the gas tank and air box to investigate. So much for my confidence that it is coming out of the stator cover, it fooled me.
 
I have the same issue that started after I installed new thermostat. Let me know if you figure it out and I will do the same
 
I certainly will, sir. The fact that yours leaked after replacing your thermostat is encouraging (for me) insofar that I am on the correct track. Yesterday I pulled the gas tank and air box. I did see signs of dried antifreeze under the thermostat housing. I removed the thermostat housing and all the connected short hoses. Everything was visually OK, and air tight as far as I can tell, but my "mouth sucking" test is far from 15 psi that the radiator operates. Indeed, the behavior of the leak is consistent with a small leak somewhere since it leaks very slowly during operation and dumps when the engine stops and the psi soars. This is also consistent with a bad cap, but I don't see how that kind of leak would travel via the channel to the stator cover, but I will double check.

My prime candidate is "Coolant Pipe 5" which connects to the cylinder head; it has an o-ring inside which I am sure has never been replaced for 76,000 miles. It *looks* ok but looks can be deceiving, and it does live its life touching the hot cylinder head. Plus it is perfectly positioned to leak into the channel.

So I am going to get a new o-ring for Pipe 5 even if it isn't the problem, simply for preventative maintenance. I will clean engine thoroughly and will reassemble and test under blacklight to see fluorescing antifreeze leak. If still unable to locate, I will pull the air box again and invest into a test Radiator cap tester & adapter (90890-01325 YU-24460-01 90890-01352 YU-33984) and watch it "realtime" under blacklight.

Thanks again.
 
I just went to order the O-ring 93210-235A1-00 and searched for images to compare to mine. It has a perfectly round cross-section, where as mine is very flat. I rechecked the fitment and it does not seem especially snug. Maybe this is the problem. Happy Labor Day.
 
Well, I replaced the O-ring and the fit was night and day; it was much tighter. So that O-ring definitely needed to be replaced. Unfortunately, it did not solve the leak at all, so I have a pressure tester coming and I will probably need to take out the throttle body and starter motor to see wha tis going on realtime under a blacklight. :(
 
I hope it is as simple as a hose, but I can't see where. Hope it isn't a gasket. It does suck indeed that the leak is right in the middle. I was hoping not to getting sucked into a time-consuming search, but it is what it is. Luckily, I have a large bottle of patience, and applying liberally! This leak is going DOWN!
 
I have made progress in finding the leak!

I looked into getting a radiator pressure tester, but the ~$50 ones on Amazon did not fit, and the Yamaha OEM testers were way too expensive. So I abandoned that approach.

Instead I added coolant dye to the radiator. To track the leak, I washed the engine clean and checked with the blacklight that nothing was fluorescing. Then I ran the engine for 20 seconds and checked for fluorescence. There was a small stream emerging from the stator cover along the wire boot. I removed the stator cover and saw the below (under blacklight UV):
View attachment 34832

View attachment 34833

So at least I have located the leak! Any idea from the wizards out there as to what is leaking? And whether or not this engine is worth saving? There is no coolant in the oil, engine runs great. I am going to pore over the mechanical drawings and try to figure out what COULD be leaking. Thanks for any help in advance, sirs.

(The irony does not escape me that it actually WAS leaking from the stator cover as I thought in the first place. This leak was diabolical!)
A weird one for sure. A leak between the 2 crankcase halves or maybe a cracked water jacket?
 

video above is about an 04-06 R1 but may be relevant. His statement is coolant good, oil bad when leaking from that area. Might be a different inlet pipe on Gen 2.
 

video above is about an 04-06 R1 but may be relevant. His statement is coolant good, oil bad when leaking from that area. Might be a different inlet pipe on Gen 2.
That coolant pipe is well below the stator cover. Additionally his statement only references the relative ease of the fix of the coolant leak vs oil
 
I may be an idiot. I hate to report this, but the problem has gone away. The temperatures have gone down here in southern Texas over 100 to 85 highs, and I went to mostly water and a little ethylene glycol instead of 50/50. Absolutely no problems now. Perhaps I had a boil over and coolant went crazy everywhere inside the engine, sort of when a carbonated drink fizzes up on you and comes out your nose. I dunno, my hope is that my reporting this helps some one else to not jump to conclusions like this idiot did. Peace to all.
 
Instead of taking things apart to find the leak I finally just added some special stop leak for motorcycles and it hasnt leaked since. Sorry for the long wait, but I’ve been on a new motorcycle so I didnt get to it until just the other day. Glad yours is sorted out!!!
 
Thanks sir. I didn't even think of that Stop Leak, but I will next time. It's been a week and a few hundred miles and cooler weather, and NO PROBLEMS yet!
 
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