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I was riding around far from home and noticed a large coolant leak. I immediately thought the home made gasket made by the PO had given up but upon further inspection it was from the transmission cover. I bought a gallon of coolant and kept flipping the reservoir every 30 minutes while I limped the bike home. What is that hole for? The leak is from the hole. Please see video.


https://youtu.be/xaKaOOnIRN4?si=4QSWL3dkrDh8ReJD

Thanks James

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Water pump tell-tale hole. You have a leaky water pump seal.

pidjones wrote: ↑Fri Oct 03, 2025 7:52 pm Water pump tell-tale hole. You have a leaky water pump seal.

Thank you. I read a lot of "how to" write ups on the water pump seal replacement. Seems like the hardest part is removing the JIS screws on top of the cover. I can't remember if I have JIS impact bits or not.

Besides Honda kits can anyone recommend a brand to order?

Start spraying the screw heads and tapping with a correct JIS screwdriver. The more soaking and tapping, the better your chances. And, yes, an impact driver really makes a huge difference.

I soaked mine with penetrating oil and used a long punch and hammer to tap the heads from the side to break the corrosion between the screw heads and cover. After that, only 1 screw needed the impact driver. I used socket head screws when I reinstalled it.

If I recall correctly the same hole can weep oil if the oil pump seal fails. I believe I replaced them both when I swapped out my well-worn water pump.

Prospect wrote: ↑Sat Oct 04, 2025 10:02 am

pidjones wrote: ↑Fri Oct 03, 2025 7:52 pm Water pump tell-tale hole. You have a leaky water pump seal.

Thank you. I read a lot of "how to" write ups on the water pump seal replacement. Seems like the hardest part is removing the JIS screws on top of the cover. I can't remember if I have JIS impact bits or not.

Besides Honda kits can anyone recommend a brand to order?

For me, the hardest part is completely removing the 40+ year old petrified gasket material, especially any that remains on the engine casing near the top of the cover, where confined spaces make it difficult to get a tool in.

I have found the best tools to be a carbide tipped gasket scraper (be careful to keep it flush wit the surface) and dremel rotating bits. Scotch brite pads are also useful if you're confident none of the abrasive residue will find its way into your engine. You'll want it to end up looking something like this.

Also, this link is very helpful in understanding the situation
viewtopic.php?f=22&t=6863&p=54053#p54053

Too,,

low-side wrote: ↑Sun Oct 05, 2025 9:02 pm I used socket head screws when I reinstalled it.

+1

If you can get them I'd recommend using the M6 with 8mm head screws like they changed to for the GL1100. The hex heads allow you to use a torque wrench for proper assembly and they don't have sockets to fill up with dirt & debris.

Thanks for all the info above.

I started the progress on rebuilding the water pump. After taking off the radiator I was very concerned about getting off the Philips (jis) screws at the top of the transmission cover because the screwdriver was misaligned as the frame is in the way. Surprising with a forceful tap of the hammer in the end of the screwdriver the bolts came out easily. Removing the trans cover revealed a huge mess of sludge and old sealant. Off to the ultrasonic cleaner for a bath and they came out looking great.


I removed the water pump. I needed to completely disassemble the water pump and it was very difficult getting the impeller out. A lot of persuasion with my mallet and there was no movement. I moved on to my hammer and it finally came out. One of the collars was destroyed during the process. Hopefully I can find one. The bearings were completely shot and it was difficult to rotate the impeller by hand. This is where I stopped. All this took about three and a half hours. I just need to find the bearings and the collar that was destroyed.

Inspect the water pump housing in the trans front cover. The alloy tends to corrode, make sure the pump O ring seal mating face is not compromised.
Jerry

Has anyone tried these Chinese water pumps? Is it interchangeable or will it fit the gl1000?
https://www.ebay.ca/itm/357104139784?_s ... R-Svr8LAZg