waterpump seals

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johnbrunning

waterpump seals

Post by johnbrunning »

I have just noticed a small milky coolant leak coming from small breather outlet at front of waterpump casing. am I wright in thinking I've got a waterpump seal problem
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johnbrunning

Re: waterpump seals

Post by johnbrunning »

just had another look the drip is coming from seepage breather outlet at rear of waterpump casing. not front looking at manual first time I posted and got it wrong
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oldjapanesebikes
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Re: waterpump seals

Post by oldjapanesebikes »

johnbrunning wrote: ........ thinking I've got a waterpump seal problem
Most probably. If it is milky rather than coolant then that is oil and would indicate the top oil seal is starting to go rather than the water seal underneath it - the weep hole vents the space between the two. Double check that you also do not have coolant in the gearbox. The seals are included in the replacement water pump cartridge you can buy as a unit under part 17400-31809, or you can replace the entire pump under part number 17400-31830 - or you can buy the seals themselves in kit form from several places and then replace them yourself. To be honest - I've had more consistent luck replacing the cartridge rather than rebuilding it myself, but your mileage may vary ! 8-)
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johnbennettgt750j
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Re: waterpump seals

Post by johnbennettgt750j »

My GT750J has has coolant leaking into the gearbox and I intend to replace the the complete water pump seal 'cartridge' assembly. Can you/anyone provide hints and tips for the job for the home mechanic? Firstly can the parts be changed with the engine in situ? I understand the cartridge is likely to be difficult to pull out. Is it likely that I will need to remove the engine and split the cases and if so can the lower half crankcase be removed without disturbing the cylinder barrel assembly?
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oldjapanesebikes
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Re: waterpump seals

Post by oldjapanesebikes »

johnbennettgt750j wrote:My GT750J has has coolant leaking into the gearbox and I intend to replace the the complete water pump seal 'cartridge' assembly.
You likely need to start a new thread, but water in the gear box on a J model is not usually a water pump seal problem. The water pump is designed so that either oil or water leakage will exit at the small drain hole at the back of the water pump cover. Water in the gear box itself is most commonly due to a leak at the mating face of the upper and lower crankcase halves by the water bypass line, or much less commonly due to failure of the nylon drain line from the water pump vent space. Both of these require pulling the engine and splitting the cases to repair. 8-)
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johnbennettgt750j
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Re: waterpump seals

Post by johnbennettgt750j »

Thanks very much. I just signed up to KC to learn about this problem so i'm having to learn the use of the Forum too - I need to find out how to start a new thread.
My expertise with computers is even more limited than my knowledge of GT750! ( I had a 2 year old GT750A back in 1979 which I kept about a year before I replaced with a GS1000S and I quite recently bought this GT750J.... but that's it!) OK so i've ordered a workshop manual which is due to arrive this coming weekend, but my basic question is whether I can remove the lower half crankcase from the engine assembly without disturbing the head/barrels etc to effect the necessary repairs?I guess my reason for asking is because I know pulling the barrels off a 48yr old motor ain't going to be easy! I suppose I'm optimistically trying to avoid a total engine gearbox rebuild!!
The annoying thing being the bike runs very well - or at least it did before the C19 lockdown.....
oldjapanesebikes wrote:
johnbennettgt750j wrote:My GT750J has has coolant leaking into the gearbox and I intend to replace the the complete water pump seal 'cartridge' assembly.
You likely need to start a new thread, but water in the gear box on a J model is not usually a water pump seal problem. The water pump is designed so that either oil or water leakage will exit at the small drain hole at the back of the water pump cover. Water in the gear box itself is most commonly due to a leak at the mating face of the upper and lower crankcase halves by the water bypass line, or much less commonly due to failure of the nylon drain line from the water pump vent space. Both of these require pulling the engine and splitting the cases to repair. 8-)
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oldjapanesebikes
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Re: waterpump seals

Post by oldjapanesebikes »

Sorry - but if there is no sign of leakage at the weep hole (and I'm assuming here that some clown hasn't plugged it off which has been done by PO's sometimes before selling the bike - you may want to check that just to be sure) and if you have signs of water in the gearbox, then my own view is that you do have to strip the engine down completely (pull the barrels etc). While you could remove the lower case, I don't see how you could get it back together again as the kick start shaft and the selector forks would be really difficult to locate correctly. I'm sure that nothing is impossible, but on a scale of 1 to 10, I suspect this would be about a 15 or so. :( I'm sure others will comment.

If this leakage into the gearbox is currently very minor, you could try some rad seal but keep in mind you risk plugging up the passageways on the radiator if you use too much, or you could ride with the radiator cap undone. It generally just delays the inevitable. Normally what happens on the J is eventually it just lets go and you have water/oil emulsion foaming out of the crankcase vent and all over your rear wheel. This happened to a friend of mine on a ride and stopping safely was exciting. 8-)

I show a photo of the problem area I'm talking about about half way down on this page on my web site:

https://www.oldjapanesebikes.com/1972_GT750/page-31
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johnbennettgt750j
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Re: waterpump seals

Post by johnbennettgt750j »

Thanks again - its all starting to making horrible sense to me...When I say I bought the bike recently it was actually in December 2018 as a 60th birthday present to myself and I put nearly 2000 miles on last year 2019. I find time passes increasingly quickly etc..I changed the gearbox oil approx July 2019 and noted it was slightly milky....noted it but didn't panic into immediate action. Towards the end of last season maybe September, I drained and flushed the cooling system before refilling with fresh 'pink' coolant.....the bike then did maybe less than 100 miles before being put away for the Winter. Due to C19 lockdown boredom, I changed the gearbox oil again last week and this time the first flow from the gearbox was high quality double cream with a few clotted cream lumps before something nearer resembling lubricating oil as the draining continued.... bear in mind the bike had been out of service for previous three winter months....I surmise that a minor leak at the time I bought the bike has been amplified by the mileage and the 'leak finding' properties of the new coolant....The dilemma is whether to commence an expensive project to rebuild it when it might be a long time before I can use it...at this stage I probably need therapeutic more than engineering help?? Thanks again
oldjapanesebikes wrote:Sorry - but if there is no sign of leakage at the weep hole (and I'm assuming here that some clown hasn't plugged it off which has been done by PO's sometimes before selling the bike - you may want to check that just to be sure) and if you have signs of water in the gearbox, then my own view is that you do have to strip the engine down completely (pull the barrels etc). While you could remove the lower case, I don't see how you could get it back together again as the kick start shaft and the selector forks would be really difficult to locate correctly. I'm sure that nothing is impossible, but on a scale of 1 to 10, I suspect this would be about a 15 or so. :( I'm sure others will comment.

If this leakage into the gearbox is currently very minor, you could try some rad seal but keep in mind you risk plugging up the passageways on the radiator if you use too much, or you could ride with the radiator cap undone. It generally just delays the inevitable. Normally what happens on the J is eventually it just lets go and you have water/oil emulsion foaming out of the crankcase vent and all over your rear wheel. This happened to a friend of mine on a ride and stopping safely was exciting. 8-)

I show a photo of the problem area I'm talking about about half way down on this page on my web site:

https://www.oldjapanesebikes.com/1972_GT750/page-31
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BAZ
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Re: waterpump seals

Post by BAZ »

The J casings don't have a oring for the water pass through and can leak into the crankcases at this location, but don't panic pike.. k seal rad seal may well seal it so you will have to refill oil and experiment. let us know how you get on. Cheers Barry.
johnbennettgt750j
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Re: waterpump seals

Post by johnbennettgt750j »

Baz, Thank you very much for your response and the ray of hope! I have ordered K seal and will report back as you suggest .... Thanks again. John
BAZ wrote:The J casings don't have a oring for the water pass through and can leak into the crankcases at this location, but don't panic pike.. k seal rad seal may well seal it so you will have to refill oil and experiment. let us know how you get on. Cheers Barry.
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