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 Mystery oil leak saga

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racepics
Montanarolo
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PostSubject: Mystery oil leak saga   Sat Dec 08, 2018 10:25 am

A perplexing situation solved..

I had just done the rollerisation job and been for a blat around the block. When I got back noticed an oil leak on the left side around the head gasket area..
How can this be? Its got new gaskets and yes the dowels are all in place..
A squirt with degreaser and a hose down revealed the oil was running down from further up somewhere.
Pete suggested maybe the o-rings on the spark plug tube were leaking, but there was no visible oil inside that cavity.
I finally found it was leaking from the oil pipe fitting and seeping around the outside of the head gasket, to drip off at the lowest point.
No problem, I'll get some new copper washers for the banjo fitting....
Did that and tightened it up as much as I dared.
Another test ride and still the leak is there. Must be the oil pipe says me!
I removed the pipe completely and it looked fine, no kinks or frays in the webbing.
Sealed the ends with rubber blocks and vice grips, put it in a bucket of water and applied compressed air to the open end.. No leaks..
So the pipe is fine and its got new copper washers and its done up tight but leaks..  
At this stage I'm thinking the situation is impossible but then it is an Italian motorcycle and there will be some ridiculous reason for this to occur.
So i screwed the banjo bolt into the head as far as it would go without the hose on it.
Then measured the gap between the head mating surface and the bolt mating surface,
I then measured the banjo end of the pipe plus two copper washers only to find that there was less than 1mm of crush being applied to the washers before the bolt bottomed out in the hole..
So when I thought the bolt was done up tight it was just out of thread (or bottomed in the head) and not actually clamping the copper washers..
Two copper washers on each side - oil leak fixed..

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tvboy
Tanabuso
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PostSubject: Re: Mystery oil leak saga   Sat Dec 08, 2018 2:27 pm

Nice detective work!
Why wasn't it leaking before you started the project?
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tvboy
Tanabuso
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PostSubject: Re: Mystery oil leak saga   Sat Dec 08, 2018 3:20 pm

Racepics,
I checked the parts manual and it calls for a part number GU01154230.
The picture shows a steel washer style with a rubber o-ring type insert.
Google calls it a Dowty washer. Named for the inventor.
Technically it's not a crush washer in that it relies on the compressed rubber to provide the seal.
The metal part isn't crushed. (Correction: the metal is crushed slightly)
I'm wondering if that rubber part is thicker than the copper crush washers you used and the copper wasn't thick enough as you discovered. What kind of washer was on it when you took it apart?
As Pete Roper stated in another post, it shouldn't matter what type of washer is used as long as it works.


Last edited by tvboy on Sat Dec 08, 2018 3:27 pm; edited 1 time in total
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Pete Roper
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PostSubject: Re: Mystery oil leak saga   Sat Dec 08, 2018 3:23 pm

Chances are it didn't leak because of the type of washers used.

The hose only delivers oil to the cooling circuit in the head, it's at comparatively low pressure compared to the lubrication side. Guzzi uses dowty washers for the banjos. These have a plastic/rubber insert in the middle to assist with sealing. They washers are also, unsurprisingly, designed to crush slightly under torque. On initial use they may of been adequate in this situation but on re-use and coupled to the lack of thread depth for the bolt they simply may not of been able to seal.

The bike is a 2008, an early one. Little things like insufficient threads are more likely to occur on early production models simply because of inaccuracies in the jigging up of castings in tooling and the like. After a few months things like this tend to become rarer and that holds true for all manufacturers not just Guzzi.

Pete
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racepics
Montanarolo
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PostSubject: Re: Mystery oil leak saga   Sat Dec 08, 2018 3:28 pm

Yeah mine definitely had copper washers, not steel/rubber - probably early production issue like you say.
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tvboy
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PostSubject: Re: Mystery oil leak saga   Sat Dec 08, 2018 3:45 pm

I just checked mine (2011)  and it has thin copper washers on both sides of the Banjo.
Not the steel type the parts manual refers to.
Recently, both cylinders were removed (to replace the base and head gaskets) when the engine was roller-ized so the washers should have been replaced too. They do look very bright and shiny.
I'm curious which washer type would show up if that part number was ordered.
Anyway, thanks for pointing out the potential leak source and your solution.
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