Author Topic: T140 strange oil leak  (Read 93 times)

Offline Eedward

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T140 strange oil leak
« on: July 12, 2019, 07:34:00 AM »
I have recently been lucky enough to be the proud owner of a 1979 T140. I owned one a few years ago though sold it, now my garage is happy again with another one in it's place !
All is fairly well, apart from a serious short when the neg terminal wire touched the frame and burnt out 2 wires. A pain, though a fairly easy fix.
What has me scratching my head is an oil leak. An oil leak I get, it's a Bonnie. It's where it is coming from that really puzzles me. There is a fairly constant drip/dribble from the bottom of the head stock, which does not make sense !
I get it's an OIF model, though the max oil level is much lower than where it is coming from, and I don't understand how it gets there, to then leak out, over pretty much everything, as the wind does a great job in covering pretty much everything behind where it leaks from.

Has anyone experienced this before, and if so, or if you have any thoughts, I would be very appreciative for some enlightenment.
Thanks a lot,
Edward

Offline L.A.B.

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Re: T140 strange oil leak
« Reply #1 on: July 12, 2019, 09:06:00 AM »
All is fairly well, apart from a serious short when the neg terminal wire touched the frame and burnt out 2 wires. A pain, though a fairly easy fix.

1979 is the model year they changed to negative earth electrics so are you sure it's a 1979 model? 


What has me scratching my head is an oil leak. An oil leak I get, it's a Bonnie. It's where it is coming from that really puzzles me. There is a fairly constant drip/dribble from the bottom of the head stock, which does not make sense !
I get it's an OIF model, though the max oil level is much lower than where it is coming from, and I don't understand how it gets there, to then leak out, over pretty much everything, as the wind does a great job in covering pretty much everything behind where it leaks from.

The T140 frame oil reservoir has a breather vent immediately behind the headstock between the plates and should have a hose connecting it to the exhaust rocker-box on T140E models (or a connection to the atmospheric engine breather on earlier T140V models) so the oil could be coming from there? 

L.A.B.

Offline Eedward

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Re: T140 strange oil leak
« Reply #2 on: July 12, 2019, 04:13:02 PM »
Thanks L.A.B.

Sorry, yes, it's an S reg = 1998 T140V, a positive earth model.
There is no breather from the exhaust rocker cover anywhere, just the crank breather where it exits behind the barrels on the left.
It does chuff a little smoke on over run, which suggest worn valve guides or rings ? Though why would oil, not just fumes, be exiting from the breather behind the head stock ? Could it be pressurising the oil in the frame, A - because there is no exhaust rocker breather, and/or B - because the valve guides/bores are worn, and therefore sending it out the frame breather that way, along with some oil ????
Also, where does the exhaust rocker cover actually breath from, as my last 1981 T140V didn't have a breather there either ?

Your further thoughts would be much appreciated.

Thanks,
Edward


Offline L.A.B.

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Re: T140 strange oil leak
« Reply #3 on: July 12, 2019, 04:39:07 PM »

Sorry, yes, it's an S reg = 1998 T140V, a positive earth model.

1978.


There is no breather from the exhaust rocker cover anywhere, just the crank breather where it exits behind the barrels on the left.

Yes, for a 1978 T140V that's normal as I previously described. The T140E, also T140D and later T140 models had the exhaust rocker-box breather connection, not 'V'.


It does chuff a little smoke on over run, which suggest worn valve guides or rings ?

Probably, but could carry on like that for ages. 


Though why would oil, not just fumes, be exiting from the breather behind the head stock?

More likely it is being forced up the tube from the engine breather connection so it sounds as if that pipe joint is not secure and could be leaking?


Could it be pressurising the oil in the frame, A - because there is no exhaust rocker breather, and/or B - because the valve guides/bores are worn, and therefore sending it out the frame breather that way, along with some oil ????

I wouldn't have thought so. If there is any pressure then it's probably coming from the engine breather.


Also, where does the exhaust rocker cover actually breath from,

A 'V' would breathe through the exhaust pushrod tubes to the crankcase same as the inlet rocker box does through the inlet pushrod tube, not that there is much breathing taking place in the rocker-boxes just that the exhaust rocker box is a convenient place to have the breather to frame connection on the E model. 



as my last 1981 T140V didn't have a breather there either?

Unless it was 1981 registration, T140V production ended in 1978 so a 'V' can't be later than 1978 model year.




« Last Edit: July 12, 2019, 04:51:27 PM by L.A.B. »
L.A.B.

Offline Eedward

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Re: T140 strange oil leak
« Reply #4 on: July 13, 2019, 08:34:19 AM »
Thanks a lot for your thoughts. I will have another look / head scratch and take it from there.
Thanks again,
Edward