Belt Service Reminder!!!

Ok..I'll bite...what's the story?

 

it is a while ago and I can not find anymore my postings because of this broken shaft.
so here it comes again:
have a look at the pictures how the pump is installed. the return bore for the oil is not at the bottom when the vacuum pump is installed, it is about 90°, so the complete oil can never drain.
I installed the vacuum pump 90° so the drain hole is in the bottom and installed a 90° elbow.
when the oil can not drain and the engine get started the rest oil can not be compreesed like air and the shaft will brake - weakest part

this broken shaft I never had on a BB, and there the drain hole is at the buttom
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So, I replaced mine with a copy of an OEM part, and here's why. First off, this isn't anything bad on Kerry's part at all - I'm sure it's made well. My concern is that it's not the oil pressure problem others have mentioned which is the cause of the breakage. When I took my pump apart, one of the little inserts that are in the swastika-like grooves was actually LOOSE inside the housing. This made me think that one of the swastika grooves became jammed on the loose insert and sidewall of the housing, and that's what caused the sprocket to break off. And given that that sprocket hooks in to an exhaust camshaft and plenty of much more expensive parts from there, I'm ok with the weak point being the sprocket on this part, if it saves damage further down the valvetrain.

Again, nothing against Kerry's part and the cause of the breakage is purely my own thought.

 

Grinning Me2!

Joe, the vanes that slide in the quasi-swazi grooves are part of the design for an offset centrifuge pump... the same principle that operates in the bosch fuel pumps for the fuel injection.
The air pump is driven by the LH Exh cam and its operation creates the vacuum for the brake booster at idle revs by the same principle in reverse.

The problem is not exactly with the design as it was installed IIRC on the boxers originally; and the drain hole was at the bottom, the install on the Testa motor places the drain hole at 90deg rotation causing the vanes to be 50% open and pushing oil that is thicker when cold. This I believe is the cause of the breakages, mine had 3 replaced over its 1st 10 yrs(not under warranty either)

Kerry's design is exactly how it should have been machined in the first place; with no sharp corners to provide a weak spot for breakage.

I appreciate yr view on the more valuable reciprocating mass, however that is housed within the body and frame of the car that would be the first point of crumple if the vacuum failed and yr brakes would not have been capable to stop the car quick enough.
Just my 2 shekels worth
Pete K

 

Is this only Testarossa issue, or does BB shafts fail too?

 

as I have written on a BB I never had this problem, only TR
so I thought over why this happens and my result is this with the oil drain or the not oil drain

 

I like the idea of that shaft having a built-in fuse whether an accident or by design. Taking teeth off a timing belt would turn my smile upside down pretty fast.

 

this built in fuse would be ok if this fuse would be a little stronger
because for a fuse it is very expensive

 

Hey again,

I guess I didn't explain what I meant by being loose inside the pump. I didn't mean that the shims / fins were loose inside the swastika grooves, that's to be expected. I meant that one of the fins was loose inside the *housing*. That was how I surmised that the sprocket must have sheared off due to the fin being stuck in a lip of one of the swastika grooves and the side of the housing.

How cold does it have to get where engine oil has the mass / inertia to shear off a cog? I don't understand that.

 

you have a photo joe?

never has seen this before

 

No unfortunately I didn't take one. I should have - I'm feeling like a guy who spotted a UFO!

 

may be it has been an UFO
or the whiskey has been to good

 

How is that vacuum obtained in the 512TR Kerry ?

 

K Jetronic engines have low manifold vacuum at low rpm. The 512 with electronic injection had higher manifold vacuum so it was not needed. Many carbureted 12's had a vacuum pump too for the same reason but they often only depended on one or two cylinders for the vacuum.

 

Thanx for reply !