<VV> I'm thinking maybe the starter motor...

[Hugo Miller]

I cannot buy your theory about bushings. If they are going to do 
anything it will be to expand. And if you imagine the torque that a 
starter for a commercial diesel engine puts out, it wil not be deterred 
by a tight bushing here or there - it will just tear them out of the 
casing and keep spinning.
Definitely an electrical fault on the ones I have experienced. Dirty 
solenoid contacts sounds just about plausible - definitely increased 
resistance somewhere.

On 2020-08-07 03:08, FrankDuVal via VirtualVairs wrote:
> Hugo:"But why - and indeed how - would a winding 'fail' when hot?"
>
> Response: It is not a winding, but the bushings that change dimension
> when hot. They wore while cold, now the worn bushing is changing 
> shape
> due to heat, and capturing the armature shaft at a different place
> than when new. Replace the bushings. And the brushes while you are in
> there.
>
> Now, it could be a bad connection that increases resistance with heat
> also....  aka Chuck's solenoid contacts idea, but any connection in
> the starter might be the culprit. Heating of the connection should be
> obvious when it is taken apart.
>
> Frank DuVal
>
>
> On 8/6/2020 10:11 AM, Hugo Miller via VirtualVairs wrote:
>> I would vote for the latter. If it's a mechanical fault, there is no 
>> reason why it should only happen when hot - especially as the starter 
>> has more work to do when cold. I've experienced it on a number of 
>> vehicles - the most embarrasing being a 10 litre diesel in a 
>> double-deck bus. You would swear the battery was flat - but leave it 
>> to cool down & it will spin over as good as new.
>> But why - and indeed how - would a winding 'fail' when hot?
>>
>> On 2020-08-06 15:00, Jim Becker via VirtualVairs wrote:
>>> I'm pretty sure it is the coriolis effect because they didn't put a
>>> left hand spiral on the Bendix.
>>>
>>> Seriously, when you take the starter apart, the reason us usually
>>> obvious. The armature has been dragging on the pole shoes.  New
>>> bushings will usually fix it.  If this isn't it, the problem could 
>>> be
>>> a winding that fails when it is hot.
>>>
>>> Jim Becker
>> _________________________
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