On 3/24/05 0:01, "Jonathan Farrugia" <jfarrugi@UMICH.EDU> wrote:

> we don't measure the pressure differential because of the cost to
> implement the system, ie the plumbing.  this is done industrially
> primarily where the system doesn't have a relief valve, or one is not
> desired.
> 
> jonathan
> 
> On Wed, 23 Mar 2005, Jere Hawn wrote:
> 
>> HI again,
>> 
>> In the Navy we use pressure differential across the filter to determine if
>> it needs to be cleaned or serviced.  If my memory is correct if the pressure
>> from the inlet side of the filter was 10 lbs greater than the outlet side
>> then the filter needed attention.  Why don't we use this?  Has anyone heard
>> of it?  Is there any way to tell?
>> 
>> 
>> 
>> Jere

VW makes some heavy diesel and gasoline commercial engines and it would not
surprise me to find that system was brought over from the commercial engine
side of the house.

 The high pressure oil pressure switch is on the outlet from the oil filter.
If the filter becomes clogged up it will not be pushing out enough oil to
close the switch. (lower switch is NO) the switch on the head is NC. Because
of the setting of the lower switch, it will trigger very easily if oil is
too thin, filter not flowing well enough, or if oil has foamed, or tube
sucked air.  Any of these and you can still have enough oil getting to the
heads but pressure to the bearings may not be enough and you will get oil
pressure lights.  However anything more than a momentary that also effects
the upper pressure switch will trigger as well, then you get the oil light
at full light and alarm(if your vehicle had the alarm).

 experimenting I did with a jetta that had failure of the dynamic system was
interesting. I replaced the or/nor gate system with two oil pressure lights.
I have done this on two jetta.

 
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jimt
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