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Author Topic: Slow vac build up along with low oil pressure when hot  (Read 211 times)

August 27, 2019, 08:07:33 am

mk3pete

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Slow vac build up along with low oil pressure when hot
« on: August 27, 2019, 08:07:33 am »
Has this seal caused you issues before? Tell me your woes.... I'm unsure if this is the correct way to install the seal, lip facing up towards the vac pump(like in pic) or down towards oil pump. Can any veterans here please explain the purpose of this seal and what its supposed to do.
Link to Facebook for photos, sorry on my phone atm
https://www.facebook.com/groups/VWDiesel/permalink/2346962722047430/?sfnsn=mo

Can this seal cause slow vacuum pressure and can this also cause low oil pressure especially when oil is hot??
AAZ motor, has had a full rebuild, top to bottom.
Cheers any assistance 😘



Reply #1September 09, 2019, 12:06:14 pm

sgnimj96

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Re: Slow vac build up along with low oil pressure when hot
« Reply #1 on: September 09, 2019, 12:06:14 pm »
have you checked the check valve on the vac pump.    Just unscrew the lid and test/clean out the check valve.    I saw a thread somewhere where they replaced that check valve with on from mcmaster.
 
BTW,  that check valve on the top of the vac pump just presses in and can leak around the base.    I put some silicone gasket maker around the base of mine because it was loose,   think it got hit or something from the PO.

Low oil pressure when hot is normal,  you'd have to give some numbers.
81 Scirocco 1.6D (conversion)               86 Gofl 1.6D                          1985 300TD

Reply #2September 09, 2019, 10:31:14 pm

ORCoaster

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Re: Slow vac build up along with low oil pressure when hot
« Reply #2 on: September 09, 2019, 10:31:14 pm »
I am not sure I ever saw a gasket between the vac pump and the oil shaft.  Maybe mine always stays down on the shaft. 

But due to the fit of the vac pump on top of the oil pump driver it might be that having a gasket keeps it from engaging all the way.  That might cause the oil pump to not turn all the time or only part of the time.  Or just slower than it should to keep up the pressure. 

I had one vac pump with a really worn out slot and it would tend to jump over the oil sump driver at times.  I replaced the old style diaphragm pump with a rotary  one and it seemed to solve that problem. 

For sure check the amount of vacuum you have at the top of the pump with engine running and then at the booster.  Are all check valves doing their job? 

As for low pressure the seals on the intermittent shaft are known to leak and replacing them brings the pressure back up. 

Keep us posted. 
Turbo and Exhaust finally on, Time for tuning!

Reply #3September 13, 2019, 05:33:07 pm

theman53

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Re: Slow vac build up along with low oil pressure when hot
« Reply #3 on: September 13, 2019, 05:33:07 pm »
there is an o ring type gasket between the vac pump and the oil pump shaft. You used to be able to buy them, but I don't know now. Mine was green and ribbed on the inside.

 

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