Oil pressure drop, 712 Pinz

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Pinz aus
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Oil pressure drop, 712 Pinz

Post by Pinz aus » Wed Feb 19, 2020 12:33 am

Hey guys

Looking for some technical advice on my 712 Pinz
It has been off the road for going on ten years now and i have been slowly getting it back into shape to make its return over the past 18 months since I purchased it.

It has an issue with the engine dropping oil pressure quite suddenly after a period of running time.
When I drove it home on a permit the oil pressure light came on after around 45 minutes of driving, I pulled up and checked everything over and gave it a break and when i restarted it the light stayed off. It came on again after 20-30 minutes when i was very close to home and I gave it another break and got home okay. Not knowing the vehicle at all I thought it may well be a faulty sender switch, i also thought from that experience that I didn’t like not having a pressure gauge so I installed one and an oil temp while i was at it.
I hadn’t done any serious driving in it since, only moving it around in the shed or on and off the trailer.

So on the weekend after getting it back together i decided to run it around our property to test everything out. On start up cold its getting almost 400kpa (58psi) of oil pressure but after approximately 45 minutes use it put the pressure warning light on, i then glanced across to the gauge and noticed it was back virtually at zero, i had been watching it prior and it was holding 300kpa (43psi) at idle hot.

The weird thing was that after turning it off for no more than a few minutes upon restart it was back around 40psi again. I ended up having to put it back in the shed before doing further testing to establish a trend but it does take quite a bit of running before it happens.
I have read a few mentions about an oil temp thermostat and maybe some bypasses? Would any of these have the ability to drop your oil pressure right off if not functioning correctly?

Look forward to hearing your advice

Cheers Geoff

ChickenPinz
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Re: Oil pressure drop, 712 Pinz

Post by ChickenPinz » Wed Feb 19, 2020 11:59 am

Hi, Geoff.

I'm just ramping up on the Pinz, but have lots of VW and aviation experience to leverage.

Given that you have redundant sensor sources (switch & sensor), and they agree, let's assume that the oil pressure you're seeing is real. I'd first look for some type of obstruction in the oil pick-up path. Is it possible there's something in the crankcase that could be obstructing the intake, and when you turn it off that moves free until it gets sucked up again with motion? That'd explain the quick recovery after turn off the suction (engine) and restarting.

Tim
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Jim LaGuardia
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Re: Oil pressure drop, 712 Pinz

Post by Jim LaGuardia » Sat Feb 22, 2020 9:41 am

Pull the pan. Make sure the oil pump mounting bolts are all there.
If the one on the pickup port side is loose or broken the copper gasket will shift.
Other items to check are oil pump bypass valve or cam end plugs
Use 30wt oil only.
8qts with filter.
Cheers, Jim LaGuardia
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4x4Pinz
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Re: Oil pressure drop, 712 Pinz

Post by 4x4Pinz » Sat Feb 22, 2020 10:19 am

would also be a good time to change the oil filter itself. Have had oil pressure issues in other older vehicles when the insides of the filter became loose. As Jim has mentioned the oil pick up tubes can be a common issue when dealing with oil pick up and they are not that difficult to check.

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Pinz aus
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Re: Oil pressure drop, 712 Pinz

Post by Pinz aus » Wed Mar 18, 2020 3:25 am

Thanks for your replies guys.
I haven’t had a chance lately to get back to it but did finally get a little time.

It’s certainly a strange one.
I started an ran it stationary in the shed with initial good oil pressure. I ran it up to approx 3000rpm and held it there to warm it up. The problem appears to be more about time than temperature as the oil temp went up to 100 degrees Celsius (212 Fahrenheit) with no effect on pressure.

I suspect that with the revs maintained it may not drop pressure and possibly its when it goes back to idle or lower revs that it begins to drop.

It’s not an immediate drop but once it starts to go its a progressive decline back to nothing.
As mentioned before if its turned off and left a couple of minutes and restarted it recovers some pressure, the longer you leave it (Up to ten minutes or so) the more pressure it will have but after a few minutes running it will drop off again.

The drop off does make me think that its loosing prime at the oil pump but i cant quite follow why it would pick it back up after being shut off other than something restricting the pick up.

How difficult is it to access the pump, anything special to know?

Thanks in advance for your advice

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Hotzenplotz
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Re: Oil pressure drop, 712 Pinz

Post by Hotzenplotz » Wed Mar 18, 2020 3:52 am

Pinz aus

Once you remove the pan, you have access to the pump.
There is a service-note about the fastening bolts; you might want to check that

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Cheers
Albert
========================
My Pinz has NEVER been with any army

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Pinz aus
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Re: Oil pressure drop, 712 Pinz

Post by Pinz aus » Wed Mar 18, 2020 7:47 pm

Thanks Albert

Jim; from my description and your experience would you think it’s likely to be an oil pump issue?

To my knowledge there was no issue prior to it being laid up, I couldn’t rule out an obstruction finding its way into the sump. The old oil filter which I drove it home on was very corroded externally but from memory looked okay internally.

Almost think I have talked myself into it, sump off sounds like a starting point regardless.

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