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914World.com _ 914World Garage _ Sticky pressure relief valve?
Posted by: RoadGlue May 27 2019, 07:22 PM
Hey everyone, hope you're all doing well.
My newly built four banger's oil pressure is all over the board and I'd really appreciate any advice you might have.
When the pressure is behaving normally, I'm seeing a pretty normal fluctuation from 10 PSI at idle to 40-something at cruise. However it seems that depending on direction I'm turning (maybe!?) the pressure can jet up to 65+ PSI which of course is alarming. Worried I'm going to blow out seals.
It doesn't always jump up though. It's rather inconsistent.
At idle I've had it stick at around 60 lbs as well. Giving the throttle a jab seems to free it up and it'll drop back down to where it's supposed to be.
I think it's a stuck pressure relief valve. If it were stuck in a high pressure state, would cornering have some effect on the pressure spikes?
I'm using Penn 20-50 and everything I listed was at normal operating temps (130-180 F).
Thanks!!
Posted by: ChrisFoley May 28 2019, 05:46 AM
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I think it's a stuck pressure relief valve. If it were stuck in a high pressure state, would cornering have some effect on the pressure spikes?
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This is unlikely.
Posted by: RoadGlue May 28 2019, 11:29 AM
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I think it's a stuck pressure relief valve. If it were stuck in a high pressure state, would cornering have some effect on the pressure spikes?
...
This is unlikely.
Due to the pressure changes when cornering as that wouldn't be related to the relief valve, right?
I'm at a loss. If it's something related to the pick-up tube, then I'd expect to see drops in pressure, not spikes.
The gauge and sender are old, so I'll get new gear just to rule those out.
If it's not that, then what next?
Posted by: ChrisFoley May 28 2019, 06:35 PM
I say its unlikely because the pressure relief valve doesn't work the way you imagine it does. But it is hard to imagine how going around a corner could affect the relief circuit.
Another point - oil pressure above 65 psi will not blow seals. My modified pressure relief valve raises the max pressure to 75 psi. In fact, the first thing to fail if oil pressure actually gets too high will most likely be a galley plug.
Cold oil pressure can easily exceed relief valve design pressure simply because the return passage is too small to bleed off all the excess oil when it's thick.
Posted by: Tdskip May 29 2019, 09:28 AM
Gauge / sender correct for each other and everything right?
Posted by: McMark May 29 2019, 11:21 AM
You running a tuna can on this beast?
Posted by: RoadGlue May 29 2019, 12:59 PM
I say its unlikely because the pressure relief valve doesn't work the way you imagine it does. But it is hard to imagine how going around a corner could affect the relief circuit.
Another point - oil pressure above 65 psi will not blow seals. My modified pressure relief valve raises the max pressure to 75 psi. In fact, the first thing to fail if oil pressure actually gets too high will most likely be a galley plug.
Cold oil pressure can easily exceed relief valve design pressure simply because the return passage is too small to bleed off all the excess oil when it's thick.
Thanks for this! The more data the better.
Posted by: RoadGlue May 29 2019, 01:01 PM
Gauge / sender correct for each other and everything right?
Yes! They're matched. However I'm starting to think that perhaps the sender is intermittently sticking internally.
I've ordered a new sender/gauge. Hoping it's just that, but I'll report back either way.
Posted by: RoadGlue May 29 2019, 01:03 PM
You running a tuna can on this beast?
Hey Mark!
Nah, not on this motor.
The windage tray seals are new from 914rubber.com, but if the new gauge and sender combo doesn't fix this, I'll drop the screen filter and plate and see if there's anything that could possibly be floating around in the sump. I'd just expect to see pressure dip vs. spikes if that was the case.
I'll report back once I have the new sender and gauge installed.
Thanks buddy!
Posted by: Mark Henry May 29 2019, 03:14 PM
You don't have a dangling, cut or loose wire anywhere? You go around a corner and something touches another wire?
I agree with Chris, plus another area for too high of pressure would be the filter can blowing up like a frozen pop can. Seen this happen with cheap filters.
BTW I think you guys call them soda cans.
Posted by: jim_hoyland May 29 2019, 03:15 PM
Connections? At the sender ? Sender grounded ?
Posted by: RoadGlue Jun 24 2019, 09:28 PM
I replaced the pressure sender this evening and now the oil pressure is rock solid at 60 psi when cold, 50 psi cruising when warmed up and idles and 10 psi.
The old sender seemed to be leaking a little oil from a seam too.
Thanks everyone! 
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