July 09, 2020, 09:48:57 AM

Author Topic: Oil Pressure Issues Phantom or Real  (Read 247 times)

Offline Stubbs

Oil Pressure Issues Phantom or Real
« on: June 29, 2020, 01:59:02 PM »
So I did my first track day in the RX8 at Eagles Canyon last weekend.  The car did well, me, not so much.  It's been 8 years since I was last on track and it definitely showed.

Anyways, after my last session as I pulled off track the factory RX8 oil pressure gauge in the cluster started twitching and the oil pressure warning light was intermittently going on and off.  It was acting like a gauge with a bad ground.  Didn't notice anything while on track, but wasn't paying close attention since I was on a cool down lap.   The gauge in the cluster is just a dummy gauge and is run from a canbus converter.  The converter takes the GM oil pressure sensor from the GM Canbus.  The GM sensor on the LS3 is a 3 wire pressure sensor, so bad ground is unlikely. 

I shut the car off immediately and after about 30 seconds fired it back up and the gauge was acting normal again.  I pulled it into the paddock and shut it down, oil level was unchanged, and no sign of leaks.  The car sounds normal with no knocking noises, and no lifter clatter.  An hour later I fired it up and it took about 15-20 seconds for the dummy gauge to show oil pressure.  I used Torque to watch the oil pressure through the OBD2 port, and it showed no oil pressure during the 15-20 second period then it instantly jumped up to 45-40psi, and it tapered down to 28psi over about 10 minutes as it warmed up which is normal.  I shut it off, waited a few minutes and fired it back up and had pressure immediately.  I ended up driving it home and it had normal oil pressure(~40PSI at 2000rpm viewing the gauge on Torque) the entire hour drive back.  I parked for a few hours and at startup it took about 10 seconds to read oil pressure again.   
When I get home from work today I'm going to pull the oil filter and check it for metal, and see what happens with a mechanical gauge during startup.
I did a little bit of research and there were some people saying that that particular GM sensor is prone to failure with similar symptoms as mine.  GM went so far as to add a filter screen to the pressure port as a bandaid fix in later cars(spoiler: it didn't help.) 
Has anyone else seen similar behavior with the factory sensor?  I've got my fingers crossed that it's just the sensor and not a bigger issue.  I'll be finding out soon enough.
I'll be adding a standalone pressure gauge.  I was using Torque to monitor my pressure and coolant temps, but my phone died after my first session.  Oil pressure was fine during the first session with no drops during cornering or other bad behavior.

A few notes on my setup that may be relevant:
LS3 with F-body pan ran an extra half quart over full Mobil 1 10w-30
OEM RX8 Oil cooler and thermostat (driver side cooler only, second cooler removed)
Improved Racing non-thermostat low profile oil cooler adapter -8 lines going to cooler no check valves
The RX8 has the fittings for the cooler at the bottom so potentially it could be draining back to the pan causing the long delay in startup pressure.  Haven't seen this behavior previously though. 

Offline largeorangefont

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Re: Oil Pressure Issues Phantom or Real
« Reply #1 on: June 29, 2020, 03:14:59 PM »
I believe the screen is there for DOD engines so no junk goes into the lifters. The screen will clog over time and you'll destroy lifters and the cam, especially if you run longer oil drain intervals.

definitely add a standalone oil pressure gauge.
Quote from: cool
Sell it to spacevomit.  He'll finish it.

Offline radiomike

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Re: Oil Pressure Issues Phantom or Real
« Reply #2 on: June 29, 2020, 05:24:00 PM »
Just a thought but might this be the infamous LS3 oil pressure relief valve problem?  It happened to ours at Zandvoort, the steel piston runs up and down in the aluminium pump housing and creates a burr which will intermittently seize the piston.

Offline Stubbs

Re: Oil Pressure Issues Phantom or Real
« Reply #3 on: June 29, 2020, 06:21:19 PM »
Just a thought but might this be the infamous LS3 oil pressure relief valve problem?  It happened to ours at Zandvoort, the steel piston runs up and down in the aluminium pump housing and creates a burr which will intermittently seize the piston.

It's possible that's what's happening.  I ran across a post by 4packet with a similar description to what happened. 
It's a little odd that it'd happen at such low miles.  I've got less than 5K miles on a GMPP crate LS3 with 95% of that being easy commute driving.  Double checking the pressure with a mechanical gauge and a look at the filter will be telling.
My optimistic side is hoping it's a sensor, but it rarely ever is.

Was there any damage on your motor from the loss of oil pressure? 
Any recommendations on a replacement pump if needed?

Offline radiomike

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Re: Oil Pressure Issues Phantom or Real
« Reply #4 on: June 29, 2020, 06:50:53 PM »
Yes, same car, we had it transported back to the UK and fitted a replacement GM pump.  We didn't check the bearings and seem to have been lucky.

Offline Stubbs

Re: Oil Pressure Issues Phantom or Real
« Reply #5 on: June 29, 2020, 11:11:13 PM »
Turns out it was real.


The oil that came out had a slight shimmer to it and there was some flakes in the filter.
Likely a sticking relief valve. 
Now I've got to decide if I want to throw a hail Mary and just replace the pump or if I need to throw a set of bearings in too.

Offline Cobranut

Re: Oil Pressure Issues Phantom or Real
« Reply #6 on: July 01, 2020, 10:43:32 PM »
With that much metal in the oil, I'd definitely tear it down for inspection at least.
Much better than scattering expensive parts all over the track.  :banghead:
1995 FD, 7.0 Liter stroked LS3, T56, 8.8, Samberg kit.

Offline Stubbs

Re: Oil Pressure Issues Phantom or Real
« Reply #7 on: July 02, 2020, 12:16:07 AM »
Yeah, I was in a bit of denial about tearing it down.  Moving on to acceptance. 
I looked in the filter pleats and there were some decent sized chunks, the ruler on top is in MM.  There was also a small flake of copper in there, so, definitely needs a tear down.

Offline Cobranut

Re: Oil Pressure Issues Phantom or Real
« Reply #8 on: July 02, 2020, 06:31:53 AM »
Check your oil pump carefully too.😱
1995 FD, 7.0 Liter stroked LS3, T56, 8.8, Samberg kit.

Offline FC3S Murray

Re: Oil Pressure Issues Phantom or Real
« Reply #9 on: July 02, 2020, 09:55:45 AM »
Oh man that sucks. Sorry to read but time to upgrade since you are going to be in the engine.



9 years of abuse and still running STRONG!
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Offline kinger

Re: Oil Pressure Issues Phantom or Real
« Reply #10 on: July 02, 2020, 11:30:43 AM »
Disappointing with a new crate engine.  I loved this build it was clean and well done.  Unless it can be pinponted to that RX8 oil cooler being the culprit I would be upset.  Sorry for you luck! 
93 Touring, 6.3L, T56 Magnum, Mamo RPS BC2 clutch, FAST 90, NW 90TB TB, 8.8, samberg everything, AC, PS, TC, Cruise, LED Tails, HID head lights

Offline Cobranut

Re: Oil Pressure Issues Phantom or Real
« Reply #11 on: July 02, 2020, 02:40:01 PM »
I'd also upgrade to -10 lines and a better oil cooler.
Mine on my FD are -10, and I'm using -12 on the dry sump 4-cylinder in my racer.
1995 FD, 7.0 Liter stroked LS3, T56, 8.8, Samberg kit.

Offline largeorangefont

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Re: Oil Pressure Issues Phantom or Real
« Reply #12 on: July 03, 2020, 12:11:39 AM »
How much oil was the car using per session? Were you tracking that? It was likely using quite a bit if you were running it hard.

Id recommend running 1 full quart over full, and getting the Improved oil pan baffle for your F Body oil pan.

I agree on the -10 lines to the cooler.
Quote from: cool
Sell it to spacevomit.  He'll finish it.

Offline Stubbs

Re: Oil Pressure Issues Phantom or Real
« Reply #13 on: July 03, 2020, 12:52:23 PM »
I'm definitely taking this opportunity to fix a few of the weak spots in my swap.
Oil cooler lines and thermostat need to be improved.  The RX8 thermostat runs too hot, and the setup was never my favorite.  It was just too easy to do it that way at the time.  I don't think the RX8 cooler was draining back as the lines between the cooler and engine run above the top of the cooler.  I'll measure how much comes out of the cooler when I pull it out, that should tell me for sure.
It's disappointing that this engine failed so quickly.  I'm going to do my homework to find out if it was my fault or just bad luck. 
There's a couple places I could have caused an issue.  Oil cooler and lines, but also I had to swap the pan and pickup tube.  It's possible I put the wrong o-ring on the pick-up tube when I swapped them, or maybe the bolt holding the pickup to the pump came loose.  I don't think that's the case, but you can't learn from mistakes unless you identify them. 
How much oil was the car using per session? Were you tracking that? It was likely using quite a bit if you were running it hard.

Id recommend running 1 full quart over full, and getting the Improved oil pan baffle for your F Body oil pan.

I agree on the -10 lines to the cooler.
It didn't use any oil over the two 30 minute sessions.  I wasn't pushing too hard as I was keeping my pace low to learn the track and car.  Only started picking up the pace toward the end of the last session.  I still need to check my catch can though.
I've got the Improved Racing pan baffle already installed.  I was thinking about adding the crank scraper and an accusump.  I'm looking into options for larger capacity pans too.  I wish I had been able to keep the LS3 Camaro pan since it held 8qts.

I'm looking into options for upgrades while I've got the engine out.  I've got a 418 stroker on the brain right now.  At minimum I think a cam is mandatory. I'm looking at sending my heads off to get ported, but it's a little hazy as how much benefit there is as most people just throw a set of aftermarket heads on probably worth it if I go with the 418.