Oil pressure buildsduring startup then drops
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Launching!
Joined: Nov 2008
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From: Pembroke pines FL
Oil pressure buildsduring startup then drops I just finished my heads and cam swap on my ls6 and I started it and oil pressure builds to about 60psi then drops to 0 psi. I turned it off and on again and the same thing happened. Oil pump is a melling high pressure. If the oil ring was bad wouldent it build pressure at all? i am currently using 10W-30 Mobile 1 Full synthetic
Last edited by VerdeZ28; Feb 3, 2014 at 07:36 AM.
Thread Starter
Launching!
Joined: Nov 2008
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From: Pembroke pines FL
I always thought an o-ring not sitting well would not allow pressure to build at all. I am seeing alot of pressure after first starting it up then suddenly drops to zero from about 60psi. I havent confirmed this yet with a mechanical gauge, i will do this first before tearing into it again.
I always thought an o-ring not sitting well would not allow pressure to build at all. I am seeing alot of pressure after first starting it up then suddenly drops to zero from about 60psi. I havent confirmed this yet with a mechanical gauge, i will do this first before tearing into it again.
If the o-ring is pinched or torn, when cold, it will build pressure. As the oil gets warm, along with the pick-up and everything else, that's normally where you'll see the pressure drop.
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I know on a standard SBC if the relief valve is stuck open they usually lose all pressure and will not work from that point on. I've seen it happen several times over the years. Broken spring will do the same thing.
Thread Starter
Launching!
Joined: Nov 2008
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From: Pembroke pines FL
Ill be installing a mechanical oil pressure gauge today. I have never used these before, anything I should know about them before I do this? should the little plastic tube get filled with oil? and How soon should I see it reading pressure?
Thread Starter
Launching!
Joined: Nov 2008
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From: Pembroke pines FL
So I installed the mechanical gauge (is a sunpro gauge btw) and let the car run for a while. Coolant temp got to 184 when the gauge in the cluster( stock gauge) goes to zero but the mechanical gauge read a little under 60psi. The gauge in the car read about 65psi when suddenly nothing. I replaced the oil pressure sending unit when I did the h/c swap btw. What could be wrong to cause it to happen. I don't think it's the cluster because the ecu also thought the oil pressure was low and turned on the ses light. Mechanical gauge is installed just above the filter where the oil temp sensor normally would be. I bought an eBay adapter with 1/8 npt thread.
I'd you can, get someone else in the driver seat to watch the gauge, and with the car running, stick you hand back there and wiggle the wires around the plug in.
If it starts skipping around, you need to grab a new OPSU pigtail and solder it in.
Only two things it could be. Bad wire, or bad sending unit.
Thread Starter
Launching!
Joined: Nov 2008
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From: Pembroke pines FL
I have replaced the oil pressure sending unit with a AC Delco unit and that seems to have done the trick. Does anyone know what pressure I should be seeing with the melling 10295 oil pump? right now its about 60psi cold Idle.
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Hey man I’m having the same problem just replaced my cam and installed a new oil pump melling high oil pressure pump and now when I start I got around 60 psi and then it starts to lower down to zero. I haven’t tried a mechanical gauge yet but will do this weekend and see what it reads
It is still relevant, but he may not get any responses except ours. Not trying to impersonate Mr. Obvious, but OP would probably benefit from starting a new thread....