VerdeZ28

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

JakeFusion

iTrader: (7)

Symptom of bad oring is losing pressure. Of course as oil thins pressure will drop. What's it dropping to? What oil?

60 seems low at cold idle.

VerdeZ28

It's running mobile 1 10w30 synthetic. It's dropping to zero.

VerdeZ28

bump. not a good idea posting a thread at the start of super bowl

dr_whigham

iTrader: (49)

Sounds like an O-ring to me...

VerdeZ28

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.

dr_whigham

iTrader: (49)

I was going to suggest the mechanical gauge as well, but figured you'd know that.

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.

lmt0705

iTrader: (7)

Is The Motor Making Any Noise When The Pressure Drops?

VerdeZ28

not anything out of the usual like knocking or such.

VerdeZ28

What would the symptoms be if the oil pump relief valve is stuck open? Would it build pressure at all?

LLLosingit

iTrader: (4)

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.

VerdeZ28

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?

pimpin78transams

iTrader: (1)

The whole line doesn't get filled with oil. Air is trapped in the line and you can't get it out this is normal. The reading will come up almost as quick as your electronic one

VerdeZ28

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.

VerdeZ28

Also I am not sure if it matters but the oil pressure on the stock gauge cluster goes from 65 to 0 almost instantly. Not gradually.

dr_whigham

iTrader: (49)

Sounds like either your sending unit is bad out of the box, or the wires perhaps pulled out of the clip on the body harness side.

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.

VerdeZ28

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.