DirtyRyada

On my LS1 that I the just installed when motor gets hot to about 210°F my psi drops to about 5psi. On cold starts it's at 40-50psi then drops to about 25-35 psi at around 190-200°F. When I bought the motor it was running in another car. I didn't check oil pressure gauge but the valvetrain sounded dry. The rockers weren't loose so im believing lifters and cam are healthy. Motor runs strong no hesitation. When I got it running on my T/A I used MOB1 5W30 and oil pressure was fine on cold starts but once temperature is at 210°F oil psi is at 5psi at around 600-700rpm idle. All this led me to replace the oil pump. Installed a brand new Melling M295 oil pump with new O-Ring (used the green tight O-ring). Started the car oil pressure was better at cold starts either with 5w30 (MOB1) or 10w30(Valvoline VR1) l once motor gets to 210°F oil psi is at 5.

I believe 3 things are the culprit. 1st is that I pinched the O-ring that when oil gets hot and thin, the oil isn't being pumped through due to losing pressure through the O-Ring. 2nd is that the motor has 200500miles on it that the bearings are worn out that when the motor reaches 210°F metal expands which is bearing clearance due to the oil thinning out there is loss of pressure through the bearing clearance. 3rd culprit is that my oil passages and oil pick up tube are clogged up.

Oil pressure sending unit is brand new before even putting the motor in I replaced it. I want to do a motor flush since its a thin substance to test if the O-ring is pinched and clean the oil passages along with the pick up tube. Since I'm believing that when the motor is cold started with that thing substance the oil pressure should be low but also culprit the bearing clearance and that is where im stuck at.

I don't know how else to test it since I have no mechanical gauge and dont want to tear into the motor again. I know for a fact oil pressure is low because the lifters get somewhat dry and start chattering when motor reaches 210°F. Im just starting to learn about internals and how parts and such work in a detailed way like bearing clearance and lift duration etc.

My temporary solutions that I haven't tried is running redline oil 10w50. Adding a 16row oil cooler, adding a lower temp thermostat and a tune the high fan to kick on when motor gets to 200°F in order to maintain temperature down and keep oil from thinning out. Oil pressure when cruising on the freeway about 50mph+ is about 29-30psi at 1-1.5krpms and moves to 40-45psi at around 2krpms and temperature is around 190-200°F.

This issue is burning a hole in my brain since im I just starting to learn more deeply into motors. I know the oil pressure sending units aren't accurate but thats I can depend on right now. I thought about just rebuilding and machining the block etc, but I want to figure out what exactly is the culprit. I want to know how to test my theories without having to tear into the motor but if there is no other way then I'll do it.

Jays_SSZ28

iTrader: (2)

The bearings are worn. If it has a new oil pump and 5psi hot. And 205,000 miles. Worn out engine IMO.

01CamaroSSTx

iTrader: (3)

Did you buy this engine and just install it?

01CamaroSSTx

iTrader: (3)

Remember that the oil feeds the cam and lifters before the rods and mains. Are you sure your not sucking air and its causing lower than normal oil pressure? Could it be that the old o-ring was worn out and causing lower than normal oil pressure and you installed a new pump and used the wrong o-ring and its now causing lower than normal oil pressure. You should use the proper o-ring for the pick-up tube as installing the wrong one could cause oil pressure issues especially if its too fat and gets pinched. On the LS1 its the blue o-ring and on the Melling pump I just installed on my LS370 build it said to use the black one for the LS1 pick-up tube.

Tyler Dietzenbach

iTrader: (5)

I agree. It sounds like you used the wrong o ring. The other "solutions"you mentioned seem like a bad idea. Better fix the problem the right way

G Atsma

If the pickup tube has a groove rolled into it near the end, use the fat O-ring. No groove, (straight) use the thinner one.

DirtyRyada

When I replaced the o-ring I got 2. A black one that fitted to loose and a green one which fitted perfect. I put the green o-ring. The one I took off originally was black o-ring. When I bought the engine all I did was replace all the seals. Didn't even think of cleaning the pick up tube.

G Atsma

Which pickup tube do you have? Grooved or smooth?

dreadpirateroberts

iTrader: (1)

you got the aftermarket rings. yeesh.


it does sound like you put in the thicker one, though, when it needed the thinner one. also sounds like someone before you changed the pump and/or o-ring before. IIRC the GM o-rings are all either orange or blue. listen to what G Atsma says.

DirtyRyada

Yeah that is what confuses me. It occurred to me while changing out the pump someone already did some work around the pump. Didn't really check if the pump is OEM. I ordered myself a brand new OEM GM pick up tube with o-ring on it. Going to install and hope for the best.

My idea is to jack the car up, put a jack under the pan while lifting the motor enough to loosen motor mount bolts. Engine hoist the motor and lift as much as possible, remove strut bolts and 4 rear k-member bolts. Loosen the front k member bolts and remove oil pan. I'm hoping just lifting motor with hoist is good enough clearance to remove oil pan without having to touch the k-member. Can anyone confirm this?

01CamaroSSTx

iTrader: (3)

Set the back tires on some blocks or if you have some other rims with tires use that. Jack the car up using floor jacks and get the car up high enough off the ground to work. Use the engine hoist to support the engine by using some chains and bolt then to the front of the cylinder heads. Disconnect the sway bar and put a floor jack under the k-member. Now remove the through bolts to the engine mounts and the six bolts for the k-member. Now using the floor jack slowly lower the k-member down until you get the clearance you need to drop the pan.

01CamaroSSTx

iTrader: (3)

I forgot to mention that you may need to disconnect the brake lines for the front brakes to avoid damage to them.

DirtyRyada

**O-Ring I used when doing the oil pump was black**
​​​​​​Just dropped the pan a bit and wiggled pick up tube out the way without undoing k-member. O-ring wasn't pinched or damaged so to my understanding motor is shot, bearing clearance is to excessive from what it looks like.