Oil pressure issue cross posted tech question

[rich]

Some may remember awhile back I posted I was having an issue with my oil pressure. I have a fresh 5.0 Hybrid built with a bored out 1980 euro "S" M28/11 block, heads and CIS. The engine has about 15,000 miles on it now.

I was traveling at freeway speed when I noticed my pressure drop from + 80psi to 40ish. The pressure popped back up then back down. I got off the freeway. When I stabbed the clutch to down shift on the ramp the pressure fell off with the drop in throttle. Long story again but I ended up flying home and traveling 600 miles to get the car with my trailer.

I had the oil tested and posted the results here awhile back now. No metal or anti freeze in the oil and the results were normal. This leads me to believe I do not have a spun bearing or any other friction failure or issue.

I thought I may have a loose pickup tube. I just dropped the pan to check. The pickup tube is fine and all looks normal. I discovered I had a kind of sludge in the bottom of the pan. For a 15,000 mile engine this didn't look normal. The sludge is thicker than the 20/50 Castrol GTX I usually run.

As I was cleaning out the pan looking for anything that may be out of the ordinary I discovered a sand/flake like carbon in the sludge. It's hard like a grain of sand unitl you roll it between your fingers. Then it crumbles.

Q.) What would cause this carbon in the bottom of the pan? The inside of the block looks perfect and clean.

Q.) Is it likely this carbon is getting into the pressure relief valve causing it to stick and drop pressure?

Q.) Where does the oil go when it leaves the pump?
1) Through the filter?
2) Through the pressure releif valve then to the filter?

[Maleficio]

I would switch oils now. Don't make a move until you verify that your oil is not just worn out. Royal Purple is great for sustaining viscosity for a long time. So is Redline. Also, your oil filter may have something to do with it, too. It has a bypass valve in it that responds to over-pressurizing due to being clogged, and allows oil to flow around the media to feed the engine (while not being filtered). Yours may be defective in some way.

[rich]

Thanks for the reply. I have used Castrol GTX since Kendall went out of business. I have never seen this before. Maybe there was some reformulation in the past couple years.

Maybe time for Brad Penn.

I'm pulling the pressure relief valve next. I'm thinking the carbon caused the bypass to stick.

Q.) What happens when the pressure relief valve sticks? Pressure drop? What? How much of a drop?

[Maleficio]

Originally Posted by rich

Thanks for the reply. I have used Castrol GTX since Kendall went out of business. I have never seen this before. Maybe there was some reformulation in the past couple years.

Maybe time for Brad Penn.

I'm pulling the pressure relief valve next. I'm thinking the carbon caused the bypass to stick.

Q.) What happens when the pressure relief valve sticks? Pressure drop? What? How much of a drop?

That crumbly crud you found is interesting. I wonder if it's old gasket material?

[rich]

No, I thought about that also but it's definately carbon.

I cross posted over on the list and a oil curcuit diagram was posted.

kind of confirms the chain of events. Because of the limited space in my engine bay I eliminated the oil cooler and moved my oil pressure sender up to the top cooling line location. I gutted the cooling line T Stat so it's just a hollow chamber where the cooling lines attach.

Based on the diagram If # 3 valve is hung open the oil circulates back to the pump and not to the second pressure valve, cooler line location or filter. If the carbon/sludge is sent up through the pump it's the first place the it ends up. Hmmm...

[rich]

Originally Posted by rich

No, I thought about that also but it's definately carbon.

I cross posted over on the list and a oil curcuit diagram was posted.

kind of confirms the chain of events. Because of the limited space in my engine bay I eliminated the oil cooler and moved my oil pressure sender up to the top cooling line location. I gutted the cooling line T Stat so it's just a hollow chamber where the cooling lines attach.

Based on the diagram If # 3 valve is hung open the oil circulates back to the pump and not to the second pressure valve, cooler line location or filter. If the carbon/sludge is sent up through the pump it's the first place the it ends up. Hmmm...

Forgot the diagram.

[Maleficio]

I'm reading that thread, too.

At this point in the game, I think you are nuking this gripe.

I would change the oil to a premium syn like Royal Purple, and install a fresh oil filter, and see what happens.

Not trying to reduce your thought process, it's fascinating, but you've got to rule out the basics first.

Castrol GTX is known for losing most of it's viscosity retention at the 800 mile mark. Not sure why. GTX is great for sealing the rings, but it is also known for what's called "Castrol Tan", the varnish found in engines that run GTX. It's not sludge, just varnish, and GTX causes it. The only cure for it is not using GTX.

[stepson]

Rich,
Did you have any part of your intake soda blasted?

Richard M's engine rebuild - Rennlist Discussion Forums

[rich]

The valve covers were powder coated but they were maked off so only the outer exposed surface was coated. I didn't have these done myself. I ended up aquiring them with a parts engine and decided to use them They were really clean. Anyway, the stuff I found in the pan was hard enough to feel like media but crumbled when rolled between your fingers.

[dcrasta]

I read your post on Renns .

I think you oil is overheating. You need the oil cooler man. Check the post I left on Renns.

Best of luck

Hugh

[rich]

Thanks Hugh and all. I added the dino GTX today because it was cheap. I used a Mahle filter because it was all I could get in town today. Not that Mahle is a bad choice. I just usually use Mann. I fired it up and let it idle at 150 psi. I drove it about 10 miles. There was a fluxuation but only to 60 psi when I lugged the engine once. after warm up the pressure dropped around 90 psi for a short while while I was driving at 55 mph. So far I think it's ok.

I'm planning on draining the GTX I just put in and getting synth. I'm going to start a cooler thread and let this one die for now.