Confirmation snowdrifter, above is correct with machanical at the block outlet port closest to pump, and sending unit location value is with sensor. However, this is the values after replumbing the oil cooler lines and removing the machanical gauge which was on the bypass plate. When all 3 gauges, 2 machanical and 1 sensor readings at hot idle 10, 7, an 7. Both post filter machanical gauge at cooler bypass and sensor at sending unit location were identical. So I deleted and replumbed cooler back up. I was attempting to eliminate possible causes or variable in this puzzle. Sorry for the long winded However, I'm attempting to be precise and clear with the data and information that I have. Thanks again everyone.
10 psi when warm
- Thread starter JohnnyA
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Thanks Rockola1971 I will look into the kits. I always wanted to rebuild a engine just not this one... i have to roll with it. I'm at a place that the owner is a engineer designer and loves his calipers.... very precise. I was thinking pull the engine, replace with a tow cam (just reading and I'm ignorant to all this), change cam and main bearing, and beef up tyranny for tow.
SnowDrifter
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Before we start looking at a rebuild, I'd like to do some diagnostics.
Here's what I'm trying to get to:
Oil pressure vs. rpm: 10psi is well below bypass valve threshold in the oil pump. I would expect the pressure to raise linearly with engine RPM. If it does not, that would suggest a pickup tube problem (seal, cracked, clogged) or an oil pump problem (bypass, seal to block).
The ΔP between the oil pump and sending unit could be caused by a couple things
- An obstruction of some sort in that line. Piece of a shop rag or something
- Dislodged 'barbell' (unlikely, but here we are)
- Faulty oil pressure bypass valve. These engines have the valve located on the engine side, not in the oil filter. There are also kits to 'delete' this such that oil is forced through the filter at any cost. If the oil filter is low flowing or collapses under pressure, then you'd see a pressure drop from this as a result.
Here's what I'm trying to get to:
Oil pressure vs. rpm: 10psi is well below bypass valve threshold in the oil pump. I would expect the pressure to raise linearly with engine RPM. If it does not, that would suggest a pickup tube problem (seal, cracked, clogged) or an oil pump problem (bypass, seal to block).
The ΔP between the oil pump and sending unit could be caused by a couple things
- An obstruction of some sort in that line. Piece of a shop rag or something
- Dislodged 'barbell' (unlikely, but here we are)
- Faulty oil pressure bypass valve. These engines have the valve located on the engine side, not in the oil filter. There are also kits to 'delete' this such that oil is forced through the filter at any cost. If the oil filter is low flowing or collapses under pressure, then you'd see a pressure drop from this as a result.
Tonyrodz
Resident Resident
Do you have a diagram or pic of the oil pressure bypass valve? I'm having a very similar issue with my Express van--so I've been closely following this thread.
SnowDrifter
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Not a good one. But it's accessible by taking off the oil filter. It's a circular press fit doohickie
Of note: that's only for our 'older' engines without cylinder deactivation. The newer ones (07+) have a different system that bleeds oil back into the sump during 4 cylinder mode.
@SnowDrifter You stated it was pressed in, so my assumption would be that it can't be replaced while the oil pan is installed?
rockola1971
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The oddest thing is that at 7PSI oil pressure I would expect to hear some valvetrain noise anything much above idle rpm if not at idle.
OP to save down time you can buy a core 6.0L and rebuild it if thats the path you take. I would not even think about towing with engine thats running just 7PSI. That is just begging to throw a rod through the block.
OP to save down time you can buy a core 6.0L and rebuild it if thats the path you take. I would not even think about towing with engine thats running just 7PSI. That is just begging to throw a rod through the block.
SnowDrifter
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Awesome. Thank you.
