No oil at cyl heads

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  #1  
Old 10-17-08, 05:27 AM
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No oil at cyl heads

1994 Chev Silverado, 5.7L, auto, 2wd, ac, 98k miles.

This truck was run low on engine oil. Starts and runs fine but once warm starts lifter noise. Cylinder heads are getting no oil on either side. I suspect a spun cam bushing? Oil pressure at idle, semi-warm, is 40 psi. Engine oil is black and tar-like. It was reported the oil pressure was fluctuating wildly prior to shutting the engine off. The driver also stated the truck began to run very badly before he shut it down.....valves sticking?

I'm just trying to get a few ideas before I travel 1,500 miles to look at the truck. This truck belongs to my gf but her son is (was) the driver. I had a friend look at it but his mechanical experience is somewhat limited although he confirmed the cylinder heads are dry.

Thanks for the assistance.
 
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Old 10-17-08, 08:55 AM
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I would say the cam bushing would be a pretty good guess. I would add the poor running would be the lifters bled down and the valves not opening. All that could be attributed to a spun bushing. With no oil to the stems, sticking could be added to the list.

I would get new filter and oil in it, but I would expect upper end problems, needing a tear down. If you go that route, I would think about doing the entire engine. It's not overly high mileage but it'll depend a lot on what the lower end looks like. The cylinders/rings may have taken a lot of damage with the low oil - then the crank, etc. It may or may not be salvageable.
 
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Old 10-17-08, 04:30 PM
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Thanks for confirming what I thought. You're right about the lower end...it looks like the rear main bearing is fed by the rear cam bushing. It's a nice looking truck and I was looking forward to getting it here but it's not cost effective now. $2k for towing myself and another $1500 or so for a long block/components.
 
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Old 10-17-08, 04:40 PM
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Thanks for confirming what I thought. You're right about the lower end...it looks like the rear main bearing is fed by the rear cam bushing. It's a nice looking truck and I was looking forward to getting it here but it's not cost effective now. $2k for towing myself and another $1500 or so for a long block/components.
 
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Old 10-17-08, 04:41 PM
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The Silverados have an oil shut down sending unit under the distributor, so it could have not had enough oil to keep the fuel pump pumping causing the rough running, to. But if the oil is black and gummy it could be the passageways are gummed up as well.
I agree with the other analyzes as well.
 
  #6  
Old 10-30-08, 10:01 AM
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no oil the heads

I only saw this once but if the oil looks like you describe its a possibility. I had one that the oil passages leading away from the rear cam brng were plugged. In any case its probably a tear down. RW
 
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Old 11-23-08, 03:13 PM
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Originally Posted by Fleetman View Post
1994 Chev Silverado, 5.7L, auto, 2wd, ac, 98k miles.

This truck was run low on engine oil. Starts and runs fine but once warm starts lifter noise. Cylinder heads are getting no oil on either side. I suspect a spun cam bushing? Oil pressure at idle, semi-warm, is 40 psi. Engine oil is black and tar-like. It was reported the oil pressure was fluctuating wildly prior to shutting the engine off. The driver also stated the truck began to run very badly before he shut it down.....valves sticking?

I'm just trying to get a few ideas before I travel 1,500 miles to look at the truck. This truck belongs to my gf but her son is (was) the driver. I had a friend look at it but his mechanical experience is somewhat limited although he confirmed the cylinder heads are dry.

Thanks for the assistance.
Sounds like a bad oil pump to me. Also sounds like someone needs to give advise on auto maintenance. Oil is the lifeblood of the engine. The pressure, correct me if I am wrong, comes from the rear cam bearing where the oil pump drives off the dist. shaft which is driven by the cam. Pick-up screen may be partially blocked due to lack of maintenance. I would drop the pan and check the pump. While there, spot check a couple of rod bearings and mains. Especially the rear, front and center mains. You can remove the dist. and drive the pump with a drill motor and check the pushrods and guage for oil supply and pressure prior to pulling the pan if you like. Luck!!
 
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