waterhound
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2002 Tahoe 5.3 4wd w/top end low/no oil pressure and tapping
ok here goes..
My brother has a 2002 Tahoe LT 5.3 4wd with 78k on the truck.
While driving low pressure light came on and started hearing a tapping. He checked the oil dipstick it was in the bottom of normal range so he added 3/4 -7/8 of a quart. Light went off but tapping continued on passenger side on the motor around cylinder 2-4 part of the block.
He calls me, I assume he has a collapsed or gummed up lifter. We pick up oil, filter, motor flush, and carb cleaner. I planned on pulling valve covers and rockers to spray down to stuck lifter with cleaner, do motor flush and then change the oil.
I pulled the passenger valve cover to inspect rocker arms and push rods. I couldn't find any rockers with slack in them. (side note I didn't, but I should had rotated the crank by hand to see make sure) Then I hooked up ignition packs and started it up to watch rockers. No clacking/slapping or loose pushrods. BUT oil pressure seemed low, barely any oil comes up pushrods but oil did ooze out the tops of the pushrods and was even across 2,4,6,8. So, i went ahead and did the motor flush for 5 min and changed oil. Tapping still there.
I do have a video if someone tells me how to upload a video.
He took it to a shop that started looking it over. All cylinders are 140ish on compression and oil pressure at sensor location is 45psi with mechanical gauge. Computer shows missfire at cylinder 5 and 6. Passenger valve cover was off and mechanic started it up for me, now there is NO oil coming up pushrods.
Their conclusion is spun cam bearing.. That just seems unlikely to me with seeing as it only has 78k on the clock but possible I guess.
I have been trying to find oil flow diagrams to come up with with why we are loosing oil pressure. If you have one let me know.
Well I called the machine shop I know and talked with them about it. And called my uncle and cousin both career mechanics.
Machine shop tells me if it has spun a cam bearing, block is no good since GM doesnt make oversize bearing. Bummer. He does tell me about a TSB where the oil pump pickup tube o-rings get brittle with time and causes problem with pump getting oil to the top of the motor because of aeration it cant quite push to the right elevation in the motor.
My uncle tells me to drain oil and change filter. Fill with transmission fluid and run on idle for 30 min. He feels using the fluid as a detergent will help clean out any sludge in passages and lifters.
As I see it we have two problems
1. low to no oil pressure at rockers - loosing it between the sensor and rockers
2. tapping lifter or stuck roller in lifter as a result of no oil Or a spun cam bearing which is worst case scenario
Questions for all
1. Does anyone have a link or TSB for oil pump o-rings?
2. Any idea why we are losing oil pressure from sensor to lifters?
3. What the tapping is in? I can upload a video - I'll try once I post this
My plan is too
1. drain oil and pull pan to replace pump orings then fill with tranny fluid and run for 30min to see if it cleans it all out.
2. If that doesnt fix oil pressure or tapping, I pull the motor and take it to the shop.
Thanks for the help
ok here goes..
My brother has a 2002 Tahoe LT 5.3 4wd with 78k on the truck.
While driving low pressure light came on and started hearing a tapping. He checked the oil dipstick it was in the bottom of normal range so he added 3/4 -7/8 of a quart. Light went off but tapping continued on passenger side on the motor around cylinder 2-4 part of the block.
He calls me, I assume he has a collapsed or gummed up lifter. We pick up oil, filter, motor flush, and carb cleaner. I planned on pulling valve covers and rockers to spray down to stuck lifter with cleaner, do motor flush and then change the oil.
I pulled the passenger valve cover to inspect rocker arms and push rods. I couldn't find any rockers with slack in them. (side note I didn't, but I should had rotated the crank by hand to see make sure) Then I hooked up ignition packs and started it up to watch rockers. No clacking/slapping or loose pushrods. BUT oil pressure seemed low, barely any oil comes up pushrods but oil did ooze out the tops of the pushrods and was even across 2,4,6,8. So, i went ahead and did the motor flush for 5 min and changed oil. Tapping still there.
I do have a video if someone tells me how to upload a video.
He took it to a shop that started looking it over. All cylinders are 140ish on compression and oil pressure at sensor location is 45psi with mechanical gauge. Computer shows missfire at cylinder 5 and 6. Passenger valve cover was off and mechanic started it up for me, now there is NO oil coming up pushrods.
Their conclusion is spun cam bearing.. That just seems unlikely to me with seeing as it only has 78k on the clock but possible I guess.
I have been trying to find oil flow diagrams to come up with with why we are loosing oil pressure. If you have one let me know.
Well I called the machine shop I know and talked with them about it. And called my uncle and cousin both career mechanics.
Machine shop tells me if it has spun a cam bearing, block is no good since GM doesnt make oversize bearing. Bummer. He does tell me about a TSB where the oil pump pickup tube o-rings get brittle with time and causes problem with pump getting oil to the top of the motor because of aeration it cant quite push to the right elevation in the motor.
My uncle tells me to drain oil and change filter. Fill with transmission fluid and run on idle for 30 min. He feels using the fluid as a detergent will help clean out any sludge in passages and lifters.
As I see it we have two problems
1. low to no oil pressure at rockers - loosing it between the sensor and rockers
2. tapping lifter or stuck roller in lifter as a result of no oil Or a spun cam bearing which is worst case scenario
Questions for all
1. Does anyone have a link or TSB for oil pump o-rings?
2. Any idea why we are losing oil pressure from sensor to lifters?
3. What the tapping is in? I can upload a video - I'll try once I post this
My plan is too
1. drain oil and pull pan to replace pump orings then fill with tranny fluid and run for 30min to see if it cleans it all out.
2. If that doesnt fix oil pressure or tapping, I pull the motor and take it to the shop.
Thanks for the help
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