2002 Tahoe 5.3 4wd w/top end low/no oil pressure and tapping

[Waterhound]

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

 

[steveo346]

Any luck? Ive never heard of someone running tranny fluid in their motor, what exactly does that do?

 

[Waterhound]

No progress yet. I haven't been able to work on it because of all the rain. The transmission fluid acts as a lubricant and as a detergent to clean out the engine.

 

[afpj]

http://www.tahoeyukonforum.com/threads/no-oil-pressure-at-start-up-2001-tahoe.67664/

It's a sticky at top this section.

 

[Waterhound]

afpj,
I read the sticky no oil pressure problems and plan on changing the oil ring tomorrow. The difference in my case - I have 45 psi by manual gauge at the oil pressure sender unit location. But I don't have pressure past that.

 

[Waterhound]

Figured out the problem.. I found with pan off..

Number 6 piston knocking the crankshaft

 

[afpj]

Figured out the problem.. I found with pan off..

Number 6 piston knocking the crankshaft

Please explain...connecting rod broken?

 

[ccapehartusarmyINF.(ret)]

okay so with mine it clatters for a few seconds when you start it up cold and my oil pressure stays around 20 psi at idle and 35 40 at speed and some times at idle untill it warms up for a about 10 min when its at 20 PSI it slowly drops but after it warms up for 10 minutes or so it never drops below 30 psi

 

[Waterhound]

I loaded a video to youtube to show the problem

The first part of the video is the engine running with valve cover off on pass side. The next part is from under the truck looking up after oil pan is removed.

The #6 piston rear wrist pin is coming in contact with crankshaft counterweight. It looks like the connecting rod got bent somehow. We will be doing an engine swap in the next week or two to get him back on the road. Once that is done I will bring the motor home and disassemble it to see what failed.

Then I will be making a plan for my first home rebuild. I have a 2005 tahoe with 165 on the clock and can install the rebuild when its ready. I will spend the winter saving and buying parts for the rebuild. Im a pretty meticulous person and feel confident I have the patience to rebuild it with a good machine shop along the process.

Videos from Petes garage are crazy good step by step info top to bottom. https://www.youtube.com/user/CoolCarsHotGuitars

 

[ccapehartusarmyINF.(ret)]

okay the wrist pin or piston pin is what holds the piston head on the connecting rod the only thing that could come in contact is the skirt
did you turn the engine over to see were Bottom dead center on that piston