'04 Yukon 6.0L Oil Pressure Reading Lower Than it Used to

[Tonyrodz]

Thanks all!! I appreciate the advice. In the worst case, even if it does cost $700 or a little more, that would be about the cost of me registering a new vehicle. Our other taxes here aren't bad (western Colorado), but bend over when you want to register a vehicle.

I'll let you know how this turns out.

I bought out with about 90,000 on out and it had a great carfax with it. Apparently the former owner changed the oil often. I've changed every time the computer tells me to with synthetic and a quart of Lucas oil treatment.

I have a huge **** for an F150 with the 3.5L and the max tow package because it will add about 4,000 lbs to the max with this Yukon, but my bank account says to hold off

Be careful with the fords--they make your hair fall out--teeth fall out---go blind etc lol.

 

[wjburken]

Be careful with the fords--they make your hair fall out--teeth fall out---go blind etc lol.

Hey, I have a F150!
I still have all my teeth!
Hair..........Not so much.
Oh........I also wear glasses.

 

[JonnyTahoe]

Don't take it to the shop that charges 2 hours for spark plug wires!

The O-ring replacement is one of those "4-hour jobs to replace a 20-cent part" kinda deals. You have to drop the oil pan, which is pretty straightforward on a 2WD but more complicated on a 4WD/AWD.

You mean 10+ hours. It takes four hours just to clean the oil pan and related parts. I did this Job two years ago on my 4X4 Tahoe maybe if you have access to a shop with a lift but to do the job on your back in the garage or outside four hours is never going to happen.

 

[JonnyTahoe]

Danjy3737 - Yes!!! It's something like 6 hours labor to replace the plugs and another 2 for the wires. That's what shops get by 'the book' I hadn't done anything on a car since I was 19 and I'm now 62 but I had the whole job done by lunch.

They were looking up the wrong vehicle. Must of been one with the engine in sideways.

 

[Mudsport96]

wjburken - thank you very much. I'll try that this weekend. What will happen to the extra oil I put in? I assume I should drain it back out after the test?

Also - if a bad o-ring is the problem - any guess on how much that repair might be? My wife and I have already decided that with 200,000 on it, we're not going to sink a lot more money into it.

Thanks!!!

If it is the oring, 200k is well worth the repair if the truck is otherwise solid. I did the oring on the Silverado my father in law gave my daughter. The truck has 400k on it and after the repair she carries 40psi highway and 20ish idle.
It's just a bit difficult without a lift, but I did it over 3 days (only a couple hours a day and 1 day soaking pan in solvent) last winter. On a decent day i probably could have done it in 6 hours but it was 10 degrees in a non insulated non heated garage on the floor. Had to take warmup breaks and short days.

 

[mikeyss]

I'm pretty neutral between GM and Ford, but I will not knock the 3.5 Ecoboost..that motor is powerful and isn't a bad engine. There's a million of them running around these days, lol

 

[ScottTheEngineer]

My 6.0 had a failed oil pressure relief valve in the oil pan every so often the pressure dropped to 0psi. They had to drop the front diff to get to the oil pan to replace it. $1500
I had them replace the pick tube o-ring also. $2.50
I was quoted an additional 2,000 for replacing the oil pump.
I paid because I don't work on cars when its its below 40deg.
My average pressure after the replacement dropped to 40 psi where before it was 60 constant.
My understanding is that there are 2 pressure relief valves. One in the pump, one in the pan. The pressure sending unit is on top of the engine in the rear.
Also, if you have AFM lifters don't use the Lucas.

 

[cam3439]

Have you added any additives or cleaners to the oil? A clogged/failing oil filter (rare but it happens) can give similar oil pressure results.

 

[iamdub]

My 6.0 had a failed oil pressure relief valve in the oil pan every so often the pressure dropped to 0psi. They had to drop the front diff to get to the oil pan to replace it. $1500
I had them replace the pick tube o-ring also. $2.50
I was quoted an additional 2,000 for replacing the oil pump.
I paid because I don't work on cars when its its below 40deg.
My average pressure after the replacement dropped to 40 psi where before it was 60 constant.
My understanding is that there are 2 pressure relief valves. One in the pump, one in the pan. The pressure sending unit is on top of the engine in the rear.
Also, if you have AFM lifters don't use the Lucas.

Gen3 engine doesn't have AFM, so no pressure relief valve in the oil pan. On all LS engines, the oil pump has a spring-loaded valve to bleed off pressurized oil to limit the maximum developed pressure within the engine oil system as a whole.

On the Gen4 engines with AFM, the relief valve in the oil pan is a limiter for maximum oil pressure within the AFM system itself. Since the AFM system operates by varying oil pressure to lock and unlock the lifters, its pressure relief circuit has to be isolated from the engine's primary oil circuit. Otherwise, the oil pressure gauge would swing drastically as AFM engages and disengages.

 

[georgebuhr]

Definitely check the oring. Replaced mine at 200,000, at 350,000 now and still going strong, no oil pump necessary. This engine is solid as a rock otherwise.