2017 Yukon Dying

[WaxOnWaxOff]

Good Morning all, bear with me for a moment as I describe the journey here....

 

2017 Yukon Denali, 6.2L. So I had a collapsed lifter, which bent a pushrod. I went with a Texas speed replacement set. I tore everything down, there was no scarring or damage to anything that I could see when doing so, just the bent rod.

 

Anyway, everything was torn down to the block. Lifters replaced, new cam, new oil pump to be safe (parts list attached). There was no visible metal but I wanted to be sure. I also had it tuned because of the DOD delete, etc.

 

 

Everything fires up great, it starts and drives. After 5-10 minutes of running and driving, it's almost like the oil pressure starts to drop (it does seem to be low, but it is a 6.2) then suddenly the engine shuts off and cannot be started until you wait about 24 hours or so for it to cool down I guess. It's like it is too hard to turn over. But if you wait, it fires right up like nothing happened.

 

The only other symptom I can describe is that it almost feels as if the torque converter has too high of a stall, and is killing it that way. So....I replaced that too just in case. Prior to the engine issues there was some slight skipping/slipping on the transmission as this year has. So I figured why not.

 

I'm a bit at a loss, I figure something I did when replacing the cam and lifters caused it because it ran fine before doing everything. I'm just hoping someone smarter than me can help me diagnose what I messed up! The truck has 54k miles on it but is like a paperweight for now.

 

Let me know if more information is needed or there are more questions!

Edited November 29, 2025 by WaxOnWaxOff

[newdude]

Sounds like you've got bottom end bearings failing (starts to seize when it gets hot, it cools down and it runs again).  Either connecting rod(s) or main(s).

 

 

Edited November 29, 2025 by newdude

[WaxOnWaxOff]

2 hours ago, newdude said:

Sounds like you've got bottom end bearings failing (starts to seize when it gets hot, it cools down and it runs again).  Either connecting rod(s) or main(s).

 

 

Thanks for the suggestion. Does it make sense this ONLY would've happened after the topside work I did? It ran fine for probably 50ish miles with none of these symptoms, the ONLY thing I did was the topside work and then these symptoms started.

[newdude]

20 minutes ago, WaxOnWaxOff said:

Thanks for the suggestion. Does it make sense this ONLY would've happened after the topside work I did? It ran fine for probably 50ish miles with none of these symptoms, the ONLY thing I did was the topside work and then these symptoms started.

 

 

Possibly.  My thought here being metal made its way into the oiling paths and started to destroy bearings or is starving out bearings.  Or it was more than just a bent pushrod (valve hit piston and damaged rod bearing).  Could be a plugged oil galley in the crankshaft.  Or something happened during oil pump installation and the pump is no bueno and is starving oil to the engine (your theory on pressure dropping).  

Edited November 29, 2025 by newdude

[WaxOnWaxOff]

Appreciate the reply again. There was nothing that hit the piston and I did have the heads machined. Forgot to mention that. I did not put a new pickup tube on only the new pump itself. Was hoping to avoid debris recirculation if there was any and figured just would change the pump while it was all off.

 

I'm concerned it's a plugged galley. I just fired it up today to gather as much more data as possible.

 

60psi at cold start (55degrees out).

Engine up to temp, oil pressure slowly dropped to 20psi, held there for several minutes before falling to about 10psi and then the warnings came on.

I shut it down.

 

Unfortunately the battery was dead so couldn't try a recrank but it didn't seem to seize this time, or I haven't waited long enough.

 

I'm not a mechanic, unless YouTube mechanic counts, so I've just watched videos and I'm pretty meticulous and detailed (electrical engineer background).

 

I'm thinking of pulling the pan again and inspecting the pickup tube, possibly orring on the tube. I reused those after cleaning it out before.

[WaxOnWaxOff]

So, I waited a few hours while the battery charged back up and gathered data comparing it to the dashboard gauge, but also used the Torque Pro app to get actual PSIs (I think):

55psi at cold start (65 degrees out) on dash, 51.9 on Torque Pro (TP) ~1200RPM

Coolant at 120*, ~1100RPM, 25 on dash, 31.9 on TP

Fully warmed up, 220* Coolant, 745RPM, under 10 (maybe 8ish on dash, 13.7 on TP (before my 5 mile drive described below)

 

I gathered the following PSI's by revving to RPMs as well:

1000RPM - 15 on dash, 18.2 on TP

2000RPM - 30 on dash, 37.4 on TP

3000RPM - 50 on dash, 61.2 on TP

 

So, not sure this helps or further muddies the water. I drove the truck about 5 miles during this time as well. No odd sounds or anything the whole time, nothing locked up. I shut it down after letting it idle for a few minutes. Again the dash showed maybe 7-8PSI, and Torque Pro showed 13.7PSI at 746RPM. This much, at least, is consistent.

[WaxOnWaxOff]

Spoke too soon. It died today after some light driving during a test....

[newdude]

That oil pressure was not great hot.  Minimum is 22psi @ 1000rpm and at normal oil/coolant operating temps.  Idle these engines typically make 18-25psi hot idle.

 

Might be time for an out of vehicle teardown or at minimum pull the upper oil pan and start pulling some bearing caps and inspect for damaged bearings.  Definitely seems like there is an oiling issue going on, be it the new pump or a restriction or damage if metal made its way around from the original camshaft if it had a lobe ground down.  

Edited December 1, 2025 by newdude