2017 Yukon Denali Dies after Lifter Replacement

[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! Thanks in advance!

 

[Joseph Garcia]

Welcome to the Forum from NH.

Lots of knowledgeable folks here who freely share their knowledge, experiences, and perspectives. Knowledge is power.

I hope that you will become a participating member in the Forum's discussions.

Pics of the truck, please.

I cannot personally assist you with your issue, but other members of this Forum much more knowledgeable than me in this area will chime in.

 

[strutaeng]

I'm not familiar with direct injection (DI) engines, but i would think you go through the same checks as port injected engines: are you losing spark, fuel or something electrical/sensor data related?

No CEL codes? I would imagine something has to be thrown with all the logics built in on these modern engines controls.

What is the oil pressure when it stalls? You say it's hard crank after it stalls? Have you tried taking out the spark plugs and spinning it by hand with a ratchet?

As far as the bent rod: did you check for any potential damage to the associated cylinder valves?

Hopefully someone with more knowledge can chime in...

 

[WaxOnWaxOff]

Hello,

Thanks for the reply. No CEL's. 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 when I changed the pump, 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 just fired it up today to gather as much more data as possible (using the dashboard gauge):

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. It did NOT stall out at this time, last time it seemed to do that around the 10 psi last time if I remember.

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 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 8) 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 8PSI, and Torque Pro showed 13.7PSI at 746RPM. This much, at least, is consistent.

 

[Joseph Garcia]

Well below 20 psi hot oil pressure is simply no good.

You state no codes. Are you using a quality bi-directional scanner, one that reads the deeper codes?

So, you did not change the oil pickup tube O-ring? That could be an issue, and there is a simple test for that.

Is it possible that the VLOM is not fully torqued down, thus allowing oil to seep out and back into the block, thus reducing pressure?

Just trying to think of areas of the motor/block where you've been/touched on this project.

 

[WaxOnWaxOff]

Whelp, I lied. It stalled today after the drive and won't crank again.

Yes, bi directional scanner. Same one I use for my Ford vehicles and can read all the modules.

 

[strutaeng]

Ok, that provides better information, thanks.

Have you dropped the pan to inspect for any glitter? How about cutting open the oil filter? And checking the fuel pressure with a mechanical guage?

Unfortunately, it sounds like your bearings may be worn out based on those symptoms.

I had the 4.3 on my 99 Silverado develop low oil pressure: check guages light would come on, and oil pressure on the cluster would dip below the first tick mark. Glitter on the oil change, but otherwise ran good. I didn't have money for a rebuild, so I changed to 50 wt. oil and ran it for another 10-12k miles. Oil pressure increased from 5 psi to 8 psi at hot idle. I eventually pulled the engine and all the bearings had severe wear and scoring. Clearances were around the 5-6 thousands checking with a mic/dial bore guage.

Could your engine oil pressure be dropping so low that the engine stalls? That would be a really bad situation.

 

[Fless]

Need to determine if this no crank is electrical, or if it's physical. When it won't turn over with the starter, can it be turned over by hand with a large ratchet and socket?

 

[WaxOnWaxOff]

Need to determine if this no crank is electrical, or if it's physical. When it won't turn over with the starter, can it be turned over by hand with a large ratchet and socket?

Brand new starter yesterday. It can turn but it's a very tough turn over.

It's squealing pretty loud now when it started back up so I'm sure it's something internal.

 

[bazec]

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.

View attachment 473021

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! Thanks in advance!

I had issue with low oils pressure when up to temp 14 Tahoe sometimes getting scary low try changing oil filters mine now stays around 30psi
its a cheap easy fix if it helps

 

[gwoods71]

Well I am watching this, as I just did a DOD delete and now fighting an electrical short (I think).

Are you sure you didn't wipe out a cylinder? Ours bent/broke a pushrod when picking up the kids from school and i told her to limp it home 10 miles. It ended up being out .004" on #4 cylinder even though it LOOKED ok.