2003 yukon 5.3l flex fuel lifter noise and code misfire PO300 235,000 miles

[Summajet]

Motor has 235,000 miles, 5.3l flex fuel
I have noticed I have loud lifter noise coming from the passenger side of yukon.
i am not sure if it has a LS motor. I thought I had read a Ls motor requires removing the heads?
I am looking for suggestions for diagnosing?

Would a failing/collapsed lifter cause code PO300 (random/multiple cylinder misfire detected)????
Here is what I was thinking to check,

1. compression check each of the 8 cylinders. What should compression for a un-modified 5.3l flex fuel?

2. remove valve covers on each side and check for broken valve springs, loose rocker arms, collapsed lifters, and bent push rods.

3. If there is a collapsed lifter or bent push rods is this the process for removal and repair,

Remove valve covers
Remove the intake and leave the injectors on the intake?
Remove the valley pan
remove rocker arms
use push rod tool and tap out the push rod
remove lifters (2 per cylinder and 16 total)
purchase a intake gasket-felpro?
valley pan gasket-felpro?
brand preferred for lifters, and push rods?

When installing the push rods, lifters and rockers arms are there any special tools needed to remove or install the parts mentioned above?

Was going to use ac delco parts and do repair. I really appreciate any advice anyone can offer to help me make the repair and save money

 

[Summajet]

From what I read online last night I will need to remove the LS heads to access the lifters.

 

[Kraig]

You will need to remove the heads if you need to change lifters, it do the diagnostics you described first—remove the valve covers and check for play in any other rockets, crank it over and see that all rockers are moving, etc.
What are your oil change intervals, how long since last oil change, what oil and filter, and did this noise start suddenly after the last oil change or some other event? Also, make sure you aren’t actually experiencing an exhaust leak at the manifold/head, which can sound like a lifter ticking.

 

[Kraig]

Oh, and the only ‘special’ tool you’ll need is to remove the fuel line.
And you don’t need to remove the valley pan to change the lifters, but you might want to and change the knock sensors while you’re in there. AC Delco parts made it this far—don’t cheap out on parts store knock sensors or you’ll be doing it again. Change the knock sensor harness at the same time it’s cheap insurance.

 

[Summajet]

If I understand correctly, to replace the lifters I only need to remove the two heads. There are no bolts on the valley pan that are bolted into the heads? I also will check with the stethoscope sounds for a exhaust leak at the manifold.
Oil was changed two months ago. Truck driven about 600 miles a month.
I think I used 10w30 oil and definitely used an Ac Delco oil filter.

Between compression and removing valve covers should help to diagnose it quickly.
When doing the compression check I would,
1. remove all 8 spark plugs
2. compression check each cylinder on driver side
3. compression check each cylinder side on passenger side.
4. compare compression readings and should not differ more than 10% per each cylinder reading?

When installing heads does this sound right,

1. check heads for square and no warping.
2. new heads bolts
3. new head gaskets any particular brand?
4. any procedure or tips in making sure the heads sit correctly on the block?
read something mentions an angle at 90 degrees?
5. Should I worry that the needle bearings could have failed or fallen out in the lower block?
Thanks,

 

[Kraig]

The valley cover bolts directly to the block, no connection to the heads.
The heads have locating dowels to properly align.
The head torque sequence has you torque to a certain number of foot pounds, then you use a torque angle gauge to get to the final torque, but some daring individuals like myself might eyeball it.

 

[Schemmer]

I’m about to replace my lifters and I have the exact same engine. Since you have the flex fuel engine, I’d recommend getting all of the AC Delco flex fuel gaskets if you ever run E85. I got all of my gaskets from rockauto.com. I’d also recommend ARP head bolts. Since the head bolts are torque to yield, they stretch. So don’t reuse your old ones. If you’re using AC Delco head bolts, you’ll need a torque wrench and a degree tool bc you tighten to a certain torque then another set degrees of a turn. The most important thing when doing this is that there is a torque sequence. You’ll need to look up the specs on all of that bc I don’t have it handy but I’ll find something and pm it to you.

 

[Summajet]

How long before you start your lifter replacement? Might by chance you take pictures to help me and others on the forum.
Had read that you torque heads in 4 steps and angles also.
Also when replacing lifter do the valve seals, and new lifter trays.

 

[mattt]

Check your oil first. Does it not look normal? If not, you may have water in it from a cracked head or compromised head gasket. One day last year out of the blue my 04 5.3 flex fuel engine started with lifter clanking. I tracked it down to water in the oil causing all the issues. Drained oil, changed twice, and fixed the leaky head. No more lifter clacking and I did not replace them. YMMV....

 

[Summajet]

I will check that. Where was your head leaking at? On drivers side or passengers side and did you remove head to fix the leaking head gasket?

After 6 weeks I finally got to replace my water pump and timing chain on my 00 mercury mountaineer. Bearing/seal failure on water pump. Broke one of the bolts and removed timing cover. Did timing chain as it had too much deflection.. Anyways one done and time to get to diagnosing the yukon.
Asked mechanic at shop and said it is not too hard to do it when removing heads. Important to torque new head bolts in 4 steps. I will look at the oil and water as if head gasket is failing there will be one of the other mixed in.

I am not sure if the previous owners regiment of maintenance. It has 235,000 miles and am sure the timing chain has more than the acceptable chain deflection.

I do not know what date the Water pump was changed. We have owned it since June of 2015 at 199,500 miles.

Once I check compression and change oil I'll proceed from there.