1999 Tahoe/Lifter or Exhaust Manifold?

[Eman85]

My 1998 has been doing tat for about 12 years now, also has piston slap when it's cold. Runs just fine and just keeps on going. Bought a 99 Yukon and it did it a little. Put some Marvel Mystery oil in it and it doesn't do it any more. Be happy it's a old design SBC, if it was an LS lifter tick is bad news.

 

[CTUBS8732]

Check your manifold bolts and see if one has broken or is loose.

What is your oil pressure like at start-up? Does it come straight up and level off right away or does it build?

Might put a can of Seafoam in your oil, run it for 50 miles or so and change the oil and filter out with fresh synthetic and see what happens.

I did this and had a few loose ones and 2 broken ones. Replaced the ones I could and used a repair clamp on the broken ones.

 

[newtahoeguy87]

Check your manifold bolts and see if one has broken or is loose.

What is your oil pressure like at start-up? Does it come straight up and level off right away or does it build?

Might put a can of Seafoam in your oil, run it for 50 miles or so and change the oil and filter out with fresh synthetic and see what happens.

Hey @wjburken,
Thank you for the sea foam suggestion. After reading the comments and comparing my ticking sound, I was leaning towards a lifter issue over the manifold leaks. I put half a can of sea foam into my oil and ran it for 215 miles (this took about a week). I noticed no real improvement in the ticking sound the entire week but aimed for the 200 mile mark. Yesterday I took it in for an oil change and initially the ticking sound was still present but much softer. Drove about 15 miles and went home.
Woke up this morning and the sound is gone. Truck sat overnight for about 15hours which normally would guarantee the ticking sound for a short period but this time did not. Sound has not returned so far.

Any recommendations on if I should run the other half can of seafoam through the oil to “extra clean” or is there risk of causing damage if I do?

Thanks again to all for the guidance and support. (I purchased a stethoscope as well and just waiting on delivery)

 

[wjburken]

Hey @wjburken,
Thank you for the sea foam suggestion. After reading the comments and comparing my ticking sound, I was leaning towards a lifter issue over the manifold leaks. I put half a can of sea foam into my oil and ran it for 215 miles (this took about a week). I noticed no real improvement in the ticking sound the entire week but aimed for the 200 mile mark. Yesterday I took it in for an oil change and initially the ticking sound was still present but much softer. Drove about 15 miles and went home.
Woke up this morning and the sound is gone. Truck sat overnight for about 15hours which normally would guarantee the ticking sound for a short period but this time did not. Sound has not returned so far.

Any recommendations on if I should run the other half can of seafoam through the oil to “extra clean” or is there risk of causing damage if I do?

Thanks again to all for the guidance and support. (I purchased a stethoscope as well and just waiting on delivery)

Glad to hear things are improving.

I personally wouldn’t put any more Seafoam in again until right before the next oil change. If you went with a quality synthetic oil, that will help as well, and I might go with a reduced oil change interval, and change the oil again after 1000 miles.