5W-30, 140k miles, GMC Sierra 1500 High Potassium

[c_johnsen]

I just got an oil analysis on my 2004 GMC Sierra 1500 5.3 with 140k miles. I replaced my thermostats 8k miles ago because my truck overheated (got to ~240 degrees for about a minute) when the thermostat failed. Over the last 8k miles ive had to constantly add a little coolant. I was hoping the system just had bubbles in it so i kept topping it off. Ive used about half a gallon of coolant over the past 8k miles.

Well today i got my oil analysis back with very high levels of sodium and potassium. Up until the thermostat failed i hadnt touched my coolant in 132k miles. I did some research and found that GM had issues with Castech heads that would develop small cracks in the oil return ports in the head causing a very small coolant loss into the oil.

Code:
OIL 5W-30

MILES IN USE 3.2K

MILES 140K





METALS



IRON 16

CHROMIUM 1

LEAD 11

COPPER 9

TIN 2

ALUMINUM 5

NICKEL 0

SILVER 0

TITANIUM 0

VANADIUM 0





CONTAMINANTS



SILICON 4

SODIUM 721

POTASSIUM 520


My wear metals all look good. My oil isnt milky at all. If i keep frequent oil changes and as long as my wear metals dont go up do i need to worry about my engine grenading until i can fix this cracked head issue?

 

[MolaKule]

Quote:
I did some research and found that GM had issues with Castech heads that would develop small cracks in the oil return ports in the head causing a very small coolant loss into the oil.


If you overheated the engine you may have warped the heads causing coolant ingress.

And not changing your coolant every two to three years didn't help either.

 

[daves87rs]

Same coolant? Tough to say

 

[c_johnsen]

Originally Posted By: MolaKule
Quote:
I did some research and found that GM had issues with Castech heads that would develop small cracks in the oil return ports in the head causing a very small coolant loss into the oil.


If you overheated the engine you may have warped the heads causing coolant ingress.

And not changing your coolant every two to three years didn't help either.


I very well could have warped the heads I'm really not sure what exactly happened that caused the coolant issue. I would hope heads wouldn't warp after a failed thermostat when it got to 240 for less then a minute. I didn't get any warning tones which if the coolant was dangerously high I would think gm would put fail safes in.

In any case I've got a coolant in oil issue now per the UOA. So the main question is, is driving it like it is with that UOA going to cause catastrophic damage if my wear metals stay low and I do frequent oil changes

 

[c_johnsen]

Originally Posted By: daves87rs
Same coolant? Tough to say


What do you mean same coolant. For the first 132k? Yes. Since then I've done a coolant flush when I did the thermostat

 

[Oil Changer]

Yes, it will cause catastrophic damage. Unless you change the oil and filter everyday, your wear metals will not stay that low. Sorry but your cost to fix has exceeded the cost to replace. Start shopping.

Originally Posted By: c_johnsen
So the main question is, is driving it like it is with that UOA going to cause catastrophic damage if my wear metals stay low and I do frequent oil changes

 

[Doog]

Originally Posted By: MolaKule
Quote:
I did some research and found that GM had issues with Castech heads that would develop small cracks in the oil return ports in the head causing a very small coolant loss into the oil.


If you overheated the engine you may have warped the heads causing coolant ingress.

And not changing your coolant every two to three years didn't help either.


^^^this

 

[zrxkawboy]

Originally Posted By: c_johnsen


In any case I've got a coolant in oil issue now per the UOA. So the main question is, is driving it like it is with that UOA going to cause catastrophic damage if my wear metals stay low and I do frequent oil changes


I sure wouldn't risk it, if it was mine, but that's just me.

 

[Chris142]

It has aluminum heads. They need to come off.pressure tested and surfaced at the least.

 

[bigt61]

Just throw in some Bars Leaks pellets (available at NAPA) or GM sealant pellets (both are the same product) and call it a day. Pulling the heads is an absolute last resort, the pellets will fix leaks a lot bigger than what you're experiencing.

 

[Rat407]

Originally Posted By: bigt61
Just throw in some Bars Leaks pellets (available at NAPA) or GM sealant pellets (both are the same product) and call it a day. Pulling the heads is an absolute last resort, the pellets will fix leaks a lot bigger than what you're experiencing.

The over heating might have caused head warpage. But if not then the Castech heads are an issue in our older GM trucks. Every time I flush my coolant system I just throw in those tablets. 155k with no issues and UOA's look good.

I did a little research a while back and I read somewhere that GM put these tablets in from the factory on the engines with aluminum heads and iron blocks. It was to prevent coolant leak issues from the differences of the two metals and their expansion and contraction rates. I think it was on a Cadillac forum.