1997 Sierra 350 GXT 5w30 with coolant leak update.

[Chris B.]

Bought this 97 GMC Sierra used back in March 2011 with 76,000 miles on it. It is in like new condition and runs well and I plan on keeping it for the rest of my life. I only drive it when I need a truck and only put about 125 miles a month on it but I always get it up to full temp before garaging it till next time.
Blackstone is the lab and they warned me about coolant contamination the has been in all 3 oil samples. When I bought the truck the intake manifold was leaking badly and had the repair done. Potassium keeps dropping it seems and my question is do you think the coolant seen is still left over from the repair? Maybe since I don't drive this truck much I have not done enough oil changes and miles to fully flush the coolant. Of maybe the repair was not done properly and still leaking coolant into the oil?
The coolant overflow tank is very stable and I only have to top it off once a year with a few oz. to keep it right on the full hot line. I was thinking this amount was from evaporation rather then internal leaking in the manifold?
What do you guys think? Also look at copper, silicon, lead all still dropping and Iron leveled out. And why is boron up? TBN is 5.1 even after 17 months in use and insoluble are low at 0.2 so this is a clean engine I think! Here is some details on the truck and sample:

*84,271 miles on engine/truck
*2,086 miles on oil and 17 months.
*Oil in use from 82,185 to 84,271 miles and from 4/11/2012 to 9/11/2014(17 months)
*Castrol GTX 5w30
*Napa Gold oil filter.
*Napa Gold air filter has 2,000 miles on it now.
*1st UOA was a auto RX cleaning cycle and the 2nd UOA was the rinse cycle and the 3nd UOA is this sample with just 2,086 miles and 17 months in service.

1st number is 1st UOA with the 3rd column being this sample is this UOA. Both UOA's have 3,000 miles on them:

ALUMINUM 3/4/3
CHROMIUM 1/1/1
IRON 22/10/8
COPPER 104/51/27
LEAD 24/13/8
TIN 0/5/4
MOLYBDENUM 2/3/2
NICKEL 2/1/0
MANGANESE 1/1/0
SILVER 0/0/0
TITANIUM 1/0/0
POTASSIUM 44/34/24
BORON 8/7/35
SILICON 79/61/38
SODIUM 274/342/117
CALCIUM 1515/1784/1873
MAGNESIUM 10/9/9
PHOSPHORUS 640/703/653
ZINC 686/843/746
BARIUM 0/0/0

SUS Viscosity @ 210 F 56.3/56.1/55.8
cSt viscosity @ 100 C 9.16/9.10/9.02
Flashpoint 415 F 415/420/435
Fuel 0.5/0.5
Antifreeze POS/POS/POS
Water 0/0/0
Insolubles 0.3/0.3/0.2
TBN 4.2/2.9/5.1

Any advice or comments is appreciated! Here she is:

 

[dustyroads]

You're headed in the right direction, but you'll need a couple more oil changes to finish flushing out. I don't have experience with coolant intrusion but after using an oil with sodium as an additive it can take a few oci's to flush it out.

I can't guarantee you're problems are fixed but I think they likely are. The potassium/sodium is likely residual. Maybe someone else has dealt with coolant intrusion and can answer with more certainty. It appears to be getting straightened out anyway.

The boron is an additive. GTX has boron but your first two apparently did not.

The silicon will continue to drop and with healthy, non contaminated oil your wear metals will level off and look fine. Actually they're almost fine now. Eventually will be better.

Nice truck!

 

[mrsilv04]

An excellent example of one of the best trucks that GM ever made...

 

[barkingspider]

Just keep driving and change oil when it's time, that will last u forever.

 

[Bgallagher]

Originally Posted By: barkingspider
Just keep driving and change oil when it's time, that will last u forever.


+1

 

[bullwinkle]

How does it look under the oil fill cap? Any milky deposits? If not, keep doing what you're doing, it'll eventually all flush out.

 

[Chris B.]

Originally Posted By: bullwinkle
How does it look under the oil fill cap? Any milky deposits? If not, keep doing what you're doing, it'll eventually all flush out.


Oil fill cap is dry with a light tint of brown on it. No milky residue to be found.

 

[Nick1994]

That's a gorgeous truck. I still miss my 96' Silverado.

 

[Chris B.]

Originally Posted By: Nick1994
That's a gorgeous truck. I still miss my 96' Silverado.


Thank you!

 

[Chris B.]

Do you think a couple very short oil changes back to back will flush out the rest of the coolant?

 

[wtd]

Very nice truck. I have a 98 chevy Silverado Z71 that I bought new and now has 127,000 miles on it. The potassium/sodium levels should go down each time you change your oil. I've had three intake gaskets installed on my truck over the years and I did oil analysis during the time of some of the changes and is how I caught it twice.

Depending on which gasket version they used will determine if you will have future problems. There has been at least three versions that I know of.

If your coolant overflow tank level continues to go down, you could still have a leak. The torque values for the intake bolts are not very high and have to be pretty exact or you will have issues.

Wayne

 

[Chris B.]

Originally Posted By: wtd
Very nice truck. I have a 98 chevy Silverado Z71 that I bought new and now has 127,000 miles on it. The potassium/sodium levels should go down each time you change your oil. I've had three intake gaskets installed on my truck over the years and I did oil analysis during the time of some of the changes and is how I caught it twice.

Depending on which gasket version they used will determine if you will have future problems. There has been at least three versions that I know of.

If your coolant overflow tank level continues to go down, you could still have a leak. The torque values for the intake bolts are not very high and have to be pretty exact or you will have issues.

Wayne


Thanks for the tip! If I have to replace the intake again 'll be sure to follow up on tq values. What gasket is the best for this?

 

[wtd]

As far as the gasket goes, you can either get the GM gasket or Fel-pro also makes the newest style gasket which I believe the number is MS98000T. It is metal gasket. The original style was plastic and the second style were plastic with metal inserts around the bolt holes.

Wayne