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1997 GMC Sierra 5.7 V8, Castrol GTX #4081527 04/27/16 07:22 PM
Joined: Mar 2003
Posts: 3,541
Chris B. Offline OP
OP Offline
Joined: Mar 2003
Posts: 3,541
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 4 oil samples. When I bought the truck the intake manifold was leaking badly and I 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 10,000 miles ago? Maybe since I don't drive this truck much I have not done enough oil changes and miles to fully flush the coolant? Or 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 4.7 even after 14 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:

*85,745 miles on engine/truck
*1,474 miles on oil and 14 months.
*Oil in use from 84,271 to 85,745 miles and from 9/11/2014 to 11/19/2015(14 months)
*Castrol GTX 5w30
*Napa Gold oil filter.
*Napa Gold air filter has 3,474 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 4th column being this UOA. First 2 OCI's have 3,000 miles on them and 3rd UOA has 2,086 miles on it. All GTX 5w30 oil.

ALUMINUM 3/4/3/3
CHROMIUM 1/1/1/0
IRON 22/10/8/5
COPPER 104/51/27/13
LEAD 24/13/8/6
TIN 0/5/4/4
NICKEL 2/1/0/1
SILVER 0/0/0/0
TITANIUM 1/0/0/0
POTASSIUM 44/34/24/14
BORON 8/7/35/53
SILICON 79/61/38/32
SODIUM 274/342/117/58
CALCIUM 1515/1784/1873/2196
MAGNESIUM 10/9/9/8
PHOSPHORUS 640/703/653/708
ZINC 686/843/746/820
BARIUM 0/0/0/0

SUS Viscosity @ 210 F 56.3/56.1/55.8/57.3
cSt viscosity @ 100 C 9.16/9.10/9.02/9.45
Flashpoint 415 F 415/420/435/395
Fuel <0.5/0.5/0.5/0.5
Antifreeze POS/POS/POS/POS
Water 0/0/0/0
Insolubles 0.3/0.3/0.2/0.2
TBN 4.2/2.9/5.1/4.7

Re: 1997 GMC Sierra 5.7 V8, Castrol GTX [Re: Chris B.] #4081578 04/27/16 08:17 PM
Joined: Nov 2008
Posts: 1,249
ArrestMeRedZ Offline
Joined: Nov 2008
Posts: 1,249
At the risk of restating the obvious, antifreeze contamination is reported positive, but it doesn't show the level. Water is zero on all samples. Potassium is dropping in a very linear manner.

If potassium is an indicator of antifreeze contamination (sorry, I'm not informed on this. but I'm sure someone who reads your post is), it looks like you are gradually flushing it out of the system. If is isn't an indicator, you may still have a leak.

Is your truck a C1500 or a C2500?

Re: 1997 GMC Sierra 5.7 V8, Castrol GTX [Re: Chris B.] #4081588 04/27/16 08:35 PM
Joined: Aug 2004
Posts: 2,570
double vanos Offline
Joined: Aug 2004
Posts: 2,570
With most everything trending down , I wonder, if this truck was in normal usage as a daily driver, would we be having this discussion ? There are some really good UOA dissecters on this forum, hopefully one will chime in.

Sabine Schmitz is the Queen of the 'Ring; Svetlana Kapanina is the Queen of the SKIES...
Re: 1997 GMC Sierra 5.7 V8, Castrol GTX [Re: Chris B.] #4081690 04/28/16 04:23 AM
Joined: Aug 2009
Posts: 135
csx7006 Offline
Joined: Aug 2009
Posts: 135
Check the intake manifold gasket between the intake manifold and the block. Its a common problem with the 350 vortec.

Re: 1997 GMC Sierra 5.7 V8, Castrol GTX [Re: csx7006] #4082160 04/28/16 04:39 PM
Joined: Nov 2008
Posts: 1,249
ArrestMeRedZ Offline
Joined: Nov 2008
Posts: 1,249
Originally Posted By: csx7006
Check the intake manifold gasket between the intake manifold and the block. Its a common problem with the 350 vortec.

I believe he was referring to the lower intake manifold gasket being replaced when he mentioned the leak being repaired in the intake manifold.

Re: 1997 GMC Sierra 5.7 V8, Castrol GTX [Re: Chris B.] #4082257 04/28/16 07:10 PM
Joined: Mar 2015
Posts: 235
Carbon12 Offline
Joined: Mar 2015
Posts: 235

My wife's 2003 Monte Carlo had a intake manifold gasket failure that allowed coolant in the crankcase. The 3.4L engine is famous for the leaks but I didn't find that out until after the leak had occurred. The coolant loss was severe and I'm surprised we didn't lose the engine before I finally caught it. The combo of water, ethylene glycol and oil makes a very sludge-like emulsion. Following the repair I changed the oil and the filter was completely full of the sludge and I could see a lot of sludge through the fill hole. I kept OCIs short until the sludge finally was gone.

I think in your case with the limited miles on each oil change not all the sludge has been eliminated. As it gradually breaks up potassium will continue to be released into the oil. Drive this baby daily for a few months and put some miles on the oil to give it a chance to clean out.

Re: 1997 GMC Sierra 5.7 V8, Castrol GTX [Re: Chris B.] #4105208 05/24/16 10:57 AM
Joined: Jun 2002
Posts: 2,346
wtd Offline
Joined: Jun 2002
Posts: 2,346
I have this same engine in a 98 K1500. I bought this truck new and it currently has 131,000 miles on it. I have had the intake gasket replaced three times since new.

If your potassium levels continue to go down, you are probably ok but the fact that you do have to add some coolant to the overflow tank could mean you still have a slight leak.

Do you know what version gasket was used in your repair? There have been three gasket revisions since this engine was developed.

My truck currently has revision #2 so I'm sure mine will leak again.

I will say that oil analysis did catch the leak the last two times so I probably should have it done again.


2014 Mustang GT
1998 Chevy K3500
1998 Chevy K1500
(2) 1992 Cavaliers
1970 Monte Carlo
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