1997 Tahoe 5.7 Vortec 2,500 miles Castrol dino 5w30 with Auto Rx rinse cycle

[Chris B.]

I think I confirmed my fear of an internal coolent leak. Potassium is up again!

1997 Chevy Tahoe with 104,500 miles total.
Castrol dino 5w30
Did an Auto Rx last oil change and this oil was used for the rinse cycle.
Oil was in use from 12/24/04 to 3/31/05 and has 2,500 mils on the oil.

This OCI / Last OCI

Aluminum 2/3

Chromium 1/1

Iron 7/8

Copper 5/4

Lead 11/13

Tin 0/1

Molybdenum 15/14

Nickel 1/0

Manganese 0/0

Potassium 69/25 This has to be coolent!?!?!?!

Boron 6/3

Silicon 10/9

Sodium 46/18 What does this mean????!!!!

Calcium 1965/2060

Magnesium 11/0

Phosphorus 610/682

Zinc 700/837


SUS Viscosity @210F 58.5

Flashpoint 400

Fuel 0

Water 0

Insolubles 0.4

Can anyone tell me if I have an internal coolent leak? I'm loosing antifreeze and it is not leaking on my garage floor. Wear still seams low but I'm thinking i need to repair my intake manafold soon. Am I right? Thank you very much!!!

 

[Al]

Potassium/sodium=coolant leak. Some ois have sodium..but potassium is usually the giveway. Usually silicon is up also and viscosity can be heavier. I'd say its reeasonably certain U have a leak.

 

[Chris B.]

Ok so where does coolent leak into the oil from? Please list all possibilitys for the engine if you know it.

I think the intake manafold might be one but that is all I know.

Thank you!

 

[JHZR2]

intake manifold is usually the failure point. Where the coolant line or the EGR tube crosses through is what Ive heard.

I had similar readings in my 4.3 vortec, until I got the gasket changed. The first 3k oci since then has been coolant, Na and K free, though Al is elevated all of a sudden. Im waiting on the next UOA in a few more months.

Thing is, my wear numbers were always good, despite the presence of a TINY bit of glycol, sodium and potassium. My numbers were actually better than yours, and your numbers are good. So I wouldnt worry about it, but Id get the cooling system checked (to rule out headgasket seepage), and then think about getting the intake manifold gasket done.

JMH

 

[Chris B.]

What would an honest shop charge to fix this on this engine? Thank you!

 

[wizzells]

Not sure how much yours would be on the 5.7, but on my 3.8 I think it was $320 for mine - an upper intake manifold gasket replacement. My intake manifold luckily wasnt ruined. This, of course, is assuming that this is your problem. Probably is since most GM engines seem to fail in this area at one point or another.

 

[wtd]

Chris,
Its probably your intake manifold gasket. A common failure on this engine. I have a 98 silverado with the 5.7L and have had to have my intake gaskets changed twice in 78,000 miles. The last one started happening around 50,000 miles. I caught the second one by oil analysis because my potassium and sodium levels kept increasing and the coolant level in the overflow tank kept going down.

When I priced this job, I had quotes from $192 all the way to $800. I had mine done for the $192 at a small local garage. My truck was the third he had done in a week. I haven't had an oil analysis done in awhile but my Potassium/Sodium levels kept going down but the Potassium level never did go back to 0 in about 11,000 miles of driving.

I need to have another analysis done soon to see whats going on.

Wayne

 

[JohnBrowning]

I have a friend with a 1996 GMC 1500 and his upper intake manifold gasket let lose about a month after the water pump failed at 120,000 miles. You could see the coolant leaking out of his maifold down the backside I belive. If I remember correctly the intake upper intake manifold was fine it was just the gasket!

 

[Chris B.]

Thank you guys! I can't find any sign of an external leak.

Are there any other possibilitys other then the intake manafold for coolent to get into the oil? Thank you!

 

[Chris B.]

quote:

---

Originally posted by wtd:
Chris,
Its probably your intake manifold gasket. A common failure on this engine. I have a 98 silverado with the 5.7L and have had to have my intake gaskets changed twice in 78,000 miles. The last one started happening around 50,000 miles. I caught the second one by oil analysis because my potassium and sodium levels kept increasing and the coolant level in the overflow tank kept going down.

When I priced this job, I had quotes from $192 all the way to $800. I had mine done for the $192 at a small local garage. My truck was the third he had done in a week. I haven't had an oil analysis done in awhile but my Potassium/Sodium levels kept going down but the Potassium level never did go back to 0 in about 11,000 miles of driving.

I need to have another analysis done soon to see whats going on.

Wayne

---

Why such a huge difference in price? Don't these kinds of jobs have a standard rate the auto mechanics have to fix by? One shop should not differ to much from another shop right?

 

[Geoff]

I'd ask what gasket they are using to replace the old one also. There are lots of alternatives, and worth some research.

 

[OffOrWFO]

Chris we've gone over this before. Just replace the intake gasket and stop worrying about it. Should cost between $250-$450. The dealer would probably quote $800. The exact same thing happened on my 5.7l. The potassium and sodium was creaping up over a few UOA but the wear wasn't affected. My bros on the other hand let his go until he had some super high wear numbers.

How much coolant are you loosing. Mine was loosing about a 1/2Qt per 3 months. I only saw a leak on the ground once every week or two, mostly when it was short tripped alot during the really cold part of the winter. Coolant can dribble out and set in small spots in hard to see holes. Then when you drive it, it evaps off and you never see it hit the ground.
It could be some other problem like a head gasket or cracked head/intake gasket. But chances are (99%) its the intake gasket. All these motor have this problem. After I changed mine the UOA #s went back to normal after a couple of OCIs. Plan to do it at the end of a OCI because you need to change the oil afterwards. Flushing the system beforehand is a good idea too. Send it in with straight water in it. That way only water will get into the oil-no coolant. I'd do a water pump while your at it. Mine just died at 110K. Good luck!

 

[T-Keith]

My father's '98 actually started leaking at the lower gasket, not the upper one. Reguardless since the wear isn't very high, it looks like it hasn't done any damage yet.


-T

 

[wtd]

Chris,
Just because you don't see an external leak, doesn't mean its not the intake manifold gasket. The first time mine leaked, it leaked externally in two places and would leave coolant on the garage floor after the motor cooled off. The second time, I had no external leaks, just an increase in Potassium/sodium levels in my oil.

The shop that fixed mine gave me the old gaskets and you could plainly see where the leaking was coming from. He used a Felpro gasket for the repair. GM has come out with a new gasket that probably is better.

As far as the price differences, my quotes were from various dealers and independent repair shops. The $800 dollar quote was from an independent shop. The two GM dealers I called were about $200 different in their quotes so I don't know how these places were figuring up their prices. Get it fixed because it won't get any better.

Wayne.

PS. Check under the oil fill cap to see if you are getting water droplets building up. Mine was and thats when I knew my leak was probably getting worse and I then had it fixed.

 

[Chris B.]

Ok I'll post back with the damage report!