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The dreaded milky sludge under the oilcap

Tabb

Tabb

ROLL TIDE! AGAIN!
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I changed the oil on my '01 tahoe and when I took the oilcap off i saw that all too familiar mixture of motor oil and dexcool.:doah:

It's been a few years since I replaced intake gaskets on a 5.3L vortec and I am really not looking forward to doing it again.
My question is, in most cases, just the upper plenum intake gasket that usually starts leaking? or will I need to remove the entire intake manifold to see what the problem is? I can't remember and would like to have a little idea what I'm in for. Maybe once I get into it I'll start remembering how to do it.:dunno:

Any tips or advice would be greatly appreciated.
 
No coolant in the intake on the 5.3. Are you loosing coolant from the surge take post up a pic of the cap.
There is this bulletin from gm I ran into a few that had this problem while working for gm.
#06-06-01-019B: Information on Gradual Coolant Loss Over Time with No Evidence of Leak Found - (Jun 12, 2007)


Subject: Information on Gradual Coolant Loss Over Time With No Evidence of Leak Found


Models: 2004-2006 Buick Rainier

2001-2006 Cadillac Escalade Models

2001-2006 Chevrolet Avalanche, Blazer, Silverado, Suburban, Tahoe, TrailBlazer Models

2001-2006 GMC Envoy, Jimmy, Sierra, Yukon Models

2001-2004 Oldsmobile Bravada

2005-2006 Saab 9-7X

with 4.8L or 5.3L VORTEC® GEN III, GEN IV V8 Engine (VINs V, T, M, B, Z -- RPOs LR4, LM7, LH6, L33, L59)




--------------------------------------------------------------------------------

This bulletin is being revised to include engine RPO L59. Please discard Corporate Bulletin Number 06-06-01-019A (Section 06 - Engine/Propulsion System).


--------------------------------------------------------------------------------

Some vehicles may experience a gradual coolant loss over time. A very low percentage of cylinder head(s) manufactured with an embossed Castech logo may develop a porosity crack in a very specific area.

Inspect the cylinder head assembly to determine if the casting was manufactured by Castech. This can be accomplished by inspecting for their casting logo located on top of the intake port, under the rocker arm support rail and in the spring deck cavity portion of the cylinder head.

Important: If the cylinder head(s) are Not a Castech casting, follow normal diagnostic procedures in SI to determine the cause of the coolant loss.

Refer to the following illustrations on how to identify Castech casting and/or the very specific areas of the cylinder head(s) for a coolant leak from porosity.
 
It doesn't get driven much, just short trips around town 2 or 3 times a week so condesation could be a factor. I guess it could be just condesate mixing with the oil residue under the oilcap and filler neck. I've already wiped it all out so I can't take a pic.
The coolant level in the surge tank is about normal level and the coolant is clean but here is the really strange part. After I filled it back up with oil (6 quarts and just a little extra from a 7th quart to top it off at full) It was reading a quart low! I was thinking that there were coolant passages running through the intake mainifold and the oil was leaking out into the cooling system and/or vice versa.
 
texas4x4rebel said:
No coolant in the intake on the 5.3. Are you loosing coolant from the surge take post up a pic of the cap.
There is this bulletin from gm I ran into a few that had this problem while working for gm.
#06-06-01-019B: Information on Gradual Coolant Loss Over Time with No Evidence of Leak Found - (Jun 12, 2007)


Subject: Information on Gradual Coolant Loss Over Time With No Evidence of Leak Found


Models: 2004-2006 Buick Rainier

2001-2006 Cadillac Escalade Models

2001-2006 Chevrolet Avalanche, Blazer, Silverado, Suburban, Tahoe, TrailBlazer Models

2001-2006 GMC Envoy, Jimmy, Sierra, Yukon Models

2001-2004 Oldsmobile Bravada

2005-2006 Saab 9-7X

with 4.8L or 5.3L VORTEC® GEN III, GEN IV V8 Engine (VINs V, T, M, B, Z -- RPOs LR4, LM7, LH6, L33, L59)




--------------------------------------------------------------------------------

This bulletin is being revised to include engine RPO L59. Please discard Corporate Bulletin Number 06-06-01-019A (Section 06 - Engine/Propulsion System).


--------------------------------------------------------------------------------

Some vehicles may experience a gradual coolant loss over time. A very low percentage of cylinder head(s) manufactured with an embossed Castech logo may develop a porosity crack in a very specific area.

Inspect the cylinder head assembly to determine if the casting was manufactured by Castech. This can be accomplished by inspecting for their casting logo located on top of the intake port, under the rocker arm support rail and in the spring deck cavity portion of the cylinder head.

Important: If the cylinder head(s) are Not a Castech casting, follow normal diagnostic procedures in SI to determine the cause of the coolant loss.

Refer to the following illustrations on how to identify Castech casting and/or the very specific areas of the cylinder head(s) for a coolant leak from porosity.
Click to expand...


Do you know if you can see this casting logo on the cylinder head without having to remove anything major?
 
most likely condensation. Is there milky oil on your dipstick? change your oil and if it still loooks fine its just the moisture from the air gathering on the cap. My truck does it sometimes
 
Ya I second (or 3rd or 4th) the water/oil mix. If your dipstick looks fine, and it's only on the cap, especially that you say you only drive it a few short trips. Go on a road trip, drive it non-stop on the highway for an hour, with the colder/wet weather the engine perhaps isn't getting warm enough, or warm long enough from the short trips to remove all the moisture, so it's turning to steam rising, and collecting and mixing with the oil and settling on the cap. Happened to my Bug all the time and there's no coolant on those :D Don't know anything about the 5.3s, but whatever crankcase breather it has, check those too. Just like a old v8 wth pcv valve and filter/hose on the other valve cover, fresh air entering the system. All the moisture should turn to steam and get sucked in and blown out the exhaust. If your cap looks like sludge, your valve covers and anything on the 'top' of your engine probably does too. IMO if it's a little old, might wanna think of putting in some seafoam, unless any of these guys with 5.3 knowledge has a reason otherwise. But otherwise running it for a good long time should clear it all up.
 
Thanks for the input guys. I'm now thinking it's just condensation since the oil is clean on the dipstick.
 
Tabb89k5 said:
Thanks for the input guys. I'm now thinking it's just condensation since the oil is clean on the dipstick.
Click to expand...

You said you just changed the oil and saw milky oil under the cap, what did the actual oil look like you drained out? If the oil looked fine obviously it's just condensation.
 
Years ago, a good buddy had the 'whipped coffee latte' stuff on his oil cap and valve cover breather on his 427 BBC. Oil looked good on the dipstick and when drained. Ended out being a cracked cylinder wall next to a water jacket; the antifreeze was vaporizing in the chamber, and showing up in the top-end of the motor. Just a suggestion.
 
Tabb89k5 said:
Do you know if you can see this casting logo on the cylinder head without having to remove anything major?
Click to expand...

You have to pull the valve cover off to see the logo but just cause it has the logo doesnt mean that the heads are bad. My 5.3 on both trucks gets that weird stuff under the cap. All the ones I repaired at the dealer came in with coolant loss issues. If your coolant level doesnt drop I wouldn't worry about it.
 
My 6.0 does, and I`ve seen others. It is just condensation, GM isn`t the only one, saw it on numerous Volvo`s also. Keep the fluids full, should be fine.
 
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