Cracks on 706 heads?
08-22-2013, 08:58 PM
#21
I just recently purchased a 04 5.3 with about 130000 on it. The reason the guy took it out was the truck over heated on him; water pump was replaced as well as the radiator. The truck never did it again, but they also couldn't find anything wrong with the old water pump or the radiator. I have no clue how they checked the water pump im guessing by just seeing if there was any play in the shaft? Anyway I pulled the valve covers and heads last nite and the valve covers were absolutely nasty. Had horrible milky oil residue under them and some was chunky. Im guessing I will find a cracked head when I have them tested.
08-22-2013, 10:51 PM
#22
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Let me know how that goes because I was told that residue is typical in an ls motor that doesn't get beat on and has milage. I know I've pulled a lot of oil caps off and found moisture and that yellow slime on them and had no issues. My ls had that same stuff on the vc's but oil in the pan looked great!
08-23-2013, 04:58 AM
#23
Let me know how that goes because I was told that residue is typical in an ls motor that doesn't get beat on and has milage. I know I've pulled a lot of oil caps off and found moisture and that yellow slime on them and had no issues. My ls had that same stuff on the vc's but oil in the pan looked great!
08-23-2013, 05:58 AM
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so if you did have the cracked heads, the coolant system would have a pressure relief path thru the block, because normally the coolant system is a closed system. If the pressure goes down, the boiling point of the coolant goes down, so symptom number one is overheating, because the coolant boiled and is less efficient at cooling.
Then second, the path for the coolant is into the oil system, which is (sorta) a closed system as well, but does have a vent path, the PCV. so the result is when coolant gets in there in any quantity, instant milkshake.
The LS engine is a really great design, and the cracked head events may actually be very few, but once a service bulletin goes out it becomes a world-wide epidemic.
If you have a good running vehicle, and no big signs of coolant in oil (a little slime is there from condensation which is normal) then you may be worrying about nothing.
That being said, I take overheating events very seriously and when I have one, I make sure I find the cause. With my truck (stock 5.3), I can tow a trailer on a hot day with the AC on in the SOUTH and the coolant stays right where it should be and my truck has castech heads and 80k on a 2004.
When service bulletins are sent out, the concern of GM is cars under warranty, as that is the risk GM owns. Once the warranty is out, WE own the risk.
Then second, the path for the coolant is into the oil system, which is (sorta) a closed system as well, but does have a vent path, the PCV. so the result is when coolant gets in there in any quantity, instant milkshake.
The LS engine is a really great design, and the cracked head events may actually be very few, but once a service bulletin goes out it becomes a world-wide epidemic.
If you have a good running vehicle, and no big signs of coolant in oil (a little slime is there from condensation which is normal) then you may be worrying about nothing.
That being said, I take overheating events very seriously and when I have one, I make sure I find the cause. With my truck (stock 5.3), I can tow a trailer on a hot day with the AC on in the SOUTH and the coolant stays right where it should be and my truck has castech heads and 80k on a 2004.
When service bulletins are sent out, the concern of GM is cars under warranty, as that is the risk GM owns. Once the warranty is out, WE own the risk.
