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Extreme Coolant Loss


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#1 gm4ever

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Posted 19 January 2011 - 10:29 PM

I have an 04 silverado with 5.3 vin T that has been losing about a quart of coolant a week, for 6 months. My oil looks normal but I have a lot of sludge. The oil filler cap has become hard to remove and there is some yellow gel in the neck of the filler tube. I have been changing my oil every 1500 miles, because the annoying knock starts about 1000 miles after an oil change. After the oil change the knock or tick disappears for a while. I had the cooling system pressure tested and it held pressure overnight and the garage said they couldn't find the leak, they said it may be a water pump gasket. I have read a lot of things about castech heads and afraid they may be my problem. I wonder why the pressure test was good, when I am losing so much coolant? Also if I have to replace the engine, are spartan engines from advance a good option?

#2 Wingnut

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Posted 20 January 2011 - 03:53 AM

If you're losing coolant, and it's not leaking out anywhere externally, pretty much the only place it can go is into the engine...Where it is either burned off or it's in your oil.

My guess is head gasket or cracked head. And the sooner you fix it, the less chance there is of you needing a new motor.
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#3 8.1HD/ALLISON

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Posted 20 January 2011 - 06:26 AM

+1, Had a lot of problems with internally "pourous heads" Very hard to find. If there is no external leaks, and its not leaking into the oil, more than likely the heads are leaking.

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#4 snakedoctor

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Posted 20 January 2011 - 09:05 AM

http://ww2.justanswe...nt_loss_5.3.pdf

#5 gm4ever

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Posted 21 January 2011 - 08:56 PM

+1, Had a lot of problems with internally "pourous heads" Very hard to find. If there is no external leaks, and its not leaking into the oil, more than likely the heads are leaking.



Thanks for the info, my bet is on head issues also. Guess I will start checking prices on new heads!

#6 rogersbowtie

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Posted 22 January 2011 - 07:08 AM

I have an 04 silverado with 5.3 vin T that has been losing about a quart of coolant a week, for 6 months. My oil looks normal but I have a lot of sludge. The oil filler cap has become hard to remove and there is some yellow gel in the neck of the filler tube. I have been changing my oil every 1500 miles, because the annoying knock starts about 1000 miles after an oil change.

Normal looking oil does not have sludge or develop yellow gel in the filler tube...likely getting coolant in the oil. Cracked heads or bad head gaskets usually cause over presurization of the cooling system and the pressure vents (boils) out through the overflow tank. What you describe sounds more like leaking intake manifold gaskets. GM's long-life Dexcool antifreeze is known to slowly disolve the factory gasket materials over time. A lot of GM engines have this problem.

Fixing the problem...a lot of labor to teardown the top half of the engine. Most shops will recommend replacing head gaskets at the same time. Use a quality aftermarket gasket kit such as Felpro. A good shop should recommend pressure-testing the heads (and/or rebuilding them) due to the labor already invested in the gasket job.

Or do as I did...Barsleak and get rid of it.

#7 dlewis1111

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Posted 22 January 2011 - 09:44 AM

I have an 04 silverado with 5.3 vin T that has been losing about a quart of coolant a week, for 6 months. My oil looks normal but I have a lot of sludge. The oil filler cap has become hard to remove and there is some yellow gel in the neck of the filler tube. I have been changing my oil every 1500 miles, because the annoying knock starts about 1000 miles after an oil change.

Normal looking oil does not have sludge or develop yellow gel in the filler tube...likely getting coolant in the oil. Cracked heads or bad head gaskets usually cause over presurization of the cooling system and the pressure vents (boils) out through the overflow tank. What you describe sounds more like leaking intake manifold gaskets. GM's long-life Dexcool antifreeze is known to slowly disolve the factory gasket materials over time. A lot of GM engines have this problem.

Fixing the problem...a lot of labor to teardown the top half of the engine. Most shops will recommend replacing head gaskets at the same time. Use a quality aftermarket gasket kit such as Felpro. A good shop should recommend pressure-testing the heads (and/or rebuilding them) due to the labor already invested in the gasket job.

Or do as I did...Barsleak and get rid of it.


Barsleak will not fix anything if you have the Castech heads. Pull a valve cover off and check to see if you have them. If you do, it's time for heads right away or a new engine very soon after. There is no coolant running through the intake on this truck so leaking intake gaskets do not make sense.

Edited by dlewis1111, 22 January 2011 - 10:12 AM.

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#8 The John

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Posted 22 January 2011 - 09:56 AM

I was just a victim of this myself and I will say with 100% certainty that you have the same porous Castec heads I had on mine. All of your symptoms match mine to a T. The reason the leakdown test didn't show anything is because the engine is cold. In my case, both heads had developed cracks in the porous areas and they would only open up wide enough for coolant to seep through after the engine had been run for some time (four hour road trips to my mother's house). The only way they found them at the shop was by pressure testing the heads with them off of the engine and using dye.
I opted to replace the entire motor because I had changed the oil the day before I left on my most recent road trip and went back outside to the garage after the shop told me of the cracked heads and found coolant in the oil jug. Apparently it had been rolling around in my crankcase for some time. How long, I don't know. I just didn't want to take the chance on just replacing the heads (which I was originally going to do) and having to pull the motor again in 15-20k to rebuild to bottom end because of failed bearings.
Now I've got a 92,000 mile truck with a brand new engine and couldn't be happier with it. Sure it's a nice chunk of change, but I've basically got a new truck again. And you'd be amazed at the power difference between your old motor and a new one.
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#9 LeoS41280

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Posted 22 January 2011 - 10:00 AM

I have an 04 silverado with 5.3 vin T that has been losing about a quart of coolant a week, for 6 months. My oil looks normal but I have a lot of sludge. The oil filler cap has become hard to remove and there is some yellow gel in the neck of the filler tube. I have been changing my oil every 1500 miles, because the annoying knock starts about 1000 miles after an oil change.

Normal looking oil does not have sludge or develop yellow gel in the filler tube...likely getting coolant in the oil. Cracked heads or bad head gaskets usually cause over presurization of the cooling system and the pressure vents (boils) out through the overflow tank. What you describe sounds more like leaking intake manifold gaskets. GM's long-life Dexcool antifreeze is known to slowly disolve the factory gasket materials over time. A lot of GM engines have this problem.

Fixing the problem...a lot of labor to teardown the top half of the engine. Most shops will recommend replacing head gaskets at the same time. Use a quality aftermarket gasket kit such as Felpro. A good shop should recommend pressure-testing the heads (and/or rebuilding them) due to the labor already invested in the gasket job.

Or do as I did...Barsleak and get rid of it.

The 5.3 intake has no antifreeze in it. The 5.3 intake manifold is a fairly easy R&R. I would stay away from a shop that wants to do head gaskets without a reason other than the intake is all ready off.
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#10 sixfundr

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Posted 17 March 2011 - 12:27 AM

Can these type of heads be repaired at a machine shop? or is new the way to go?
Have a 05 1500 with 93000 miles have internal coolant loss and very noisy lifters for 5-10 min.

Edited by sixfundr, 17 March 2011 - 12:31 AM.





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