Coolant Loss

jbutton1462 · April 29, 2013

Hello,

I have a 2003 Silverado Z71 with a 5.3 engine. About 2 months ago my low coolant level light came on. Coolant was low so I topped it off. I have gone through 2 gallons of coolant since then. Engine idles a little rough, but has done that since I got the truck 2 years ago. Had the cooling system pressure tested and it held at 15 with no signs of external leaks. Started researching and learned about the Castech heads. I changed the oil the other day and did not notice any coolant mixed with it. It was dark, but did not look like choc milk shake. That same day I noticed I had water pooled up inside the tail pipe after I let the truck warm up a little to change the oil. Started the truck and a lot of water shot out. But there is no water when I first start it or when it's at normal operating temp. Oh, and about the same time I started losing coolant, I started getting a horrible "knocking" sound for about a min on cold starts. I believe it's a cracked head or gasket but the coolant is not mixing with the oil which is throwing me off. Any suggestions on what this could be before I really start throwing money into it?

jbutton1462 · April 30, 2013

Well I'm going to have it checked tomorrow and the mechanic is almost positive it's the water pump. I hope he's right and I'm wrong. But I don't see any signs of a leak

gmtech4 · April 30, 2013

like he said ,it dries before it hits the ground leaving a trace on the block/other places

txab · April 29, 2013

The water in the exhaust could simply be normal condensation. Water pump and gaskets are the common leak point. Look closely for signs of leakage that has dried. For the castech problem you can pull the valve covers and check. You can also buy test strips that will check for the presence of combustion by-product in the coolant. you can have your oil tested for the presence of coolant in the oil as well

http://www.agcoauto.com/content/news/p2_articleid/148

DSparx · April 30, 2013

I have an 04 in the shop right now having some reman heads installed. The symptoms were exactly the same. I hope yours is something different. Was your oil pressure low on the gauge too?

jbutton1462 · April 30, 2013

I'm only getting moisture out the exhaust when it's warming up so it may just be condensation. Took it to the shop today and they could not find a leak on the water pump. It also passed the head gasket test and no combustible gases (I believe that's what it was) were found ruling out cracked head or gasket. Just replaced the overflow cap and going to keep an eye on it. Thanks for the replies

bossier62guy · April 30, 2013

Put some dye in it man....2 gallons doesn't disappear w/o leaving a trace.

txab · May 1, 2013

Agreed. That amount (2 gallons/ 2 months) should be able to be tracked down

rdnkcpa · May 1, 2013

My 2004 had the same problems. The horrible noise you hear on start up is a collapsed lifter, another byproduct of the Castech head problems. The only way to really tell is to pull a valve cover. Once you open them up you will see the Dexcool snot.