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Hi, I am new to the forum, I have a 2004 Chevy Silverado 5.3 with just over 150k miles on it. Over recent months I have noticed that I slowly lose coolant over time (about a quart or so every 500 miles). There are no signs of external leakage, but every now and then I think I can smell antifreeze. I particularity seem to get a whiff of coolant after backing a trailer up hills, this at first made me think it was coming from the exhaust, but I'm not sure since there is no smoke. My biggest concern is that I cant find any coolant leaking anywhere. I did notice once a couple months that the floor was wet under the mat, however it did not smell like antifreeze and has not occurred again so I have pretty much ruled out heater core. I have read some about Castech heads having problems cracking, but there is no way to tell if I have them without taking the engine apart. Also head gasket is an obvious possibility. So my question is before I go and tear apart the engine and take the heads off to see if its head gasket or if I have the faulty Castech heads am I over looking any "simpler" problems that could be to blame? Thanks!
 

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OEF/OIF USMC
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water pump maybe? mine leaked at about 1/2 that rate. after some flashlight work, i was able to trace it back to the water pump.
 

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TSB for castech heads. It will show you how to identify the castech heads without pulling the heads.http://ww2.justanswer.com/uploads/Bluegorilla/2008-12-05_142924_Coolant_loss_5.3.pdf
My system had a slow leak like tht in the plastic piece where the reservoir hoses meet down by the exhaust Mani. Replaced and haven't had issues since. Not saying that's your problem just another thing to check. Mine was cracked ever so slightly I kept over looking it.
 

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This place sucks dicks
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Get that coolant tightened up. Never ever have loose coolant. That's bad.
 

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Discussion Starter #5
Re: 2004 Chevy 5.3 losing coolant

I think it was water pump. I took the skid plate off where I could see up there better and found evidence of some minor leakage. Considering the mileage I think I will just go ahead and replace the entire pump. Thanks for the help.
 
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