My 2001 Silverado 1500 4.8L loses coolant and I don't know where it goes. It takes less than 200 miles for it all to disappear. I have never seen moisture under the truck, and there is no leakage apparent under the hood. The thermostat seems to work ok, and the oil looks clean.Today, I took out the aircleaner assembly, refilled the coolant reservoir, and waited 15 minutes with the engine running for leaks to appear. Nothing happened.
Any advice for solving this baffling problem would be greatly appreciated.
Joe

 

I have 2 words for you:
1. get under the truck and find water pump gasket. It is said to be poor quality and leaks right onto exhaust. gone puff!
2. first 1 is the easy one. bad news is - internal blowby into exhaust or combustion chambers. Are you dripping excessivly from the tail pipe? WHite smoke on start up or under accelerations? That's head gasket. Don't try any silly additives, you'll mess your radiator and will have to replace more parts.

 

Just found mine leaking around water pump gasket today. Been loosing coolant for a while but slow enough not to be a real concern. What tipped me off was when I was greasing the front end today and removed from plastic splash guard and found the A/C belt had a reddish stain on it. Further investigation showed the water pump leaking a bit around the gasket. It's a 2000 Silverado with the 4.8L.

 

Thanks for the advice. Sounds like you nailed it as a water pump gasket. There is no smoke nor water leaving the tail pipe. I've had this problem for a year, so it cannot be a head gasket. Tell me: how much trouble is it to change the water pump gasket? I assume the radiator has to come out.
Joe

 

Water Pump Replacement (4.8L, 5.3L, and 6.0L Engines)
<A href="http://gsi.xw.gm.com/si/showDoc.do?docSyskey=642629&pubCellSyskey=37160&pu bObjSyskey=642629&from=sm&laborOpCode=&cellId=3716 0#ss1-642629">Removal Procedure

1. [*]

<A href="http://gsi.xw.gm.com/si/showDoc.do?docSyskey=642629&pubCellSyskey=37160&pu bObjSyskey=642629&from=sm&laborOpCode=&cellId=3716 0#ss2-642629">Installation Procedure

Important: All gaskets surfaces are to be free of oil or other foreign material during assembly.

 

I took off the water pump but couldn't see where coolant was leaking. Replaced the two gaskets between the pump and the engine ($9 each), and the rubber o-ring under the case on the rear of the pump ($1.70). I found the AC belt was starting to crack, so I replaced it ($17), and threw in a new water pump just because I was in there ($26). The whole job took a couple of hours and nothing was difficult (thanks in large part to the diagrams a list member posted). All parts were bought at NAPA.
The leak seems to have stopped, so I guess I found and fixed the problem.
Thanks to all who helped me.
Joe

 

I'd replace the intake manifold gasket if you haven't already.

 

The 4.8, 5.3, 6.0, 6.2, & 7.0 liter GM V-8's don't have water going through the intake. The throttle body does have water going through it, but I've never seen one leak.


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