Coolant loss

I have a 2003 Silverado 1500 4.8 L. with 120,000 on it. I am loosing about 16oz of coolant every 300-400 miles. There is no visible leak around the intake , hoses, water pump, coolant tank,or radiator. The oil is clean with no contamination caused by coolant in it. Could it be the intake gasket leaking into the exaust port on the head causing the cooling loss? The truck runs great except for this problem that just started.
Thanks.

I have a 2003 Silverado 1500 4.8 L. with 120,000 on it. I am loosing about 16oz of coolant every 300-400 miles. There is no visible leak around the intake , hoses, water pump, coolant tank,or radiator. The oil is clean with no contamination caused by coolant in it. Could it be the intake gasket leaking into the exaust port on the head causing the cooling loss? The truck runs great except for this problem that just started.
Thanks.

Have you done a coolant system pressure test to see if you can locate the leak? Try autozone to see if they have a coolant pressure system tester in there loan a tool program. They have a deposit on the tool which is returned when tool is returned.

Also spray carb cleaner around the intake to see if you have a intake leak, engine will increase in rpm when carb cleaner finds a leak.

As said do a pressure test and look for leak.
Test it cold and warm and hot.
They also make a leak check dye to put in the coolant for the hard to find leaks.
And will also show any coolant getting in the oil.

I have changed alot of water pump gaskets, they fail usually before the pump does. They leak right onto the engine and burn off before you even see a puddle. the easiest way to check is to let it warm up and slide under it and look at both sides of the water pump where they bolt to the engine. like I said ive done many of these for buddies and it has always been the gasket. I have done the 4.8s,5.3, and 6.0s and alot that I have done have over 100,000 miles on the original water pumps and are still going. I also flush and replace the coolant while I am at it, because it only makes sense to.

I'm having this same problem. Small amount of coolant disappearing and no evidence of where it's going.

2001 5.3L
110,000mi

I'll have to give the pressure test a go and see what I come up with.


P.S. I might be crazy, but it seems to leak more when it's extremely cold outside. I live in Western MN and in our last spell of -10 degree weather it seemed to lose quite a bit, compared to in the summer it hardly leaks.

I'm having this same problem. Small amount of coolant disappearing and no evidence of where it's going.

2001 5.3L
110,000mi

I'll have to give the pressure test a go and see what I come up with.


P.S. I might be crazy, but it seems to leak more when it's extremely cold outside. I live in Western MN and in our last spell of -10 degree weather it seemed to lose quite a bit, compared to in the summer it hardly leaks.


A lot of leaks are cold leaks.
That is why check cold and warm and hot.
Post back what you find.

My bet is that the wp gaskets are leaking and drying up before they hit the ground. If you are leaking get it fixed now, dex cool makes MUD whenever it hits air. I disagree with the previous poster though, if you are pulling the pump why not replace the pump at the same time, they are not that expensive compared to a cooling system that is full of mud.

If its not an external leak I feel sorry for ya. GM had a TSB to dealers about certain casting number heads being porous and leaking coolant internally. The ls blocks do not run coolant through the intakes, so if its not a porous head or block it may be head gaskets. Napa sells sniffers you can check the degas bottle for hydrocarbons, if you have a blown head gaskets it will have hydrocarbons in the coolant system.