my 2001 gmc / 5.3 has an antifreeze leak. on 2001 GMC Sierra 1500

I have put in a new water pump, flushed coolant and put in new antifreeze. There has not been any water in the oil. The cooling system was tested. There was no co2 in the coolant and it keeps pressure. I am lost as to where the antifreeze goes. The surge tanks stays fine for days then will start going down.

by in Anchorage, AK on November 13, 2012
2 answers 6 comments
ANSWER by on November 13, 2012
No "C0" in cooling system, that is good. Have system pressure tested, may have to let pressure stay on for a while. Maybe with engine running, poss. intake gasket. But this eng. isn't known to have any intake H20 leaks. Also while under pressure look closely at radiator! No water in oil is also a good thing as that means no cracked heads or gaskets! I say external leak.
COMMENT by on November 14, 2012
Thanks for the reply. I'm going to check the intake manifold this weekend. This engine has a radiator hose from the radiator going to the throttle body. Could there be a leak in the throttle body. ??? What is this line for. I figure it heats the throttle body so ice crystals don't form. I have been told to check the charcoal canister. I have no idea why that has anything to do with the coolant leak. ???
ANSWER by on November 14, 2012
some of these eng have defective cyl heads and crack around valve springs which will cause this issue. pull the valve covers and look around valve springs for cracks or a wash area that is clean from oil residue
COMMENT by on November 14, 2012
Pressure test!
COMMENT by on November 14, 2012
ok I will pressure test. 1st time I've ever tried doing forum. thanks
COMMENT by on November 14, 2012
You are welcom, i don't see the connection with the evap. canister either.
COMMENT by on December 11, 2012
Hi you all. I'm also having problem with coolant leak in my 2001 GMC 1500 Sierra. The cooling system pressure has been tested and it was found OK (15PSI). The light comes on (coolant low level) every 100 miles driven. I' ve read at AA1CAR.COM that some GMC V8 are notorious for leaky intake manifold gaskets. Is that true? The truck spent about 1 hour at the mechanic. What did they miss? The water pump has been replaced on 12/2011.Thanks a lot.
COMMENT by on December 11, 2012
How long was the 15psi applied? May take an hour or more on a warm engine to show up. Uv sensitive dye is also useful.

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