Re: 99 5.3 z71 overheating? Group: alt.autos.4x4.chevy-trucks Date: Mon, May 30, 2005, 10:32pm (CDT+5) From: snipped-for-privacy@hotmail.com (shiden_kai) Trailblazer wrote: I have a 99 chevy z71 with the 5.3. Whenever i get over about 65, it used to spike from around 175-180, to almost 210 on the gauge. Anyway, i replaced the thermostat with a duralast thermostat from autozone and flushed the radiatior, put new anti freeze in it. It used to only run hot when i got up to those speeds, but with the radiator flushed and new thermostat, it's running at about 208 or so after i just let it idle up. I haven't driven it since i replaced it and did the work, i just let it run 10-15 minutes when i saw it jump like that. is this a normal temp for a 99 5.3? is the thermostat ok? it said it was a 194 degree, but the guy said that's what it needed to make the computer still work correctly. any input would be really appreciated. My input would be....get an original GM thermostat and stick that in there before you do anything else. Obviously, you need to make sure there is no air in the system, but frankly, the new generation v-8 doesn't have any real problems with that. You fill the overflow tank while you run the engine, and it will pretty much autobleed itself. Ian
True ....After you let it sit was it low on coolant? If he just filled it up and put the cap on the first time you ran it it wld spike unless you let it run with the cap off to burp it...But your right they do autobleed them selfs...By now he sholuld be low on coolant if it was air... S Cook