So I picked up a 95 Z28 wich what I thought at the time was a awesome deal. I bought it knowing the overflow tank was cracked. I replaced the overflow tank and custom made the overflow tube from brake tubing (Part was discountinued by GM) fired it up still ran hot with no heat in the car. Next I tried a thermostat, same thing over heating with no heat in car. Then I replaced the water pump. I now have heat in the car but it's still running hot. I noticed the fan wasn't kicking on over 200 F, I reved the car up and the fan kicked on dropping the temp to normal temps 190ish. Guy behind me says 100% its the head gasket, The upper radiator hose has a lot of pressure in it and when starting it antifreeze almost immediately comes out the cap (cap is off) he says it exhaust pushing the antifreeze out. It smokes a little at start up but no antifreeze smell or taste (Father in law). Thoughts? I hope to diagnose the fan problem.

 

Fan should kick in at 210* or when ac is turned on. With the rad cap off it's going to be the water pump pushing the coolant everywhere. Best way to check if the head gasket is shot would be a compression test.

 

Get a coolant pressure tester and hook it up. Start engine, if it take 10 minutes to build pressure that would be normal. If it builds pressure in 30 seconds that would be a blown headgasket.

Autozone loans coolant pressure testers.

 

Heading to autozone now. Expecting the worse. Mine as well rebuild the thing if i'm gonna have to put that kinda scratch into it.

 

do a build thread if you go that route

 

Roger that, it now becomes a rebuild vs. Crate debate.....

 

4th Gen LT1 F-body Tech Articles

The first fan comes on at 226 and the second fires up at 235, these engines run hot. You should see the temp gauge yo-yo between 210 and 240 at idle but that's completely normal.

How much smoke comes out of the tailpipes and how thick is it?

 

Some smoke at start up its about as thick and white as a cool morning start up no taste or smell. I pressure tested the cap which was fine, pressure tested the system and found a couple leaks that I fixed with a few new hose clamps. When I pressure tested the cooling system I didn't get a reading for the first 4 minutes then after about 8 minutes it read 7PSI. The fans didn't kick in til I turned the heater on at about 240-250. I originally had no in car heat until I replaced the water pump it worked for a couple days and I now have no heat again.
I also noticed a plug hanging down from the driver side that has the same adapter that goes into the factory airbox. I traced it to the fuse box under the Coolant fan 3 relay but for the life of me I can't find where it would plug into.

 

Anyone know of any kinda additive that would detect a head gasket?

 

Based on your pressure test you could still have a head gasket issue but it is so small it cannot really affect the way the car is running. There are kits that will detect hydrocarbons in your coolant and you can check for hydrocarbons with a common automotive sniffer many shops have. Also factory gages are crap. Make sure you verify the temp reading some other way.

Starting to sound to me like you car had the classic Dexcool syndrome. You have dex mud (left over Dexcool) all though your system. You need a real good flushing.