I've run out of ideas on this one... I have a 1999 c5, the tanks on the stock radiator cracked so I bought a new EPC radiator, fitment was good, seemed to be decent quality. When I first put it in it seemed to be fine, but after a few days of use it started overheating, bad, I couldn't get more than a 1/4 mile with it if it was warmed up, you could watch the gauge move. I turned the heater on and it blew cold air, so I figured the coolant wasn't circulating, maybe a water pump, so I had it towed home. Water pump was fine, thermostat was also working, I did however notice when I removed hoses hardly any water came out, but the tank was full, so I determined that there was a large amount of air in the system. I drained everything out and refilled with new coolant, being careful to purge any air from the system, it took about 3 gallons (more than last time). It seemed to work great at first, ran around 185-190 on the highway and wouldnt get higher than 226 sitting at stop lights around town. But today I pulled into a parking lot and it at about 220ish it blew coolant out the cap! Not very much, maybe a 1/4 gal at very most. Tried to drive it back home and after about a mile or two it climbed right back up to 260! I could once again watch the gauge go up as I drove. (also the fans are working as well, so it's not that). I'm out of ideas here... Anyone have any insight on this??

 

My only guess is air in the system still.

 

I would try this procedure before I took any other action. As long as your sure you don't have any other leaks. I copied it from someone elses post in another thread. I'd give him credit for it but forgot who it was. I've been copying usefull bits of info from here into my Z06 library.

According to the service manual:

1. Fill the system through the surge tank opening.
2. Fill half the capacity of the system with 100 percent DEX-COOL® coolant.
3. Slowly add clean drinkable water to the system until the level reaches to the base of the neck.
4. Start the engine.
5. Idle engine for 1 minute.
6. Install surge tank cap.
7. Cycle the RPM, idle to 3000 in 30 second intervals until engine coolant reaches 99°C (210°F).
9.Shut off the engine.
10. Refer to step 3 above to remove the surge tank cap.
11. Start the engine.
12. Idle engine for 1 minute and fill surge tank to 1/2 inch above COLD FULL mark on the radiator surge tank.
13. Install the surge tank cap.
14. Cycle the RPM, idle to 3000 in 30 second intervals until engine coolant reaches 99°C (210°F).
15. Shut off the engine.
16. Top off coolant as necessary, 1/2 inch above FULL COLD mark on the radiator surge tank.
17. Rinse away any excess coolant from the engine and the compartment.
18. Inspect the concentration of the coolant.


http://forums.corvetteforum.com/c5-t...-radiator.html

http://forums.corvetteforum.com/c5-t...erheating.html

 

Sounds like you "didn't" "burp" the system. Its an air bubble and needs to be blead out. There is a procedure for burping the system. There are many hundreds of posts on this procedure. Do a search at the top of the page.
Get back to us.

 

Ok thanks! I'll do that procedure and get back to you.

 

The link 8vette7 works awesome I bet that cures it. It did on mine at least

 

Quick update, I went through the burping procedure. One thing I noticed was that whenever the temp. got to, or a little over 210, it would burp fluid out the surge tank cap (cap was on). I filled to where it was about a half inch above the cold fill line, coolant temp was a little over 100 when I did that. Not sure if its supposed to do that or not...

 

Thanks!! I had no idea about this, will go try this right now and see how it works.

 

Hope you get it solved - post up what you come up with.

 

After the burping procedure and bleeding the air from the heads it seems to be ok... It took a couple of days to start acting up before, so I guess I'll see if I really did it right this time. Thanks for all the help!

 

If the radiator hose is collapsed release the radiator cap ,The cap gets gummed up .replace with new cap about $15.

 

if it was gonna do it it would have done it again right away...should be good to go

 

So.....how weeeee doing?? Update

 

So the cooling problem has been fixed, however it kept blowing fluid out the surge tank at about 220! Turns out the radiator cap was bad also! Went and got a new one for $16 bucks, works great! Also the ECP radiator seems fairly good quality, only paid $278 shipped, I'd recommend it for someone on a budget.