GTM over heating

[tkeyes]

LOL,
I know this one has been beat to death but that is what I am trouble shooting today. Tried pulling a vacum on the vent line tube that goes up the radiator. It helped for a bit but it came back. I am assuming i just have air trapped in the system. I will try the service manual fill method and see if that helps.

[65 Cobra Dude]

tkeyes,

I know following the procedure below gets all the air out:

Burping the Cooling System

I was having problems burping the cooling system and Steve and I figured out a fool-proof way to ensure it is full.

I bled the cooling system per the Corvette instructions and it did not completely get the air out. I was concerned there was lots of air left in the system because after running for a while, it would lose power dramatically and oil pressure would drop to 25 lbs. I thought maybe it was a fail-safe system for the Corvette computer that it would shut down some injectors or maybe kill spark to some of the cylinders, effectively de-powering the motor. After a little more investigation, I believe it was because the motor was getting very hot - as proved by the Ray-Tec infrared temperature gun. I think what was happening was the oil was getting too thin to charge the lifters, valves weren't opening all the way... I'm just telling you all this so you understand the symptoms I was seeing.

1. Remove the higher radiator hose at the engine (not the one connected to the thermostat) and lift it as high as possible.
2. Remove the 2 steam vents on top of the heads on the belt side of the motor (there are 2 more at the tranny side but they can stay tightened).
3. There are 2 smaller radiator hoses that connect to the pax side of the radiator. 1 goes to the overflow tank and one goes to the steam vents/TB. Pull off the larger of the two smaller hoses (if that makes sense) - the one that goes to the overflow tank.
4. Pour antifreeze mixture into the hose that goes to the radiator that was removed in step 1 until antifreeze comes out of the small hose removed from the radiator.
5. Re-attach that small radiator hose.
6. I used the old Corvette radiator hose and poured antifreeze into the block through the higher radiator hose connection on the engine. Keep filling until the antifreeze comes out of the steam vents.
7. Replace steam vents.
8. Add more antifreeze to hose that connects to radiator if needed.
9. Connect upper radiator hose back to engine.
10. Run car until thermostat opens (could be a while as mine is a 212 degree thermostat).
11. Let car cool and add fluid to overflow tank if needed.
With that procedure, I was able to completely fill the coolant system (btw - about 5 gallons) and she'll run forever now without going into the mode described above.

Henry

[VRaptor SpeedWorks, LLC]

I guess I'll throw in my procedure that I use here. I've had good luck with it so far:

1. Raise front of chassis about 10-12" above the rear.

2. [B]Make sure the coolant level in the overflow tank NEVER drops down to where air can get into the bottom port![B]

3. Disconnect the 1/4" vent line at the steam vent port at the front/top of the engine, and connect a short 1/4" piece of hose to the steam port on the engine.

4. Alternate between pulling vacuum (with a vac generator like a brake-bleeder or something similar) on the 1/4" vent hose that goes to the radiator while plugging the 1/4" short hose hooked to the steam vent.....then plug the rad hose and pull vac on the steam vent........all the while making sure you keep an eye on instruction #2! Keep alternating between these hoses.....plugging one and vac'ing the other. If you've got air in the system, you'll hear is gurgling around in there while you're doing this. You can actually hear it "pump" the air out of the heater core as you do this. I just keep doing this until I get nothing but straight coolant out of the 2 vent hoses, then re-install the vent line back onto the steam vent port.

You may want to start the engine and run it up to temp at this point. If you watch the bottom port on the reservoir, you might see that it looks "foamy" there. Run it until the coolant is running clear thru there and no longer looks foamy.....revving the engine up and down from idle to 3k rpm or so. Shut the engine off, wait for it to completely cool and repeat steps 1-4 again. Normally I get very little, if any air out the second time around.

Make sure you keep enough coolant in the reservoir so that the bottom port can NEVER suck air! You can't fill it completely or as soon as the engine warms up, it will blow coolant all over, but you do need to make sure it is more than just half full. If you are cornering or accelerating hard, and the coolant level in the tank allows that port to suck air, it's all over.

[tkeyes]

I finally got the car running ok. I think is was a combination of all the tricks. I also messed with opening the heater valve as well. It was running fine while sitting in the garage so probably Shane's suggestion to have the tank filled to a proper level is a good idea. I got on it a little while driving so maybe all the fluid rushed to the back of the tank allowing air to be sucked in.

[mmaragos]

I went the route of adding a rear coolant tank / reservoir. Makes filling very easy, then will maintain the cooling system in the long term. I left the front one in...primary because I had everything installed when I added the rear tank. The big benefit is getting the coolant reservoir above everything else - allowing it to be the high point for trapped air - instead of the heads.

I also noticed - back when I was working on this stuff, that the VA HCV would create an overheat situation when it closed (max A/C position) at least at idle. I replaced with a bypass that would recirculate back to the block instead of just stopping (dead end) flow to the heater core.

[crash]

There are parts available that will solve these issues, and they are available in kit form. Unfortunately since the company that offers them is not yet a vendor here, I can not say where to find them, but I think you guys know where I'm talking about.