CamaroManLS1

iTrader: (1)

Hey guys. I got a 99 ss. I've searched everywhere, and I just can't find anything on this fix. I just did a full rebuild on my LS1 with forged internals, heads, cam, stall, and all that good stuff. The car dynoed fine, no issues. As soon as I started driving it, coolant starting shooting out of the reservoir tank. So turned out the water pump was bad. I got a new OEM GM one, bled the system with the AIRLIFT vacuum kit (it held vacuum right at 27 psi). I'm still having issues with it. It warms up to temp fine, no overheating whatsoever. After I drive for a little bit, coolant starts coming out the overflow tank and gurgles a lot. The temps stayed right at 180-185 cruising so it's not overheating. I've tried every bleeding method, it's got new head gaskets because of the new heads, and the crossover/reservoir hoses are correct on the radiator. I've tried the radiator cap too, but it's the Stant metal one from Advance. Do I need the plastic OEM GM one instead? Cuz that used to be on the car before the work was done on it. Much help appreciated. Thanks!

jrpimp00

iTrader: (17)

Check that your hoses on the radiator aren't swapped. The overflow and the vent. I did this once and it would shoot out on after driving.

CamaroManLS1

iTrader: (1)

Overflow goes on top right? That's how mine is.

CamaroManLS1

iTrader: (1)

Could it be the radiator cap? It's new but its a cheap metal one. Doesn't seem like it covers the overflow hole all the way, which would let air in. I'll get a GM one and try that.

LS6427

iTrader: (2)

I have a Stant cap, they work great.

As the coolant crossover and overflow lines properly attached...?

Overflow hose goes on the top port.....

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CamaroManLS1

iTrader: (1)

Overflow hose is the smaller one that routes to the tank under the battery right? That's how mine is. Should I take the battery out and make sure the hose isn't pinched?

CamaroManLS1

iTrader: (1)

And the line that comes from the under the intake/throttle body goes on the lower one right?

LS6427

iTrader: (2)

Yes......that's the lower port beneath the radiator cap.

I would have to say....you need a new radiator cap. Maybe the new Stant cap is bad.......it happens.

Other than that.....only other thing that can cause the coolant to get pushed out the overflow cap....OTHER THAN AN OVERHEAT SITUATION......is a blown head gasket.

Time to get a pressure tester and see if the coolant system holds pressure.

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1_MEANZ28

iTrader: (4)

Its the cap .i already whent throu it..trust me

CamaroManLS1

iTrader: (1)

Well since my rebuilt motor has only like 100 miles on it with new heads, GM gaskets, and ARP bolts, I don't think it's a head gadket. When I used the airlift kit, the vacuum guage where the radiator cap usually is read 27 psi and never dropped. So wouldn't that mean the system holds pressure fine? Does that make the cap the issue? Ill order a GM one tomorrow, then post an update when I get it on.

LS6427

iTrader: (2)

Our systems are 18 psi systems. The caps are designed to hold that much, then the spring releases and pressure can leave the system via the radiator cap....into the overflow tank.

You say 27psi of vacuum.......you need to pressurize the system, not pull vacuum.

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CamaroManLS1

iTrader: (1)

Ok guys I got it figured out. I put a GM cap on it, and rebuked the system. And this whole time I've had my front air dam off for painting, well turns out I need that on........lol. That's what was causing the overflow when driving and not idling because there wasn't any airflow to the radiator. But she's all good now and just took her out to cruise night. Running great and pulling on crotch rockets! Lol

LS6427

iTrader: (2)

Hahahahaha.....yup, that'll do it.

Good to see ya got it figured out.....

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CamaroManLS1

iTrader: (1)

I meant rebled.....not rebuked lol. But thanks! I'm happy lol