Radiator Flush for 1996 LT1

[Jim S.]

I recently acquired a nice 20k mile 1996 convertible which has not had the radiator flushed for some time. What are the procedures to do a complete (as much as possible) flush of the cooling system? Any help appreciated.

Jim Simpson
Hendersonville, NC
jsimp413@att.net

[Bill H.]

Re: Radiator Flush for 1996 LT1

There's a few differences doing a proper flush on a LT1 , the knock sensors should be removed from the block and there are air bleeder valve(s).
Put the car on jack stands
Warm the engine to about 100 or so
Remove the radiator cap on the surge tank
Using a screwdriver, open the air bleeder valve(s). 92 - 94 LT1s have a bleeder screw on the thermostat housing and one on the throttle body (95-95 may have changed to only on bleeder).
Open the radiator drain valve (right side of the rad), it's plastic and just needs to be opened, not pulled completly out.
On each side of the block there are knock sensors, they probably have small sheet metal covers. There's a large amount of coolant/crude in the block behind these sensors. You need to be extremely careful removing these as they are easily broken, you should use a socket to break them loose and make sure the socket stays tight against the sensor and that you're not pulling the rachet handle at an angle.
After they are broken loose, screw them out with your face away from them, it's almost guaranteed that you'll get a face full of coolant doing this.
Stick a hose nozzle in the knock sensor hole and give the block a blast of water, a lot of crud will come out. repeat.
Do not remove the factory sealant from the knock sensor threads, it is reusable.

Reinstall the sensors, tighten the radiator, fill the system with the air bleeders open until coolant runs out of them. Close the air bleeders, finish the fill.
After warm up and the T-stat opens, burp any air using the air bleeder valves with a rag under them to catch the coolant. They should produce a steady stream of coolant with no spitting or bubbles.

[Bill M.]

Re: Radiator Flush for 1996 LT1

When I got my '92, the coolant showed corrosion/crud. I just changed the coolant (as Bill described). It took several changes (2 or 3 over maybe 6 years) before the coolant came out crystal clear when I drain it, but it does now.

[Bill H.]

Re: Radiator Flush for 1996 LT1

When I got my '92, the coolant showed corrosion/crud. I just changed the coolant (as Bill described). It took several changes (2 or 3 over maybe 6 years) before the coolant came out crystal clear when I drain it, but it does now.

Yea, Bill me too. The first on my 92 @64k miles was very crudy, the second was dirty. The 3rd time after 2 years was fairly clean.