Coolant Sight Glass/Air Bleeder
The coolant sight glasses are made from aluminum. The sight-glass itself is made from fused glass that is rated to 500 degrees F, and 1500 psi. The sight glass has a petcock on top for bleeding air out of the system, and, if needed, an extra 1/8 NPT fitting for a steam vent tube used on LT1 and LSx engines,
This part comes in three non-transitional versions and three transitional versions. The non-transitional versions are listed below. For transitional versions, click here.
This version has no air bleeder and no steam vent fitting. Please specify a hose size, chosen from the list below.
Please specify hose size, choose from list below.
Please choose steam vent size when adding to cart (1/4", 5/16", or 3/8") and also specify a hose size from list below.
NOTE: For a transitional version of this Coolant Sight Glass/Air Bleeder, click here
Air in the cooling system can cause big problems, from overheating due to foaming, and to corrosion that rots and clogs radiators.
According to a cooling system engineer, 2% air in the system can cause 8% less heat transfer, 4% air in the cooling system can cause a 38% loss in heat transfer.
With engine swaps, such as the LS1 into Mazda RX-7's, where the radiator is lower than the engine, many of the overheating problems are caused by air in the system. The coolant sight glass will allow you to purge the air out of the system with the bleed screw.
In racing applications, when the engine is running at high rpms, the sight glass will allow you to diagnose a foaming problem caused by cavitation. With cavitation problems, it is often necessary to slow the water-pump with underdrive pulleys, or change to a coolant that has anti-foaming characteristics.
When using Dex-Cool coolant, air in the cooling system is reported to cause corrosion problems, including turning the coolant into rust that clogs coolant passages and heater cores.
One way to prevent problems with Dex-Cool is to use a Stant 10230 pressure cap, which has a spring loaded valve that prevents air from getting into the cooling system.
The Stant 10231 cap is floppy, and the valve hangs loose, allowing air to get into the cooling system more easily when the coolant recovery tank is low on coolant.
Last updated 03/11/2013