Coolant amount in aftermarket overflow reservoir

[stros]

Hi guys - my LS3 swap Trans Am has an aftermarket coolant overflow tank.  I don’t have the original jar to refer to and was wondering what the recommended amount of coolant should be when the engine is cold?  This aftermarket aluminum tank has a capacity of 28 fl oz.

[SoupMan]

While cold, put a little bit of coolant in the reservoir (maybe 1/4 of the reservoir) and then warm the engine up to running temp. Keep an eye on the level in the reservoir as it will go up as the engine warms. Once the engine is warm there should be at least 1/3 space left to fill. This will give room for when coolant gets warmer than it's normal operating temp.

This is how you will know if the reservoir is big enough.

[stros]

While cold, put a little bit of coolant in the reservoir (maybe 1/4 of the reservoir) and then warm the engine up to running temp. Keep an eye on the level in the reservoir as it will go up as the engine warms. Once the engine is warm there should be at least 1/3 space left to fill. This will give room for when coolant gets warmer than it's normal operating temp.

This is how you will know if the reservoir is big enough.

Awesome, thanks for the tips.  Yeah I was also wondering if the size of this aftermarket reservoir was large enough as well, as the shop that installed the LS3 also installed this reservoir. 

[SoupMan]

I've encountered enough people running a simple water bottle as a coolant reservoir. It doesn't expand that much but the reservoir for the firebird was like 2L.

[stros]

Pretty certain I’ve resolved the issue.  There was some fluid underneath the car - right below the reservoir.  The aftermarket reservoir was not secured very well.  It was bouncing around and I believe loosened the cap, causing the fluid to dribble out probably after hitting a bump.

I added a pipe clamp to better hold the reservoir tightly.  It’s not going anywhere now.

Tested it out briefly.  Added 9oz of coolant (slightly less than 1/3rd full cold).  Ran the TA up to about 200 degrees and it filled up to about 2/3.  No leaks either.  I’ll keep an eye on it but I think it’s in good shape now.