Coolant catch can

[Brd.Prey]

Not that Subaru tank with 4 connections but the overflow bottle. Should I drill the cap or not. It is aftermarket. I can decide if it should be vented or not? I think not vented so when it cools it will go back in the system but I’m not sure.

Please a little help

[DSR-3]

I have no idea what part you are referring to, but typical systems use an reservoir/expansion tank (bottom coolant connection), not a catch tank. In that case yes, it needs to be vented. Need to let air in to replace the coolant as it cools and moves back, and you need enough coolant reserve when cold that no air gets sucked back. What's the capacity? My H6 N/A system expands over a quart when hot. Catch tanks are typically vented too.

[NAZ]

If using a "catch can" as a recovery tank it must be vented to atmosphere. A recovery tank operates on pressure differential, as the coolant in the radiator cools it contracts leaving a vacuum (negative pressure to engineers). The vented recovery tank is pressurized by atmospheric pressure (~14.7 PSI at sea level) which will open a check valve in the radiator cap allowing coolant in the recovery tank to be forced back into the radiator until the pressure equalizes. Make sure your radiator cap has a check valve -- some don't. So like DSR-3 said, make sure you have enough coolant in your recovery tank so that air is not introduced into the system. Once the coolant is hot it expands and increases the system pressure until it burps coolant into the recovery tank and the process starts all over again. That expasion can be calculated so that you can size your recover tank to accommodate coolant expansion. This is important on a cross flow radiator.

[Brd.Prey]

#2 on this diagram
117927
#6 has radiator cap and those 4 lines turbo, metal coolant crossover Wayne mod then it connects to #2. I need to know if #2 on the car has a vented cap or not.

[redbudrr]

According to the manual page 302, there is no vent in the overflow tank.

[Brd.Prey]

According to the manual page 302, there is no vent in the overflow tank.
Thank you,

[STiPWRD]

#6 is the expansion tank and has a vented cap that goes to #2 (coolant overflow tank/reservoir). As long as the tube inside #2 goes all the way to the bottom of the tank, it will suck the coolant back into #6 when the engine cools off. #2 does not need to be sealed it can be as simple as a water bottle with a rubber tube that goes to the bottom and it will still work - just get a container that can handle coolant temps slightly below boiling.

[Brd.Prey]

Thanks I appreciate the info!