Coolant Overflow Tank Vent Hole
 

Where exactly is the vent hole for the Coolant Overflow tank? When I was filling coolant in the overflow tank, the coolant was pouring out from the rubber piece between the neck and the tank. By the way the rubber piece looks really brittle. Do I need to replace the overflow tank? or is this where the vent hole is at?

There is only one easy way to get to the overflow tank, and it's not really all that easy. I found that the easiest way to get to it is to remove the front bumper. Mine was already off since I'm replacing it with an aftermarket piece.

Why the hell are you filling that tank??? Only add to it when it's below the low mark. It's called an expansion tank for a good reason -- you need to leave room in it for the coolant expanding when your engine's hot.

You shouldn't let it get above the F mark (when the engine is cold).

Fill coolant at the filler neck. See section 5: Maintenance...

The Big Fat FD3S Cooling Thread:
https://www.rx7club.com/3rd-generation-specific-1993-2002-16/big-fat-fd3s-cooling-thread-571088/

-s-

Got it, fill from filler neck and AST. But I am still curious where the vent hole is located at.
I was looking down the end of the neck area where it meets the base (a black rubber piece that looks hard and cracked) and saw the coolant leaking out from there. I'm kinda freaked out from there. But I hope that's the spot.

I don't there is a vent hole per se -- it's not supposed to get that full. The neck simply acts like a funnel into the reservoir, so it'll leak from the top if you overfill it (or it boils over).

You can get to the expansion tank by removing the right side fender liner. Not that hard... you can also remove that tank once you have done that.

someone just post a pic of the damn thing

There is a vent hole on top of the recovery tank (I know because I put an elbow with a tube in it so the coolant would come out in a specific spot if it overflowed instead of it going all over the belly pan and frame work to wher eyou only had a general idea of where it originated from.

Is their supposed to be a black spongy thing with tape at the very bottom of the neck when it connects to the tank?

Yes, my brand new one I just bought from Ray has that.


The hole at the top of the overflow tank is a vent to equalize pressure, so that coolant has a spot to flow easily when it is vented from the ast, and so that coolant recovery can happen easily without fighting a vacuum in the overflow tank.

J

You're right -- I never noticed it. Good idea with the tube, btw.


Interesting, mine (an early '93) has just the white plastic fill tube going into the tank. For the OP, the arrow points to the vent hole: