I see what you are getting at with regards to the mix of oil and glycol, however, the glycol isn't pumped in as such and is actually mixed with the P2.4 air from #1 engine and sprayed onto the hottest parts of the box. I think I'm correct in saying it sprays periodically rather than dump it all in one shot. Also, the actual volume of glycol isn't that much (can't recall exact volume) and as such, I don't think venting out the box would be too much of an issue especially when 1. I'd hope the crew would be landing sooner rather than later and 2. The box vents to the aft of the mgb area and would run along outside of sliding cowl