Coolant level confusion after change

[jonboy99]

Advice needed please. 2015 BRZ. 30,000km. Not sure if i've just got the obvious answer of air in the system and need to bleed more, or it's just a quirk of these cars. Problem is the coolant level at the radiator filler cap always seems a bit low - I top it off to the brim of the filler neck, but after a drive and cool down the level drops by an inch or so. If I stick my pinky in the opening, there's half an inch or so of coolant there. This is probably roughly level with the top of the return hose. I just don't see where the air is coming from.


Background: 2015 BRZ. No issues until now (car never used much coolant if any), so time for a routine coolant change.


Followed the shop manual pages on how to bleed, all seemed to go well. Coolant at the bleed nipple by the firewall. Did the usual revving to 3000rpm x6 within 45seconds, and no level drop. However then did the second part and let the car warm up until the radiator fan kicks on and off a few times, and when the car's cooled again, there's the little bit of a level drop.


I decided to buy one of the no-leak funnel kits, and used that, letting the motor fully warm up, fan cycled a few times, got a few bubbles out. However I still get the level drop after going for a drive, or leaving the car overnight to cool down.


So should I expect the coolant level to drop a little bit like this, or should it be right at the filler cap brim?


When the car warms up the level in the overflow reservoir goes up a bit as expected, and then drops a bit when it cools down - as expected. If the system is sucking a bit of coolant back through the overflow pipe like it should, I just don't see where this air gap is coming from.


Help my head not explode!
Jon

[smackrel]

It seems as if it is functioning as designed by moving coolant in and out of the overflow reservoir. Although I thought it should only push out to the res if it is overheating?

With that being said, have you tried keeping it to the full mark on the res when cold after driving a couple times and not opening the rad at all?

[jonboy99]

Originally Posted by smackrel

It seems as if it is functioning as designed by moving coolant in and out of the overflow reservoir. Although I thought it should only push out to the res if it is overheating?

With that being said, have you tried keeping it to the full mark on the res when cold after driving a couple times and not opening the rad at all?

It pushes the fluid out as the system warms up as well (the fluid expands a bit). You're right, i'm going to keep an eye on the reservoir level for a few days without removing the cap.

[EndlessAzure]

You might have an air bubble still in the system during the change/bleed process.

Just keep driving the car around. Warm it up, drive the car around, actually rev out/redline the car out a few times, run the heater system, check it again overnight.

You can continue to top it off at the radiator until it stabilizes - keeping an eye on the overflow level. If the overflow level starts to rise over time, then you know the system is pretty much at capacity/topped up