PSA - Expansion Tank Cap

[TheFixer]

I did an entire cooling system refresh last month. All OE/OEM bits.

I was getting the deflated upper hose after cool down. Often associated with improper bleed of system. But, my temps were good and heating was good. No air in system.

One cause could be a bad expansion tank cap. Swapped the old one back.

That was it. No more deflated hose.

The cap, mahle behr, was bad. The old cap is uro.

So, watch out for bad bits even when buying quality parts.