Heater issue

[2008tdihighline]

My b6 hasn't had what I call a really warm heater for some time. It's ok but I expect it should blow quite hot?

The top pipe to the matrix on the engine side is really hot but the bottom isn't.

I read thst even if the matrix is blocked that coolant should still flow through meaning both pipes should be hot?

I can't help but think I've got sir stuck somewhere after doing some work on it last year. I often hear water going thru the matrix at high revs.

I've tried bleeding the system. It warms up fine and sits at 90 degrees all day so a bit stumped.

Also the blower temp on vcds reads around 35 degrees on full heat.

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