Heater hot then cold

[Dave]

Hi all.
I have recently had a lot of fun with my cooling system in a 1.8t I’ve bled the system and had the heater working! In my way to work this morning it was warm. Even though set to ‘Hi’ although the matrix pipes were red hot.. It then went cold after ten miles and the top matrix pipe was noticeably cooler than the bottom one. Any ideas really appreciated.

[SD1too]

Originally Posted by Dave

... the matrix pipes were red hot.. It then went cold after ten miles and the top matrix pipe was noticeably cooler than the bottom one.

I'd activate the digital temperature display Dave to see what the engine is doing. If that shows a stable temperature, your heater matrix might benefit from a more rigorous flushing.

Here's my tip. To deter scale formation in the matrix, use de-ionised/distilled water for your coolant mix. It's available from a good motor factor for a few pounds and is well worth it!

Simon

[Dave]

Originally Posted by SD1too

I'd activate the digital temperature display Dave to see what the engine is doing. If that shows a stable temperature, your heater matrix might benefit from a more rigorous flushing.

Here's my tip. To deter scale formation in the matrix, use de-ionised/distilled water for your coolant mix. It's available from a good motor factor for a few pounds and is well worth it!

Simon

Thanks for the reply. I had the digital readout on the entire 20 mile
Journey and it sat at a steady 87-90 all the way!

[SD1too]

Well that's something! The focus is back on the heater matrix then.

If you used plain water for flushing you could try a solvent solution. The late MG John had success with Holts Speedflush by leaving it in the system for a few days whilst he drove around. Or you could use a descaling product provided that it's safe on aluminium.

Simon

[Dave]

Thanks for this information I will try this. 👍