Hi there. I'm new on here so please be kind 😁.... I have a 2002 mk 6 fiesta with duratec engine. Heater blows cold. The engine is reaching temperature. The heater hose into matrix is hot yet the one out is warm, nearly cold. The cable is working the flap behind the o/s footwell panel. I was told by a mechanic that the matrix will most certainly be blocked. I run a tin of gunge cleaner through the system without success. The big question is.... is it a big job to swap the matrix? I 've just watched a video on here on how to remove front dash panel and stereo , presuming that's all part of the job. I'm ok with that but how much further do I have to go to remove the said matrix. Thanks in advance....👍

You'd have to remove the entire dashboard to access the matrix, it's not a quick job!

If possible, I'd remove the pipes at the bulkhead and run a hose through to try and flush it through.  We rarely see blocked matrices, usually leaking ones!  Does the coolant look clean in the header?

Should you have the 1.3 8v Duratec engine, the thermostat has a relief valve which bypasses the flow to the matrix.
 

Yeah Tomsfocus, the coolant is clean.

1 hour ago, Dan62 said:

Should you have the 1.3 8v Duratec engine, the thermostat has a relief valve which bypasses the flow to the matrix.
 

Cheers Dan62. We do have a 1.3 duratec engine. Is there a fix regarding this relief valve or do I need a new stat?

If you disconnect hoses and try to flush the matrix, make sure flow is in opposite direction to what it normally would be when in use

Many thanks isetta 

17 hours ago, Steve3539 said:

Cheers Dan62. We do have a 1.3 duratec engine. Is there a fix regarding this relief valve or do I need a new stat?

Without knowing the history it's possible the stat has been removed, so yes a new stat.