help needed please on my heaters

[simon turbo]

hi everyone im new to this site so i hope i have put this in the right place my golf 1.8 turbo has started blowing cold air and does not get hot my car doesnt over heat or anything doesnt use any water does anyone have ideas what it cold be cheers
   

[tweed]

Does the engine get up to temp in couple of mins? Or does it sit at 70C?

could be thermostat stuck open or the flaps in the unit are broke.

[simon turbo]

it sits at 90 all day long mate wont go past it on some cold days it will take a bit longer to get to 90

[dom]

Heater matrix?

[Thom89]

My money is on you needing a new water pump, the impeller is spinning on the shaft, and not circulating fast enough to heat the matrix, though your rad fan will start to do overtime trying to keep the engine cool...

Thom

[tweed]

My money is on you needing a new water pump, the impeller is spinning on the shaft, and not circulating fast enough to heat the matrix, though your rad fan will start to do overtime trying to keep the engine cool...

Thom

it doesnt over heat and takes longer to get up to temp. Surely it would get up to temp faster?

But doesn't rule it out.

[Thom89]

My money is on you needing a new water pump, the impeller is spinning on the shaft, and not circulating fast enough to heat the matrix, though your rad fan will start to do overtime trying to keep the engine cool...

Thom

it doesnt over heat and takes longer to get up to temp. Surely it would get up to temp faster?

But doesn't rule it out.

The flow rate is reduced, because the impeller is spinning on its own shaft, radiator pipes have a large bore and can still cope with cooling a greater quantity of hot water, but the heater matrix has small bore pipe, delivering a smaller amount/flow of hot water, when this happens, the heater fan cools the water too much because its flowing too slowly... once you get your head round the problem, its obvious

Thom

[tweed]

My money is on you needing a new water pump, the impeller is spinning on the shaft, and not circulating fast enough to heat the matrix, though your rad fan will start to do overtime trying to keep the engine cool...

Thom

it doesnt over heat and takes longer to get up to temp. Surely it would get up to temp faster?

But doesn't rule it out.

The flow rate is reduced, because the impeller is spinning on its own shaft, radiator pipes have a large bore and can still cope with cooling a greater quantity of hot water, but the heater matrix has small bore pipe, delivering a smaller amount/flow of hot water, when this happens, the heater fan cools the water too much because its flowing too slowly... once you get your head round the problem, its obvious

Thom

that makes sense.
New water pump then 

[simon turbo]

thanks alot guya great help looks like i got a job this weeknd now then