Mk3 Galaxy heater blows cooler at higher speeds

[SiC]

I have an 08 1.8tdci Galaxy. When the heater is set to high it blows hot (as expected) at urban speeds.

However, Ive noticed that whilst holding a higher speed (e.g. 70mph on motorway) that the heat drops off and is luke warm at best.

Exiting the motorway and going back to lower urban speeds the heat returns.

Is this normal for a Galaxy?

I've read of other people not being impressed with the heating system in the mk3, but none have described the heat trailing off at high speed.

The car has recently had the headgasket done approx 200 miles ago. The engine temp remains normal when the heat trails off.

[insanitybeard]

Have you only noticed this drop in heat from the blowers at higher speeds since the head gasket was changed or was it like it before? I can understand a slight drop in heat from the blowers at higher speed due to greater airflow through the main radiator but if it's a marked difference then that sounds a bit suspect to me. Is it losing any coolant at all?

[SiC]

I never really paid attention to the heat at high speed prior to the HG failure as we had good weather at the time so I mostly had the AC on to cool the car.

It's only after the HG was done that I've paid attention to it, more so now as the weather is getting colder.

I would say that the heat out of the heaters at lower urban speed is as hot as you would expect. However, hold 70mph for several miles and the heat drops to luke warm - the higher the fan speed the greater the effect. But even on the lowest fan speed on High temp I'd say it's warm at best.

The HG was done by local engine company who provide a 1yr /12,000 mile warranty.

I've taken it back to them and they checked everything over and believe the HG is ok and there has been no coolant loss.

[insanitybeard]

If the loss in temperature in the air coming out of the blowers is that noticeable for it to be luke warm when travelling at speed, something doesn't sound quite right to me. Without having another Mk3 Galaxy with the same engine to compare it against it's impossible to say if it's abnormal, but I'd still expect hot air out of the blowers regardless of vehicle speed! It may be completely unrelated but cooling system faults quite often play a part in contributing to engine overheating in the first place- and head gasket failures are often a result of overheating, did the people that changed the head gasket suggest or investigate any cause of the head gasket failure in the first place?

[barlidge]

Funnily enough I would have actually expected the opposite, when the engine was under load (higher speed) then I would have expected it to be warmer.  Under urban driving (low load) I would have expected it to slightly cooler.  Different engine/body I know but that's how it played out on my mkII when the aux heater wasn't working in colder weather.

As Paul said it would be good to ascertain if this is normal behaviour but if not then I think the thermostat would be first on my list to be tested.

[SiC]

Thanks for the replies guys.

I'm not sure how much investigation work was done to discover the cause of the HG failure,  but they took a couple photos of the block and you could see the HG failed in 2 places on seperate cylinders (cant remember which specific cylinders now).

In order to provide the warranty on the HG they changed the water pump and thermostat too...as well as doing the usual checks to the head/block for cracks and warping.

As its under warranty and the air not being as hot as expected on max temp at high speeds I dropped it back at the garage.

They checked it over and believe the HG is good. No leaks found and no coolant loss.

I've also replaced the header tank cap as a precaution (ford part - not aftermarket).

In my old car, a 2001 Seat Alhambra tdi, if I set the heat to max and did motorway speeds for an hour I'd have to open a window as it would be uncomfortably hot.

In the galaxy there is no fear of that sadly. Its a head scratcher!