05 4.4i Heating Issue

[CalgaryX5]

Alright i put this out to tender a few days before it heads to the dealership.

When i request heat, say 32 deg (max in this example) and I am not in Auto mode - simply entering the temp desired and setting the fan speed myself,
I get NO heat at all at speeds above about 90km/hr ... 50mph ish...

It isn't until I slow down in the lower speeds say below 60km/hr that I start getting heat again..

Through all vents when I am on the highway I am getting cool external air. even if 32 deg is demanded.. again not in auto mode.

Outside temp during this time is -10 deg celcius on average....

coolant levels all good / blower motors replaced last summer.

Has anyone seen this before ??


JMW

[BrianX54.4is]

Is your engine temperature also dropping at the higher speeds? If so it could be a faulty thermostat causing overcooling with that low outside air temp!

[bsteel]

I am having exactly same issue. Any other suggestions. Temp gauge reading normal.

[diyanich]

I would think it's the duct gate or how would you call it..
Try to play with the recirculating button.I bet the gate is either stuck or broken,so you get the excessive outside air pushed by the fast driving into the mixing chamber where the heater core is.

What do you think?

Originally Posted by bsteel

I am having exactly same issue. Any other suggestions. Temp gauge reading normal.

[dpuyen]

Had the identical issue just before the holidays. Dealer replaced thermostat and water pump with no change. They then changed out all the other bits associated with heat system. still no joy. Then they blasted out the coolant system (their words). Appears there was a air lock that did not clear with normally bleeding.

[bsteel]

Wonder how they blasted the cooling system. Connected a high pressure hose to the heater hoses ? I travelled 300 miles non stop with this issue. I would have expected an airlock to clear itself but will give the blasting a try. Thanks for the help.