Engine: D5: Heater matrix burping...

[bobmccann]

Hi all,

I've recently flushed my coolant system but have a problem now with the heater. I presume that I have an airlock. I have tried running the car until hot and then (slowly and carefully) releasing the pressure from the expansion tank, also 'massaging' radiator hoses, but the heater is still blowing cool.
During the flushing process (draining, filling (with top hose off thermostat), running, 3 times over 2days) the heater did work, so I do not think I have a blocked matrix or faulty dampers or thermostat. The heat is reaching the matrix but doesn't seem to be flowing through it, hence suspect airlock.
I don't know what I've done wrong, but hope that a gem of advice can be given here.

Thanks

Bob

[cheshired5]

Do both the heater pipes in the engine bay get equally hot?

[petey]

It's also wise to leave the cap off u til the top hose gets warm whilst you massage the pipes. Leave the cap off as the engine cools down too, overnight is ideal.

[bobmccann]

Thanks guys.
Yes Si, both pipes get hot. The air blowing out is just off cold, but during the flushing process it was hot which is why I am thinking air lock.

Ps. Si your videos have saved me a lot of money and have solved many problems, excellent videos thank you.

[cheshired5]

Originally Posted by bobmccann

Thanks guys.
Yes Si, both pipes get hot. The air blowing out is just off cold, but during the flushing process it was hot which is why I am thinking air lock.

Ps. Si your videos have saved me a lot of money and have solved many problems, excellent videos thank you.

No problem and you're welcome.

Assuming your flush of the system ran clean and clear, with both pipes being hot, that will mean the heater core is hot and there's no airlock.
If the climate control is set to auto and temperature dials aren't at maximum, it's unlikely that hot air would be blowing at this time of year.
To begin with, put the temperature dials on maximum heat and get the car up to temperature to see if this changes the situation.
Getting Dice and Vida on the job would be my next step to recalibrate the climate control module (CCM) and checking that the cabin temperature sensor and other elements of the system are working correctly.

[bobmccann]

Thanks Simon. I will get dice/vida onto it, see what turns up and report back for the information of others.

[cheshired5]

No problem.
Your issue does have echoes of this thread and hopefully the fix will be equally quick and simple.

[bobmccann]

Ok, I've had at look at VIDA and have found the following....

No error codes logged for the CCM
Ran a calibration, no errors logged
Checked all air damper requests and actuals - no issues

BUT the cabin temperature was showing a lot of fluctuation between high 20's to mid 30's and the outside temp was showing 18 (doors were open!). Could this be the problem? I blew into the sensor to clear any dust and can see the thermistor is clear. Could this be a thermistor or solder problem?

However, when I set the heat on max (which I would have thought would override any heat setting) there is still little or no heat blown out.

Any ideas welcome!

[bobmccann]

Further to this, just been on a drive and the aircon is blowing full fan cold only on auto! I now presume that blowing into the cabin sensor has disturbed what was a damaged thermistor so the ecc thinks the cabin is hot and must be cooled.

Next step ecc out to check!

[cheshired5]

Originally Posted by bobmccann

the cabin temperature was showing a lot of fluctuation between high 20's to mid 30's and the outside temp was showing 18

The ECC won't give heat if it thinks that the cabin temperature is so high already.

I think you'll be finding the thermistor is indeed the issue.