MP4.2+6.0

Again, figure you basically have a certain amount of water flow through the heater panels. The faster the fan runs, the faster you cool the panel down in general, and the greater volume of air into which you are putting the same volume of heat from the engine coolant. As Misha pointed out, in Econ mode you also aren't further fighting against some cooling by the AC panel also in line w the air flow.

Since you did the thermostat and water pump (correct?) with the belt, to me that leaves the valve block as the obvious suspect, and again more so than heater core theories. This also assumes your cooling system isn't in fail safe mode. Are your cooling fans on all the time by chance(a sure sign it is in fail safe mode, plus often some dash lights)? Scan the ECU for codes too to be sure it doesn't have a cooling system failure one, assuming you have a real VCDS cable. On the valve block, assuming the other stuff is in order and no cooling malfunction codes, I would g back to bypassing it and see what you get heat wise.

There was already a post on the D4 board the other day with a confirmed (by a dealer) heater valve failure . Part apparently costs much less on D4's now, but Art still can't get it solved I guess.

allenst

So recently it was suggested I rin the Econ ON.
I did that

but what developed is the total loss of my blower. No forced air at all.
I could also NOT take Econ from ON to OFF position.

I could get to it via Setup but when I tried to select Econ OFF it would not take. I would only run in Econ ON.
this lasted the whole day.

This morning the Blower works and I am able to switch between Econ ON and Off.

laychooba

this week's adventure - i'm going to try and run CLR and pressured air through
the heater core. try and get a proper flush going on.

going to have to make my T-fitting contraption to get this done.

i'll also pop the caps off the heater valve block and see if i can see these things
moving.

MP4.2+6.0

Hard to guess at some of this from a distance, but non working fan at first sounds electrical. Could be the blower motor itself, but also can be system doesn't see coolant temp being warm enough so it won't let fan turn on. Remember except in defrost mode, fan won't run until initial warm up.

But then you say it wouldn't switch out of Econ mode, leading me to speculate you could have an underlying electronic issue of some kind rather than a faulty fan or some such.

Net, it needs a scan to have better info. A lot of just guessing at this point without better diagnostic info.

laychooba

SOLVED.
well for now - heater core flush did the trick.
i removed the valve block and CLR'd both heater cores with a
hose and low pressure air (25 psi).



i would say a pretty substantial amount of crud came out.



as i was opening the bleeders to get the air out, i heard something kick
on and the blower motor just started pouring in hot air. within minutes i had
the car at unbearable cabin heat temp. YESSSSSSS!

now, on to my ABS problem.

allenst

Congrats for now.
but wow a lot of build up cam out.

I wish you had a few clearer photos of your setup and connects.
If bleeding doesnt work for me I think I will try this method.

Better pics, and did you flow clr both directions ?

laychooba

and that was just ONE of the heater cores.
yeah i should of taken more pics, but i was doing it after work and i didn't want to be there all night
so i was trying to get it done as fast as possible. i basically went off a couple of youtube videos that
i saw online. same principle basically.

or


i had some barb fittings and 2 hoses laying around, hook the hose into the inlet and
the other outlet hose into a bucket, even just doing that most of the crud came right out.
A -----> B
C -----> D
then reverse.



after all the coolant was out of the core, i blew it out with air until there was no more
water coming out. then put a funnel on the inlet hose and poured CLR until it came out
the outlet hose.

sit back and wait 30 mins. then rehook the hose and let it flow, you can give shots of
compressed air to dislodge anything else in there. on the return, i didn't CLR it. i just flipped
the hoses and let the water run and run till till it was clean clean clean.

repeat the steps for the other heater core. just a tight work space, you'll definitely have to take
the valve block to access the hoses.

allenst

Yes I have watched those YT videos before.
some here think the method is crude.
I think it is more dangerous in sense of breaking stems and causing more damage, or using too much pressure in the system.

The amount of crud you pulled out is more that that I've seen on any YT video.

How long did you run process for ?
Did you flow back and forth in both directions, or just reverse flow ?

and.....where is the second heater core ?.....I have not see it dealt with on any videos.

laychooba

crude? yeah i can see people here being against it. i'm more against taking my dash apart
and changing two $500 heater cores or whatever they cost. it was definitely a risk i was willing
to take.

both sets of hoses for the heater cores go into the valve block, so they 4 hoses are there.
the stems that come out of the firewall are metal, not plastic and even from there there's a couple
inches of hose extension that come from them so it would be pretty hard to break them. A4's have
plastic fittings that come from the firewall directly, so those you would have to watch out for. none
of the videos i found online we're A8 specific, but it's the same basic concept.

i flowed at least 4-5 large buckets worth of water in each direction. i let the CLR sit in the heater cores for about
30 minutes each. you basically just keep flowing it until it's clear clear.

parkrog

I had similiar no heat situation and final found heat regulator was bad. It works on a pulse basis and switches water frm left to right.
Took control apart and found no clogs or issues. Electro magnetic units went bad. Got used one and everything is now fine.
Unit has two bleed screws to bleed any air. Bleed system as a start see if getting hot coolent.