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It's that time of year again, let's fix this no heat issue once and for all

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It's that time of year again, let's fix this no heat issue once and for all

Old 09-27-2011, 10:56 PM
1st Gear
Join Date: Sep 2011
Location: Lake Stevens, WA
Posts: 7

It's a 5mm hex on mine
Old 09-28-2011, 09:22 AM
jdahlen24's Avatar
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Thread Starter
Join Date: Nov 2010
Location: Rochester, MN
Posts: 695

Thank you, sir!
Old 10-29-2011, 08:39 AM
jdahlen24's Avatar
2nd Gear
Thread Starter
Join Date: Nov 2010
Location: Rochester, MN
Posts: 695

Just wanted a post an update on my no heat issue. I finally gave up and took the car into my Audi mechanic, where he performed the SNO-BOL flush on the heater. Unlike me, he has a very powerful air compressor, and that combination worked for him. He told me he got lots of junk out of the heater core, and now I have my old glorious heat back...even at idle!

$75 well-spent.
Old 10-30-2011, 03:49 PM
markymarc's Avatar
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Join Date: Apr 2009
Location: Des Moines, IA
Posts: 675

HAHAHA, I'm still laughing at myself...I've had heat issues since I got this project car...THEDEVIL has tried to help as well.....just FYI, the previous owner used stop leak (see pics of heater core) DON'T EVER USE STOP LEAK!!!!!

Anyway, when I finally DID do my heater core, I had/have all the same symptoms you guys have, HIGH RPM heat, then no heat etc....but I still have intermittent heat WITH a new heater core...I was going to do a DIY on heater core replacement, but didn't have camera at the time....it's not hard, just time consuming (the 300+ zip ties behind the dash don't help either)..guess What? I still have heater problems, so maybe someone can help me think outside the box?

When I saw my heater core, I thought for sure that was it (see pics). Since installing the new heater core, I have flushed the system over 20 times, to clean out all the stop leak etc. with a machine, re-bled it etc...and I still have the following issue (remember NEW heater core):

Start the car to let it warm up, car warms up, heat stays at 60 degrees UNTIL I give it RPMS then it warms up, but if RPMS are lower, heat drops...I have noticed that if I drive it until it warms up, then shut it off for a few, turn it back on, I get 120 degree+ heat?? and it stays warm?? BUT, if I just drive it without shutting it off, heat comes and goes according to RPMS....I know, I know, sounds like AIR in system right? I've bled this system so many times, more than most, and it still does the same thing. I even MADE a gadget with a water heater overflow valve (lets air out) that I put on the heater core hoses to bleed and I still have the same issue and it hasn't gotten any better.....Could it be the inside temperature sensor? If so, where is it at? My outside temp sensor works fine.... my flaps work fine, timing belt and thermostat new, etc....any NEW ideas would help, I'm trying so hard to say it's not AIR in the system, but that's what it points to....

Thanks for any new info and good luck to everyone....enjoy the pics..

Attached Thumbnails It's that time of year again, let's fix this no heat issue once and for all-photo-1.jpg   It's that time of year again, let's fix this no heat issue once and for all-photo-2.jpg  
Old 10-10-2018, 06:23 AM
1st Gear
Join Date: Jan 2017
Location: NZ
Posts: 43

I pulled the heater unit out of my ''Spare parts.98 A4 B5'
Honestly, the plastic housings for the vent tubes are distorted direct from the factory.
Connected to the front of the centre consul air box which contains the heater core & 3 motorised flaps. There's two plastic housings. One that shifts the air up to the centre 3 vents, and another which vents across the dashboard to the side vents.
The side vents housing flange pulls off the central air box exit port, so air just vents (pisses out) there & the central vents housing helps pull that first housing off too. So most of the vented air just escapes into & around the central housing box inside the centre consul.

More bad news.... If you notice bits of polyurethane foam comming out of your vents. That's the foam that covers the motorised flaps inside the centre consul air box.
There's 3 flaps, a large double flap, a smaller single flap, both made of sheet metal & vertical, & another horizontal plastic flap.
The two metal flaps have foam glued across both sides of the flap so they seal against the faces they are supposed to touch.
That polyurethane foam breaks down, that's the same stuff that's supposed to hold your cars headlining up, and the reason that its fallen down...
The sheet metal flaps have 3 large holes in them, approx 50.8 mm diameter.. If the foams broken down, those flaps will do new nothing at all, they will just mix hot & cold air & vent it randomly inside the centre consul.

The smaller horizontal flaps not so bad, it's plastic & nearly covers the port it's supposed to. The flap ( the recirculation/ outside air flap) that's directly under the cabin filter, you can see it if you remove that filter from under the bonnet & look down there with a torch. The foam covering will be broken up, but the flaps got no holes in it & will still do most of its work too, even with damaged foam.

I'm trying to figure out a way to remove the old foam from the metal flaps without taking the central box out. It might be possible to break the foam up & suck it out with a vacuum cleaner, but then you need to cut a slice of closed cell foam the exact size needed ( bigger than the flaps in certain places) ,& glue it into the exact position. And you will be only able to do one side of the flap.

Since I have 3 A4's that I'm using, & a spare parts car (+ 2 A4's I'm not working on at the moment.. ) I do want to sort this problem out 100%.
Removing the central plastic consul from around the handbrake & then the central housings not too hard. You have to remove the stereo & climate control & ashtray & row of buttons. There's a specific order to it, like remove the stereo first, which gives access to the next lot of bolts/screws.

But, the centre 3 vent plastic ductings held in place, 3 staples @ the base where it connects to the central air box, & a couple of springs up top at the ends of the 3 vent area. Those springs can be popped off & probably not needed layer on anyway (besides, it's impossible to get them back on )
Once it's been quite forcibly removed, the next housing to the dash side vents is impossible to remove without taking the dashboard out.
That's as far as I have got... LoL
I expect to cut thru that housing with a 'Hot wire'. A NiChrome wire connected to a battery. Since the housings too long vertically anyway ( the cause of 1/2 the problem ) once everything to do with the flaps has been fixed, I think the cut ends of the housing will overlap & it will be possible to use Silicon sealant to seal it together again.
I will update this post once I have acheaved something of substance. Photos might be a possibility.
Old 10-17-2018, 12:41 PM
1st Gear
Join Date: Jan 2017
Location: NZ
Posts: 43

An update on my progress.
Well if you intend to do any of this, having a ''spare parts car' or being able to reference another identical car while doing this job will make things a LOT easyer.
I removed the heater box with the flaps in it with some difficulty.
Disconnect the battery.
You need to remove all the plastic from the centre consul, from the OBDII connector forwards, the glove box & under steering column plastic.
Now at some point somebody's cut my carpet under where the air box is, I dunno if that helped, I think it did.
Removing the glovebox, I connected a long zip tie to the wires just behind the spade clips for the glovebox light, with a tiny zip tie. So I can grab the long zip tie from inside the glove box, mine didn't work because it was disconnected because they couldn't pull the wires out thru the hole to connect them to the light.
So once the plastic central bits out, remove the stereo & from inside the gap, undo the screws which hold the plastic spacers in there, that then gets you to the bolts that hold the facia around the buttons/stereo/ climate control on. Remove that, undo the screws holding the under dash facia/surround on. Remove that, there's at least 3 screws, 2 near the join & 1 up under the dash.
I have a right hand drive car too...
Disconnect the hazard lights switch & the light switches beside it.
Theres a temp sensor on the facia panel with another wires & clip to the small motor/fan setup there.
Lift the plastic covering for the (auto) gearlevers plastic slip & undo 2 bolts & remove the aluminium bracket.
Then remove the 2 aluminium brackets on each side of the centre console.
Now remove the plastic ducting under the heater box, now remove the 3 flap motors. 2 ( blue & red) come off together, the others on ( the drivers side,) the side & if you unscrew one underside vertical screw, it pops down & off.

Remove the water hoses off the heater core under the bonnet. Squeeze the clips & slip them down the hose.
At this point I used tapered needle nose pliers, not the parralell slip jaws because I couldn't find them.....
The tapered jaws slipped off & I snapped the little plastic spigot on the side of the plastic brake fluid resiviour tank....
I shoved a rag under it, plugged it with a screw wrapped with Teflon tape & used warm soapy water to wash the loose fluid away, clear the drain holes in that area, ones under the battery platform.
I got another fluid resiviour tank off my spares A4 B5, very handy to have & pretty much any two or three items used off it will pay for buying the spares car in the first place.
I have got, spigot bush & brackets for it, left suspension arm, various plastic clips, bolts, nuts & the Brake fluid resiviour from it so far.
It cost me $150....
When I went to remove the broken brake resiviour, it pretty much crumbled in my hands. So, like some other Audi plastic, it's a part that needs replaced @ 200,000kms....
Popped the other one on & topped it up with brake fluid & it works great. F----- fantastic !
Remove the rubber boot from around the heater pipes.
With all of the bolts & brackets. Photo them so you know where the go back. Sounds silly when removing them, but by the time you do the job, you would have forgotten which & where they go.
Remove the clips holding the heater box to the outer Aircon/scroll fan box. If you have the spare parts car, or can view a wreckers one, you will know where the clips are, there's 2 vertical up the back between the firewall & the heater box, the rest you can see.
You need a mirror & torch to see them.
Now pull out the 3 staples on the ducting at the connection to the heater box, ducting goes up to the dash centre vents.
With swearing & such, remove that ducting, it's held up top to the dash with clips, don't worry if you break them, & 2 springs, use a screwdriver to pop them off. You don't need them anyway. Now pull that ducting out.
The ducting behind it, goes out to the dash side vents, it's impossible to remove without taking the whole dash out.
But since it's the cause of 1/2 the problems.. ( it distorts & pulls the ducting away from the heater box) it's going to get cut out.
I used a length of NiChrome wire from a heater & a car battery... Lol. The wire was ribbon shaped, get the plan round wire, it makes a cleaner job.
I slipped the wire around the back (actually cars front) of the ducting just over the hump in the ducting, try and go as possible as possible on it.nthen connected the ends of the wire to the batter terminals &'it heated up ( slowly ) & finally cut thru the ducting.
The shorter the wire the better. YMMV depending on your wire. Not as difficult as I imagined. I got the heat gun out & reformed the ducting face back to where it should be. Oh, there's a single nut nut holding it n too.
Once that's done, you can manhandle the heater box out. From memory the heater core pipes get caught on the soundproofing around the hole they go thru. & The box gets caught up on the far rear vertical vent to the windscreen demister.
though I had left the 3 flap motors on while removing the box.
Pull towards you, then ( in my case, right hand drive ) 90 turn anticlockwise & it will pull out.

Now you can take it apart.

​​Buncha clips & a screw or 2. Pry it apart evenly, you don't need to unclip or operate anything on the built in plastic tab clips.
if you pry it apart slowly & evenly, it will pop apart quite nicely without breaking anything.

You can now see the problem with the flaps foam disintegration.
I took out the screws holding the heater core in place & washed it out several times with hot water & different substances, dishwash liquid, dishwasher powder, dessert spoon of caustic soda, rust remover & hot water.
im surprised, not much rubbish came out. Some oil crap from the oil cooler failure, a bit of brown crud, a small chunk of plastic divider seen in a above photo.
About now I realised that hot coolant moves thru this core all of the time. Most other heaters in cars I see have a 'Tempering valve's to control the temp of the heater core. Audi control the heat by varying the amount of air going past the heater core.
I picked the double sided tape off the heater core & inside the box & washed it out.

The flaps. I used ADOS Superstrength spray glue & some closed cell foam A4 size.. lol.i got from a hobby art Asian 5 & dime type shop. I tested it for heat with the heat gun, against the other foam, the closed cell foam was surprisingly good against heat.
Where the plastic tabs on the metal flaps are, I scribed around them with a felt pen & then covered that area with insulation tape.
Cleaned the flaps with sand paper to get rid of oxide & roughen up the surface.
The closed cell foam needs 3 sprays with the glue. The first seals the surface, the 2 nd fills the surface, the 3rd actually glues it.
So I used 3 A4 sheets of yellow closed cell foam. 50 cents a sheet. Spray it with glue, spread it out evenly, let dry overnight.
Spray & spread again. & Spray the metal flaps all over, spread out glue too. The plastic flap will use the left over foam, you need to remove the strip of foam off it & sand that face to roughen up it's it's surface before spraying the glue on it.

The big metal flaps needs a sheet per side. The small metal flap can use 1 sheet. I cut it in two & sandwiched it. In hindsight I would use one sheet & fold it over the edge that's away from the hinge side. Less edges to the foam the better. It's off cuts are used on the plastic flap.
So, foams been sprayed twice, metal flaps & plastic flap has been sanded & sprayed once. And dried.
Now spray the surfaces again & glue it into the flaps, clamp edges in place with clothes pegs or such or put it on surface with something on it to hold/squash it down firmly.
let it dry overnight. Check edges the next day, open up edges if loose & spray more glue in & squash again.
Once it's all stuck.
You need to cut the foam away from where the hinge tabs clip on, over the insulation tape tabs, to suit. The edges need precision & there's some tiny slots to cut to suit the inside of the box. Once all that's done, grease the hinge pivots & the motor arms pivots.
Apply double sided foam ( door seal?) Tape to around the heater core where it's needed. And assemble.

You can operate the motors by connecting 12 volts DC to the 2 pins side by side, the other row of 3 pins is the rheostat connections to tell the computer what position the flaps at. If possible I'd connected up a proper plug from a wrecked car to the sockets, rather than fiddling around with 2 ,live 12 volts wires inside the socket, touching the wrong pins. Reversing the wires reverses the motor.
Assemble the box, there's only 3 clips I think, & 1 screw, about 5-6 tabs.

Get back into the car & refit the box, mine was with the heater cores pipes to the left ( right hand drive, fan box is on the far left.) Once it's in, turn clockwise 90 & fit the heater cores pipes thru the firewalls oval hole.
Push it n place & match it up with the fan - aircon box. Fit some clips. Get mirror ,& torch & fit the clips between the box ,& firewall. About 5 all up.
Reconnect, bolt/screw the flap motors in place again, grease & connect up the arms.
Fit the underneath plastic ducting, it probably needs a spacer or a foam block to hold it up in place. My carpet under there has been cut out by somebody at some time.
The dash side vent ducting you cut thru earlier will need to be siliconed back in place. Since I haven't actually done it yet, I expect just to silicon seal both of the cut edges & let it harden a tiny bit, then add more & fit the vent in place, Then wrap some packingptape, or Duct tape ( since its a duct...,) around the ducting over the silicon to make it cover the gap & make it seal.
it will need double sided foam sticky tape, like 12mm wide by 2 mm thick to reconnect the flanges @ the heater box, it's got one nut to hold it in place but I will add some metal clips to help it. The flap hinge is directly under one side of the flange, so there's no chance of screwing a self tapping screw in thru there, or a metal clip or such.
Once that ducting is in place, the dashboard central (3) duct can be fitted in place. I expect to double sided sticky foam tape it, with plastic zip ties, into place as well. Originally there was just 2 staples from a staple gun holding it n place, along with what's up top ( which isn't needed, once it's innplace up top, it will stay there & reasonably sealed tight.

Refit Ali bracket dash side of the year lever & the airbag sensor box, then the centre consoles 2 Ali brackets.
Connect up the coloured plugs to the corresponding colour motors. Refit the temp sensor onnthe side of the heater box. There's another sensor onnthe centre dash ducting near the heater box, and another sensor in the facia of the heater controls, plus a plug for the small fan motor/ blower ( which tests in car temps)
I didn't unplug the climate control. BUT, I did find the small black plug was loose. After I plugged it in again, the ' E ' on the LED dash display turned to a 5C indicating outside temperature !
The indicators won't work if the hazard lights switch is not plugged back in.
Replace the rubber boot around the heater pipes under the bonnet, I cleaned & sprayed it with car interior finish spray ( it's actually mostly hair conditioner type chemical & a silicon type chemical for gloss) so it's supple & slippery & easy to fit.
Reconnect the heater hoses & battery lead.
Start car up, let it warm up, top up coolant, as you do.
That's as far as I have got so far. Tomorrow I will sort out the stereo wires, somebody's cut some. And refit everything else & maybe the stereo.
Oh, I took out the sub woofer. It's got the same self disintegration foam on it as a speaker cone suspension. So it's ruined too.
It's a 6 or 6 1/2 inch speaker with Two coils in it. I can get a replacement speaker just a little bigger than original, but there's enough to space in the box to fit a slightly larger speaker.

Last edited by marteA4; 10-17-2018 at 12:58 PM.
Old 01-09-2019, 10:54 AM
1st Gear
Join Date: Jan 2019
Location: Fond du Lac WI
Posts: 20

Are you using a pump to circulate water when flushing? I did, and also found poor circulation. Hooked up the water to the hoses and "back-flushed" the engine cooling system. Heat GTG!
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