Hi Guys

Back again for a little more advise.

So I own a 2015 (b8.5) 163 ultra. The problem I'm having, (and please tell me if anybody else is the same) is the heater just does not get hot, at all. Doesn't matter if I just drive to work or drive for two hours, it just gets warmish, and mainly on the passenger side. I've felt the pipes going in and out of the heater core from the engine bay and they are hot, but not uncomfortably so. I do believe that I need to change the blend actuator on the drivers side, but, that still doesn't answer the question as to why it's not getting hot out of the passenger vents or to the screen. I'm contemplating disconnecting the flow and return pipes and flushing the core with my garden hose, good idea? Can't really see how it would hurt. Does anybody else have any suggestions please I'm proper at a loss.

Just an after thought and don't know if it is connected in any way, but I'm pretty sure the AC needs regassing as it doesn't blow as cold as I'm sure it should.

Thanks in advance for any and all suggestions. There really can't be any bad ideas at this point.

1 hour ago, Confused said:

Hi Guys

Back again for a little more advise.

So I own a 2015 (b8.5) 163 ultra. The problem I'm having, (and please tell me if anybody else is the same) is the heater just does not get hot, at all. Doesn't matter if I just drive to work or drive for two hours, it just gets warmish, and mainly on the passenger side. I've felt the pipes going in and out of the heater core from the engine bay and they are hot, but not uncomfortably so. I do believe that I need to change the blend actuator on the drivers side, but, that still doesn't answer the question as to why it's not getting hot out of the passenger vents or to the screen. I'm contemplating disconnecting the flow and return pipes and flushing the core with my garden hose, good idea? Can't really see how it would hurt. Does anybody else have any suggestions please I'm proper at a loss.

Just an after thought and don't know if it is connected in any way, but I'm pretty sure the AC needs regassing as it doesn't blow as cold as I'm sure it should.

Thanks in advance for any and all suggestions. There really can't be any bad ideas at this point.

Hi I wouldn't worry about the aircon that just needs filling, flushing the heater core will probably cure the problem but you will also need to flush the block and radiator, most likely the silica bag has burst and the silicate is blocking the heater matrix, if you do research on this site there is plenty of posts and solutions, if in doubt contact Magnet and he will point you in the right direction.

Steve.

Hi Steve 

Funny you mention the silica bag, a friend of mine mentioned that only today. I do a bit of research and give that a go.

Thanks Simon

Simon see this:

https://www.youtube.com/watch?v=39ngHGvMzEg

 

Hi Cliff,

Thanks for the info, actually watch that video after Steve's reply.

Simon

Ok, I've just been and checked my expansion tank, and it doesn't say anything about "mit sillikat" what do we reckon the chances are there was still one in there. My mate who first mentioned this bag to me has an A3 14 plate and he had this exact problem 

Not all affected expansion tanks are marked "mit silica". Can you see any remnants of a bag in the tank?

11 minutes ago, cliffcoggin said:

Not all affected expansion tanks are marked "mit silica". Can you see any remnants of a bag in the tank?

You know what, I did have a little lot around, only had my phone torch at the time as I was at work, but I couldn't see one. But that's not too say there wasn't one and has already split and wondered off in to the system to play havoc. Guess I'll just have too live with it till I get a chance to blast the garden hose through the heater core and see what comes out. Really hope it's not fubared, cause that's a massive job.

If you have to open the system for flushing, it might be worth replacing the reservoir as a precaution. Chinese replacements are only £25.

51 minutes ago, cliffcoggin said:

If you have to open the system for flushing, it might be worth replacing the reservoir as a precaution. Chinese replacements are only £25.

I seen something about that on a video, why is that? Never had to change one before ever.

Just now, Confused said:

I seen something about that on a video, why is that? Never had to change one before ever.

Don't worry just figured out why. Just in case it's stuck in there

1 hour ago, Confused said:

Don't worry just figured out why. Just in case it's stuck in there

Hi my A6 never had a warning about the silicone bag but they are definitely in there mine only presented itself when I hit the tank with a jet wash then what remained flew out in bits, I also used a jetwash when I flushed the heater matrix it deffo gets the bits out and is wonderful when flushing the block, its a pain but the silica gets in the thermostat and jams it open.

Steve.

Sorry just checked back on this. Thanks for all the advise. Just one more thing, would it be best to just use my standard garden hose with the jet fitting or use a small pressure washer. Plus how do you get all the water out after. I'm thinking just fill the system with coolant and when it runs out the return line it the water should be out right? Gotta change the timing belt in a couple of months        (waiting for the better weather) so won't be doing this untill then so all the coolant will be out anyway. Any advise on glow plug removal, hear they can be an absolute b@#*h.

Edited February 5Feb 5 by Confused
Changed a word

If you can live without cabin heating for a few months then sort out the cooling system when you change the belt. Note that it is worth changing the water pump at the same time if it is driven by the cambelt.

I would be cautious about using a pressure washer on the heater matrix because they can make 100 bar pressure if you seal it onto the fitting. Take Steve's advice on this. A pressure washer will be fine on the rest of the system.

Draining the water should be no problem. Open or remove the lowest hose connection on the system, usually the bottom radiator hose. Refit all hoses and refill the system. Be prepared for possible air locks which may need to be cleared by vacuum on the reservoir.

Thanks cliff, yeah like I said was gonna wait for the weather. Just ordered a kit for £ 266 inc. the pump, all genuine Audi parts from the dreaded eBay. Can't believe, well I can really, but, Audi want £288 for the kit WITHOUT the water pump, jokers. As for the pressure washer was just checking that that's not what he was referring to. Was planning on using the hose on jet setting. Just one question, is there any way to vacuum fill at home? I was thinking maybe using the spare tyre like when bleeding the brakes.

On 2/6/2026 at 4:38 PM, Confused said:

 Just one question, is there any way to vacuum fill at home? 

I see several kits on Amazon for less than £30. Never tried one myself.

On 2/7/2026 at 5:33 PM, cliffcoggin said:

I see several kits on Amazon for less than £30. Never tried one myself.

Ok thanks. I have a vacuum pump for draining the oil through the dipstick, do you think this would create enough pressure?

1 hour ago, Confused said:

Ok thanks. I have a vacuum pump for draining the oil through the dipstick, do you think this would create enough pressure?

Hi yes due to the viscosity of the oil is much reduced when warm.

Steve.

Thanks for the reply stevey, I actually meant do you think it would create enough pressure to draw the coolant around the system. My mistake, I should have made the clearer, I can see why you would have thought otherwise.

10 hours ago, Confused said:

Thanks for the reply stevey, I actually meant do you think it would create enough pressure to draw the coolant around the system. My mistake, I should have made the clearer, I can see why you would have thought otherwise.

 HI YES what I was driving at was if it will pump oil it will definitely do water, as forAudi they are just spiteful when you consider the cam belt kit I bought from VW for my Passat only was available with the pump, so I ended up buying a Gates kit with pump but a couple of hundred quid cheaper.

Steve.

Thanks Steve,

I was thinking along the same lines. I really don't understand these car companies, you buy there products and then they think that good customer service is to sting you on the spare parts. Let alone the hourly rate for there, and I say this I very loose terms               "mechanics". Don you know, when I called to get a price for the timing belt kit, the parts guy didn't eveen know they sold it as a kit let alone that there is a shelf life on the belt. I mean surly if your going to try and con people out of there money, you should at least know what you're talking about, it's only good practice.

I'll climb down off my soap box now.

Simon