Heater problem

[Ian1006]

I have read tons of threads both on this forum and others. 2003 a4 1.8 tip tronic with 106k miles for the details.
Changed timing belt two months ago with metal water pump. Just discovered heater isn't working. Bled from bleeder screw, bled from upper heater core with hole in it, tried loosening cap then bleeding when hot, back filled heater etc. I've bled and tried it all for last 4 hours. Both heater core metal pipes are hot after revving in neutral.no overheating, no loosing coolant.
I have heat holding 2-3k in neutral, within half mile or mile of driving its cold air. Possible partial clogged heater core or some how air is in system still? Ideas?

[jacobsen]

Air

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[jacobsen]

Let the motor cool off completely and bleed both bleeder over the course if the week, eventually you'll get it all out. Raise tank when you do it, only do it when motor is totally cold.

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[Ian1006]

I've been trying to do it warm or hot. Thank you for the advice, will try tomorrow.

[jacobsen]

You bring air into the system if you do it hot.

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[Ian1006]

Got some air out today, will drive it a short while tomorrow then let it cool and try again. Need to have a good heater up here, already getting to freezing at night!

[jacobsen]

Got some air out today, will drive it a short while tomorrow then let it cool and try again. Need to have a good heater up here, already getting to freezing at night!

Where are you? Just keep doing a little each time. The top heater core hose hole and the hard pipe bleeder. Open until the stream of coolant is solid and close it.

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[Ian1006]

Yup that is what I'm doing, thanks for the help. In Montana, looks like it will be a cold winter. Snow yesterday on the hill behind us.

[old guy]

You may end up having to flush the heater core. It isn't too difficult of a job. Clicky click®

[Ian1006]

I would probably just replace the heater core if this doesn't work. I need heat with a one year old in the back and taking an afternoon to replace it for gauaranteed heat would be worth it.

[jacobsen]

I would probably just replace the heater core if this doesn't work. I need heat with a one year old in the back and taking an afternoon to replace it for gauaranteed heat would be worth it.

I always advocated 1 gallon distilled water with 1 gallon muriatic acid circulated through the heater core for 10 minutes in both directions. I did it and it really improved my heat. But working with acid candy no fun for some people. You have to have all your ducks in a row. Rinse it a lot afterwards.

I suspect your issue is caused by air. Because if your heat works when you're on the throttle but not when you're stopped that pretty much tells you what you need to know.

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[old guy]

Not necessarily always the case. I have had to flush my hearer core twice in the 13 years of ownership. In both incidences the heat was weak to nonexistent at idle but worked OK once the revs were up. Both times it seemed to occur out of the blue. No repairs or changes were made prior to the heat loss.

I bled multiple times and nothing changed. As soon as I flushed the heater core the heat returned. Both times that I flushed the core I filtered out numerous scale particles. Apparently I still had some circulation, just not enough to provide adequate heat transfer in low flow conditions.

[jacobsen]

Not necessarily always the case. I have had to flush my hearer core twice in the 13 years of ownership. In both incidences the heat was weak to nonexistent at idle but worked OK once the revs were up. Both times it seemed to occur out of the blue. No repairs or changes were made prior to the heat loss.

I bled multiple times and nothing changed. As soon as I flushed the heater core the heat returned. Both times that I flushed the core I filtered out numerous scale particles. Apparently I still had some circulation, just not enough to provide adequate heat transfer in low flow conditions.

When I did mine at about 120k I had sandy colored gritty stuff in the expansion tank and in my flush bucket. I've always used distilled... I thought the coolant just broke down and possible Silicon and the solution was separating from itself. It's a curious thing, such a big issue in the audi. My simple Galant never lost heat once and its been flushed like 2 times 200k, but, it's not a pressurized system.

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[16vCorey]

Not necessarily always the case. I have had to flush my hearer core twice in the 13 years of ownership. In both incidences the heat was weak to nonexistent at idle but worked OK once the revs were up. Both times it seemed to occur out of the blue. No repairs or changes were made prior to the heat loss.

I bled multiple times and nothing changed. As soon as I flushed the heater core the heat returned. Both times that I flushed the core I filtered out numerous scale particles. Apparently I still had some circulation, just not enough to provide adequate heat transfer in low flow conditions.

Yep, what he said. I've probably flushed a dozen of them in the past five years and have never had to do one again. The heat would just about cook you when I was done, in every one of them that I've flushed.

[Ian1006]

Maybe I'll try flushing, have a 1500 mile road trip I leave for tomorrow, seems like you guys have had good luck with it

[Ian1006]

I picked up some radiator cleaner, I don't know if I have a pump to recirculate it with though like old guy did, what's the next best option? Since I did the water pump 2 months ago I just filled it with brand new coolant....I would like to just clean the heater system. Could I let it sit overnight just in the heater with the hoses blocked off? Ideas please

[jacobsen]

I picked up some radiator cleaner, I don't know if I have a pump to recirculate it with though like old guy did, what's the next best option? Since I did the water pump 2 months ago I just filled it with brand new coolant....I would like to just clean the heater system. Could I let it sit overnight just in the heater with the hoses blocked off? Ideas please

The kind of cleaner you're going to need to burn the crust out of your heater core you wouldn't want to leave in there overnight. On the mild Spectrum you could use ZEP Industrial drain cleaner. But like I said myself, I used the muriatic acid. 10 minutes in either direction. You just need a cheap sump pump and two 10 foot section of clear hose, A fitting to fit on your pump and like 5 gallons of distilled water. I flushed mine with a garden hose. Then I flushed it again with the bucket with distilled water.

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[old guy]

I picked up some radiator cleaner, I don't know if I have a pump to recirculate it with though like old guy did, what's the next best option? Since I did the water pump 2 months ago I just filled it with brand new coolant....I would like to just clean the heater system. Could I let it sit overnight just in the heater with the hoses blocked off? Ideas please

Submersible pump $15 Clicky click®

[Ian1006]

Picked up a submersible bilge pump from Wally World today...it already has a 3/4 inch outlet and it supposedly does 500 gph haha that seems like it will give the flow I need and it's 12 volt so I'll hook it up to a spare battery.
I'll try tomorrow with a back flush first, then flush the other way, probably try to make a filter of some sort and get as hot as water as possible.

[jacobsen]

Picked up a submersible bilge pump from Wally World today...it already has a 3/4 inch outlet and it supposedly does 500 gph haha that seems like it will give the flow I need and it's 12 volt so I'll hook it up to a spare battery.
I'll try tomorrow with a back flush first, then flush the other way, probably try to make a filter of some sort and get as hot as water as possible.

I stress you need a powerful acid. The water that goes through there is already hot.

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[Ian1006]

Yes acid is my back up plan, I already have a source for it. I want to try to use a radiator cleaner first, if it doesn't work I'll try the acid or clr or the like. I want to start gentle then work my way up I think, feel more comfortable doing it that way and it's all going to be set up so switching shouldn't be hard.

[jacobsen]

Yes acid is my back up plan, I already have a source for it. I want to try to use a radiator cleaner first, if it doesn't work I'll try the acid or clr or the like. I want to start gentle then work my way up I think, feel more comfortable doing it that way and it's all going to be set up so switching shouldn't be hard.

That's a good idea. I used muriatic acid. There were two formulations at Menards one was stronger than the other and I picked that one. It was about $6 for a gallon of it

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[maurizio]

flush the entire system a few times before (if) replacing the core.

[jacobsen]

flush the entire system a few times before (if) replacing the core.

Good idea. Crud that is in circulation throughout the entire cooling system will Lodge itself once again in the heater core. I went super OCD, I filled mine and drained it a bunch of times over the course of a month before I did the acid thing. And the only reason I did the acid thing is because it's cheaper.

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[Ian1006]

It's been drained and filled twice now, which is why I'm not wanting to loose a bunch of pentofrost at the moment. I'll drain the coolant low enough to not loose a ton when I pull heater hoses and plug them.

[Ian1006]

Hooked up 7 ft lengths of hose to in and out of heater core and blew compressed air backwards. Then did old guys method and backflushed with a filter I made out of a shirt and radiator cleaner with hot water, after that for a while I reversed the flow, finished up by blowing it out. I got maybe 2 full tablespoons of grit out of it, I also cleaned out the reservoir too and refilled with Pentofrost.
I've looked around and it seems like it's not super uncommon for grit if it was accidentally mixed before with green. It has air so I need to bleed, then I'll report back

[old guy]

I have always maintained my cooling system properly with the correct coolant and distilled water. I started with G12 (Pentofrost SF). Switched to G12+ when it came out. Currently running G13 (Pentofrost-E). Both times that I flushed my heater core I filtered out several tablespoons of grit. Not sure where it comes from it isn't necessarily from having run green coolant.

[Ian1006]

So when I reassembled I bled it, ran it to temp then shut it off. After it cooled I bled again and now I have heat at idle which I didn't before and it is probably around 120 degrees or so before it's up to half on the gauge. Before I was at max getting 80 while revving it. I'll bleed again after it cools but I think I am winning!

[Ian1006]

Btw I had a question about the reservoir...does it mix itself with the rest of the coolant or just sit there and kind of ebb? Like if I put fresh in it after draining the reservoir will that slowly mix itself with the old?

[old guy]

Btw I had a question about the reservoir...does it mix itself with the rest of the coolant or just sit there and kind of ebb? Like if I put fresh in it after draining the reservoir will that slowly mix itself with the old?

Yes the reservoir mixes with the rest of the cooling system. It enters from the small hose and exits from the large hose. And once up to temperature it will mix every time the thermostat cycles.

- - - Updated - - -

So when I reassembled I bled it, ran it to temp then shut it off. After it cooled I bled again and now I have heat at idle which I didn't before and it is probably around 120 degrees or so before it's up to half on the gauge. Before I was at max getting 80 while revving it. I'll bleed again after it cools but I think I am winning!

Yes you most certainly are winning

[Ian1006]

I bled it again and the heat is very very hot while the gauge is even at 1/4. At idle or throttle heat is consistent and very hot on HI. Glad I tried to clean it first, I'll bleed one more time just to be sure but I think it's there. Thanks to everyone on advice on how to bleed properly and how to clean the heater core, very appreciative.

[GTA]

Hmmm. I've been getting heater issues forever. I'd flushed the heater core (forwards and backwards flow), changed the thermostat, J-plug, reservoir cap, and finally did a timing belt and water pump late last year. Every single time I bleed the system as described (many times), I would get hot temps from the heater core but only for the remainder of the day of the bleeding. Afterwards the heat would be warm to luke-warm. There are no leaks and my coolant is always a 50/50 mix of G-13 & distilled water.

What I haven't tried is to bleed it when cold; always hot - maybe this is the clue.

So...can someone please explain how to bleed when cold?
I would assume this would be correct: On a cold engine, undo the hose clamp and loosen the hard pipe bleeder in preparation to bleed, start the car and bleed from the hard pipe & upper heater core hose hole immediately? Then shut it off before the engine starts to warm? The coolant should flow at these two bleed locations when cold, right?

[jacobsen]

Hmmm. I've been getting heater issues forever. I'd flushed the heater core (forwards and backwards flow), changed the thermostat, J-plug, reservoir cap, and finally did a timing belt and water pump late last year. Every single time I bleed the system as described (many times), I would get hot temps from the heater core but only for the remainder of the day of the bleeding. Afterwards the heat would be warm to luke-warm. There are no leaks and my coolant is always a 50/50 mix of G-13 & distilled water.

What I haven't tried is to bleed it when cold; always hot - maybe this is the clue.

So...can someone please explain how to bleed when cold?
I would assume this would be correct: On a cold engine, undo the hose clamp and loosen the hard pipe bleeder in preparation to bleed, start the car and bleed from the hard pipe & upper heater core hose hole immediately? Then shut it off before the engine starts to warm?

Totally wrong. Never ever run the motor when your bleeding the cooling system. There are only two locations to bleed. The first and foremost is the screw on top of the hard pipe which if it isn't metal you should replace it with the metal bleeder screw. The second is the top heater core hose which has a hole in it so that you may pull the hose back a little bit and expose the hole to atmosphere. You want your motor to be totally cold when you perform the bleeding procedure. Do not run the motor at any point.

Raise your expansion tank as high as you can with it full and the cap removed.

Open the hard pipe bleeder screw. Wait for a steady stream of coolant to come out. You will notice air and coolant burping out together until it runs steady.

Do the same thing to the top heater core hose.

For good measure and to be absolutely certain I recommend doing this over the course of a week until you're absolutely positive no more air is burping out of either bleeder.

Trying to do this with the motor warm is not possible. If you do this and you come to find that you never get all of the air out you may have a leak in your cooling system. Remember when the coolant gets hot it expands and when it cools it contracts. During the contraction cool down it's possible for it to suck in air from a leak. It is also a possibility you have a bad head gasket which is blowing exhaust gases into your cooling system. This is the least common cause but it's easy to diagnose.

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[GTA]

From what you're saying, the elevated reservoir should be enough to force coolant to the hard pipe as well as the top heater core inlet hose? I'll try doing this with the engine off and cold and see if it helps.

Thanks!

[jacobsen]

From what you're saying, the elevated reservoir should be enough to force coolant to the hard pipe as well as the top heater core inlet hose? I'll try doing this with the engine off and cold and see if it helps.

Thanks!

This is the way you bleed the system. There's no alternative way. There is actually one alternative which is completely unnecessary. And that is vacuum tool which what's the cooling system under vacuum and depressurize the system by filling it with coolant. But it's just not necessary. You do not have to elevate the reservoir. At normal height the reservoir should be good enough the push coolant through the bleeders. But elevating the reservoir puts more pressure in the system and gets it done faster.

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[GTA]

Bleeding coolant cold and with engine off runs counter to everything I know. I don't know what Bentley's says but even Shop-Key (Snap-On repair software) says to bleed with the engine hot, running and at 1500-2000 rpm.

Regardless, I'll try bleeding it the way you'd mentioned - engine cold, off and elevated reservoir, and also doing it throughout a week. I'll report back in a couple of months when the weather turns south and below freezing to see if it helped.

[diagnosticator]

All this horsing around is unnecessary, With the engine and coolant completely cold, and the engine OFF, just fill the tank to the top and allow the coolant to fill the system by natural gravity. It will take about an hour for the system to fill, but time is the key. Refill the tank when the coolant level drops, and when the coolant level in the tank stays full after an hour or so, replace the tank cap and drive the car. It is helpful leaving the bleeder screw loose until coolant comes out then tighten. There is all kinds of things to do while waiting for the coolant level to stabilize and stop dropping. You can't rush this process be patient. if possible, after the coolant level in the tank is stabilized just leave the tank cap off for another few hours. After this wait, refill if needed, it should have stayed full. Allowing the extra time practically guarantees that the cooling system is completely full, and there is no air trapped anywhere.

[Ian1006]

someone should make a diy with pics on how to properly bleed these cars then sticky it. I didn't know there were two places to bleed from until I started this thread and I also didn't know it was supposed to be cold either which made all the difference.

[jacobsen]

someone should make a diy with pics on how to properly bleed these cars then sticky it. I didn't know there were two places to bleed from until I started this thread and I also didn't know it was supposed to be cold either which made all the difference.

It's because it's a pressurized system. If it weren't a pressurized system you might be able to bleed with the car running. But I still see that being troublesome.

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[GTA]

UPDATE: I bled my cooling system cold right after my last post and, sure enough, there was a lot of air in the hard line as well as the upper heater core hose. All I did was raise the reservoir and un-screwed the cap just enough to allow air in before bleeding and topped up the reservoir after bleeding.

I repeated this procedure twice more every few days after some driving in between. The second and third time, there was no air in the system at all, which was a very good sign.

The cabin heat is much better than it has ever been under my ownership. Just yesterday, I actually had to turn the temperature down when I was driving and I haven't had the control at more than 26degC yet. In previous years, I had my control set a MAX throughout the whole winter season because it couldn't keep up with the cold outside.

Thanks jacobsen and the others on this thread. I'm a happy camper