how do i DIY flush my heater core?

**JMRQuattro** · 11-10-2008 06:28 PM

So after reading various threads and researching the topic a little bit, and also seeing the recent success of bedult1, i've decided i need to try to flush my heater core. But learning from bedult1 i also don't want to go to a shop and get charged $200 for something i could probably learn to do on my own.

Symptoms:
1. My heat is very fussy, works sometimes, sometimes not. When it does work, it takes a very long time to get warm. But it never gets as hot as you think HI should be. And it usually has the most problems the colder the weather outside gets. When the weather is in the lower 40's or below there is absolutely no heat no matter how long i have it on, it just fills the cabin with cold air; when it is 50 and above it gets warm but not hot. And the warmer the weather the faster it gets warm. It took about 10 minutes when it was about 64 degrees the other day and about 20 or longer when it was in the low 50's. So very iffy heat.
2. I have/had a coolant leak, up until yesterday which i tried to fix with a new hose clamp where i could see a leak. Still waiting to see the results from this so i know if i have a leak elsewhere.
3. Every time i open my coolant reservoir there is tons of excess pressure that spits out of the bottom of the reservoir through the bleeder valve (regardless of whether it is hot, warm, or cold; i've tried all 3 various times and it's always the exact same, just far worse when it's hot).
4. Of the tubes that go through the firewall, 1 gets hot while the other stays cold.

And because of this coolant leak that caused me to have to refill my coolant every 3 days because i would get that annoying beeping from my information center saying my coolant was low, i've been using water (coolant is too damn expensive to refill that tank every 3 days with). So i need to do a coolant flush once i see the results of my new hose clamp.

If anyone has any input or can tell me how to do the heater core flush i would really appreciate it. TIA for any help!

**JMRQuattro** · 11-10-2008 06:41 PM

Also in order to flush my heater core do i need to flush my coolant at the same time as well?

**JMRQuattro** · 11-10-2008 08:37 PM

No one??

**downhillracer** · 11-10-2008 10:55 PM

just take the lines off that go to it and backflush it (put water in, where it normally comes out) with a hose... or low psi air

**JMRQuattro** · 11-10-2008 11:04 PM

ok cool thanks. Is there a certain way to do this? Like with the water do i just put a regular hose up to the opening?

**downhillracer** · 11-11-2008 02:49 AM

you could make a nice little piece to hose clamp on both ends and then turn the hose on... I would start with a lower pressure then go from there.

**JMRQuattro** · 11-11-2008 01:24 PM

cool. I went to home depot and i got some extra hose and a female adapter so i'm gonna hook it up and try that out.

**JMRQuattro** · 11-11-2008 05:28 PM

ok so my idea worked! And OMG! My heater core was clogged up pretty good. There was a ton of black and brown gunk and what looked like little chips of orange stuff. It came out really pink at first with a bunch of crap in it and it slowly got clearer and had less traces of crap in it. I ended up having to turn the water pressure up a little though in order to actually clear it out all the way.

Ok now on to coolant flush.... where is the radiator cap or whatever i need to open in order to flush my coolant?

EDIT: Oh and if anyone wants to do this, it will only cost you like $2 instead of $200. I bought a female hose repair kit adapter for $1.99 at home depot, had an extra hose clamp laying around, and went to action auto parts where they just happened to have the perfect length of my size heater core hose sitting there in back so they gave it to me for free. If anyone who's interested wants pics or a brief explanation let me know.

**02a4** · 12-06-2008 11:23 AM

Okay, i have the exact same problem and i would like to flush my heater core also but i can't find a write-up of the procedure... Since you have done this, can you please put up a step by step tuturial on how to do it and where everything is located??? Would really appreciate it if you can...

**Turb_Oh_A4** · 12-06-2008 11:30 AM

if you lay under your car on the left side there is a lower rad hose that clips into the Rad. also where it connects there is a coolant temp sensor, if you take the clip out of that and pull the sensor down/out. then do your flush thru there.

**02a4** · 12-06-2008 11:35 AM

The CTS is located at the top? Are you saying i disconnect from the top and the hose that goes into the radiator at the bottom and then pour water through there?

**pablo_ottawa** · 01-15-2012 07:09 PM

I too would also like to know how to do this. Come on people!!!! Cut us a break here!!!!

In the 1.8t you're saying we have to get underneath the car and then your talking about pulling the CTS from underneath the car. Well from what I know, the CTS is BEHIND the engine at the top of the firewall and very hard to remove. Why are you telling us to go under the car to remove it. Is there another CTS under the car????

I know it's a lot to ask but a step by step guide and some pics would be GREATLY appreciated.

**KFizz** · 01-15-2012 07:22 PM

I've done this before. Just disconnect the 2 heater core hoses. Buy 2 lengths of hose. Hook one from the core to a bucket. Then 1 from the other heater bung to the garden hose. Worked like a charm. Lots of crap came out. Then you gotta burp the air out, which is a bitch.

Sent from my HTC EVO 3D X515a using Tapatalk

**Dubsport Inc** · 01-15-2012 10:08 PM

http://www.audizine.com/forum/showth....-Lots-of-pics.
HTH

**mv18** · 01-15-2012 10:08 PM

Originally Posted by pablo_ottawa

I too would also like to know how to do this. Come on people!!!! Cut us a break here!!!!

In the 1.8t you're saying we have to get underneath the car and then your talking about pulling the CTS from underneath the car. Well from what I know, the CTS is BEHIND the engine at the top of the firewall and very hard to remove. Why are you telling us to go under the car to remove it. Is there another CTS under the car????

I know it's a lot to ask but a step by step guide and some pics would be GREATLY appreciated.

http://www.audizine.com/forum/showth...eater-Core-DIY

http://www.audiworld.com/tech/eng115.shtml (B5)

**Trev** · 01-16-2012 03:26 PM

[edit] Hahaha, defiantly didn't see the the thread start date on this one...

**TwinTipSkier** · 01-16-2012 03:37 PM

NECRO bump! always wanted to say that...
Just went through this after rear coolant flange, had finicky heat. You flow hose water back from both heater core hoses to the right of the battery. I shot some compressed air through too, but I doubt you have to. To bleed air: with engine at temp, have someone hold gas to 1500rpms and you pull upper hose back enough to bubble out of the side or out of the small hole proved on top/end of hose.
Wet and cold afternoon fur shure. But drive to work next day was nice and warm

**ggcrash** · 01-16-2012 11:05 PM

Yes there are 2 coolant temp. sensors...#1 is behind the engine, and it helps if your hand size is small, that one is green, #2 can be accessed from under the car, on the drivers side close to the radiator, that one is black, If I remember correct. Also, when you change your thermostat, change the "J" plug too...the little black particles were most likely bits of your "J" plug O-ring being chewed up by the water pump and flowing through your entire cooling system...