Clogged heater core

[relative4]

The '02 A4 1.8Tq I just bought has a clogged heater core. The supply hose is hot, the return hose is cool, the vent air is cool. Seems to me like this would be a good case for replacement rather than flushing in situ. From my brief perusal of the Haynes manual, the job doesn't look too tough. Any words of wisdom before I jump into this job? Thanks!

[old guy]

Clicky click®

[Preston_08]

Awesome DIY ^ Have done this twice, first when I had my previous B6 and last week with my newer USP. Followed this DIY to a T the first time. Would also be a good time to change the thermostat, j-plug, and flange if it has never been changed.

Cut a huge leaf trash bag in half and tucked in everywhere around the console to keep from getting coolant everywhere.



And here's where the core is.




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[relative4]

What sort of experience have people had with the various price levels of heater cores? I don't mind spending the $150 if necessary, but if the $50 cores are tried and true...

[Preston_08]

My previous B6 I put a core in I ordered from Autozone for $60 and it did just fine the next year I owned it so I did the same thing this time.


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[Furly]

Ive never done it on my b6 but on my old b5 i simply flushed it and a ton of brown crap came out into my bucket. It worked flawlessly for 5 years afterwards til i sold the car. Worth trying a flush before replacing it.

[john_gonzo]

Gotta agree with Furly on this one, do first things first. If very little sediment comes out and/or the back pressure remains high(when flushing) then replace the core.

Either way, thanks for posting this question. Preston's trash bag pics = cool idea.

[jacobsen]

I submit to you my muriatic acid cure. I had an issue where my car was getting hot but not as hot as I would like. I went to Menards and bought a gallon of muriatic acid and mix that with 1 gallon of distilled water. I bought a sump pump and poured the concoction into the bucket and circulated the acid back and forth through the heater core. But before I did the acid flush I made sure to rinse the entire system with many gallons of distilled water. I found lots of little crusty chunks, bits of plastic and silicone o-ring. Much more then I would have thought would have been in there. And all that would have simply gone back in and clogged a new heater core. So it's just my 2 cents, rinse the crap out of your system until you're sure you got everything out. I rinsed my entire cooling system before I gave the heater core the acid treatment. The acid will clear the core of any crust guaranteed. If you search the forums you'll see my DIY. But of course if you just want to throw some cash at it go for it. I'm on my original core with perfect heat.

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[Preston_08]

Gotta agree with Furly on this one, do first things first. If very little sediment comes out and/or the back pressure remains high(when flushing) then replace the core.

Either way, thanks for posting this question. Preston's trash bag pics = cool idea.

Definitely didn't want to get coolant on my carpet, worked out perfectly I just figured while I was replacing everything else in my cooling system why not just replace the core with a new one for $60 since it was clogged. Had to replace the supply line to mine as well because it was so clogged it wasn't letting any coolant pass and it melted the plastic connect to the flange oh well, got super hot heat now


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[seanf86]

flush it first, if that doesnt work then replace the core, I bought a spectra premium from rock auto, its all alum and has been holding up just fine for over a year, avoid the cores with the plastic end tank where the alum pipes attach, there are pics here of one that blew and it wasnt pretty, imagine hot coolant all over your feet.

[16vCorey]

Between A4s and Passats, I've probably flushed a dozen of them and haven't had to replace a single one yet. I'm still in contact with a lot of the owners, and after several years all that I know of are going strong. I made a kit with hoses, a ball valve, and a garden hose hook up to flush them, and it seriously takes less than an hour to do. Just flush it.

[16vCorey]

Also, pour some Liquid Plumber (NOT THE GEL TYPE!) into it and let it sit for five minutes, then flush it.

[jacobsen]

Nothing beats acid!

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[old guy]

Nothing beats acid!

Somehow I didn't place you as a child of the '60's.......

[Human Garbage]

What sort of experience have people had with the various price levels of heater cores? I don't mind spending the $150 if necessary, but if the $50 cores are tried and true...

I went cheap on the only core I've ever bought, in my old Passat. It lasted two years before crapping out. Spat hot water out of my dash vents in rush hour traffic. All over my hand and stereo. Stereo was fine after drying out a few days. Makes me laugh now, not so much when it happened.

If I had to make the choice again I'd pay for a better core. Then again the Passat was terrible to change it on, the whole dash had to come out basically. I'm a bit biased after having to do the job twice in as many years...

[john_gonzo]

Somehow I didn't place you as a child of the '60's.......

He's had his half of the sunshine blotter.

[BARRY]

the same amount of time you would spend cleaning out the heater core is the same amount of time it would take to replace the heater core. replacing is much less comfortable as you're working on your back. i personally replaced mine with the cheap plastic end tank heater core. works awesome...but if i were to do it again, i'd probably go with the aluminum just for longevity.

FYI, replacing the heater core will return better performance than the best flush job as there will be absolutely nothing to hamper output.