Coldest day of the year today. I have heat..or maybe I should call it "warm". Here's what VAG-COM reads with motor warmed up and heat turned up all the way. Group 007 in the bottom row shows 29C (84F) at the center vent and 34C (93F) at the footwell doesn't seem that warm from 92C coolant. Gotta be a clogged heater core doesn't it? Oh, and I can see the blend door go through it's range in VAG-COM when I change the temp setting.

 

Yes , very , very , very , very , very common problem!

Go down to your local hardware store , get your self a couple of bottles of CLR , remove both hoses from heater core at fire wall , flush out with fresh water , blow out water with air , fill the heater core with CLR & let sit over nite. The next day flush out CLR with fresh water , fill & bleed cooling system. Repeat as necessary.

 

That's my mission this weekend. Those first two VAG-COM temps in 007, what should those read from a healthy heater core with a coolant temp of 92C?

 

I'm hoping to try to a flush this weekend myself. So just to be clear: I don't need to drain any coolant from the radiator first, right? Just disconnect the firewall hoses, let a bit spill I'm guessing, do the flush, and then when I refill should I pour coolant directly into the heater core first before reconnecting the hoses or just do the whole refill from the expansion tank as with a regular coolant flush?

Also, I've read that it's important to flush in *both* directions, not just input->output. And also run many many rinse passes with distilled water, since you don't want a trace of CLR getting out of the core when all is said and done.

One more question: should I buy a connector that lets me use an air hose to help run the flush? There was an old thread on this forum about doing that but I've also read that you risk blowing a leak that way, which is the last thing I want to deal with.

 

Yea if you don't mind some mess, you don't have to drain anything from the radiator. Those heater core hoses are a very hight point in the system. The core has a pretty small capacity, so yes, it's no big deal to flush it out several times to get rid of all the CLR.

I've got some old heater hose I'm going to use to refill the heater core. Then when it comes time to blow out the core, I'll use my lungs on the old hose connected to the core. Then I'll put some fresh coolant back in just to eliminate any air bubble drama. But mine's the 2.8 and that system works out it's bubbles pretty well by itself. I think the 1.8 needs a bit more help that way.

 

Mrchicen, do be careful prying the heater hoses off that old heater core. When those plastic pipes are old, they get brittle and if you break them you'll be solving your heater core problem an entirely different way.....

 

yes PLEASE be careful pulling the hoses off!

straight out with only slight right-left wiggle. dont wrench on them left and right to get those hoses off.

pre-rinse as much as possible before using CLR as you want that working directly on the issue, not misc stuff that could easily come out with a pre-rinse. and yes pre-rinse both directions.

if you can, get an air compressor to do the same through the inlets and outlets. it can get a ton of crap too

dont connect the heater core back up to the hoses with CLR in it, you don't want that stuff getting into the rest of your coolant system

after it has sat overnight, rinse to get all the CLR out, again in the inlets and outlets

use the air compressor again if you have it to blow out any crap (inlets and outlets)

rinse a few more times

re-connect normal coolant hoses and make sure to get coolant flowing through it.

 

Thanks all. I think I'm all prepared, this is gonna be fun. I plan on being extremely careful taking the hoses off. I also read that it helps to soak the drainage/cleaning hoses in hot water first before slipping them on to loosen up the rubber.

 

Well, I let it sit all Fri night full of CLR. Sat AM I hooked up some hoses to it and blew (lung pressure) it out, filtered the CLR and kept running it through. Then kept flushing that out with boiling water. A lot of small particulate's came out, but no big chunks like I've seen some people describe.

I have better heat now, but nothing like my friend's B5 Passat.

 

I did my flush too. I'll post some pics/video soon. No big chunks but the stuff that came out was *very* dark and dirty. So far I seem to have very good heat, almost perfectly hot, but I need to test it some more. Previously I was getting no heat at all, so if this works it's a huge step up.

One thing I had a bit of trouble with was bleeding the system of air. I reconnected the core with it completely empty, and added some coolant to the reservoir and left the outlet hose open to the "bleed hole". I ran the car for a while in the driveway but never really got coolant to pop out of the bleed hole, and the coolant didn't drop a ton from the reservoir. I did disconnect and lift the reservoir quite a bit. However after driving around for an hour I opened the hood and the coolant had lowered in the reservoir at that point, so I'm assuming the core finally got refilled and I'll try bleeding it one more time from the bleed hole today. Is coolant supposed "spurt" out from the hole or just dribble lightly?