Hello all, ive searched for answers and decided to make my post… My s6 heat works great at low rpm and cruising around the b-roads but as soon as i get into the rpms ~2300 rpm the heat changes to blowing cool/cold air. I recently did a coolant drain and fill…could it be air? Ive taken apart the heater control valve and cleaned it…could it be acting up? No codes when i scanned it with the vagcom. Any ideas are welcome!
I replaced the heater valve and no heat at all now…i will try to rebleed the system when i get home.
This sounds like it could be air trapped in the system. Not 100% on the 5.2 C6, but on my 2003 2.7t I had to bleed the heater core in addition to the bleeder screw that is found on top of the engine. Check out the link below for what you should be looking for: http://s19.photobucket.com/user/walky_talky20/media/heater-core-bleeder.jpg.html (pics are from the 1.8 setup)
I’ve only had my 5.2 for about 6 months now, so I’m sure one of the other guys more experienced with this platform will be able to confirm but I figured it’s a good start in the mean time!
Yeah I remember the little bleeder hole on my b5s4. I did find and bleed the plastic bleeder screw under the cowel…not sure if there is another one somewhere or not. Thanks for the input
I wonder if your heater core is clogged. Try taking the rubber hoses off the metal pipes at the cowl area and use a garden hose to flush water backwards of the normal flow through the metal pipes for a few minutes until clear water is coming out. The idea is to use the water to push the metal shavings, rubber particulates, and dirt out. Then put the rubber hoses back on, fill the coolant, bleed the system, and drive around a bit to see if that solved the problem. Fair warning though, you will make a mess so be prepared with a mop and bucket and try to do this in a spot where the water/coolant can easily be cleaned up.
I had to do that a lot for the older 1.8T A4s while still at the dealership because replacing the heater core sucked! That procedure would clear up 7 out of 10 cars for a while until we just had to replace the heater core finally at something like 16 hours of labor. One more reason that I will likely never buy a B5 or early B6!
Yeah maybe flushing the core is a good thing to try…the car has 70k on it. Im trying to locate the inlet and outlet hoses that feed the core…i may have to take out the blower box assembly to get access to both hoses…this should be fun
I did get a code that came up after replacing the valve…00739
http://uploads.tapatalk-cdn.com/20161222/87f2b7c3ecb72c70fe6d40124deb6522.jpg
That should be for the after run pump. That would further suggest there is a clog in the system. If you dont see a rise in the coolant temps on the dash there is a very good case for a clogged heater core as jimmy suggested.
The heater core flush would be a good idea. Ill try to pull some pictures from another thread and show you where they are at. You should be able to tap into them semi easy as they are just under the cowl.
Well it’s been awhile but here’s what I’ve tried since last time. 1 heater core flush with water hose and coolant flush. Still blows cold at/around 2k rpm. Replaced thermostat with oe unit, new coolant and used my ecs/schwaben coolant pressure filler(awesome tool btw). Still same issue. I tried another heater core flush using clr this time and same result. When doing the flushes there is no particulates or dirt coming back out only clear water/clr mix. Could it still be an air trap issue even with the coolant pressure bleeder? There is a plastic bleed screw on the thermo housing…should that be used along with the top bleed screw to bleed air? My only other idea is water pump but the needle doesn’t fluctuate at all and never runs above the middle (even in the middle of the Alabama summer with a/c on).
I do notice when I accelerate over 2k rpm the fan blower automatically goes to the lower setting before blowing out cool air. So maybe a blend door actuator issue and/or blower motor issue?
do you have access to vagcom? you should be able to check those items in the climate control settings.
when I bled my S6 I just ran it with the cap off until it boils over. Seems to be always giving good heat.
Well I finally got a vagcom by way of the odbeleven. All the air door actuators are working within spec according to the live module data and the parameters that they should be within. The only codes that reoccur is a sunroof photo sensor circuit, alarm horn codes, and door lock codes…but nothing in the a/c and heating section. I did notice that one of the air temp sensors was reading about 30degrees higher than the 44 degrees that it was outside i wonder if something like that would cause a total heat loss over 2k rpm issue…all while sitting in the driveway at operating temp. so I ruled out an outside air door stuck open
I noticed the odbeleven does have a featured app called heater unlock that claims after 5 failed attempted starts the heater is locked? I’ve never heard of such! Either way when i try to access that it asks me if the ignition is on and try again, so it doesn’t seem to work. Could be an obdeleven issue i guess but worth a try.
Anything else i should try checking or watching on the scanner?
Hey @2003svtjrc did you ever resolve this issue? Currently having the same issue as you were and currently trying to diagnose the issue.