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Discussion Starter #1 (Edited)
Hey there guys,

VW: Adopted 2002 GLX Wagon 4Mo 2.8L Automatic with 131k miles.

Did a bunch of stuff to get it all nice and happy. For the most part, it is (shy of a hole in a flex pipe) running pretty well. With winter coming up I wanted to check the heat...and it is still being wonky.
Last spring I did a reverse flush of the heater core, which was a problem, given the crap that came out. When I was testing the heat this week, it was not working as expected.
Things I have checked / done:
The fans are fine (AC is fine, lots of airflow)
The thermostat, i believe, is fine (ECT sensor is new, was replaced in the spring) and i do not have any over heating issues.
I bled the system from the top hose by the firewall...there may be some air in there, but not a lot.

The heat does come on under load (going uphill), but high RPMs alone (like 3rd gear, 50MPH) do not bring the heat.
I am not sure where to go next...
Could it be the serpentine belt? - I have no issues with my alternator, power steering, AC (AC is nice and cold after the refrigerant was topped off)
Could it be the pulley on water pump? - but wouldn't that lead to overheating issues?
Could it be the pump itself? - again wouldn't that lead to overheating issues?

help please

Edit: So I am not a mechanic, is there a tensioner or something of the like on the main belt that might be shot? if that was the case, again would there not be an overheating issue?
 

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Last spring I did a reverse flush of the heater core, which was a problem, given the crap that came out.help please
I would say with a high likelihood the heater core is clogged up and needs either replacement or serious flushing to get the gunk out of it. Have you used anything other then G12 coolant?
 

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Discussion Starter #3 (Edited)
I would say with a high likelihood the heater core is clogged up and needs either replacement or serious flushing to get the gunk out of it. Have you used anything other then G12 coolant?
I plan on doing another flush with it this weekend. but in the spring I did a thorough flush of the core, and the whole system, and CLRed the core as well.

no idea what was done to or with it before it ended up in my hands this spring. I used "PEAK OET European Vehicle Extended Life Pink" to refill it. I have no idea what was used before given the not clear what color it was when it started fluid that I drained.

Just to ask, if the heater core is clogged (again)....why would it be intermittent instead of nothing at all?
I have not seen any discoloration or changes to the coolant, or seen anything floating in it.
 

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I don't have a V6 but I've heard they are difficult to bleed properly. I think there are actually 2 bleed ports and they need to be bled in order. Search for the procedure to bleed a V6 and then do that first. Intermittent heat could easily be due to air in the system.
 

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Discussion Starter #5
I don't have a V6 but I've heard they are difficult to bleed properly. I think there are actually 2 bleed ports and they need to be bled in order. Search for the procedure to bleed a V6 and then do that first. Intermittent heat could easily be due to air in the system.
The other bleed port on the hard line is stripped/rusted and on a very very soft piece of metal. I fear if I try to get that thing free, I am going to rip the metal it is attached to.
also it is lower on in the system then the one by the firewall...
 

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My 2 cents from Wisconsin and having gone thru last winter with no heat : G12 is a headache and you should switch over to traditional Prestone. I did that and I haven't had one problem with air in the system since.

You will need to drain the entire system - lower radiator hose and engine block drain plug removed.

Being from Vermont, if you want to make the switch, your time is running short. But if you do, me and others on the forum will help you out along the way.
 

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The water pump is run by the timing belt. If the belt, WP and all the rollers have not been replaced, you are living on borrowed time. The thermostat is likely to fail open, causing low coolant temps and poor heat. The gauge should read right on 190 once the car is warmed up. If not, the Tstat has failed. Considering the heat works better under load, it's quite possible.
 

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Just dealt with the same on the 03 v6 we bought. Heat while driving but nothing at idle. I used two sections of 3/4 heater hose about a foot and a half long. I blew the heater core out with compressed air to remove any coolant and flushed with water once there after. I then filled the heater core with straight lime-away. I let it sit for approx 25 min then blew it out with compressed air. I kept pouring water in to fill the core again the blew it out over and over going back and forth with the air between the the inlet and outlet. I captured everything in milkjugs besides what blew all over. So much garbage came out it was unreal. Once I wasn't getting any debris I hooked up the core again and bled it. I can cook eggs on my vents now. I'm leaning towards a clogged core. Idk why but I've had this several times on the v6 cars.
 

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That same " brown sand" that came out of your heater core is probably sitting in the bottom of your radiator. When I opened that valve, it was practically clogged with it.
 

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Discussion Starter #10
The water pump is run by the timing belt. If the belt, WP and all the rollers have not been replaced, you are living on borrowed time
So I have zero idea what was done to this thing in its first 125K. I adopted it in the spring because it was basically going to be scrapped. This is something I plan to do....just not sure when. the parts/kit isnt too bad in price, but time and weather are going to be the biggest factor in my getting it done before april or may.

The gauge should read right on 190 once the car is warmed up.
it does. I am not at all worried about the thermostat, because the engine side of things is fine. its cold when it starts, and sits perfect at 190 on the gauge, and usually is around 189 off the OBDII.

Also the ECTS was shot when I got it, so that was also replaced. again giving me confidence that I am not getting false information.

So much garbage came out it was unreal. Once I wasn't getting any debris I hooked up the core again and bled it.
Yeah I am going to try to do another reverse flush (and a radiator flush too) this weekend if I get the chance.

yesterday I finally got a chance to speak to someone locally that is known to be a very good VW/Audi mechanic. Given the conversation we had, he told me what happens when people mix the g12 with the "green" stuff, a precipitate is formed and clogs everything up. Given the almost 3cm of "chalk" that were in the original coolant reservoir when i got the vehicle, I think that several more flushes (including a nice flush of the radiator) will help things out. Same mechanic suggested I actually run the heater core backwards for a while (not just in terms of a reverse flush) but reverse for use to help push shit back out while its hot.
He even had mentioned that he knew of at least one person that put an inline filter of some sort.
 

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Discussion Starter #11
blew the heater core out with compressed air to remove any coolant and flushed with water once there after.
useful little tool:
97557


I hook this up to one side of a Y, h20 to the other, and then the "in" side of the y goes to the hose clamped to the "out" side of the heater core outlets on the firewall.
 

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G12 is a headache and you should switch over to traditional Prestone.
I don't think these cars are designed to work with any other coolant than G12 properly. I've seen many stories where people used other coolants with adverse effects. In 19 years I own my Passat I have exclusively used G12 and never had any heater core or other kinds of issues. After 19 years the heat is the same as the first day.
 

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I don't think these cars are designed to work with any other coolant than G12 properly. I've seen many stories where people used other coolants with adverse effects. In 19 years I own my Passat I have exclusively used G12 and never had any heater core or other kinds of issues. After 19 years the heat is the same as the first day.
Well, mine is running like a top after making the switch. The trick is to be sure that all that G 12 is drained.
You must be lucky, in both owning yours since new and not having heater core issues. Most of us, it seems, have adopted ours.
 

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If the pump impeller is slipping or otherwise damaged (like broke off fins or something) then there's less movement and yes a symptom of that is overheating. I've read reports of that in this forum and the reporter will usually have some story about how they first noticed it on the highway at high speeds. I just recently unclogged my heater core and I'm hoping it gets me through winter. In my case when I would turn on the heat it would come on and feel warm but only for a second or two then it would go cold. Though I unclogged it reclog is a big concern, due to residue carried from elsewhere in the system.

Also +1 for sticking with G12/G13, why risk it.
 

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I don't have a V6 but I've heard they are difficult to bleed properly. I think there are actually 2 bleed ports and they need to be bled in order.
I've never had a problem with them; it's all about the procedure. Basic rule #1 is Don't Run the Engine. Counter-intuitive to many people, but the faster the engine (coolant pump) goes, the more air is kept within the system. There is also nothing special about the bleeder screws. They just expel air that otherwise will be trapped, so those are opened several turns, and closed again when a continuous stream of coolant appears, which later will occur at the heater hose bleeder hole. Be sure to keep the reservoir raised as far as hoses allow, kept full, and cap off or loosened.
 

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There is also nothing special about the bleeder screws...and cap off or loosened.
Isn't that if the reservoir cap is off the system should bleed air out of itself? At least a few time that worked out fine for me.
 

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If that were the case, there wouldn't be a need for vent locations to let out trapped air. So if the heater operation is marginal, an easy first step is to lift that reservoir, and pull the return heater hose so the vent hole is exposed to coolant/air. If it takes awhile for the coolant to appear, then there was trapped air.
 

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Discussion Starter #19
Since I've had it I have never had over heating issues. I have no idea what it did before hand.
I did not get a chance to flush as planned past weekend. will try for this weekend!
 

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I was going to go with a faulty thermo but you stated the temp gauge is reading 190 so I think we can assume that's OK. This being a GLX, I believe you have the Climatronic head. There may be a sensor issue that is preventing the unit from delivering heat. I had a reverse issue with my 2000 whereby the heat went on full blast on 97 degree day because one of the sensors was making the head unit think it was way cold.

There are a number of data points you can get from the Climatronic through the front panel. There are a number of write-ups on how to run diagnostics from the head unit. Do a search on climatronic diagnostics to narrow it down.
 
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