Radiator replaced, No heat

[kabukie]

First off, I have used to search function with no positive leads

I recently replaced a leaky radiator. I bled the system and have run my car for about 2 weeks.
After discovering I had no heat I bled the system from the heater core and removed a huge amount of air. Still no heat.
I have tried raising the reservoir, bleeding from the upper heater core hose. Everything seems as it should other than my heat not working.

Any ideas?

[BCsniper]

thermostat may be dead. they stick open when they fail.

no real reason that it would die at the same time as the work you did, but it is possible

[kabukie]

It gets up to operating temp within a few minutes. Doubtful that it’s a thermostat issue.

Is there another spot that could possibly be trapping air?

[xhackerekx]

before replace radiator did u use some stop leaks ?? made flush whole system ?? heater core maybe just clogged .

[jmcS4]

air pocket in the heater core i bet

[kabukie]

before replace radiator did u use some stop leaks ?? made flush whole system ?? heater core maybe just clogged .

No stopleak. Might have to flush the heater core. That was next on my list but thought I’d check with the zine first.

air pocket in the heater core i bet

Bled the system at the heater core twice so that shouldn’t be the issue.

[Mehsin]

in the reservoir on the back side where the small hose connects can you see coolant pushing or flowing into it? also did you unplug the aux pump behind the driver side rad when doing the install by chance?
if you bled the system at the heater core that means coolant was pushing out the hose coming from the heater core? it could also be an issue with the blend door in the dash not allowing air to pass through heater core.

[VinnysS4]

Sounds like a blend door issue, or possibly air in the heater core. You have no heat because of 1 of 2 things:
1: there is either no hot coolant in the heater core to blow air through to make hot air
or
2: there is no air being blown through the heater core because it's being redirected elsewhere


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[kabukie]

So the blend door that’s something I can test through VCDS?

[jmcS4]

No stopleak. Might have to flush the heater core. That was next on my list but thought I’d check with the zine first.



Bled the system at the heater core twice so that shouldn’t be the issue.

I bet it’s still your issue. Sometimes it takes multiple tries to bleed the heater core. It sucks tryin to do it without a coolant evac tool. You could have also clogged it if it was run dry or if any sediment was agitated while moving things around like the radiator or whatnot


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[VinnysS4]

Try this. A common issue amongst other cars is the heater core being higher than some other engine components. In this case we want to raise the front end of the car up as high as you can possibly get it. Whether you use Jack's, ramps, or if you find somewhere you can actually park the car at a very steep incline, this would be optimal.
Make sure to take the cap off of the expansion tank.
Run the car for a few minutes to let the air excape the heater core.
Make sure to bleed the air at the heater core hose.
Return car to flat.
Run for a few more minutes.
Make sure coolant level is correct.
Replace expansion tank cap.

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[kabukie]

Try this. A common issue amongst other cars is the heater core being higher than some other engine components. In this case we want to raise the front end of the car up as high as you can possibly get it. Whether you use Jack's, ramps, or if you find somewhere you can actually park the car at a very steep incline, this would be optimal.
Make sure to take the cap off of the expansion tank.
Run the car for a few minutes to let the air excape the heater core.
Make sure to bleed the air at the heater core hose.
Return car to flat.
Run for a few more minutes.
Make sure coolant level is correct.
Replace expansion tank cap.

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Still nothing
Raised and bled a few more times. Still no air coming out of the bleed hole.
Good thing Im in LA where you only turn the heat on a handful of times

[Kambesama]

Still nothing
Raised and bled a few more times. Still no air coming out of the bleed hole.
Good thing Im in LA where you only turn the heat on a handful of times

Did you feel the hoses running to the heater core? Both should be hot when at operating temps.

[kabukie]

Did you feel the hoses running to the heater core? Both should be hot when at operating temps.

Yea both were warm. Squeezed both and saw the fluid level rise in the resevoir

[SprintBlueWorld]

It gets up to operating temp within a few minutes. Doubtful that it’s a thermostat issue.

Is there another spot that could possibly be trapping air?

Im thinking the thermostat is not allowing hot water, once up to temperature, to travel through the heater core, and so no heat. Perhaps this is correlary to the original issue, producing too much pressure, causing a leak.

Once all the most likely scenarios have been ruled out, the unlikliest must be more plausible.

[a4lownslow]

You never actually specified whether or not you had heat prior to replacing the radiator or any certain time frame before that.

So did you?

As I’m sure you know at this point, it’s very common for the heater core to become clogged on the b6/b7. And based on everything else you’ve noted I’d be looking here.

Sure you can try flushing it, but you will never get it completely clean. The passageways are far to small, and all you’ll do is buy time if it works at all.

I’ve replaced over half a dozen cores and the best thing to do is just install a new one and not have to worry about it again.

As far as the bleeding goes I can guarantee you if the cooling system is working properly you will never have to touch the bleed hose or any other bleed screw (engine depending).

All you need to do is add coolant, drive the car, and heat should return within minutes. Air will get trapped in the reservoir, and once the car has cooled you remove the cap, air is released, and you top off fluid as necessary. It’s really quite simply, and no need for all the special bleeding bs.

That’s my experience servicing probably two dozen Audi’s from b6-b8. Where I have completely drained coolant for repairs similar to yours.

Whether I use a vacuum tool or simply pour in coolant result is the same.




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[kabukie]

I had heat prior. But the last time I had used it was probably last “winter”
Going to try flushing the heater core next.

You never actually specified whether or not you had heat prior to replacing the radiator or any certain time frame before that.

So did you?

As I’m sure you know at this point, it’s very common for the heater core to become clogged on the b6/b7. And based on everything else you’ve noted I’d be looking here.

Sure you can try flushing it, but you will never get it completely clean. The passageways are far to small, and all you’ll do is buy time if it works at all.

I’ve replaced over half a dozen cores and the best thing to do is just install a new one and not have to worry about it again.

As far as the bleeding goes I can guarantee you if the cooling system is working properly you will never have to touch the bleed hose or any other bleed screw (engine depending).

All you need to do is add coolant, drive the car, and heat should return within minutes. Air will get trapped in the reservoir, and once the car has cooled you remove the cap, air is released, and you top off fluid as necessary. It’s really quite simply, and no need for all the special bleeding bs.

That’s my experience servicing probably two dozen Audi’s from b6-b8. Where I have completely drained coolant for repairs similar to yours.

Whether I use a vacuum tool or simply pour in coolant result is the same.




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[Mike50design]

Did you try massaging the upper rad hose with the engine running to try and force bubbles out of the system?

[Kambesama]

Yea both were warm. Squeezed both and saw the fluid level rise in the resevoir

From my experience, if both hoses are the same temperature (hot) that's a good indication that there is water flow through the core. Im leaning towards it being an mechanical or electrical issue with your blend doors.

[Nemesis2747]

Hoses shouldnt be warm, they should almost burn you when you touch it. What did your coolant look like before? Mud? Rust? If so core is clogged. Happened to me on an a6 c5 and a b6 a4. Core was filled with sediment. Comes out above the gas pedal and is easy enough to just replace.

[kabukie]

Flushed to core. Happy to report no sediment.

Previous coolant before the radiator swap was the g12/13 pink.

Trying to find someone local to test on my blend doors.

[kabukie]

But while Ive been trying to track down this heating issue I saw that the reservoir was developing a crack.
Nice new and fresh in place. What a difference it makes.

[VinnysS4]

Just so I understand.... zero heat from the vents right? If you turn the car on and push the hvac buttons, do you hear the blend door moving?

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[kabukie]

Just so I understand.... zero heat from the vents right? If you turn the car on and push the hvac buttons, do you hear the blend door moving?

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Nope or at least I don’t think so. Hard to say with the digital temp (+ -) Is it an abrupt change when I can only go slowly from Lo to Hi?

[kabukie]

Took the glovebox out to check out the motors. Ran through the hvac gambit. Only the white motor moved.

Going to try resetting them through VagCom and see if that fixes it. Really would hate to replace all the motors.