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  #1  
Old 10-01-2009, 09:08 PM
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Default '02 A4 1.8T Quattro - No Heat - Audi Dealership Can't Figure It Out

Hey All,

I've been having this problem for 2 years now. Here's the story. I have no heat in the car. I let it warm up completely first, which is does to normal temperature. Heat comes out initially and then goes cold. The heat never returns whether driving or at idle.

- The car has never overheated
- I'm not losing coolant
- I see no smoke of any kind from anywhere

Here's what's been done to the car so far:

1. Replaced Water Pump
2. Replaced Heater Core
3. Replaced Timing Belt
4. Replaced Thermostat
5. Replaced A/C Servo (Supposedly the blender in the dash)
6. Replaced Water Temp Sender including O-Ring and C-Clip
7. Replaced Radiator
8. Replaced Bleeder Screw on top of engine
9. Replaced Plug in Engine Block
10. Replaced Climate Control Head Unit
11. Flushed several times with core attached AND unattached
12. Replaced all coolant

*On a side note, my A/C started blowing hot and cold this summer. I plugged a coolant recharge kit into the system and the pressure was in the dangerous red zone. It started at 70psi, rose to around 150psi, then dropped back down to 70psi. That just kept repeating. The dealership had to replace a fan which did fix the problem.


Now the dealership says they have to replace the head gasket. Does that make any sense given the circumstances I've listed??

Thanks in advance,

Rob
  #2  
Old 10-02-2009, 01:41 AM
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1.8T gaskets do go bad quite often, but I really don't see how that could affect your heating system. It does however make your car overheat because it sends the coolant into the cylinders and then it starts runing out. Have you had to refill your coolant in recent days/weeks?
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  #3  
Old 10-02-2009, 09:41 AM
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Thanks for the reply. No, I'm not losing coolant...
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Old 10-02-2009, 11:11 AM
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It could affect the heater by not allowing the system to pressurize.

Does the heater work at higher rpm??

I would try watching the res with the cap on while revving the engine. If the level goes down take the cap off while holding the revs and fill it up. Then repeat that process until the level doesn't lower.
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  #5  
Old 10-02-2009, 11:52 AM
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No, once I heat the car up I turn it on HI. It begins hot, then gradually goes cold (does this pretty quick). From that point, it only blows cold air whether I'm driving, parked revving the engine, or at idle.

I'll check the level in the reserve tank today but I've had them flush and refill the system several times...I'll let you know how it goes...thanks...
  #6  
Old 10-02-2009, 12:49 PM
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If the thermostat has only been replaced once it is possible the replacement was/is faulty.
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  #7  
Old 10-02-2009, 12:50 PM
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Also, on your list I don't see coolant sensors. Have those been replaced??
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  #8  
Old 10-02-2009, 12:59 PM
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Find the coolant hoses that run into the firewall. Get the car good and warmed up and feel both hoses. If one is hot and the other cold then your heater core is plugged up or possibly the replaceemnt was installed incorrectly. Hot coolant isn't flowing through hte core properly if this is the case...if you got the car good and warmed up and didn't run the heater for awhile you would get heat out of the vents for a minute or less after turning on the fan, but it would cool off the heater core faster than the hot coolant heats it up.

If both hoses are hot then your probable is more likely the blend door that allows you to select hot air adn cold air. Its not opening properly and allowing hot air to come into the cabin from the heater core.

Based on your description I'm betting on the core being the problem. It sounds like thye're replaced like $3000 worth of parts at this point for you...I bet they made a mistake when hooking something up or used a bad part.

When the system was flushed, was it flushed or backflushed? When you flush a system and you have crap in there you're only wedging it in tighter, the couple times I had a situation like this I was only able to get the blockage out by backflushing.
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Old 10-02-2009, 01:04 PM
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Personally, I'd look at the temp sensor in your cabin. If its bad, it'll tell the climate control its too hot and make the blended air servo go to cold.
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  #10  
Old 10-02-2009, 02:11 PM
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Wow, thanks for all the quick replies so far...

Yes right now they actually want to replace the head gasket and the thermostat. If the thermostat was not working correctly, would my car heat up to normal temperature??

The coolant sensors were apparently replaced after talking to the mechanic...I'll ask about the temp sensor in the cabin...

I was present when it was bled and both hoses to the core were hot. I saw a steady stream of coolant streaming out of the bleed hole in the hose so the coolant was definitely flowing.

As for the flush, the dealership said they did it a few times but I'm not sure about backflushing, I'll ask them today...
  #11  
Old 10-02-2009, 02:51 PM
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It would depend on if the thermo was stuck open or closed.
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  #12  
Old 10-03-2009, 12:45 PM
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Ok, I spoke to the mechanic directly at the dealership. They called Audi with all the details and they're suggesting the head gasket replacement. The mechanic said he had a similar issue a few years ago. Basically there was a weird pressure issue that caused air to get sucked in without fluid leaking out of the engine. He had a special tool/toolkit (not sure what) that involved putting a chemical into the coolant system that changes colors if combustable material is present. But then he said he did the same test on my car and it didn't show up. So I don't get it.

He said he can get all the air out of the system by bleeding at the heater core AND the radiator at the same time. Then heat gradually gets back in. He said he's replaced the block plug twice and can't think of anywhere else air could be getting in.

This is craziness...
  #13  
Old 10-12-2009, 07:30 PM
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I have the exact smae issue... I have replaced about the exact same components, too. Next I want to look into the mix door/blend door; where is it? Also, is it vacuum or electric actuated?

Is the cabin temp sensor on the dash by the defrost vents?
  #14  
Old 10-12-2009, 11:16 PM
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Please tell me the dealership did the TSB where they replaced the little coolant O-ring for the plug under the intake manifold? The TSB for this very same problem which costs a total of $3. God dealership technicians these days are idiots.
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  #15  
Old 10-20-2009, 05:10 PM
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Default What is the TSB Number and advice sheet - please

Quote:
Originally Posted by auditech79 View Post
Please tell me the dealership did the TSB where they replaced the little coolant O-ring for the plug under the intake manifold? The TSB for this very same problem which costs a total of $3. God dealership technicians these days are idiots.

Have the same problem, engine at temperature but cab can not get very high temp. Also AC sma eproblem but does not get that cool.

Audi advised today they feel it is a plugged core from sediments????
$1500 to remove dash and replace core.. No warranty coverage.

I will ask re the tsb and if thye updated all, also if they back flushed as they put new hoses on and flushed a few months back to try and correct the problem.

Here is a tsb link, http://www.allworldauto.com/tsbs/ is it 10015099 in the engine cooling section?


Thanks,

Last edited by ramn; 10-20-2009 at 08:48 PM. Reason: add link
  #16  
Old 10-21-2009, 12:44 PM
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Default Clogged Heater Core

I saw an interesting blog about the same situation on an A4 while researching this problem on my sons A4. this guy describes the whole dealership issues and TS they did and finally decides to fix it himself. The heater core has an upper and lower section, and the only real way to tell if the whole thing is seeing fluid is to take an IR temp reding on the core with the car running, if the power half of the core is not hot, then that part is clogged. The sucky part is they can flush it all they want, but won't get teh clog. What he did was to take the hoses of at the firewall and connect tubing from the core to 2l plastic soda bottles filled 2/3 full with boiling water and CLR, then force the air and water back and forth between the bottles. The description is in post #51 at http://www.advrider.com/forums/showt...=411979&page=4. I am going to try this on my next day off.
  #17  
Old 11-11-2009, 11:15 AM
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Hi!
I have the same problem..i get a slight bit of heat from the windshield but cool air from the heater area near my feet.a
The Audi dealership is telling me that they cannot reverse flush the heater core
They said the coolant only flows one way
Any thoughts?
  #18  
Old 11-14-2009, 09:03 PM
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This a common problem on Audis and has been for years. Had the same issue. Kept contemplating ripping the dash apart and changing the heater core. Also kept thinking I should replace the thermostat. IT'S A BLEEDING ISSUE. If you run the car to operating temp and pull the heater core inlet hose off, you will NOT, have a steady flow of coolant. You need to bleed the core at the inlet hose. Sometimes it takes holding the accelerator down at about 2500 rpm for approx. 15 mintues before you will even see a flow of coolant come up through there. It's the way this system is designed. The heater core is basically a bypass with a slow moving low pressure of coolant flowing through it. Trust me and don't give up. Bleed over and over again and can take a lot of time in most cases. There is a great DIY on Audizine that I went by and got mine to work. I'll try and find it and put up a link.
  #19  
Old 11-15-2009, 04:52 PM
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Default how i fixe dmy audi heater

I traded it in on a new volvo. heat works great. Will never own a audi again.
  #20  
Old 11-15-2009, 05:54 PM
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Good luck...
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Old 11-15-2009, 05:54 PM
 
 
 
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