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Discussion Starter · #1 ·
I've got a 2000 B5 1.8T with about 140,000 miles on it. Manual climate control system.

Check engine light has come off and on without incident for a while. Service station last noticed something loose and fixed it and it went away for a long time.

Now, for the last month, as it's gotten colder, I've needed the heat more. First noticed this on a cold morning: I'm not getting heat for a long time. Usually I'd be at full heat after running for 10-15 minutes at most on a cold morning. Now, if I play with recirculate/not, heat/cold, low/high fan... no heat. When it's on heat, I get air that's just barely lukewarm compared to the cold setting.

Eventually, after about an additional half hour of highway driving, I start to get hot air. Sometimes the hot air goes away, but mostly it stays once it comes through.

I checked the trouble code at a dealer, and it's P0411 - "secondary air injection system is getting incorrect flow" or something like that. (I found other threads discussing this code, but with different problems.)

I'm hearing no unusual noises, noticing no performance problems.

I called a VW dealership, and they suggested it might be the water pump (which has never been replaced, though the timing belt has) or something about a clogged heating coil...

Any ideas? Thanks for your help.
 

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I don't think your problem with the secondary air injection pump has anything to do with the lack of heat in the passenger compartment.

Does your temperature gauge normally read 190? I trust you are not low on coolant.
 

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I'd bet water pump. sounds like the plastic impeller broke. I'd also replace the thermostat, and at 140K, if they are going to put the bumper into the service position, I'd go ahead and get the timing belt done. there's not a lot of additional labor to schedule all these at the same time.
oh, and to be on the safe side (since you have that many miles on it), I'd go ahead and replace the alternator. I'm going to do all of the above on my next timing belt change interval (150k, now at 130k - at the rate I drive, it'll be about 8 months...).
 

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Discussion Starter · #4 ·
Thanks for the reply.

The temperature gauge is reading fine at 190 degrees F, climbing to temperature at a normal rate.

I checked the coolant, and it's at (or just below) the "min" line. There was a problem several years ago where a gasket leaked oil into the coolant system and the system had to be filled and drained/bleeded several times, but I looked in the coolant and there's nothing dark in there, so I don't think the problem's recurring.

So the coolant seems fine and the temperature gauge is normal. What do you think might be going on?
 

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Discussion Starter · #5 ·
If it was the water pump, wouldn't there be a noise? Or overheating? Or both?

(I did have the timing belt done already under warranty...)
 

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I bet your thermostat is dead, and it's not letting the coolant circulate when it heats up enough. That's what was wrong with my dad's old van, it too was throwing a code about the engine staying cold too long. (your ECU is probably comparing the reduced airflow from the secondary air pump and the lack of hot coolant in the overflow tank and it's freaking out.)
 

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Discussion Starter · #7 ·
Cool. How much should I expect to pay to replace a thermostat? (Is it something worth trying myself? File me under: reasonably handy but no expert.)

Any other theories as to what the problem is?
 

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Actually, you should be at full heat when the temp guage reaches 190*F which should be in 3 to 5 minutes (maybe a little longer but not 10 to 15 minutes). My guess is also bad waterpump. Sounds like its time for a water pump, thermostat, and coolant flush.
 

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Discussion Starter · #9 ·
So it's possible the water pump is bad, even though I'm not hearing any unusual noises or seeing overheating?
 

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For the P0411, take off the engine cover and look for a short silver can between the head and the firewall. That's your kombi valve. There is a vacuum hose that runs off towards the drivers side and under the intake manifold. I bet it's cracked. Just changed one on a friends A4 this weekend.
 

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What is this "kombi valve"? I've heard it mentioned before but I've never heard an adequate description of what it does. Also, does the AEB engine have one?
 

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Discussion Starter · #13 ·
What's the degree of difficulty removing the engine cover and changing that hose? Do you have a part number for the hose attached to kombi valve?

Also, do you think this is related to my heat problem?
 

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No, the Kombi valve does not relate to the lack of heat.

A bad water pump will usually overheat on the highway. It may still be bad and only provide minimal circulation. If the plastic impeller is slipping on the shaft, there will be no other symptoms.

A bad thermostat will stick open or closed. You would either overheat or run cold all of the time. Once the go bad, they usually stay open.

The thermostat is not hard to change. The hardest part is putting it back in without it falling out as you put it back together.

When was the timing belt changed?
 

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If you replace the waterpump, get a Hepu pump from ECS. They have metal impellers. God knows why VW specced a plastic pump -- probably to reduce the most evil of evils, rotating mass. (recoils in mock horror, pretends to faint.)
 

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Discussion Starter · #16 ·
OK. So the kombi valve just relates to the error code (P0411). Is this an urgent fix?

The timing belt was done at 81,200 miles in December 2003; I'm now at 139,000 miles or so.

So if I'm getting heat at times, it could still be the thermostat, but not as likely? Is it the kind of thing I can look at and tell if it's bad?

Could you source me a link for purchasing the Hepu water pump from ECS, in case I end up in that direction and my service center doesn't offer one?

Does anyone think this might be a clogged heater core? Is that different from TwoManyPassats' suggestion of bleeding the hoses? (That is, could the core itself be clogged as a problem separate from the hoses having a problem?)
 

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that's right getting cold , and looks like Im having same problem ....

re water pump, when you turn off engine and open the hood , you see that refrigerant is still circulating , for me that's means that the water pump is working properly , I'm I right?
 

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OK. So the kombi valve just relates to the error code (P0411). Is this an urgent fix?

The timing belt was done at 81,200 miles in December 2003; I'm now at 139,000 miles or so.

So if I'm getting heat at times, it could still be the thermostat, but not as likely? Is it the kind of thing I can look at and tell if it's bad?

Could you source me a link for purchasing the Hepu water pump from ECS, in case I end up in that direction and my service center doesn't offer one?

Does anyone think this might be a clogged heater core? Is that different from TwoManyPassats' suggestion of bleeding the hoses? (That is, could the core itself be clogged as a problem separate from the hoses having a problem?)
The combi can be urgent. If it is bad, it can allow exhaust to flow into the air pump. It will eventually destroy the pump. The combi itself may not be bad. A bad vacuum hose can cause the code.

Was the water pump replaced with the timing belt? A bad heater core is possible, but I would look into the other issues 1st.
 

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that's right getting cold , and looks like Im having same problem ....

re water pump, when you turn off engine and open the hood , you see that refrigerant is still circulating , for me that's means that the water pump is working properly , I'm I right?
No. The 1.8T water pump only runs with the engine. The V6 has a secondary pump that runs after shutdown.
 

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Discussion Starter · #20 ·
Hoping for some final feedback before I take this in for service...

- Could the lack of heat be due to a bad thermostat? What should I expect to pay for this repair? (parts and service)

- If it's a clogged heater core, what should I expect to pay for that service?

- Bleeding the hoses -- is that related to either of the above, or its own problem?

Thanks.
 
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