B6 A4 No heat and over heating

[bspellman]

I have seen multiple threads on both but was wondering what the best procedure would be to trouble shoot problem.

I just purchased a 2004 Audi A4 B6 Quattro with a 1.8l Turbo and have had it 4 days. The one thing I did not test when I bought it was if the heat worked since it was a nice day out- lesson learned.

My son is driving the car and called me because the temp gage went to 3/4 and then he called back an said it dropped to 1/2 and coolant light came on . I told him to bring it home and he also mentioned he has no heat in the car.

So I did some research and not sure what is the best plan of attack for this problem I don't want to just throw parts at it. From what I have read it can be the thermostat, head gasket, heater core, air in the system???

Since this was the easy one on the list I ran the car until temp reached 1/2 way on gage and opened the reservoir to burp the air out of the system nothing seemed to happen I also felt the bottom hose on the radiator and it was still cool to the touch.

So at this point should I replace the thermostat and see if this fixes the problem. Is there a way to test it before you replace it?
Also looking on line for thermostats I see then priced from $35 from DAP to $156 and they all look the same does one mfg make a better one than another I would obviously like to pay less but don't want to regret this decision later.

Thanks

[MacFady]

Personally, I'd try a proper coolant flush first yourself; straight forward and not expensive, there are guides on here and online if you're not sure yourself how to do it. Once you're confident it's not simply air in the system then I'd try trouble shooting the other things you mentioned. Hopefully the car wasn't overheated before you bought it.

The fact that it went up to 3/4, then dropped down to 1/2 with a coolant light makes me think there is air in the system. I'm guessing some air was purged, some cool coolant from the reservoir entered bringing it down to half on the temp gauge, but now leaving you with low coolant giving you the light. The bleed screw for the coolant is on the hard line on top of the engine but the reservoir cap is vented too I believe.

Do you see any crusted pink coolant anywhere around the engine bay? Any signs that you might have a head gasket issue like coolant in your oil?

[SJorge3442]

Flush the system. Start there and see where you go. Also, these systems dont play nicely when it comes to getting the air out.

[moyzes]

Since the heater doesn't work, check if there's water coming from behind the dash to your feet. if so, you have a bad heater core...

[bspellman]

Thanks for everyones feedback, while I was waiting for replies I went out to play with it some more I started it and let it run for about 20 minutes got turned it off felt the return hose and it was warm so I was happy the thermostat was opening. I got back in started the car and turned on the defrost and gave it some gas and it did get warm so I had heat. So I think I am on my way to fixing this and decided it was probably air in the system. I am going to do a flush of the system just to be safe. I did not see any crusty radiator fluid around the head but also my fluid is green not pink?

[SJorge3442]

Thanks for everyones feedback, while I was waiting for replies I went out to play with it some more I started it and let it run for about 20 minutes got turned it off felt the return hose and it was warm so I was happy the thermostat was opening. I got back in started the car and turned on the defrost and gave it some gas and it did get warm so I had heat. So I think I am on my way to fixing this and decided it was probably air in the system. I am going to do a flush of the system just to be safe. I did not see any crusty radiator fluid around the head but also my fluid is green not pink?

yeah get that green coolant out and fill it with some G12, properly diluted with distilled water.

[MacFady]

yeah get that green coolant and fill it with some G12, properly diluted with distilled water.

I think he means get that green coolant "out". I think you'll find it is just air after all.

[Audi body]

If you keep getting the same problem with the temp going to 3/4 then back to 1/2 go get some strips from auto zone to check for combustion gasses in the coolant.

[SJorge3442]

I think he means get that green coolant "out". I think you'll find it is just air after all.

fixed that.

[bspellman]

Did some more playing around with the car and I noticed if it sits and idles the heat does not get warm. If I sit in the car and keep the RPMs around 2K-2500 the heat works and if I let I go back to idle speed it gets cold again???? Not sure what this means but I do know this is not the normal operation of a heater.

[sinistervii]

It could be many things going on.

While you flush the coolant. Go ahead and flush the heater core.

I get the air out, yes use the hard line to get out, but what also works is that you unscrew the coolant resivuor and unscrew the cap. The raise the back end of it vertically. Start car and that should get the air bubbles out. After it warms then open the hard line that is black the runs across the intake manifold just enough for coolant to run out. I did mine for about 30 seconds. Tighten and put all back together. Make sure also that the heat is on low.

When flushing the coolant. You going to have to flush 5 times or so to get all the cap out of the block also. Flush until it is clear. Fill with the pink stuff and report back

[ECS Tuning-Audi]

First of all drain the green coolant out ASAP. Once that is done refill with G13 and bleed the coolant system. After that the heat should come on normally.

It might be a good idea to grab some DEI Radiator Relief which will aid in cleansing out all that green coolant and possible gunk left over by mixing coolants.

Check out the link below as I have included Radiator Relief, G13 coolant, and a coolant tester to insure you have the proper mix of coolant to water ratio.

Click HERE to order or for more information

Jason

[cschuster]

Most likely just air in the system, but if coolant is only circulating at higher RPM, your water pump could be the culprit. I experienced this on a subaru awhile ago, it would overheat at idle and then the temp would drop to normal above 2k rpm.

As for thermostats, anything over 30 bucks is robbery. They are filled with wax, which melts, allowing the valve to open and coolant to circulate. You can test your old one by putting it in a pot of water on the stove with a thermometer in it. When the water temp reaches the thermostats rating (190F?), you will see the valve open. If nothing has happened when the water starts boiling, then its stuck.....replace it.

[old guy]

As for thermostats, anything over 30 bucks is robbery. They are filled with wax, which melts, allowing the valve to open and coolant to circulate. You can test your old one by putting it in a pot of water on the stove with a thermometer in it. When the water temp reaches the thermostats rating (190F?), you will see the valve open. If nothing has happened when the water starts boiling, then its stuck.....replace it.

The A4 B6 utilizes a map controlled thermostat. It's not the same thing as a standard thermostat. You will not find one for 30 bucks. The cheapest aftermarket ones are ~$60. One from an OEM manufacturer will be closer to $100 or more. A map controlled thermostat opens the same way a standard thermostat when exposed to the the correct coolant temperature. A wax heater is also added so the ECM can apply power to the heater and open the thermostat at a lower temperature when certain conditions exist.

Cheers!

[bspellman]

I found this one on Ebay but a little concerned since it I so cheap( $34.95 )and you usually get what you pay for from my experience

http://www.ebay.com/itm/181239240701

Thanks

[customa4]

This is about the cheapest you'll find one that's not a cheap knock off. Click

[SJorge3442]

Cheap Electronics + Audi = No Good. Its not worth it to save $30. I would just get the proper OEM thermostat or equivalent such as the one posted above and use that.

[customa4]

Cheap Electronics + Audi = No Good. Its not worth it to save $30. I would just get the proper OEM thermostat or equivalent such as the one posted above and use that.

This^^ Buy nice or buy twice.

[cschuster]

Interesting, disregard my post about thermostats lol. Thanks to oldguy for expanding my knowledge yet again!

Sent from my XT907 using Tapatalk

[bspellman]

Thanks everybody so plan of attack is to flush the green out the system completely and fill with the Pink and see how it behaves after that and then if not resolved start to throw parts at it LOL. I will let you know how it goes,

Thanks again

[customa4]

Make sure you run a few gallons of distilled water through the system to get rid of all green coolant. Here is a great thread on testing some of the cooling system. Click Here's some more good info on testing if your problem is the coolant temp sensor or thermostat.(post #10) Click


Here's a tip from diagnosticator forgetting air out of the system

Sounds like that is the case here. Do this: with the engine cold, and the coolant tank filled to the MAX line, and the tank cap removed, remove the bleeder screw in the metal coolant pipe running past the injectors. (1.8T) When coolant flows out of the bleed screw hole, replace the bleeder plug and refill the coolant tank to the max line. Replace the coolant tank cap and tighten fully. Start the engine and run at 2000 RPM until the radiator fan runs, then turn the engine off and allow the cooling system to cool down then recheck the coolant level in the tank and top up as needed. Do not remove the coolant tank cap until the engine and coolant are cooled down to outside ambient air temp. Reinstall the tank cap, then drive the car and you should have heater function working again. If the heater function fails again, after bleeding the system, and subsequent bleeding produces more air in the system, then there is a coolant leak somewhere allowing coolant to escape and air to enter the cooling system.

Here's a tip from OG on getting air out.

Now that it is getting colder I noticed that my heater wasn't working very well. The problem was being caused by a large air bubble somewhere in the heater circuit. I know when the bubble was created. Back in September the clip holding the rear CTS cracked and consequently the sensor blew out of the motor. At that time I had a difficult time getting all the air out. Apparently I never got it all out.

Here's any easy way to tell if you have air trapped somewhere. Get your motor up to temperature. Then SLOWLY crack open the reservoir cap. If you have an air entrapment you should be able to hear the coolant gurgling and the coolant level in the reservoir will noticeably increase as the entrapped air is allowed to expand. The bigger the bubble the more the tank level will increase. If the bubble is big enough it will push coolant out of the overflow port on the bottom of the reservoir so be careful that you don't burn yourself. Even if you don't have any entrapped air the level will rise just a little as the coolant hoses contract back from the pressure release. However, you probably won't hear the gurgling noise that accompanies the bubble as it expands.

Now that you have the cap off you can release some of the air by cracking opening the bleeder valve in the center of the upper coolant hard pipe. Open it just enough for the air to escape. As soon as you get a solid stream of coolant close it off. You may have to repeat this process numerous times before you manage to work all the air out. The reservoir cap needs to be off when you perform this procedure so the static pressure in the reservoir will act on the hard pipe and push out the air. I just kept a 5mm Allen wrench in the car and a wad of paper towels stuck under the hood. whenever I took a short trip I just popped open the hood, shoved the wad of paper towels underneath the hard pipe and used this procedure to bleed the air off.

Unfortunately in my case this didn't release all the air so I had to take more extreme measures. Apparently I had a large bubble located in the heater core that wasn't bubbling out. After releasing all the system pressure I reinstalled the reservoir cap and then separated the quick connect on the out-feed side of the heater core. If you unscrew the coolant reservoir you can move it out of the way for easy access to the quick connect. I had a plug ready to block off the lower coolant line when I opened the quick connect. I used a long necked funnel to pour coolant directly into the heater core via the out-feed line. I then reattached the quick connect. After I did this I had to repeat the bleeding procedure outlined above three or four more times to get the rest of the air out.

I now have heat!

Here's some info from WalkyTalky on the topic

Even if the heater core was completely clogged, the car still should not overheat. Some cars like Honda and Toyota even have a shut-off valve to completely stop flow through the heater core when heat is not requested in the cabin (this helps keep the cabin cooler in the summer by keeping the hot coolant from ever entering the dash).

I'm going with air-lock for $800, Alex.

I like to use a cooling system pressure tester to aid in bleeding the air out. I put pressure on the reservoir, then crack the bleeder(s). Test drive to operating temp, and repeat. It really helps to fill the system quickly and get the air out without a bunch of messing around.

This is the kit that I use:
http://www.ebay.com/itm/ATD-Tools-33...fb8bd0&vxp=mtr

There are cheaper ones out there, too:
http://www.harborfreight.com/radiato...kit-65053.html

If you were determined, you could probably make one with a spare reservoir cap and a bike pump or something:
http://www.dsmtuners.com/forums/arti...re-tester.html

[bspellman]

Well I flushed the heater core with CLR and then cleaned out all of the green stuff which was painful process. Then I filled it up and bled the system with the hard pipe and the heater core hose and I now have heat at idle and so far it is not overheating or dumping fluid in my driveway. So with that all said my lesson learned with my new Audi is if you have no heat at idle before you start throwing parts at he problem it is most likely and gunked up heater core and some air in you system. I also learned what FML means and I am now a veteran in A4 B6 coolant systems. Then just when I thought I was done I look under the front of the car and see it dripping coolant and thanks to Old Guys post I bought some Liquid aluminum and the leak is fixed for $6.99.

Thanks everybody for your help