2.0t no heat, or water flow

[cdh9400t]

I know there are several threads about plugged heater cores, but I am confident that is not my problem. Heat problem started a few days ago. Would come and go. Like run you out of the car hot, but let it sit over night than nothing. Now no heat at all. Thought it might have been an air bubble so I tried to rebleed the system. No help. In fact I get no coolant flow to the heater core. So since I have heard about water pumps failing I decided to pull it apart and check the pump. No issues there,. Tbelt and pump kit was installed 11k miles ago and I had no problems. so I flushed every hose and line and I have water flow. Even through the heater core. Could the thermostat be stuck closed? It's an Audi stat with 30k miles on it. Engine temp jumps right up and stays there. No over heating and no loss of coolant. Any help would be great.

[Andrew149]

Could it be the flap that did you do a flush on the heater-core? Just wanted to check.


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[cdh9400t]

What flap? Are you talking blend actuator? If so that functions just fine with no vag codes. I did flush the core, and water flows with no gunk or debris.

[a4lownslow]

Coolant is always flowing through the heater core regardless of thermostat position. And It doesn't take much of a restriction in the core to impede coolant flow.

Do you get some heat when driving at higher rpm?


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[cdh9400t]

No heat at all now. And like I said I removed the heater hoses with the car running and got no coolant flow out of them. That's why My first thought was water pump. I can run water through the core and hoses with no problem at all.

[Okedokey]

You sure you have got all of the air out? Did you replace coolant in the correct manner?

[cdh9400t]

Coolant was replaced when the t belt and water pump was done. 11 k miles ago. Never had problems last winter. Haven't lost any coolant. So yes, the system was obviously bled or I would have had issues then.

[flowhigh]

I would try again to burp - not drain - the system using the spigot on metal hard-line running above the manifold, just to make sure. Who knows if air circulated around since then.

There's a proper way of doing so. A lot of diy'ers don't do it properly the first time.

[Okedokey]

If this were me, I would drop the coolant, replace with a radiator flush and hose water. Bleed by the book and with the heater on MAX auto. Wait for the fans to kick in and be ready to replenish the overflow when it drops. Run it for the necessary time once hot and then drop the coolant again. This may dislodge build up in the engine/heater core. I suspect a rear coolant flange or hose. If there is a air lock you may not see coolant loss but still have restrictions. A pressure test may be worthwhile.

Either way, you need to remove what is blocking your flow. You can confirm the water pump is good by removing the return hose on the overflow once the fans kick in it will flow back.

[Andrew149]

Could it be the blend flap. Also did you do a flush on the heater-core? Just wanted to check.


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[cdh9400t]

Ok time for an update. Rebled the system and not real happy with the results. All seemed to be going good, but then I realized the bubbles in the coolant reservoir were not stopping or slowing down. Seems worse when the thermostat cycles. Now I think I need to perform compression and leak down test to see if I might have a headgasket Issue.

[Okedokey]

Are you following the legit method of coolant bleeding or are you going on what you think ?

WITH THE CAR OFF:

– Top up the coolant until it emerges from the bleed hole in the coolant hose (near heater core) without bubbles.

– Push coolant hose onto connection and secure with hose clip.

– On vehicles with auxiliary heater, switch heater on (for about 30 seconds) and then off again.

– Tighten filler cap on expansion tank.

– Start engine.

– Set heater/air conditioner on both sides to “HI”.

– Run the engine for 3 minutes at 2000 rpm.

– Allow the engine to run at idling speed until the two large coolant hoses at main radiator become warm.

– Run the engine for 1 minute at 2000 rpm.

– Switch off ignition and allow engine to cool down.



– Check coolant level.

l The coolant level must be at the MAX marking when the engine is cold.

l The coolant level can be above the MAX marking when the engine is warm

[cdh9400t]

Yes it's bled correctly. This isn't my first time working on a car.

[a4lownslow]

Head gasket is not common on these engines, and if you aren't losing significant amounts of coolant or overheating, I doubt that's the issue.

Have you pressurized the cooling system and checked for leaks?


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[cdh9400t]

I am taking my pressure tester home tonight, and I am going to test to see if combustion gas is present in the coolant.

[cdh9400t]

Ok, fixed the car. after I did the pressure test and combustion gas test, I pulled the thermostat and tested it. Stat wouldn't open until water temp hit 232 degrees. So I guess the coolant was boiling until the old stat opened causing my airlock. But new thermostat and fresh coolant, good to go!!

[a4lownslow]

Interesting. Surprised your temp gauge never went over half. You'd think with the thermostat not opening properly, and all that air in the system the car would have got hot. Either way, glad you fixed it. Nice job!


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[cdh9400t]

Thanks. Yeah it had me puzzled for a bit.

[Okedokey]

Ok, fixed the car. after I did the pressure test and combustion gas test, I pulled the thermostat and tested it. Stat wouldn't open until water temp hit 232 degrees. So I guess the coolant was boiling until the old stat opened causing my airlock. But new thermostat and fresh coolant, good to go!!

Thats not hot. I recently did a thermostat and rear flange change. Your inital bleed will get that hot irrespective (as I monitored VCDS). 111oC I saw and stressed a bit but shortly after and by releasing air from the bleed screw it almost instantly pushed all of that through, dropping the level in the reservoir and temp going back to 90oC.

No offense, but that temp is normal for a bleed, I simply think you didn't bleed it correctly.

[a4lownslow]

Thats not hot. I recently did a thermostat and rear flange change. Your inital bleed will get that hot irrespective (as I monitored VCDS). 111oC I saw and stressed a bit but shortly after and by releasing air from the bleed screw it almost instantly pushed all of that through, dropping the level in the reservoir and temp going back to 90oC.

No offense, but that temp is normal for a bleed, I simply think you didn't bleed it correctly.

I don't think he bled the system wrong. Before I invested in a vacuum bleeder I would simply add coolant with the car running, reservoir cap off. When the system is working properly it should self bleed any air. Ive never had issues with either method.

You may be correct on the coolant temp though. I personally think the thermostat was either leaking or compromised to the point where it was allowing air into the system.


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[Okedokey]

I don't think he bled the system wrong. Before I invested in a vacuum bleeder I would simply add coolant with the car running, reservoir cap off. When the system is working properly it should self bleed any air. Ive never had issues with either method.

You may be correct on the coolant temp though. I personally think the thermostat was either leaking or compromised to the point where it was allowing air into the system.


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He wasn’t loosing coolant so that discounts that theory, plus my post above is the Elsawjn procedure and it is not “it’ll work itself out”

This is a case of failed bleeding.

[a4lownslow]

OP never actually verified if he was losing coolant. And it's still possible to pull air without a major external leak.


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[cdh9400t]

Actually yes 232degrees is hot for an opening temp of a thermostat. Considering 1:1 coolant mixes have a boiling point of 228 degrees. The thermostat should start to move at 185-190 degrees. That's not initial bleed temps, that's actual thermostat sitting in a pot of boiling water to test. I know it's not as common for thermostats to fail this way vs open, but mine did. And these cars are not that hard to bleed.