Trying to get an idea if I have a bad thermostat or water pump on my B6 A4

[tfish90]

My B6 A4 just recently had its radiator replaced due to it leaking coolant. Previous to getting that done, I wasn't getting hot air blowing through my vents except for once in a while at high RPMs. Right before my radiator started blowing coolant out of the side, my coolant temp gauge was going crazy. Normally it sits at about half way, but it was fluctuating between a quarter of the way and all the way at the bottom.

Driving it home from the mechanic last night, my heat was working perfectly and the temp gauge was behaving normally. This morning, the gauge was fluctuating again and the heat in my car didn't work at all.

Also, correct me if I'm wrong, but when your car is warmed up, the coolant level should go down a bit right, due to the car pulling he coolant into the engine? The coolant level went up once my car got warm.

I read in one forum that one possible test for the water pump failing is to open the coolant reservoir when the engine is warm and see if it is pressurized. I did this, and it apprears it is pressurized.

Thoughts?

[sincteuro]

Had a b6, it's the thermostat, or the coolant temp sensor.. they go bad all the time and it's a 12 dollar part, I replaced mine 3 times .. had the same prob you are... look at the thermo plumbing to the plastic piping cracks and corrodes after awhile.. look behind the head and you'll prob see dried up coolant.... replaced both. If it was the water pump it would over heat and never fluctuate.


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[sincteuro]

http://www.pelicanparts.com/techarti...eplacement.htm


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[EuroxS4]

A sign of a bad or failing water pump is the following.At idle warmed up the temperature will be in the norm.Under load of acceleration the temp with sky rocket but go back to normal when not under load.This is due to the plastic impleller spinning on the metal shaft instead of spinning with it.Assuming you have a 1.8T

[coffeysm]

Maybe you have some air left in the system? The fluctuating temp gauge is probably just the ECT, I had the same thing with my B6. I put a replacement sensor in and problem is resolved.

[refueler]

The cooling system in these cars is complex. Coolant is always circulating through the engine and the thermostat only opens up and allows coolant to flow through the radiator when additional cooling is required. I think that the symptoms you are experiencing is due to air trapped in the cooling system somewhere interfering with the flow of coolant. After driving the car and it is fully warmed up feel the radiator hoses to see if the lower hose is hot. If think there is no coolant flowing through the heater core based on no heat and none through the radiator because the lower hose is not hot. You need to determine if when the radiator was replaced if all of the air was removed from cooling system, or if there is another source of air being introduced into the system such as a bad head gasket, leaking rear coolant flange, J-plug. I had the same problem with my B 6 and as near as I can tell there was a crack in the AMB cylinder head. Because replacing the head gasket twice didn't fix the problem, when I installed another head and gasket that solved my problem. Since having that problem I use a vacuum fill device to refill the cooling system and have had no problems with air getting trapped in the cooling system( I probably should have suggested this in the beginning). Good luck