Does waterpump failure cause thermostat to stop working?

[AudiSeefu]

I am about to dive into my B6 overheating problem with no heat and think I will start with replacing the water pump. Does water pump failure cause the thermostat to stop working?

[AudiSeefu]

also, anyone know of a DIY? I have found for B5 but not B6

[dirtybrd]

It could if there was an overheating issue.

[Duchenbagen]

No, the waterpump failing will not cause a thermostat to fail. If anything the thermostat should fail in the open position. If I were you I would just replace them both while you have the car apart and depending on how many miles your car has on it I would also consider the timing belt as well. The thermostat is way to cheap not to replace if you are having cooling problems. I don't know if Audi redesigned the waterpump, but in the B5 there was a problem while the waterpumps failing prematurely due to plastic impellers.

[Duchenbagen]

Also, if you have found the B5 writeup you could definetely use that one as a guide. There really isn't that many differences.

[AudiSeefu]

the reason I ask is because the thermostat in the b6 is electronic and another member said that if the waterpump failed the thermostat would be inoperative.

[diagnosticator]

the reason I ask is because the thermostat in the b6 is electronic and another member said that if the waterpump failed the thermostat would be inoperative.

To answer your main question, Yes.

The reason the "thermostat would be inoperative", is because without proper coolant circulation throughout the cooling system, the t-stat cannot control the coolant temperature. It is an issue with the coolant not flowing properly because of the bad coolant pump, NOT the failure of the t-stat itself.

There are a couple of typical failure modes for the coolant pump. The first type is when the plastic impeller gets loose on the drive shaft and slips when the engine is at above idle speed. The second, is when the seal fails and coolant leaks from the pump. This is usually caused by running the engine with very low coolant level, or by pump bearing failure.

[AudiSeefu]

cool. so I should start with the water pump first.

[diagnosticator]

cool. so I should start with the water pump first.

Yes, because the heater receives hot coolant flow regardless of the thermostat position, either open or closed. If the t-stat was bad causing the engine overheat, you would not also have the no heat problem with the cabin heater. The symptoms you described, both engine overheating and no cabin heat, indicate that there is practically no coolant flowing in the engine cooling system or cabin heater core.

[F16HTON]

I am about to dive into my B6 overheating problem with no heat and think I will start with replacing the water pump. Does water pump failure cause the thermostat to stop working?

Yes it does...I know from first hand experience the B6 thermostat is electronic...my water pump failer (intermittent) and the car would ony overheat every now and then...the biggest way to tell if the waterpum has failed is that the fans will not come on when the engine is hot as hell.

An indy shop should be able to do the waterpump and timing belt for under $800

[20vturbo]

Yes it does...I know from first hand experience the B6 thermostat is electronic...my water pump failer (intermittent) and the car would ony overheat every now and then...the biggest way to tell if the waterpum has failed is that the fans will not come on when the engine is hot as hell.

An indy shop should be able to do the waterpump and timing belt for under $800

you are talking about the thermoswitch right??
the thermostat is the valve that allows coolant to the radiator ince the engine is at operating temperature

[Jeff]

A thermostat is a valve that stays partially shut when cold, then opens up when it hits a certain temp. Temps can range from 120-190 deg. On the B5, it uses a mechanical thermostat set at 190deg. When closed, it blocks most of the coolant flow into the radiator, so that the car can warm up quicker. Once temps reach 160-170, the thermostat will begin to open, passing coolant through the radiator, and then completely open when the it's at 190. This is when your car is completely "warm", and your temp gauge need is in the middle.

The B6's thermostat works the same way, but on an electrical signal. Your ECT (Engine Coolant Temp) sensor is what see the coolant temps. As temps start to climb, it begins to open up (like a throttle body) until it opens completely.

So to answer your question, a waterpump simple CIRCULATES coolant through out the block, head, and the turbo. Inside the waterpump is an impeller shaft (fan blades). The waterpump is spun by your crank (via crank pully/timing belt, or drive belt). If the waterpump WERE to fail, you simply wouldn't circulate coolant... meaning that coolant temps would climb VERY fast, giving you hotspots and eventually make you overheat because the coolant cannot flow through the radiator and cool. Your thermostat (unless it was broken), would open up once the overheated coolant reaches it's temp. Even with a now fully opened thermostat, a failing waterpump would not be able to circulate the coolant through it, and you'll still overheat.

We have two ECT's in the car. One operates the gauge, the other feeds raw data into the ECU tell it when to open the thermostat.

[AudiSeefu]

thanks everyone. I am changing water pump and timing belt tomorrow afternoon. thermostat should not need to be replaced, right?

[norcatalyst126]

^^^ IMO, if its easy to do and the part itself is cheap, why NOT change the thermostat at the same time??

[fbottone]

The thermostat isn't that cheap on the B6 (~ 180 iirc) because its electronic.

My 2004 had a water pump with a plastic impeller, the replacement I got from ECS Tuning (tb kit) was a metal impeller, fwiw.

If you were really crazy like me, you could take off a coolant line somewhere (cool engine of course) and crank the engine to see if you get any flow...that might tell you if the pump is moving anything at all.

[diagnosticator]

^^^ IMO, if its easy to do and the part itself is cheap, why NOT change the thermostat at the same time??

Yes, that is reasonable, in the general case, but AFAIk, the ECU controlled t-stat used in the AMB 1.8T, is about $100.

[20vturbo]

I had no ideea that thing is electronic it looks like a normal thermostat housing I thought the blue connectio is a temp sensor..here is the questio since it is electronic if not working should't that involve a check engine light???

[F16HTON]

No CEL...the coolant light will go crazy and start beeping if there is no flow.

[AudiSeefu]

no coolant light on mine.

[quattrotman]

waterpump and themostat could both be part of the issue but you should change both.