Water Pump Vacuum Line??

[scalbert]

I finally got my PCV out and was about to tackle the T-State and Water Pump when I noticed a vacuum line on my water pump and not on the replacement. See the below blurry image of the vacuum line on the side of the water pump. It sits at about 3 o'clock when looking at it from the front. This caused me to hold up progress as the replacement did not have this line and was unsure of the purpose. The line runs to, what appears to be, a solenoid that sits in front of the drivers side hardline bolts.



I looked around but did not find anything quickly. When looking on ECS's website, I found the pump I have. The problem is that it states: Fits from production date 1/30/2015. I have a 2013. One option may be that it was replaced already???



https://www.ecstuning.com/b-genuine-...mp/06e121018f/

Any thoughts or input???

On the bright side, after some work and examination, I did find a way to remove the upper coolant pipe fairly easily. With post up on that soon. And that ridiculous PCV assembly is out. Now just trying to clean up everything with the mix of coolant and oil in the valley.

[Morritse]

Bump, also was confused by this

[S4'ed]

Did your S4 get a replacement engine sometime in its past? Are you the original owner?

[Morritse]

Did your S4 get a replacement engine sometime in its past? Are you the original owner?

I just put a b8?5 motor into my b8

[chi123]

The B8 and B8.5 have different water pumps. The B8 doesn't have that water line, only the B8.5 has it to my knowledge.

[rtl5009]

It has to do with coolant flow to the heads I believe, I had that solenoid fail and my car would over heat. Its a vacuum line.

[Morritse]

It has to do with coolant flow to the heads I believe, I had that solenoid fail and my car would over heat. Its a vacuum line.

What solenoid? Does it need to be connected to something?

Is the solenoid on the motor or chassis?

[rtl5009]

What solenoid? Does it need to be connected to something?

Is the solenoid on the motor or chassis?

It’s on the motor. To the right (drivers side) of the coolant pump looking at it from the front. I would imagine it definitely needs connected.

[Morritse]

It’s on the motor. To the right (drivers side) of the coolant pump looking at it from the front. I would imagine it definitely needs connected.

My ECU is from a b8, won't it not be able to control that solenoid?

[rtl5009]

My ECU is from a b8, won't it not be able to control that solenoid?

I don’t know man lol. The Solenoid is located right here.

[scalbert]

I question if there is coolant in that. I am pretty sure the line to the solenoid was tied to a vacuum connection. First of all, the line is small and there would little flow to cool much. There is no clamp on the hose connection. If hot coolant was in there, it would blow off without a clamp.

I just checked my wife's '15 Q7, and it does not have the nipple on the side of the water pump. My guess is that it is a vacuum line to control a clutch in the S4 pump. One thing I notice is that my S4 gets up to temperature much quicker than my wife's Q7; nearly twice as fast. The Q7 carries more weight and is APR stage 2 so it should heat up quicker with all things the same. My guess is the S4 pump with vacuum line runs slower (or not) when cold to get coolant up to temperature quicker by way of the solenoid and vacuum line connection.

[rtl5009]

It’s definitely vacuum. I have had the whole thing apart before.

[scalbert]

My ECU is from a b8, won't it not be able to control that solenoid?

You may be able to just wire up switched 12V to the solenoid so it is always open and would be similar to the way your previous engine did if I am correct about being a vacuum line.

[scalbert]

It’s definitely vacuum. I have had the whole thing apart before.

Has to be a clutch in the pump then. No other reason to have solenoid controlled vacuum to the water pump.

[scalbert]

You can also see the body is different in the two. The one without the nipple has a smaller body but the mounting is the same:



And the one with the nipple has more to it:

[Dewar]

Vacuum line. Thought I read somewhere it controls a diaphragm that controls coolant flow based on ecu demandIMG_20200205_195918.jpeg

[Morritse]

Has to be a clutch in the pump then. No other reason to have solenoid controlled vacuum to the water pump.

So is the clutch engaged with, or without vacuum. If it's with, then I can just cap it right

[Rs4#0198]

All B8.5 S4 have this style pump. Vacuum is supplied to the water pump which causes a round plastic piece inside the water pump to block the impeller and stop coolant flow. By doing this the engine warms up a lot quicker.

[scalbert]

So is the clutch engaged with, or without vacuum. If it's with, then I can just cap it right

Good question. May be a bit of trial and error. If it wasn't so darn tight in there I would out in a tee and measure it with a vacuum gauge. Considering what rtl5009 said in that his solenoid failed and his car would overheat. But we do not know which state the solenoid failed in; open or closed. I would hope they had designed it such that a failed solenoid would cause the pump to run at 100%. But we all know that doesn't always happen.

You may need to try and if it starts to get too hot, just bypass the solenoid and tie in constant vacuum. The worst case is that it will heat up slower.

[scalbert]

All B8.5 S4 have this style pump. Vacuum is supplied to the water pump which causes a round plastic piece inside the water pump to block the impeller and stop coolant flow. By doing this the engine warms up a lot quicker.

So the solenoid is not duty cycle controlled; just on/off? But is it normally open or normally closed. If a supply of vacuum causes the pump to stop, then he could just cap the nipple and it will run 100% all the time but with a longer warm up cycle?

[Morritse]

So the solenoid is not duty cycle controlled; just on/off? But is it normally open or normally closed. If a supply of vacuum causes the pump to stop, then he could just cap the nipple and it will run 100% all the time but with a longer warm up cycle?

That's what I was asking. I capped it, if my pump doesn't run, I'll know it needs constant vacuum. It seems logical it's the other way around though.

[Rs4#0198]

Solenoid is only activated by the ECM when the engine is cold. Once the solenoid is activated vacuum is then supplied to the pump. If it’s capped then the engine will take longer to warm up.

[Morritse]

Solenoid is only activated by the ECM when the engine is cold. Once the solenoid is activated vacuum is then supplied to the pump. If it’s capped then the engine will take longer to warm up.

Cool, that's fine with me.

[RPMtech147]

:Revive:

Is this confirmed that capping off the vacuum lets the pump run all the time? I've T'd into the vac line at the solenoid and drove the car and it never stops sending vacuum to the pump. Turning off the car, the solenoid closes, so it's not a sticking solenoid. The issue I'm having with this one is a Coolant System fault message. Only related codes is 21421 Coolant pump P1B1C 00 [047]. The car will not come up to temp, lucky to see 90C. Usually closer to 80. If I use a vac pump or just remove/install the line from the solenoid with the engine running, I can hear the vacuum actuator in the pump clicking. This really seems like a thermostat issue, but why wouldn't it throw a fault like a P0128(coolant temperature is below the thermostat regulating temperature) I did cap off the pump's vac line and it made no difference.

[Smac770]

The B8.5 version of the 3.0T coolant pump has the additional N489 "coolant valve for cylinder head" solenoid. This is pointed out in the workshop manual, Exploded view - coolant pump and thermostat. According to the manual, it's located right below the bank 1 vacuum pump at the front of the head, pretty much just to the left of the coolant pump.

The Audi SSP on the EA837 3.0T (PR-TC6) is for the original version in the B8.0. But the Audi SSP on the EA837 evo 3.0T (PR-TM8, the CRE) does cover this modification, referring to the coolant pump as "switchable coolant pump". The evo (CRE) calls it a N492 and locates it in the back row of vacuum solenoids, but the coolant pump management seems to be the same.

But that is a presumption. Though they look the same and are the same base part number, the TC6 switchable coolant pump is a different revision letter chain than the TM8 switchable coolant pump. Regardless of the location or the electrical schematic designation, the electrically controlled vacuum solenoid is the same part number in both cases, 037 906 283 C. Failure exhibit is pointed out on page 31 of the SSP 624. I don't know if the

The wiring diagram for the B8.5 3.0T seems to also confuse Cylinder Head Coolant Valve -N489- with Engine Temperature Control Actuator -N493-, I presume it's calling both objects the same. Is the wiring to the solenoid, whatever you want to call it, red/white on 1 and yellow/green on 2?

B8.5 3.0T vacuum system.jpg

To RPM's question, the quick glance assessment is that the presence of vacuum at the pump displaces the diaphragm covering the impeller, so no coolant flows. The solenoid passes vacuum when energized. The ECM uses PWM signal to energize the solenoid at whatever duty cycle to pass a net level of vacuum to the coolant pump, depending on how much vacuum, if any, it wants to transmit. Lack of vacuum at the coolant pump means the spring force pulling the diagram from the impeller "wins", and max coolant rate flows into the cylinder head.

I'm assuming the solenoid is closed (no vacuum transmission) on no electricity; this would be simple enough to test with a vacuum pump and an output test for the solenoid in 01-engine.

[Smac770]

Note, it very would could be the evo implementation is inverted from the base implementation, thus why maybe they use different solenoid designations. This should be easy enough to confirm with a vacuum pump and the coolant pump in hand.

[RPMtech147]

After digging for a few hours we decided on a T-stat. Removed the T-stat. Two of the plastic tangs were broken. It literally shot out of the block after I took the bolts out. It was kind of funny. I figured I found the smoking gun. Put it all back together, drive and monitor engine temp, looks good park the car.

Go to drive again, same fault returns.

21421 Coolant pump p1b1c 00 [047] mechanical malfunction.

Drive it again. Now the engine temp does this thing where it runs up to 100C+ then drops to 79/80C and just stays, then the fault pops up.

In an act of desperation I just cap off the solenoid to the water pump (Water pump is new, installed by someone else)

clear everything, drive 8 miles. Engine temp stays between 92/95 the entire time and no faults. This seems to be a band-aid but when I get the car back, I need to dig deeper. It's either a faulty pump or something electrical . Not a ton of info on this code.

I'll probably get with my Audi tech support guys and see what they say....

ETA this is on a 2016 A6 3.0T so there are some differences.

[Smac770]

The coolant pump itself has no diagnostic mechanisms which can report back to the ECM I would imagine. The internal shutoff

https://static.nhtsa.gov/odi/tsbs/20...91243-0699.pdf
Presumably, a 2016 A6 3.0T would already have the updated ECM software.

But so it seems P1B1C is a conclusion code rather than a direct observation code. The coolant temp is not as it should be, there must be a coolant pump problem. Or a thermostat problem. Or a problem with anything that regulates the coolant temp. As the only direct sensor the ECM has to the state of the coolant system is the coolant temp sensors. As such, the code is not worth much directly, like a P0299. We know why it sets numerically, but root cause could be anything between the front bumper and the firewall.

Sounds directly like there's an issue with the solenoid. Either it's the wrong one, or there's a wiring issue so the PWM signal it's receiving is malformed, or its just broke.

[RPMtech147]

The coolant pump itself has no diagnostic mechanisms which can report back to the ECM I would imagine. The internal shutoff

https://static.nhtsa.gov/odi/tsbs/20...91243-0699.pdf
Presumably, a 2016 A6 3.0T would already have the updated ECM software.

But so it seems P1B1C is a conclusion code rather than a direct observation code.

Exactly. With the vac line connected, it doesn't like what the temp is doing; maybe too hot and runs the AUX pump full tilt to get it down; totally speculating.?? The freeze frame of the fault shows it sets under 80C. Vac Unhooked, the temp is stable enough to keep it happy. I'll update when it comes back.

[Smac770]

If the ECM cannot control the vacuum conveyance via the solenoid, then either the pump will see full vacuum and the diaphragm will cover and block coolant flow; the engine will overheat. Or the pump is seeing no vacuum, and there is no vacuum to counter the spring, and the pump is basically flowing max rate to the head; the engine will heat very slowly and maybe never reach intended temp. I'd pull the hose off the pump and put that into a vacuum gauge. Are you reading no vac or some vac or full vac (full being whatever the vac is in the line supplying the solenoid). How does that ratio compare to the ratio of the voltage measured on the plug to B+ (PWM signal should read an average voltage that should be a fraction of B+ related to the PWM duty cycle). (I don't have one to test, I'm assuming the control logic is the same as the CRE engine, and not inverted)

There's always the other corner options, like a problem with the vacuum system supply to the solenoid. Or a problem with the spring in the coolant pump itself.