Auxiliary pump 2010 and forward - Usage?

[Helmsman]

Hi guys, creating a new thread hoping for feedback on this.

Had the A6D1 code coming and going but now seems not possible to clear anylonger. As the "Rest heat" button was taken away from 2010 year model, my understanding is that the ignication have to be on to make the pump run. Makes me wonder about the function, and need to replace the pump at all.

Anyone with more insight in this function?

Thanks

[Helmsman]

Anyone?

[Mdriv3r]

The pump is located on the left side (driver side in USA). It cycles coolant around the system when you are stopped. It is also used for coolant flushing. After draining the coolant, if you refill the coolant and with the ignition on, put the heat on highest temp and lowest fan and setting, it will turn on and cycle the coolant through the car to get air out of the system. To engage this mode, you must have heat on highest temp, fan on lowest setting while car is off, then hold the gas pedal for 10 seconds. After this the aux pump will turn on and cycle the coolant. This will continue for some 10-12 minutes and you'll be able to hear it also. Make sure not to close your driver door, as that will shut off the sequence. The aux pump helps bleeding without starting the car, since the main water pump, is belt driven. It also turns on when driving and when the car is stopped.

If you have this code, you can buy a second hand one from eBay. I had this error as well. I bought one from eBay or around $35-$40 US. Super cheap, new it will cost around $200 +. I suggest changing it if you can. It shouldn't hurt anything to not change it though. You won't really notice a difference.

[Mdriv3r]

And yes the A6D1 code is for the auxiliary water pump. It will need to be replaced if the code keeps coming back. Check realoem.com for the part number.

[Helmsman]

Originally Posted by premo

The pump is located on the left side (driver side in USA). It cycles coolant around the system when you are stopped. It is also used for coolant flushing. After draining the coolant, if you refill the coolant and with the ignition on, put the heat on highest temp and lowest fan and setting, it will turn on and cycle the coolant through the car to get air out of the system. To engage this mode, you must have heat on highest temp, fan on lowest setting while car is off, then hold the gas pedal for 10 seconds. After this the aux pump will turn on and cycle the coolant. This will continue for some 10-12 minutes and you'll be able to hear it also. Make sure not to close your driver door, as that will shut off the sequence. The aux pump helps bleeding without starting the car, since the main water pump, is belt driven. It also turns on when driving and when the car is stopped.

If you have this code, you can buy a second hand one from eBay. I had this error as well. I bought one from eBay or around $35-$40 US. Super cheap, new it will cost around $200 +. I suggest changing it if you can. It shouldn't hurt anything to not change it though. You won't really notice a difference.

Thanks Premo. This is the way I understood its "function" but still confusing as:
1) Coolant is even according to BMW TIS suppose to be selfbleeding, aux pump is not mentioned to be used?
2) After the Rest button was taken away 2010, the only way to get the residual heat would be to have ignition on? Can't see that happen often, especially as the function isn't described anywhere?

Btw I've tryed mentioned trick to start the pump, nothing happened so yes seems dead, not surpricing as its probably never been on during its 9 years... You actually performed this on your M3? (I've seen it works on standard 3 series but obviously using their electrical main coolant pump).

I've checked the pump and can see its an easy replace, but would like to better understand why first...

[ItsGary]

I replaced the auxiliary water pump on my 09, its located under the intake box

[Helmsman]

Originally Posted by ItsGary

I replaced the auxiliary water pump on my 09, its located under the intake box

Yep, I see more of a point with the Rest function still in place.

[Theodore]

Originally Posted by Helmsman

Hi guys, creating a new thread hoping for feedback on this.

Had the A6D1 code coming and going but now seems not possible to clear any longer. As the "Rest heat" button was taken away from 2010 year model, my understanding is that the ignition have to be on to make the pump run. Makes me wonder about the function, and need to replace the pump at all.

Anyone with more insight in this function?

Thanks

In the past I read the auxiliary water pump is intended to circulate coolant between the engine and the heater core before the thermostat opens up the connection between the engine and radiator. You can see how this is done in the diagram below. This gets you heat inside the cabin earlier than if you didn't have it at all. The electronic control of the auxiliary pump may have an additional benefit that the car can probably custom regulate the flow of coolant through the heater core to make interior cabin heat control a smoother operation, though I'm not positive BMW takes advantage of that.

[Helmsman]

Originally Posted by Theodore

In the past I read the auxiliary water pump is intended to circulate coolant between the engine and the heater core before the thermostat opens up the connection between the engine and radiator. You can see how this is done in the diagram below. This gets you heat inside the cabin earlier than if you didn't have it at all. The electronic control of the auxiliary pump may have an additional benefit that the car can probably custom regulate the flow of coolant through the heater core to make interior cabin heat control a smoother operation, though I'm not positive BMW takes advantage of that.

Many thanks Theodore, finally makes sense. As I usually keep the heater down on cold days to feed the S65 first I never missed this.... Quit joking I haven't noticed any difference in cabin warm up during my 6y ownership inkl prior I got the code so maybe not such a big deak.
Big thanks again, now I know better and will decide for a correction path.

[Mdriv3r]

Originally Posted by Helmsman

Thanks Premo. This is the way I understood its "function" but still confusing as:
1) Coolant is even according to BMW TIS suppose to be selfbleeding, aux pump is not mentioned to be used?
2) After the Rest button was taken away 2010, the only way to get the residual heat would be to have ignition on? Can't see that happen often, especially as the function isn't described anywhere?

Btw I've tryed mentioned trick to start the pump, nothing happened so yes seems dead, not surpricing as its probably never been on during its 9 years... You actually performed this on your M3? (I've seen it works on standard 3 series but obviously using their electrical main coolant pump).

I've checked the pump and can see its an easy replace, but would like to better understand why first...

I still check the bleed screw while
Its on. This past wknd I did the valve cover seals, spark plugs, alternator, coolant flush, and will do oil change next. Still working on it. I have an ESS 595 kit on my car, so I have an extra coolant pump I installed for the intercooler. I did the procedure and I am fairly certain I heard it operating. I could hear fluid cycling in the coolant reservoir. I haven't started the car yet, as I still have some work to do on it, but I'll check it again.

How does TIS describe the coolant bleed procedure?

I had mine out for a couple years. I didn't notice any heat issues. Also I don't use the res feature at all, probably would be hard in the battery.

[Helmsman]

Originally Posted by premo

I still check the bleed screw while
Its on. This past wknd I did the valve cover seals, spark plugs, alternator, coolant flush, and will do oil change next. Still working on it. I have an ESS 595 kit on my car, so I have an extra coolant pump I installed for the intercooler. I did the procedure and I am fairly certain I heard it operating. I could hear fluid cycling in the coolant reservoir. I haven't started the car yet, as I still have some work to do on it, but I'll check it again.

How does TIS describe the coolant bleed procedure?

I had mine out for a couple years. I didn't notice any heat issues. Also I don't use the res feature at all, probably would be hard in the battery.

Heres the TIS mate: https://www.newtis.info/tisv2/a/en/e92-m3-cou/repair-manuals/17-cooling/17-00-cooling-check/Hq5CpsJ

Cheers

[Mdriv3r]

Originally Posted by Helmsman

Heres the TIS mate: https://www.newtis.info/tisv2/a/en/e92-m3-cou/repair-manuals/17-cooling/17-00-cooling-check/Hq5CpsJ

Cheers

Thanks. Her is a snap of the old pump I removed. The 3 rubber gromets in the back are for mounting it (super easy it just slides in). There is an inlet and output for coolant and an electrical connection.

[Mdriv3r]

Originally Posted by Theodore

In the past I read the auxiliary water pump is intended to circulate coolant between the engine and the heater core before the thermostat opens up the connection between the engine and radiator. You can see how this is done in the diagram below. This gets you heat inside the cabin earlier than if you didn't have it at all. The electronic control of the auxiliary pump may have an additional benefit that the car can probably custom regulate the flow of coolant through the heater core to make interior cabin heat control a smoother operation, though I'm not positive BMW takes advantage of that.

The 3 grommets on the back are for mounting it. It just slides into 3 small sleeves. Really simple install.

[Helmsman]

Originally Posted by premo

Thanks. Her is a snap of the old pump I removed. The 3 rubber gromets in the back are for mounting it (super easy it just slides in). There is an inlet and output for coolant and an electrical connection.

Cheers. Yep had the filterbox off the other day and checked the pump connection, seems like a very easy replace.

[ItsGary]

Originally Posted by Helmsman

Cheers. Yep had the filterbox off the other day and checked the pump connection, seems like a very easy replace.

Its messy too xd

[Redd]

Sorry for reviving an old thread. I too now have the permanent A6D1 code. I live in year round hot weather so I never use the heater function and my 2010 M3 doesn't have REST function. So I'm wondering if I should replace the pump, and if yes to use original (USD200) or China (USD50).

Helmsman - Did you end up replacing the aux water pump? Is there any impact to DCT temps?

[Helmsman]

Originally Posted by Redd

Sorry for reviving an old thread. I too now have the permanent A6D1 code. I live in year round hot weather so I never use the heater function and my 2010 M3 doesn't have REST function. So I'm wondering if I should replace the pump, and if yes to use original (USD200) or China (USD50).

Helmsman - Did you end up replacing the aux water pump? Is there any impact to DCT temps?

Don't be mate, they are meant to be woken up...

I did eventually replace the pump, I took the plunge and went with a OEM (220 Euro isch) to be on the safe side. Easy job with a couple of hose pliers (a must imo, but cheap).

As reported in below thread the pump (obviously) cleared the A6D1 code AND the sporadic DCT heat error disappeard...for quite some time. I have got it once or twice since, but it seems the pump did make a change. Unfortunately haven't got around to get a scanner that can read the temp so no factual data.

https://www.m3post.com/forums/showth...1772232&page=2

To fill in, looking at the DCT cooling diagram, the DCT fluid Tstat is selecting between the air heat exhcanger OR the coolant heat exchanger where the pump is. So the pump "shouldn't" make a difference as fluid should be going to front exchanger when hot enough. But still, it do make a difference. Please feel free to add your insight here.
EDIT: The DCT fluid is coming out of the box and goes via the coolant heat exchanger first, whereafter to the Tstat that decides whether back into the box or out via the external air heat exchanger. I.e. the fluid is always passing via the coolant exchanger regardless of temperature.

[Redd]

Thanks for the input! I've got an aux pump on order. In the meantime let me thrash the car and see if I can replicate your DCT temp warnings.

[Helmsman]

Originally Posted by Redd

Thanks for the input! I've got an aux pump on order. In the meantime let me thrash the car and see if I can replicate your DCT temp warnings.

Haha, yeah give it a good wip...
So you had the pump code coming and going for some time, but no DCT warning?

[Redd]

Originally Posted by Helmsman

Haha, yeah give it a good wip...
So you had the pump code coming and going for some time, but no DCT warning?

I never noticed the pump code before but the A6D1 is permanent now. Not sure how long it's been there though. But no DCT issues. I do hill runs nearly every weekend and engine oil temps get up to 125C/257F. Zero issues with DCT.

[Helmsman]

Originally Posted by Redd

I never noticed the pump code before but the A6D1 is permanent now. Not sure how long it's been there though. But no DCT issues. I do hill runs nearly every weekend and engine oil temps get up to 125C/257F. Zero issues with DCT.

If you dont have the rest heat buttom and no issues you may as well ignore the broken pump?

[Redd]

Originally Posted by Helmsman

If you dont have the rest heat buttom and no issues you may as well ignore the broken pump?

Yes that is also one of the options I considered. But I'm a bit OCD and don't like to see a persistent code. I ordered a low mileage used one off ebay for cheap so let's see how that works out.

I've also been thinking about bypassing the coolant hoses when I replace the pump. Since we know heat causes these pumps to fail, if I bypass it and do a heatshield around the pump itself, maybe I can get the replacement unit to last forever. Any thoughts on that idea?