E31 850i power steering pump drain plug

**sreten** · 02-10-2020, 03:15 AM

Does anyone know the part number for the hex drain bolt on the tandem vane pump? I successfully rounded off mine and RealOEM doesn't show this part separately.

**cartoonz** · 02-10-2020, 02:59 PM

There isn't one... but it is an M14 1.25 thread
I opted for one with a 13mm hex head and a small flange for a narrow crush washer... works way better..

**sreten** · 02-11-2020, 03:09 AM

Thank you, Cartoonz!

Agreed, that sounds a lot better. Original one always needs thread sealer in order not to leak. I ordered 2 types and will see which one fits the best.

**JULIAN911** · 04-02-2020, 05:21 PM

I'm attempting to remove this plug but neither a 6mm nor an 8mm allen wrench fits, is it a 7mm or some unique size? Also, I have already emptied out the reservoir so after draining the pump, would that pretty be all then refill? I have found several good threads on this but just wanted to make sure

**Timm** · 04-04-2020, 04:05 PM

https://www.bimmerforums.com/forum/s...3#post30410923

**JULIAN911** · 04-11-2020, 08:54 PM

I was able to drain the power steering pump then refilled and everything is well. However, I noticed that when I pumped the brake pedal (with engine off) to discharge the system to make sure I have enough fluid, the brake pedal didn't feel as tight as prior to draining all the power steering fluid. Am I supposed to bleed the brake system as well or will everything self adjust after taking the car for a drive? From what I've learned on this forum, the brake system is separated from the power steering system.

**clockwork** · 04-14-2020, 04:03 PM

Yes they are separated fluids but related systems/part.
The tandem vane pump means you have ASC+t so you must bleed that system according to the instructions in repair manual. I don't recall exact order of steps but it does involve the unplugging of wire harness from ASC+t module inside car, behind carpet, on left side, by kick plate/door sill.
I also believe you need to bleed the big black block's bleed nipple (bleed hose connected to it and fed into open pentosin canister). This black distribution and pressure reduction block is in engine bay, by + terminal post/left shock mount tower
It's all necessary when a pentosin drain occurs.

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**JULIAN911** · 04-15-2020, 12:04 AM

Thanks, clockwork! oh boy, sounds like I shouldn't have drained the pump - now I'm getting over my head and have to look for the repair manual

**JULIAN911** · 04-15-2020, 10:59 AM

I was restless last night thinking I'm in big trouble not knowing how to bleed the PS system so got up early this morning and found the online repair manual at http://www.frankies-bmw.com/8series/downloads/BMW_8Series_Repair_Manual.pdf

However, I must admit that it is not straight forward so I'm pleading for help

the reservoir is properly filled and bled by turning the steering back and fort, no more whining noise. So I now need help to bleed air from the "connected" braking system for the brake pedal to feel firmer.

Can anyone help with a more simple to follow step by step what I should do next? for example, do I open up the nipple by the + jumper terminal and pump the brake or turning the wheels back and forth? any pictorial of where this ASC-T module that I'm supposed to disconnect?

I appreciate what ever help you guys can provide.

**cartoonz** · 04-15-2020, 01:49 PM

why not wait and see if you even need to do that?

**JULIAN911** · 04-15-2020, 02:28 PM

Oh, I thought that by default after draining the PS pump, that I would have air in the brake system and needed to bleed. If that is not necessary the case, then perhaps I should take your recommendation and do a test drive first.

**JULIAN911** · 04-15-2020, 09:46 PM

Good news - drove the car around the block and applied hard braking at about 30mph and it felt ok. Thanks for all the help from you guys!

BTW, I looked for that nipple by the + jumper terminal and couldn't find it... Urghhhhh

**cartoonz** · 04-16-2020, 01:25 AM

Originally Posted by JULIAN911

Good news - drove the car around the block and applied hard braking at about 30mph and it felt ok. Thanks for all the help from you guys!

BTW, I looked for that nipple by the + jumper terminal and couldn't find it... Urghhhhh

I've flushed the pentosin in over a dozen of these things, and I may have had to hit that nipple maybe once. From my experience, it usually isny neccessary.

Sounds like you've got the job done.

**LappingLuke** · 03-22-2023, 08:19 AM

Originally Posted by cartoonz

There isn't one... but it is an M14 1.25 thread
I opted for one with a 13mm hex head and a small flange for a narrow crush washer... works way better..

Did BMW make different pumps with different plugs by year or anything? Mine is a 1.0 thread pitch... my plug is fine mostly but I got a little too curious and ripped off the nylon strip in the middle so I need to replace it but can't find anything that threads into the hole.

**cartoonz** · 03-22-2023, 01:18 PM

Originally Posted by LappingLuke

Did BMW make different pumps with different plugs by year or anything? Mine is a 1.0 thread pitch... my plug is fine mostly but I got a little too curious and ripped off the nylon strip in the middle so I need to replace it but can't find anything that threads into the hole.

clean all threads with isopropyl. Dry.
Use Thread SEALER (not loctite) liberally on the plug.
Install, let dry overnight.
Fill system.

This is the only reliable way to keep that plug from leaking after it is removed.

**LappingLuke** · 03-22-2023, 04:42 PM

Did you find that over time the bolt with a copper washer was not reliable?

**Albert850i** · 03-23-2023, 04:15 AM

That stripped small allen screw on the photo is probably not a drain plug but some sort of pressure regulator as it is adjustable.

**LappingLuke** · 03-23-2023, 07:57 AM

It's a drain plug.

**Albert850i** · 03-24-2023, 12:39 PM

Originally Posted by LappingLuke

It's a drain plug.

How is it supposed to seal without a washer?

**cartoonz** · 03-24-2023, 05:29 PM

It isn't actually a drain plug, that's the problem. It is well positioned for that, but was never designed to be removed/replaced. It is there to cover a hole necessary for the machining of the pump.

**LappingLuke** · 03-24-2023, 06:37 PM

Ah damn that makes sense I guess. should've used something like NPT back then but oh well. I cleaned it up and glued the plug home with a generous helping of thread sealant last night. Tomorrow I plan to fill it up and start the car for the first time in over a month!

- - - Updated - - -

The plug has a nylon (???) ring in the middle of the threads that seals and locks the plug in place. My car was a mess underneath, but I believe that ring had begun to leak by and was my main PS leak. Not sure if it had ever been removed, but I never removed it and it didnt start making a mess until I'd driven it over 7k miles.

**Albert850i** · 03-25-2023, 02:04 PM

I sealed this little plug using teflon tape, which works fine.

**LappingLuke** · 03-25-2023, 03:05 PM

I regret ever pulling this plug. Just went for the first drive and the whole underside of the car is covered in PS fluid again. The plug is leaking like I didnt even use any sealant. It had left a good puddle on the garage floor I didnt even see until I pulled the car back in. If this plug is not even meant to be removed for service, should I just JB weld it back?

**LappingLuke** · 03-25-2023, 03:36 PM

Originally Posted by Albert850i

I sealed this little plug using teflon tape, which works fine.

How much tape did you use? I just put it back with at least 2 rounds of thick 3.5mil tape and its already leaking.

**LappingLuke** · 03-25-2023, 08:43 PM

4 rounds of thick Teflon tape didn't hold either. I think I might be at a massive disadvantage since I sort of accidentally broke off that plastic or rubber ring.