Replacing Brake Vacuum Pressure Sensor

[DRLane]

Put some paper towel around the reservoir when filling or working on the brakes. If you notice any spills or overflow immediately pour water over the whole thing to rinse it off. I assume the sensor connector is made to handle moisture. That's my approach and I'm sure it's saved the sensor several times over.

[Ximian]

Anyone happen to know the specs of the torx bolts that hold the sensor? I lost one of them after it dropped to the bottom and I couldn't find it to fish it out.

[Dpc2u]

Originally Posted by Ximian

Anyone happen to know the specs of the torx bolts that hold the sensor? I lost one of them after it dropped to the bottom and I couldn't find it to fish it out.

No to the specs, but I dropped one once into the abyss and was able to retrieve it with a long extendable magnet even though I couldn't see it.

[Ximian]

Originally Posted by Dpc2u

No to the specs, but I dropped one once into the abyss and was able to retrieve it with a long extendable magnet even though I couldn't see it.

I was able to do that the previous 3 times I've dropped both, but this one disappeared. I'll have to get a borescope to have a better look for it, but otherwise might need to replace it.

[CamasM3e93]

Originally Posted by Ximian

Anyone else planning on leaving a shop rag over the sensor to avoid the issue in the future? Doesn't look like a part of the engine that gets particularly warm.

If you see my post above, I put a 2" x 3" piece of neoprene (gasket material) over the sensor before I buttoned everything back up. I have to charge the ac soon and will peek at it next week to see how well it stays in place. Shop rag should work ok too.

[Helmsman]

Originally Posted by DRLane

Put some paper towel around the reservoir when filling or working on the brakes. If you notice any spills or overflow immediately pour water over the whole thing to rinse it off. I assume the sensor connector is made to handle moisture. That's my approach and I'm sure it's saved the sensor several times over.

What I did after f@kking up although I was well aware of the issue when over filling. Plenty water, parked for drying. Believe pump buzz more than before but been fine. Keeping my spare sensor for another day.

[Fred the Beagle]

I just did this yesterday and as others have said, the location of the sensor makes this a real PITA. If it helps others:

You don't need to remove the header tank or release the ABS module. I did just the sensor without the hose.

My socket set Torx head was too fat to get into the gap to release the two screws.
Buy yourself a long Torx screwdriver and save a lot of frustration. Size is T20.
There's plenty on amazon or for UK posters try Machine Mart (set of 4 varying sizes for £11).

Once the screws are removed you can pry the module with the end of a screwdriver. I pumped the brakes before trying this to relieve any pressure. If you remove it whilst the electrical connector is still attached it's easier to get out.

Unplug and replug the new one. Best advice I've seen (and 100% worth it) get yourself a sacrificial coat hanger. lol

Lower the sensor (with electric attached) into the space and with a straightened bit of coat hanger put it through the sensor screw hole and down into the mount screw hole.
I did this on the hole that is slightly further the front as it's easier to get to.

The hanger will hold that bit steady whilst you use another long handle screwdriver to jiggle the sensor into the correct orientation. Don't try to push it into the vacuum hole, just have it resting on top.

Carefully remove the hanger and the holes should stay alligned. Get that screw on for one thread to hold it.

Make sure the alignment is good and screw the second one in, then come back to fully tighten the first. Tightening them made the sensor sit properly without trying to force it into the hole.

Bottom line - get the right long handle Torx driver. Spend 5p on a coat hanger!!

Cheers to all the others for their advice.

[kolosy]

one more successful transplant on this, and echoing what others have said here. no need to dismantle anything. i think the hardest part was getting the new sensor positioned where it needs to be.. it's a bit of a ship in a bottle building game. i ended up also using something like a coat hanger to drop the sensor in from the fender side, and then hook onto the bolt hole and pull and rotate up.

interestinly I had the same torn o-ring as CamasM3e93. sensor has original date code so i don't think it's been off before, and the tear definitely looks like it was from being screwed on, not from removal (the excess rubber is up the connector, not down). wonder if that's just expected?

either way, doing this resolved by vacuum pump running issues. went from running on every brake pedal press to only briefly on startup.

[CamasM3e93]

Originally Posted by kolosy

one more successful transplant on this, and echoing what others have said here. no need to dismantle anything. i think the hardest part was getting the new sensor positioned where it needs to be.. it's a bit of a ship in a bottle building game. i ended up also using something like a coat hanger to drop the sensor in from the fender side, and then hook onto the bolt hole and pull and rotate up.

interestinly I had the same torn o-ring as CamasM3e93. sensor has original date code so i don't think it's been off before, and the tear definitely looks like it was from being screwed on, not from removal (the excess rubber is up the connector, not down). wonder if that's just expected?

either way, doing this resolved by vacuum pump running issues. went from running on every brake pedal press to only briefly on startup.

I eventually needed to replace the vacuum pump altogether, keep in mind in particular if it was ‘over running’ for a long while

[kolosy]

Originally Posted by CamasM3e93

I eventually needed to replace the vacuum pump altogether, keep in mind in particular if it was ‘over running’ for a long while

what were the symptoms that made you do it? did it throw a code?

[CamasM3e93]

Originally Posted by kolosy

what were the symptoms that made you do it? did it throw a code?

I was fine day to day but would go into reduced engine power mode when I was driving at higher elevations, 4-8k feet. The pump would run longer in that condition. Then drive back to sea level, clear the code, fine until the next road trip. Saw someone else post about similar and followed their lead and replaced the vacuum pump. Problem resolved. It’s like the pump was operating at 80% effectiveness and was fine at sea level but couldn’t generate the necessary delta/vacuum in the mountains.

[Ximian]

Did you replace the lines to the pump as well? My pump runs frequently but I've never had a code. Might replace it this spring since I'll be installing a new fender and will update if it helps reduce the number of times the pump kicks on.

[CamasM3e93]

Originally Posted by Ximian

Did you replace the lines to the pump as well? My pump runs frequently but I've never had a code. Might replace it this spring since I'll be installing a new fender and will update if it helps reduce the number of times the pump kicks on.

I personally didn’t but others have found they ended up needing to replace the entire system, sensor and vacuum hose combined as BMW intends to sell it, to eliminate their code. So it’s definitely a possible need if you are still seeing limp mode.

I don’t think very many of us have had to change their vacuum pump. If I didn’t road trip mine so frequently into the western mountains, I probably would have never seen the issue and still be on the original.

[Ximian]

I ordered from https://www.autohausaz.com/pn/HL-34332283333 - $269 plus tax/shipping is the cheapest I've found for a new Hella vacuum pump. I'll be installing it this month as I'll be replacing the front left fender anyway.

[Ximian]

Originally Posted by Ximian

I ordered from https://www.autohausaz.com/pn/HL-34332283333 - $269 plus tax/shipping is the cheapest I've found for a new Hella vacuum pump. I'll be installing it this month as I'll be replacing the front left fender anyway.

The new pump solved the buzzing noise from the pump running every time I used the brakes. It runs on the first start and then rarely after that.

So if your vacuum pump is running after each press of the brake pedal and you've replaced all other parts, replacing the pump is the next step.

If my fender wasn't destroyed already, this would have been a very tedious DIY removing the fender without braking it and then the reinstall to get it all lined up.

[CamasM3e93]

Originally Posted by Ximian

The new pump solved the buzzing noise from the pump running every time I used the brakes. It runs on the first start and then rarely after that.

So if your vacuum pump is running after each press of the brake pedal and you've replaced all other parts, replacing the pump is the next step.

If my fender wasn't destroyed already, this would have been a very tedious DIY removing the fender without braking it and then the reinstall to get it all lined up.

Glad it fixed your issue. Do you mean the fender liner in the wheel well? The fender itself doesn’t have to come off.

[Ximian]

Originally Posted by CamasM3e93

Glad it fixed your issue. Do you mean the fender liner in the wheel well? The fender itself doesn’t have to come off.

I'm sure someone could bend the fender liner out of the way and undo the two screws on the pump to loosen it, but I can't work in those kinds of tight spaces.

Since my fender consist of two pieces and a lot of empty space, it was easy to get it off. There was also a surprising amount of tire strips below the vacuum pump along with sand in the side skirts. Cleaning all of that out was probably 1 lbs of weight savings.

[CamasM3e93]

Originally Posted by Ximian

I'm sure someone could bend the fender liner out of the way and undo the two screws on the pump to loosen it, but I can't work in those kinds of tight spaces.

Since my fender consist of two pieces and a lot of empty space, it was easy to get it off. There was also a surprising amount of tire strips below the vacuum pump along with sand in the side skirts. Cleaning all of that out was probably 1 lbs of weight savings.

I just removed the fender liner, wasn’t tight but I also didn’t get to pull out 13 years of dirt like you did. Must have been satisfying!