Lost Power Brakes

[Tex EV]

Drove the Roadster through some unusually heavy rain this morning. Got to the office, parked, and went about my day. When leaving for lunch later, I noticed that the friction brakes were doing almost nothing. The brake pedal was stiff, just as it is when the car is off. Managed to drive 80 more miles like this today, mostly depending on regen braking to slow down. To bring the car to a full stop required almost standing on the brake pedal. No warning messages displayed. I realized while pulling into my driveway that I was no longer hearing the brake vacuum pump when releasing the brake pedal at low speed.

Car is currently in the garage and partially disassembled to get to brake system parts. Here's what I've checked so far:
Fuse 22 (brake pump) - Good
Vacuum line between brake pump and master cylinder - Connected on both ends
Brake pump - Electrical connector w/ black and green wires is seated properly

Wondering how the vacuum pump is triggered - is there a switch on the brake pedal assembly?
Is there a simple way to test if the vacuum pump itself is operational?
Anything else I should check?

Thanks in advance!

 

[ML Auto]

The connector at the pump should have 12V with the key on. The pressure switch that controls the pump is part of the pump itself. I would check the connector and pump terminals to make sure they didn't get wet and burn up. If they are OK and have voltage, then you will need to remove the pump.

 

[Tex EV]

I got the pump out about an hour ago, tipped it on its side, and saw water begin dripping out of the electrical connector . The rubber grommet that is supposed to fit over the connector was hanging off, apparently allowing water to seep in. I disassembled the pump and got it cleaned up. Turned the internal mechanism by hand and verified that it pulls vacuum. There wasn't a ton of water in there... hopefully no damage, but I'm about to cross my fingers and plug it back in.

Anyone know if the bead of black sealant is supposed to be there? Doesn't look very "factory".

 

[efxjim]

I had this happen several years ago. Your vacuum pump electronics in the bottom of the pump housing may have gotten wet. The circuit board is not coated very well against moisture and the housing leaks water that cannot drain away. It is not hard to remove the pump and get to the pc board. I dried mine out and cleaned it with distilled water and a tooth brush. It tested fine when cleaned up. I then coated it with several coats of conformal coating to protect it in the future. I then fabricated a protective boot for the pump to ward off water and included a small drain hole/breather in the bottom. It has been working fine for the last 30k miles and saved me about $700 on a new pump.

 

[efxjim]

Black sealant was on mine as well.

 

[Tex EV]

Plugged it back in, turned the key, and heard the familiar increasing-pitch hum! Brake feel is back to normal, but won't be able to verify stopping power until the car is back on the ground. Now to reassemble everything.

I then fabricated a protective boot for the pump to ward off water and included a small drain hole/breather in the bottom.

Any chance you have pictures of this that you could share? Would be great to see!

 

[efxjim]

Congratulations! Sorry no pictures. The area the pump is in gets a lot of mist/water. seal it up best you can and possibly add a weep hole.

 

[thefortunes]

The connector at the pump should have 12V with the key on. The pressure switch that controls the pump is part of the pump itself. I would check the connector and pump terminals to make sure they didn't get wet and burn up. If they are OK and have voltage, then you will need to remove the pump.

@MLAUTO Sent you a PM on a different matter. Please let me know if you got it. Thanks!

 

[Tex EV]

I think I won the award for unluckiest/idiotic Roadster owner of the day. Just got the working vacuum pump back together and sealed up with a fresh bead of silicone, then decided I would drill a weep hole at the bottom of the electronics housing...
Looks like I'll be spending $700 soon.

 

[spaceballs]

I think I won the award for unluckiest/idiotic Roadster owner of the day. Just got the working vacuum pump back together and sealed up with a fresh bead of silicone, then decided I would drill a weep hole at the bottom of the electronics housing...
Looks like I'll be spending $700 soon.
View attachment 215291

IC doesn't look like it's cracked, just scratched.
Looks fixable, to me, any good EE guy should be able to fix that.

 

[Tex EV]

IC doesn't look like it's cracked, just scratched.
Looks fixable, to me, any good EE guy should be able to fix that.

I'm not an EE guy, but I tried. Looks like the drill took out one of the solder pads, so I'm not sure how that would be fixed.

Been pondering a few options...
1. Bite the bullet and order a new OEM pump.
2. Try to reuse the original pump with an external pressure switch - seems the only purpose of the internal circuit board is to tell it when to turn on/off.
3. Try an aftermarket setup with a vacuum reservoir.

 

[ML Auto]

Unless you like spending money, just get an aftermarket switch for $35 and bypass the damaged board.

 

[spaceballs]

I'm not an EE guy, but I tried. Looks like the drill took out one of the solder pads, so I'm not sure how that would be fixed.

Been pondering a few options...
1. Bite the bullet and order a new OEM pump.
2. Try to reuse the original pump with an external pressure switch - seems the only purpose of the internal circuit board is to tell it when to turn on/off.
3. Try an aftermarket setup with a vacuum reservoir.

If you like, PM me your email, I'll have my EE guy do it for you then.

 

[Tex EV]

If you like, PM me your email, I'll have my EE guy do it for you then.

PM sent! Tesla just informed me that there are 12 of these pumps left in the nationwide parts inventory. Would be ideal if this one can be salvaged.

 

[IirisSeveri]

What's one of the scariest things that can happen while driving a car. How about No Brakes! Brake failure can occur without warning. You stomp down on the brake pedal to apply the brakes and nothing is there. The pedal goes all the way to the floor and there are no brakes.

What can you do? Scream? Pray? Try pumping the brake pedal as fast as you can. It might generate enough pressure to apply the brakes and stop your car. If nothing happens, apply the parking (emergency) brake as hard as you can. It should start to slow your vehicle immediately. If you can't react quickly enough and are in danger of crashing into another vehicle, look for a way to avoid the collision. Blare your horn and try to steer your way around other vehicles or obstacles. Eventually your vehicle will coast to a stop. Pull over to the side of the road, shut the engine off, put the transmission into Park (or leave it in gear if it is a stick), set the parking brake and call for help. DO NOT attempt to drive your car until the problem that caused your brakes to fail has been diagnosed and repaired.

 

[plundy]

A similar thing as Tex EV reported just happened to me today; loss of vacuum assisted brakes. The previous night we had been out driving in heavy rain.
When I got back home, I checked the forums and TaDa! You came to the rescue. Vacuum pump started working by the time I returned to the garage after reading this thread!

 

[plundy]

Of course, that did not last long. Nothing from the vacuum pump. So very very quite. It is time to get to work.

Funny how I've have had the same car jack for 30 years. When I went to lift the car to take the wheel off . . . the old jack wouldn't fit under the Roadster! Now I have a nifty new jack. I removed the vacuum pump and after showing my wife where it is located, she laughed! It is mounted in front of the driver side wheel under the left head lamp.

I love the Velcro attached foam insulation. Not sure how I'm going to get all that crap back on the pump, but that is for later. At first I didn't really see the same things as Tex EV, or at least not as bad. The electrical connector and rubber hood were intact and clipped in place just fine. Then I noticed the water in the electrical connector. Aha! The rubber hood had cloth tape where the two power wires protrude. When I removed the rubber hood for inspection there was water!

When I took the cover off the pump housing the original sealant used did not really have good contact. It just peeled away. The circuit board appears well sealed with silicone conformal coating. There was just a very small amount of water in the housing and some minor circuit board corrosion. I flushed everything out with electronic spray cleaner. I have two test adhesives on the housing and tomorrow I'll see which sticks best. I'm letting everything dry out, then I'll put it all back.

Enjoy the photos, they are somewhat random. If there are additional photos I can add as I put things back on the Roadster, let me know.

 

[plundy]

Todays update. I resealed the dried out vacuum booster pump and used Marine Goop on the gaps as I've had good luck with it in the past. I also sealed the end of the rubber boot on the electrical connector that originally had cloth tape covering the end. I did use the 3M adhesive on the Velcro insulation straps that had come loose. Worked great. Since water had pooled at the connector contacts I also put dielectric silicone on the contacts.

Everything went back together as expected. It is a bit tight to get a couple things tightened otherwise pretty straight forward. It was comforting to hear the pump working as I started the Roadster.

Here are a few anticlimactic photos.

 

[erericic]

I am having this problem. I removed the pump found some water and indication the circuit board had gotten wet. I dryer and cleaned everything. Hooked it back up partially just to hear it run. Turned on car and no pumping. I checked and there is voltage, 13.4v. I thought maybe I just can't hear it. So I drove it and still no power brakes.
At this point it is somewhat easy to take back out, so I will clean circuit board again.

 

[erericic]

When I look at plundy's circuit board pic mine seems to have a missing pin on one of the chips.