Do I need a new brake booster?
 

I am preparing my 2000 green base model Boxster for sale, after having completed an engine swap. I went for a test drive and the first time I tried a serious stop I almost sailed through a red light. The brakes work but there is no power boost. I got it stopped but only with after applying a lot of pressure on the pedal.
Today I did the following troubleshooting.
1) pulled the vacuum line for the brake booster off the intake manifold. Engine almost stalled, put it back on, the engine returned to normal.
2) pulled the vacuum line off at the booster... engine almost stalled, put it back on, the engine returned to normal.
So I have vacuum at the booster...
3) In my Boxster S I put my foot on the brake pedal and started the car, the brake pedal went down noticeably, as I would expect with power brakes.
4) Back in the problem car I put my foot on the brake pedal and started the car, the brake pedal barely reacted.
5) Went for a short test drive and the problem is still there.
The brakes worked last fall before I garaged the car for the winter, although it did seem that the brakes were not as good as in my S. During the engine swap I didn't touch the hydraulics. The brake pedal is rock solid, so no air in the system.
I don't see that it could be anything other than the booster.
Anyone have other ideas... I wasn't counting on another $500 expense right now. :-(

Can you put one of those cheap Mityvac testers were you pulled the vacuum line off the booster, pump it up and see if it holds?

Grant, I received your message and I'll just reply here. I have replaced two brake boosters with used ones and there were no issues afterward. Both of the ones I replaced still held a good vacuum, but had internal problems. One had corrosion causing it to bind. Another had a leaking seal allowing brake fluid into the booster.

Your troubleshooting process looks logical, but before taking the trouble to replace it there are a couple more steps you can take to be sure. Check this page: https://m.roadkillcustoms.com/test-power-brake-booster/.

You might as well do a full brake system flush while you're at it. :cheers:

Thanks 78F350, I did the tests suggested. This is my test rig for verifying the check valve. I blow in the hose and air passes to the engine manifold and when I suck on it nothing happens, so the valve is good.

http://986forum.com/forums/uploads02...1713547355.jpg

I did a brake fluid flush recently, so I hope to change the booster, following the video you did, without having to bleed the system.

I checked the local scrap yards for vacuum boosters and they want $250 to $350 which is not worth it for a used part. I looked around for alternatives and found at Usp motorsports a TRW for $135USD ! ... but out of stock. At ECS tuning $216USD... and out of stock. Then I found the Cardone 53-2682 - Power Brake Booster rebuilt for $147 CDN. And according to the listing this unit fits the 1998 VW Passat and several Audi A4s of the same era.
From what I see the new VW / Audi parts are about the same as third party Porsche parts, so not worth bothering with unless you have a VW or an Audi parts car. Has anyone tried these?

It sounds like you've done some thorough troubleshooting already. Since you've confirmed vacuum at the booster and there's no air in the system, it does indeed point to a potential issue with the brake booster. Before committing to a replacement, you might want to double-check the vacuum hose for any leaks or blockages and ensure the check valve is functioning properly. If everything appears to be in order, then replacing the booster might be the next step.

Hi GudrunHelga, are you an AI Chat Bot?

I'd like to add, " Determining whether you need a new brake booster for your Porsche Boxster depends on several factors. If you're experiencing symptoms such as a spongy brake pedal, difficulty stopping, or a hissing noise when you apply the brakes, it could indicate a problem with the brake booster. However, these symptoms could also be caused by other issues such as air in the brake lines, worn brake pads, or a brake fluid leak.

It's essential to have a qualified mechanic inspect your vehicle to diagnose the issue accurately. They can perform tests to determine if the brake booster is the culprit or if there's another underlying problem. If it is indeed the brake booster that needs replacement, it's crucial to address it promptly to ensure your vehicle's safety and performance." :cool:

Yes, I needed a new brake booster.
 

I found a used brake booster at a local "recycler" ("recycler" does sound better than scrap yard) for $100 plus taxes and installed it using the following videos.
https://www.youtube.com/watch?v=mP3gDzJQtFU
https://www.youtube.com/watch?v=vlV24QnRfME
Not one of my favourite jobs. When I got to the point where I had to pull the master cylinder and the ABS controller out of the way I was sure that I was going to break one of the steel brake lines... but I got it apart and back together again without incident. Worth it to not have to bleed the brake and clutch lines.
This morning I did a road test and was able to brake hard enough to get the ABS system to activate and chirp the front tires.

Good news!
I rebuilt the fuel pump on my dad’s 1940 Buick last fall and was surprised how long a rubber diaphragm can last in the right environment. But I have no proof that fuel pump wasn’t rebuilt in 1976 😉

Hello 986tate,do you have any pictures of your dad's Buick..? :rolleyes:

Well, now that Elgy has solved his issue we can derail a bit.
Dad's had a lot of cool stuff, I sort of live vicariously through him:

http://986forum.com/forums/uploads02...1714486637.jpg

http://986forum.com/forums/uploads02...1714486683.jpg

http://986forum.com/forums/uploads02/TR31714486719.jpg

Thank you for the pictures 986tate!

Wow, a nice TR3, 356 Roadster and a very cool Buick :D, I am happy that you grew up with a very good influence (and good taste) from your Dad those got to be awesome memories.

Perhaps would be nice to start a new tread for the members to post pictures of their family rides and how these influenced our love for cars :)