snofrandy
snofrandy None
June 7, 2010 12:09 p.m.

Hi, I'm looking to purchase a 1996 Miata and I was close to buying it, but I couldn't figure out what's wrong with the brakes.

When I try slamming the brakes to test it, it takes quite a bit of effort, like it doesn't have power. Same thing with regular braking. I have to extract a bit more effort to make the car stop.

Another problem is that it makes a thud thud thud sound that gradually gets slower as the car gets slower. This only happens when the brakes are hot already (not when I started driving the car).

From my personal knowledge, i don't think it's the master cylinder because the pedal doesn't go all the way down to the floor when i press it. Also, the brake pedal goes back up after pressing it.

This is the only think that's keeping me from buying the car. Basically, my own safety.

What's you guy's opinion on this?

Thank you!

psteav Reader
June 7, 2010 12:15 p.m.

Gonna take a wild guess and say you've got a bad power brake booster? Sometimes the vacuum diaphragm in those can rupture, which basically leaves you with manual brakes that are really high-effort. IIRC, it's because the master cylinder piston is sized differently for manual brakes as opposed to power.

As for the thud-thud-thud, does it sound like a warped rotor? Does the steering wheel shake when it does it? Don't know why that would only happen when hot, though.

WilberM3 Reader
June 7, 2010 12:23 p.m.

ive heard something like the thud sound on a hot set of brakes at the track if there's some pad material left on the rotor, you might see an outline on the rotor of the pad. just something to check out. if thats the case rotors ought to fix it.

does sound like a bad booster on the pedal effort.

snofrandy
snofrandy New Reader
June 7, 2010 12:25 p.m.

hi psteav. as for the thud-thud-, the wheel doesn't vibrate when I press on the brakes so i don't think the rotors are warped.

so one possible is brake booster. Is there a test I can do for that to know it's still working w/o me disassembling it first?

triumph5
triumph5 New Reader
June 7, 2010 3:03 p.m.

In reply to snofrandy:

Do this only where you have lots of room. Disconnect and plug the vacuum line to the brake booster. If the braking is the same, you've got a shot booster. Did this on my Protege, and not only discovered the booster was shot but first I found there was a hole in the bake booster line. Replaced the line; no change. I replaced the booster, problem solved. Thudding? Did the car sit for any time? Possible flat spot on a tire. Sometimes by simply driving the car for a half hour, warming the tire, it'll go away. Otherwise the tire may simply be shot..

racerfink Reader
June 7, 2010 5:04 p.m.

I left the shim clips out the last time I replaced the brakes on my '90, and it makes quite a loud clicking noise when I apply the brakes. Wouldn't call it a thud though.

Also, on both my '90's, I've had a problem with the fixed caliper slide (not the bolt) on the right rear being bent. Wore pads out quickly on that corner, and definitely took more effort to stop the car

You'll need to log in to post.

Also on Grassroots Motorsports

Modern Day Track Junkie

23 hours ago in Articles

Christina Lam went from the sidelines to full-on track enthusiast in 8 simple steps.

How Ben_Modified Wows the Crowd: 1 Part Imagination, 2 Parts Fabrication

1 day ago in News

Ben_Modified's build combines some of our favorite things.

2017 Audi A8 L

2 days ago in New Car Reviews

When it comes to luxury sedans, Audis are usually front-runners. The A8 L is the biggest and maybe most comfortable ...

Slight Project Pause for Our BMW M3

2 days ago in Project Cars

Few things slow down our project car progress more effectively than a broken arm.

Grassroots Motorsports Experience Ticket Renewals Have Been Sent

2 days ago in News

Check your inbox for our Grassroots Motorsports Experience renewals.

First Drive: Turbo ND MX-5

3 days ago in News

We hit the track with Flyin' Miata's latest power adder.

Project Turbo Miata: Fire Fighting

3 days ago in Project Cars

We transfer the fire system to our new Miata.

Vintage Views: GMC Syclone and Typhoon

4 days ago in Articles

All-wheel drive, turbo power and a Q-ship’s stealth.

Classic Motorsports Mitty Presented by Hagerty Celebrates Porsche

5 days ago in News

Gearhead heaven? We think it looks something like this.

Meet the Rebels Who Started the Cannonball Run

5 days ago in News

Relive those desperado days through movie excerpts, and hear the real facts and wild stories from the legends themselves.

This Weekend at the Mitty: The Ultimate Auto Festival

1 week ago in News

Gates open this Friday for the Classic Motorsports Mitty at Road Atlanta.

ND Miata Turbo Kits Now Available!

1 week ago in News

Add 70 horsepower and 70 ft.-lbs!

OUR SPONSORS

Grassroots Motorsports Magazine

Subscribe Today

Also get your instant access to the digital edition of Grassroots Motorsports Magazine!

Learn More
7rYyEmeSc1KWnw6qQXv753GNtYZIRJ9U