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 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 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

Little Car Show: Celebrating All Things Quirky and Small

7 hours ago in Articles

As the name suggests, the Little Car Show is all about little cars.

Concours d’Lemons to Ruin Monterey Car Week Yet Again

8 hours ago in News

What started as the anti-concours has transformed into a major event on the Monterey Car Week schedule.

You Need This: A Quite Eye-Catching Green Over Red Ferrari

9 hours ago in News

Not your usual Ferrari color combo.

We're Back In Monterey for Car Week

9 hours ago in News

And so it begins, another trip to Monterey Car Week.

Your Projects: JDM Autozam AZ-1 Kei Car

10 hours ago in News

What are the realities of importing a JDM kei car to the U.S.?

Tonight on Grassroots Motorsports LIVE! Lee Grimes of Koni Shocks

1 day ago in News

This may shock you, but suspension is arguably the most important part of going fast.

Classic Motorsports Monterey Welcome Party Welcomes 2000-Plus Gearheads

1 day ago in Articles

Last night we threw a party, and more than 2000 people came to celebrate.

You Need This: E46-Chassis BMW M3 for $6000!?

2 days ago in News

Could this M3 donate its heart to your next project?

Deal of the Month: Free Trackside Companion!

2 days ago in News

Ever wished you had a handy guide on how to dial in your alignment or adjust your dampers?

This Tuesday: Join Us at Track Night in America

3 days ago in News

This Tuesday we'll be running at Palm Beach International Raceway

Experience Monterey With Us

3 days ago in News

We're on our way out to Monterey, California, for car week.

Tomorrow, August 15: Join our Monterey Kickoff Cruise-In

3 days ago in News

Our Monterey welcome party is taking over all of downtown Pacific Grove.


Grassroots Motorsports Magazine

Subscribe Today

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

Learn More