Brake pedal vibrate when depressing it

gtcs1 · Aug 3, 2023

Hi, my 73 351 Clev 2V has 29000 miles.

A problem that just started this summer, pedal brake vibrate (like it was with a sticky motion) during depression at initial motion.

I tried a bit of spray oil at the pivot points, it's a bit better but still present.

Anyone experienced that and or have suggestion for me. Thanks for the help.

Stanglover · Aug 3, 2023

Drums or discs? Could be warped rotors or drum. I'm really just guessing here, not a mechanic.

gtcs1 · Aug 3, 2023

Stanglover said:
Drums or discs? Could be warped rotors or drum. I'm really just guessing here, not a mechanic.

Hi, disc, in the front, drum in the back.

I thought about that too but it does that even when car is not in motion. Thanks

Stanglover · Aug 3, 2023

gtcs1 said:
Hi, disc, in the front, drum in the back.

I thought about that too but it does that even when car is not in motion. Thanks

Hmm weird! No idea then other than as you say, a sticky pedal bushing, which is just plastic I think. On my car, I added bronze bushes to the pedal shaft and at the same time added bearings to the clutch shaft as well as bronze bushes to the rest of the linkages. That made a huge difference to the operation of brake and clutch.. Could it be the power booster? Another thought.

Sheriff41 · Aug 3, 2023

It could be the piston in the master cylinder or the pivot for the pedal. If you disconnect the push rod from the pedal you can determine if the pivot point on the pedal is the culprit. If not, then I'd suspect the master cylinder.

Stanglover · Aug 3, 2023

Sheriff41 said:
It could be the piston in the master cylinder or the pivot for the pedal. If you disconnect the push rod from the pedal you can determine if the pivot point on the pedal is the culprit. If not, then I'd suspect the master cylinder.

Good thought.

MikeGriese · Aug 3, 2023

Another thing to check is brake fluid level.

basstrix · Aug 3, 2023

Do you observe any change in idle speed when the vibration occurs? That would support there being a problem with the booster.

gtcs1 · Aug 3, 2023

MikeGriese said:
Another thing to check is brake fluid level.

Hi, I’ll check that this weekend. Thanks

gtcs1 · Aug 3, 2023

basstrix said:
Do you observe any change in idle speed when the vibration occurs? That would support there being a problem with the booster.

Didn’t notice that but I’ll check it paying close attention to that. Thanks

Bentworker · Aug 4, 2023

Hydroboost or vacuum assist?

gtcs1 · Aug 4, 2023

Bentworker said:
Hydroboost or vacuum assist?

Not sure, how do I check that? And what difference would it make? Thanks

Bentworker · Aug 4, 2023

gtcs1 said:
Not sure, how do I check that? And what difference would it make? Thanks

99.9% chance your car still has a vacuum booster which looks like a couple round cake pans welded together on the firewall.

A hydro booster is plumbed into your power steering pump and takes the place of the vacuum booster, it is much smaller and would have a few lines going to it.

Only reason I mentioned hydrobooster is that the symptoms you have sound like a failing one.

rust&power · Aug 11, 2023

If the problem arises at light braking, check the tie rod ends at front suspension. Normally the trouble is there. They might wear out and have excessive play.

Brake pedal vibrate when depressing it

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