Hi. This is an interesting one that I never experienced in 35 years of driving. Since Thursday I have experienced an intermittent hard brake pedal with my 1992 Caravan. It has happened ONE TIME on each drive since. I'll step on the pedal and it will catch me by surprise by being hard and not wanting to push down. The van will slow some, but breaking ability is drastically impaired. After a few depresses, the pedal will finally function normally.

Does anyone have any idea what causes this? Also, I'll add that I had my pads and rotors changed 2 weeks ago, though it could be unrelated because the van was driven last weekend without issue, and the issue just arose Thursday (and continues).

Thank you for help with this!

 

is there any burnt brake pad smell associated with the concern?

if not, the problem could be brake vacuum booster related ie bad booster or loss of vacuum to the booster.

 

Thanks for the quick reply! I can't say that I smell anything. That doesn't mean that the problem doesn't lie there. If there was a burnt brake pad smell, what would that imply?

And as far as a bad booster, or a bad vacuum to the booster, how do I diagnose it? What are the steps?

Thanks so much!

 

if the master cylinder is not releasing fluid back to the reservoir...the brakes would drag, the pedal would be hard with no free play, the brakes would heat up and smell and the car would seem to have reduced power due to the brakes sticking on.


to test the vacuum booster...engine off...depress the brake pedal 5x to deplete the vacuum reserve. apply and hold the brake down...start the engine...the pedal should drop as vacuum assist is applied from the booster.

 

Thanks, primem, for narrowing this down for me. I'm leaning toward a vacuum assist issue, so I'll run that test. Thank you!

 

Isn't this vehicle "hydraulic brake assist" rather than "vacuum brake assist"?

 

They are Vacuum IIRC. Giant hose running from the booster to the engine (near TB).
If it's not a booster issue try checking/replacing your brake hoses.
They deteriorate over time, leading them to collapse, which will lead to many issues.

 

Hi smokesxt. I just did a lot of research, and the 91-93 models have no vacuum. They are hydraulic brake assist, and they use the dreaded Bendix 10 ABS system that had a recall.

https://www.carmd.com/Tsb/Download/3...0022dc80bbdc46

So I'm in a whole different ball of wax here. I've learned this much: a) Diagnosis is supposed to start with a DRB II scanner reading fault messages from the CAB (Anti-lock brake Controller module). Probably these days only the dealer has one? b) The recall covered the full ABS system for 10 years; now it only covers the 3 prime suspect parts. c) Intermittent issues with the system are most likely to be electrical. d) There is a chance that the ABS sensors in the wheel were jazzed during installation of the front pads and rotors.

I'm going to start with checking those sensors because there is a chance that it's not coincidence that this happened soon after pad and rotor installation.

Any input is welcome on next steps. I prefer to avoid the dealer unless I can determine the the fault lies in one of the 3 lifetime warrantied parts. Thank you!

 

What if you disconnect the abs?
Granted you won't have ABS anymore (which you probably don't now), but it may make the issue go away.

 

I wish it were that easy, smokesxt. I'd do it in a second. The brake assist is dependent on the components of the ABS System, whether the ABS is actually working or not. What some people have talked about doing on their vehicles is swapping out this Bendix 10 System with a vacuum system. I don't think I'd mess with that.