Front wheels locking up intermittently sometimes worse than others

Tiny
HANS BECK
  • MEMBER
  • 1994 JEEP WANGLER YJ
  • 4.0L
  • 6 CYL
  • 4WD
  • MANUAL
  • 75,000 MILES
We will be driving the vehicle and then all of the sudden with or without pushing the brakes the front brakes will start to lock up and start to grab and it progressively gets worse to the point to where the vehicle does not have enough power to move. Then I will get out of the vehicle pull the check valve and booster line off release all the pressure put it back on the brakes release. A short little while later during the same 10 to 15 minute drive it will happen to her three more times.
Saturday, July 13th, 2019 AT 12:23 PM

10 Replies

Tiny
BRANDON SIMON
  • MECHANIC
  • 49 POSTS
If the pressure is building up that bad in the brake booster, the booster isn't functioning correctly. There should never be enough pressure in a brake booster to lock your brakes without notice. I would strongly recommend not operating the vehicle with this issue, as it is not only a safety risk to you, but to others on the road as well!
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Saturday, July 13th, 2019 AT 3:46 PM
Tiny
HANS BECK
  • MEMBER
  • 5 POSTS
So the booster for sure. That’s exactly what I was thinking. But I cannot find a booster for it anywhere because it’s a 1994 Wrangler with ABS the boosters are different.
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Saturday, July 13th, 2019 AT 7:31 PM
Tiny
BRANDON SIMON
  • MECHANIC
  • 49 POSTS
If necessary, I am sure there are places you can find that can repair/rebuild your current booster if it is that difficult to find.
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Saturday, July 13th, 2019 AT 7:46 PM
Tiny
HANS BECK
  • MEMBER
  • 5 POSTS
I just don’t want to have to pull it off and send it in to summit racing and have them re-manufacture it but I guess that’s my best bet. Unless you can think of anything else?
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Saturday, July 13th, 2019 AT 7:49 PM
Tiny
BRANDON SIMON
  • MECHANIC
  • 49 POSTS
I can only make recommendations and suggestions, but please remember, it is not only you and your vehicle with yourself and others but also vehicles around you you put in danger with this issue. My recommendation is do what needs to be done, whether you can find a replacement or have yours re-manufactured. Look at it like this, even if you have to wait a couple of days, at least you'll know that if done properly, you may save lives by getting this problem solved.
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Saturday, July 13th, 2019 AT 7:53 PM
Tiny
HANS BECK
  • MEMBER
  • 5 POSTS
Oh I understand, I was a technician for many years, just figured I’d get a second opinion.
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Saturday, July 13th, 2019 AT 7:57 PM
Tiny
BRANDON SIMON
  • MECHANIC
  • 49 POSTS
Please let us know what you decide to do and how it works out. From the way that you are describing the problem though, it surely does sound like a bad booster. Please let us know if this solves your issue and if I was at all helpful! I wish you the best of luck!
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Saturday, July 13th, 2019 AT 8:04 PM
Tiny
CJ MEDEVAC
  • MECHANIC
  • 11,004 POSTS
I tried looking up an adjustment between the booster and master.

I'm not real up on the way Prodemand organizes stuff.

Looking through some of this stuff might help or throw out other ideas.

https://www.youtube.com/results?search_query=1994+wangler+vacuum+booster+adjustment

Keep us posted with what you find.

The Medic
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Sunday, July 14th, 2019 AT 6:03 AM
Tiny
HANS BECK
  • MEMBER
  • 5 POSTS
But it only happens when it’s hot outside.
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Tuesday, July 16th, 2019 AT 5:33 PM
Tiny
STEVE W.
  • MECHANIC
  • 15,233 POSTS
I agree with Brandon on this, the booster is applying the brakes. The engine vacuum control valve that the brake rod CJ is referring to depresses to initiate boost is opening just enough that it pulls the brakes on. An easy way to verify it would be to drive it with the vacuum line disconnected and plugged on the engine side. However it will make the brakes very hard to apply. In this case the likely issue is in the valving attached to the diaphragm inside the booster. To be sure it isn't the apply rod or something with the pedal or pedal hanger you could use a short bungee cord to pull the pedal back more and see if it still happens.
The OEM part is Mopar # 723133
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Thursday, July 18th, 2019 AT 11:16 PM

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