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Post by ddewar53 on Oct 25, 2009 19:39:06 GMT -5
The brakes on the YJ haven't been right for a while. They stop it ok if I have a lot of room, but you don't want to drive it in traffic where you can't leave a lot of room to stop. The pedal is real hard to push, but it feels like the power brake booster isn't working. You know, like when the engine stalls and you have to pull over, how hard it is to brake.
The booster holds plenty of vacuum - when I pull the line off I can hear the air wooshing in. Also, I can't see any evidence that the brakes on the rear axle are working. The rotors aren't scuffed, and the pads look brand new. Is that a symptom that the apportioning valve needs to be reset? If it is, how do I do that? This is a 90 YJ with the stock D30 in front and an 8.8 with disc brakes in the back.
Any thoughts?
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Post by Jon W on Oct 25, 2009 20:15:53 GMT -5
I had a bad caliper in front and had a high, hard pedal feel and reduced braking... Sometimes the caliper would drag.
Not sure that is really applicable here given that the rear brakes sound like they aren't working for you.
There is a spring in the proportioning valve to control residual pressure... You can pull it out and change it -- discs use less pressure than drums in the rear -- but you have to have the right one to put in. I've never messed with the stock disc/drum proportioning in my XJ since I swapped in the discs in back.
JW
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Post by Kurt on Oct 26, 2009 7:04:35 GMT -5
As long as the BRAKE light is not illuminated on the dash then the prop valve doesn't need to be "reset". You can check if the booster is working by doing the following. 1) With the engine off release all the vacuum in the booster. 2) Apply a moderate braking pressure to the brake pedal. Keep a constant moderate pressure on the pedal thru step 3. 3) Start the engine. If you feel the brake pedal drop when the engine starts then the booster is working. If there is no change in pedal position then the booster is not functioning properly. I have an extra YJ prop valve if you want it to try. My 92 YJ's (D30 & F8.8) braking performace was poor with 33's and dismal with 35's. I put in a TJ master cyl & booster (dual diaphram). Wow.... what an improvement!  |
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Post by ddewar53 on Oct 26, 2009 8:02:53 GMT -5
Thanks, Kurt, that sounds reasonable, and the poor performance started when I put the 8.8 in.
Anybody know someone who's parting out a TJ?
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Post by Kurt on Oct 26, 2009 9:13:15 GMT -5
Actually a 95 YJ uses a dual diaphram booster/MC. If you can score on of those it should be nearly a drop in job. The TJ booster and MC takes some re-working to make it work uspecially in a 5 speed. The biggie is the need to lengthen the push rod.  Here is a link with some info on using a TJ booster and some brake system upgrade solutions from others. www.jeepsunlimited.com/forums/showthread.php?t=507025&highlight=TJ+Booster |
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Post by johnsxj on Oct 26, 2009 19:51:38 GMT -5
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Post by DOUG® on Oct 27, 2009 6:26:52 GMT -5
Dan Stonisfer (NEWJO) is parting a TJ right now. I will be calling him today on a couple of things. I can ask him about the brake MC if you'd like.
Give me a call later and let me know.
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Post by Kurt on Oct 27, 2009 6:41:00 GMT -5
I believe Don would needing the booster, MC & Prop valve setup.
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Post by Captian Carnage on Oct 28, 2009 9:02:22 GMT -5
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Post by ddewar53 on Oct 28, 2009 20:09:04 GMT -5
OK, picked up a booster, mc and prop valve tonight. Now another question comes up.
I'm pretty sure that the YJ prop valve has 3 outputs - one for each front wheel and one for the rear axle. The new one only has 2 outputs. Anybody know if they make a flared T fitting, use the YJ valve, or should I look for another solution?
I'm thinking that the valve I got is for ABS, and I need to find one for non-ABS. Sound right?
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Post by Jon W on Oct 29, 2009 18:09:59 GMT -5
You could try with your existing proportioning valve... I don't know if you really need to replace it. The stock TJ uses drums in back, so it should be basically the same.
JW
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Post by ddewar53 on Oct 29, 2009 19:11:43 GMT -5
You could try with your existing proportioning valve... I don't know if you really need to replace it. The stock TJ uses drums in back, so it should be basically the same. JW That's what I'm thinking, too. I'll give it a try. thanks, all for all of the advice and pointers to parts. |
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Post by Kurt on Oct 29, 2009 20:01:27 GMT -5
I'm thinking that the valve I got is for ABS, and I need to find one for non-ABS. Sound right? Yup - The prop valve you have is for an ABS setup. They only have two lines from them to the ABS pump assy. |
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