weird brake issue

luk · **Joined:** Fri Oct 26, 2018 2:45 am **Posts:** 26

Hi all I just finished timing belt, rockers, egr delete rear pads and rotors. Now the brakes seam to work ok but if I pump them they get hard like the booster not working leave it alone for a few seconds back to fine the peddle sinks if you pump and hold. I bled the brakes twice no air . Booster ,check valve or master cylinder? I've checked all the vacuum lines thinking perhaps I cracked one while doing the engine work could not find anything. Any ideas?

GordnadoCRD · **Posted:** Wed Apr 03, 2019 3:29 am

Question. was this a sudden change, or just the next thing on the list?
Question 2. When you say the pedal sinks, do you mean it sinks lower than you expect, or does it continue to sink until the pedal is flat to the floor with no resistance left?

When I first drove mine I thought the brakes were funky, but had plenty of life when I checked. Basically, if I pushed HARD on the pedal they didn't go to the floor but quite low. If I stopped hard enough to activate the ABS, I could actually feel the floor mat, although the pedal didn't quite hit. There has been no change since then, and everything works fine, just took some getting used to.

Something else about the CRD... the vacuum doesn't come from the engine it's self per se, it's a vacuum pump inside the engine crankcase. At idle the volume is pretty low, so if you pump repeatedly, it definitely will lose vacuum and brake boost power.

If it were Master Cyl. there would almost definitely be fluid leaking somewhere. The one exception would be if it's leaking internally, and in that case you're lucky to be stopping at all. The pedal will just go to the floor and you will lose any brake power you had. In this case, it's definitely the Master Cyl.

luk · **Joined:** Fri Oct 26, 2018 2:45 am **Posts:** 26

GordnadoCRD wrote:

Question. was this a sudden change, or just the next thing on the list?
Question 2. When you say the pedal sinks, do you mean it sinks lower than you expect, or does it continue to sink until the pedal is flat to the floor with no resistance left?

When I first drove mine I thought the brakes were funky, but had plenty of life when I checked. Basically, if I pushed HARD on the pedal they didn't go to the floor but quite low. If I stopped hard enough to activate the ABS, I could actually feel the floor mat, although the pedal didn't quite hit. There has been no change since then, and everything works fine, just took some getting used to.

Something else about the CRD... the vacuum doesn't come from the engine it's self per se, it's a vacuum pump inside the engine crankcase. At idle the volume is pretty low, so if you pump repeatedly, it definitely will lose vacuum and brake boost power.

If it were Master Cyl. there would almost definitely be fluid leaking somewhere. The one exception would be if it's leaking internally, and in that case you're lucky to be stopping at all. The pedal will just go to the floor and you will lose any brake power you had. In this case, it's definitely the Master Cyl.

Thanks for your post yes came on suddenly but because i did so many things at the same time not sure if I caused it when I compressed the wheel cylinders or while I had 1/2 the engine apart.
the peddle goes what seams like all the way to the floor but the brakes still hold.
Yes I am aware that diesel engines need vacuum pumps the steel line coming from the pump seams to have good vacuum at idle and good at the booster as well as at the solenoid going to the turbo. but when I press the brakes and remove a line from the solenoid input the vacuum disappears

flash7210 · **Posted:** Wed Apr 03, 2019 6:53 pm

A problem with the master cylinder should cause the “brake” warning light to come on.

You should do a real brake test.
Find a empty parking lot, accelerate hard and brake hard.
Like, try to lock up the brakes.
You should feel the ABS system pumping in the brake pedal.

GordnadoCRD · **Posted:** Thu Apr 04, 2019 12:10 am

Have you tested your brake vacuum check valve at the booster? If you pull off the vacuum line from the booster, it should still retain vacuum for some time. Several minutes at least, and a good couple of brake pedal pressings before losing boost power.

luk · **Joined:** Fri Oct 26, 2018 2:45 am **Posts:** 26

Well thanks to all the problem seams to have corrected by itself perhaps there was a little air when I bled or just took a bit for the wheel cylinders to pump up?....sorry I feel like an idiot for posting the jeep is new to me so I'm not used to how the peddle is supposed to feel but it did not feel correct now it does

GordnadoCRD · **Posted:** Sun Apr 07, 2019 5:28 am

These dirty little lovelies have plenty of weirdnesses unique to them, and they are getting into upper middle age, where the spirit is willing but the body gets rust holes and suspensions and bearings, and brakes and...(I'd better stop) are coming to the end of their service life (for the nth time) so don't worry about asking.

The upside to the above, is that whatever problem you're having, someone somewhere has already had the same problem and solved it somehow. It's rare that someone presents a problem that is truly unique, but I suppose it's always a possibility.

We also have the unusual advantage of some unusually dedicated suppliers of our unique parts needs with excellent service and competitive prices. Not an entire industry like the Wranglers and Cherokees, but I'll take what I can get :JEEPIN:

weird brake issue

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