Help!! Wj Booster Behavior? Need Help Asap

[skidoo_j]

I just completed the wj booster and master conversion on my truck.  I picked up a reman booster and a new master.  My concern is...

 

 

When I press the brake engine idle increases by about 200 rpm.   And when I let off the brake the engine bogs a bit 

 

If I press the brake and hold it for a while the engine idle comes back down, but then when I let off the engine almost dies.

 

 

 

I'm thinking the "re-manufactured " booster is bad but am unsure.  I did several google searches and it seems up in the air pending the design of the booster.  

 

 

I'd like to get it replaced before i button everything else back up if it's bad, but now the concern is because I ground the rod if autozone would even notice i altered it and if they would replace it.    

 

If you have any input please share it right away as this weekend is my weekend to button up all my projects on the truck.  

[onlyinajeep726]

Sounds like the symptoms of a vacuum leak, which would imply the diaphragm inside the booster is torn...  As far as the altered rod, stick it in the bottom corner of the box it came in and cover it with any plastic baggies it may have come with...  They don't generally pull the item out when you return, they just open the box to make sure that right thing is there and that it's not the old part.

[HOrnbrod]

I think you bought a good reman booster from Autozone (they are fully tested of course during quality control), performed an intentional modification to fit an application it was not intended for, screwed it up, and now you are trying to defraud the seller by concealing your modification. Then someone tells you the best way to conceal it and cheat the seller. Nuff said.

[skidoo_j]

Sounds like the symptoms of a vacuum leak, which would imply the diaphragm inside the booster is torn...  As far as the altered rod, stick it in the bottom corner of the box it came in and cover it with any plastic baggies it may have come with...  They don't generally pull the item out when you return, they just open the box to make sure that right thing is there and that it's not the old part.

That's my fear.  An autozone 30 miles has one instock as I had to order it to my local store.  I"m thinking a trip to the other store, connecting it just to the vacuum line and pushing in the rod to see if I hear the same hiss 

 

I think you bought a good reman booster from Autozone (they are fully tested of course during quality control), performed an intentional modification to fit an application it was not intended for, screwed it up, and now you are trying to defraud the seller by concealing your modification. Then someone tells you the best way to conceal it and cheat the seller. Nuff said.

 

I'm not sure how I could have caused damage to it though.  I'd like to consider myself an honest individual.   I used a hand file to shave it to width and a uni bit to bore the hole, so I don't think heat could have been an issue, and I supported the base and push rod well while working on them so I don't think i tweaked it,  but I guess anything is possible.   

 

But hornbrod you too are saying it's bad?

The only thing i can think of is that the push rod was askew when i received it and i turn it the wrong way so maybe the rod is 180* out?  I don't recall if i turned it clockwise or counter clockwise to make the rod parallel to the pedal. 

[skidoo_j]

I can only hear the hiss when I put my head under the dash.  But there is definitely a hiss when pedal is pressed. 

[HOrnbrod]

I can only hear the hiss when I put my head under the dash.  But there is definitely a hiss when pedal is pressed. 

 

Based on your posts I think you are a stand-up guy. :cheers:   I learned the hard lesson buying re-manufactured / rebuilt products and there is a remote possibility it could have had a busted diaphragm. But you did mod it, turned the push rod, so who knows, you might have ruptured it. I used 95/96 XJ booster and MC for mine, and it was a simple bolt in.

 

The point is trying to conceal it for a refund. Then another member endorsing it. That's all.

[skidoo_j]

 

I can only hear the hiss when I put my head under the dash.  But there is definitely a hiss when pedal is pressed. 

 

Based on your posts I think you are a stand-up guy. :cheers:   I learned the hard lesson buying re-manufactured / rebuilt products and there is a remote possibility it could have had a busted diaphragm. But you did mod it, turned the push rod, so who knows, you might have ruptured it. I used 95/96 XJ booster and MC for mine, and it was a simple bolt in.

 

The point is trying to conceal it for a refund. Then another member endorsing it. That's all.

Re-reading what I wrote I can see where you received the impression of an intent to deceive.   I am of the opinion that re-manufactured products are often crap and I rarely buy them.    I will be speaking with the local autozone manager regarding my scenario.  Based on my record there I'm sure he will warranty it.  

Not all of us are lucky enough to have a 91.... :)      I even considered swapping pedal assemblies, but all the locals getting parted out are auto, and not jy around me now.   I'll probably be making spacers or adapters to use the rod un modified to prevent the "you modified it" so "no warranty" risk.  based on how the switch works I"m sure it's not too hard.  

 

With that said I found these steps to diagnose a booster:

 

Test Power Brake Booster

If the pedal feels "hard" while the engine is running, the booster isn't operating correctly. If you suspect the booster is defective, do not attempt to disassemble or repair the power booster. Doing so is unsafe and will void your warranty.

Test 1   Passed

1. With the engine off, pump the brake pedal to remove any residual vacuum in the booster.
2. Hold pressure on the pedal while you start the engine. When the engine starts, the pedal should drop about a 1/4", this indicates that the booster is working properly.

Test 2   Passed  - kinda I get one good push then maybe a 1/4 push then all manual. 

1. Run the engine a couple of minutes.
2. Turn the engine off and press the pedal several times slowly. The first pump should be fairly low. The second and third should become slightly firmer. This indicates an airtight booster.

Test 3   FAILED??? I couldn't hold the pedal down, as soon as the engine was off the pedal started push back hard!

1. Start the engine and press the brake pedal, then stop the engine with the pedal still pressed. If the pedal does not drop after holding the pressure on the pedal for 30 seconds, the booster is airtight.

Inspect the Check Valve   Passed

1. Disconnect the vacuum hose where it connects to the intake manifold. Do not disconnect the vacuum line from the booster. Air should not flow when pressure is applied, but should flow when suction is applied. If air flows in both directions or there is no air flow, the valve needs to be replaced.

Verify Enough Vacuum  Passed

1. Check the operating vacuum pressure when the engine is at normal operating temperature. There should be a minimum of 18 in. of vacuum. Vacuum may be increased by properly tuning the engine, checking for vacuum leaks and blockages in vacuum lines

[mvusse]

I can only hear the hiss when I put my head under the dash.  But there is definitely a hiss when pedal is pressed. 

 

That does sound like a torn diaphragm. Like Hornbrod I swapped in a 96 booster. Got around the needed modification by swapping in the 96 pedal assembly along with it and splicing the 96 pedal switch harness into my 87 wiring.

[skidoo_j]

New booster in.   The guys at autozone agreed it was faulty.  They gave me a replacement with them just razing me a bit.   

 

With the new booster the behavior is as follows and it totally makes sense. 

 

Press brake-  Instant small increase in rpm

Hold brake-   no change

Release brake-  RPM Jump slightly for a few eye blinds

 

press hold brake turn off engine-  I can hold the pedal down, held for 20 seconds or so and decided it was good as prior booster was just shy of bucking me off. 

 

Start engine  shut engine off-   Get one good easy pump  and a second about twice as hard and the third is all manual.  

[HOrnbrod]

:thumbsup:   BTW, I tried your booster test, had never done it before. All went as it should. Thanks for posting that.   

[carnuck]

You can avoid modding the booster by grabbing the pedal from a newer XJ (95 up I think) That's what I did with mine.

[HOrnbrod]

91 and up XJ or MJ.

[carnuck]

'91 was the same as my MJ's old one.

[HOrnbrod]

So what? No 95/96 booster mods required using the 91 and up pedal assembly.

[onlyinajeep726]

Wasn't '91 kind of an odd year due to all the transitions?  I've seen XJ's at the junkyard with both style pedal assemblies.  I assume it was stock since they still had the single diaphragm booster...

[HOrnbrod]

The 91 and up booster itself was single diaphragm true, same as the earlier boosters. But the booster arm used was the same as the 95-96 dual diaphragm boosters. Which is why the 95-96 booster is a direct swap (with the spacer plate). Most of the oddities unique to the 91s were electrical, not mechanical, such as the one-of-a-kind firewall harness plug.

[onlyinajeep726]

Ah, well in that case lol.  I just know that both my XJ and MJ, I've done the '95/'96 XJ booster and the WJ booster and have retained the stock light switch with success.

[Comanche County]

Well, after years of consistent JY'ing, I finally found my second manual 4.0 XJ.  Going to pull an external slave AX15 from a 99 in a day or so....guess my point is that its tough to find a manual XJ or MJ on the cheap so modifying the rod is the easiest solution unless you get lucky and find a manual jeep.

[skidoo_j]

Well, after years of consistent JY'ing, I finally found my second manual 4.0 XJ.  Going to pull an external slave AX15 from a 99 in a day or so....guess my point is that its tough to find a manual XJ or MJ on the cheap so modifying the rod is the easiest solution unless you get lucky and find a manual jeep.

Same here.