89 Brake light switch and hardware

[Ecomike]

I must be loosing it. I have done the brake light switch on my 85 and 87 Xjs and the master cylinders (more than once), which are all working. I have also previously worked on the brake light switch on the 89, but I had an odd problem last time (unfortunetly I have forgotten the exact details), which I am now trying to resolve. Last time it seems I did an emergency fix-switch replacement (maybe 2 years ago now-?), and left out the old sleeve (if it was even there before?), and this time I bought a used set up from a member, with the sleeve, bushing (1-?), what was left of it, and the white plastic spacers, bolt, nut and lock nut.

I tried installing it per the haynes manual pictures, and also used my other jeep, 85 as a guide, but the sleeve diameter is too large to fit inside the master cylinder push rod, but is the right ID for the bolt and the right OD for switch. So I pulled out some tubing the right diameter to fit inside the MC push rod end, cut it to length same the one I bought used, and except for tiny bit of slop (but nothing like I had before), got it assembled, and it looked good, and right. Then I connected the electrical connections, and find the brake lights are now stick on all the time?

So I thought maybe Autozone screwed up, and dropped by the store, and checked and the push rod is not replaced when replacing the MC, and the HL switch I had was the right one or so it seems, as the part number and picture for 87 and 89 are the same.

Has any one else ever run into this before??????

This jeep was all stuck when we bought it, except for a cattle guard bumper, and mini Uhaul trailer hitch.

Also this one has the cruise control, so it has two, 2 wire connections on the brake switch, second one being for cruise control. The OD on the sleeve I got from the XJ is 9/16" OD, while the one I made for the smaller hole in the MCylinder push rod end is 1/2" OD, and fits the push rod perfectly. The 9/16" sleeve will not go into the push rod.

So I have 2 or 3 problems here. One is the hole size, one is the sleeve, the other is that even with the smaller sleeve, the brake switch is pushed on hard enough to be on all the time!!!!! So something very odd is going on with the push rod on this beast???? :smsoap:

I can't figure out how it ever worked before. When I started on it again this week, there was no sleeve at all. just the bolt and too much slop, but it some how worked for a year or more, and got through inspections until I knocked off center fiddling with the ECU connections due to a no start-CPS problem, which is now (knock on wood), fixed. When I discovered the brake lights were out, I reset it, but re-noticed the slop, and decided to go back and try to fix it right.

But now I am really scratching my head. The used parts off the other XJ I got in has a sleeve that fits the AZone switch, and the bolt, so I suspect they not the problem, but 100% sure. The MC rod seems to be too long on the outer end, and even with the custom, smaller sleeve I made and tried, thew push rod is too large on the far side and activates the brake light switch all the time.

HELP?????? Ideas, how did this odd push rod get into what looks like a normal stock 2WD jeep non modded jeep?

 

[Ecomike]

I just looked at the parts catalog, I forgot the Vacuum booster is in between the MC and push rod I am dealing with, so now I am trying to remember if the push rod comes with the vacuum brake booster, or if it is reused when the brake booster is replaced?

Note: This on does not have ABS, and has no signs of ever having ABS that I can see.

Edit: Autozone shows the rod as being part of the vacuum booster, so now I am wondering what the pedigree is on the Vacuum booster that came with 89 when I bought it 4 years ago. I think it is the only one I have not replaced.

 

[Ecomike]

Hmm, seems the brake booster for an 87 and 89 have different part numbers for a Cherokee at Azone. I called and checked and it seems the brake booster on this 89 came with the jeep when I bought it a little over 3 years ago.

89 is 54-74071

87 is 54-74040

But my 89 is a 2 WD, and the 87 is 4WD.

and my 85, that had a 2.5 L, 4banger gas, uses the same one as the 87.

So now I am wonder what the difference was between 87 and 89?

 

[joe_peters]

Hmm, seems the brake booster for an 87 and 89 have different part numbers for a Cherokee at Azone. I called and checked and it seems the brake booster on this 89 came with the jeep when I bought it a little over 3 years ago.

89 is 54-74071

87 is 54-74040

But my 89 is a 2 WD, and the 87 is 4WD.

and my 85, that had a 2.5 L, 4banger gas, uses the same one as the 87.

So now I am wonder what the difference was between 87 and 89?

About 2 years?

My 87-90 catalog only shows one booster for all four years, but different MCs 87-89 and 90.

If you need I can take pictures of my 90 switch setup if that would be any help.

 

[Ecomike]

I doubt it will be much help, but it might be interesting?

My 87 is at my shop. I will get a look at it sometime this week.

I also found something odd about the bushings in the parts drawing, it showed 2 bushings, and the used care package I got recently off another jeep only had one bushing (as pulled of that jeep), and it did not fit the switch or the sleeves I have, and was nearly worn out, very thin on top of it.

I will look at my MCs again, they are very similar, if not the same on the 87 and 89, and the 85 is close to the same.

I know a lot of guys here have upgraded theirs to improve the brakes, so there should be some people posting up about swaps and what they learned in the process that I hope will help get me some clues.

I should add that the current 89 booster does not look 21 years old, maybe 3-5 at best, but Autozone records do not show me replacing this one yet, just the 87 and 85 boosters.

 

[Ecomike]

I finally had to swap out the brake booster, vacuum leak, and here is the side by side to complete the story here:

 

[Ecomike]

On the right side is the old one I pulled (came with the jeep), and on the left is the correct one, a new one being installed.

All I can figure is PO swapped in the wrong one and then used an undersized dia bolt to fit the smaller the hole, and thus the source of the brake light switch sticking problems. Now I need to find the OEM bolt, nuts and sleeves.

 

[djgrayxj]

Note from DJ
NAPA Auto Parts agrees with Joe

NAPA 89 Cherokee:
89 Power Brake Booster w/o Master Cylinder
Part Number: NBB 5474071

89 Brake Master Cylinder – New
Part Number: NMC M2960
Buyer’s guide information is for Jeep Cherokee 1984-1989
Brake Master Cylinder Bore Size : .9375"
Brake Master Cylinder Line Thread Size : 7/16"-24, 1/2"-20
----------------------------
NAPA 90 Cherokee:
90 Power Brake Booster w/o Master Cylinder
Part Number: NBB 5474071

90 Brake Master Cylinder – New
Part Number: NMC M3107
Buyer’s guide information is for Jeep Cherokee 1990-1994
Brake Master Cylinder Bore Size : .9375"
Brake Master Cylinder Line Thread Size : 7/16"-24, 1/2"-20

 

[Ecomike]

Found the spare parts i acquired back when I stared this thread 2 years ago, and installed them, the OEM bolt, sleeve and bushings. Got it done, finally!!

Does anyone know how much brake peddle movement it should take to activate the brake lights (and the brakes), in other words how much slop is normal on a new brake peddle system before the brakes start to grab and the light switch trips? I am getting a good 1" on 2 of mine, which makes me wonder if I should extend the bolt on the MC side of the new brake boosters. I used the same settings that were on the old ones. Now I am wondering if they were short a little.