New Humvee, ebrakes

Kirk · Post by **Kirk** » Wed Feb 28, 2007 9:04 am

Guys,
I just recently joined the ranks of the HMMWV crowd. I've had a MB for year but recently bought the HMMWV.
How does the packing brake work on a HMMWV? I mean if the caliper has a small seep, will the emergency brake still hold pressure?

Kirk

almonster · Post by **almonster** » Wed Feb 28, 2007 11:20 am

My M998 was built in 1988 so later or earlier versions may vary.

My ebrake caliper is a mechanical linkage via a cable that is tensioned so when the brake is on, it engages the caliper.

The caliper itself sits centerline with the rear diff.

I have noticed that there are issues with this implementation. For example, if I leave my HMMWV parked flat with the ebrake on and then I drive it and use it to park on a very slight incline and move the transmission to "N", the truck will slip because the calipers aren't fully engaged. I need to fix this but am not sure how since its the cable that is probably stretching just 1/300" or so.

However, if I leave my truck parked with the ebrake off and then park it on the very same incline, the eBrake engages properly.

Can anyone help dianose this? Right now, its garaged on a flat surface and I have wheel blocks front and rear of the wheel to keep the truck from moving.

Also, when parking should I always leave it in "D" to keep the tranny engaged to help keep it "parked" since I don't have a parking gear?

Note - some trucks also had the parking brake on the drive shaft. Crawl under and check yours. Another member M1025 had even a different setup than the 2 described.

Kirk · Post by **Kirk** » Wed Feb 28, 2007 11:44 am

I've inspected it. The system I have is the same as the one you described. The ebrake cable attaches to the ebrake housing on the rear axle, my question is what happens when you set the brake. Does a shaft engage the caliper manually( like pushes on the pad manually) or actuates the fluid in the caliper? My caliper is wet with brake fluid but not dripping, so I assume it has a very minute leak. Would this leak cause the parking brake to not be able to hold? I started by adjusting the Parking brake at the handle and then under the truck shortening the long shaft. It seemed to work for alittle bit and then loss pressure?

hummer4x4guy · Post by **hummer4x4guy** » Wed Feb 28, 2007 2:17 pm

Guys
If you are having issues with the parking brakes not holding tight enought you can adjust the length of the cable from the parking brake handle..
Turn the top (tip) of the parking brake handle clockwise and you will tighen up the pressure. Also it does not as far as I know use brake fluid pressure, so you can use it in an emergency situation if you have lost your hydraulics in the brakes you should be able to stop by pulling up on the brake handle..
Joel

dunsbr · Post by **dunsbr** » Wed Feb 28, 2007 3:16 pm

Hi Guys,

Heres a link to the an posting I did on the Hummer Knowledge Database
on adjusting the "old style" eBrake.

http://www.hummerknowledgebase.com/brakes/pba.html

If you follow the procedure to the letter you will get 3 to 6 months great holding out of the system.

Al, your problem sounds like a slightly warped or irregularly worn ebrake rotor. This means that on a hill the truck rolls back slightly till the pads grip the rotor. While on the flat, it doesn't roll back so you can push it forward and back a little till it grips (might be a a few inches)

Hope this helps

Cheers

Kurt Lesser · Post by **Kurt Lesser** » Wed Feb 28, 2007 7:01 pm

Kirk,

My '86 originally had the driveline E brake but whenever I adjusted it to hold the vehicle in the driveway ( ~ 5 degree slope) I burned the disc on the road.

I went ahead and installed the rear caliper brake upgrade (the dual pull barakes) along with the latching brake handle.

No brake issues now. I think this is one of the very best things to do to upgrade your truck. The latching handle adds a higher degree of safety no matter which E brake you run.

dunsbr · Post by **dunsbr** » Wed Feb 28, 2007 7:58 pm

Kurt Lesser wrote: I think this is one of the very best things to do to upgrade your truck. The latching handle adds a higher degree of safety no matter which E brake you run.

Having done the same last year, I have to say I agree with you Kurt

Cheers

Kirk · Post by **Kirk** » Thu Mar 01, 2007 10:13 am

The rear ebrake system I have is the same as the page on Rear Parking Brake Caliper Repair page on Hummer knowledge base. This seems to be a hydrolic system.. How do you adjust this if it's the parking handle and shaft have been tightened?

dunsbr · Post by **dunsbr** » Thu Mar 01, 2007 11:36 am

Hi Kirk,

If what you have is the same as in the TM extract in the Knowledge base, it is operated by cable and rod. It has no hydraulics.

Just follow the steps in the proceedure and it should adjust up OK

Cheers

Kurt Lesser · Post by **Kurt Lesser** » Sat Mar 03, 2007 11:44 am

Kirk,

The dual pull brakes that set the calipers for the E brake are adjusted by turning the knob on the top of the brake lever. There is a full proceedure for the driveline disc brake on the -20 manual.

nf6x · Post by **nf6x** » Sun Mar 04, 2007 5:25 pm

If you have the older driveline brake, then definitely follow the adjustment procedure in the TM to the letter. The knob on top of the parking brake lever can be used to adjust out minor wear, but there's another adjustment at the parking brake caliper that needs to be made first for the parking brake to work well.

While you're under the truck, inspect the parking brake disc and pads and replace them if necessary. Disassemble the caliper, clean all of the pieces thoroughly, and use some brake caliper grease on the pins and cams to keep everything operating smoothly without binding.

I have one of the locking parking brake levers that I plan to install before too long. Before the locking lever was introduced, there were plans in the back of one of the TMs to fabricate a chain to keep the lever from getting knocked out of position. I wouldn't mind upgrading to the newer parking brake system someday.

Kirk · Post by **Kirk** » Mon Mar 05, 2007 12:47 pm

I'm starting to learn something. I have the newer style, even though I have an '85, someone must of upgraded them. The manual that I read said that this ebrake adjusts only at the Handle, just like Kurt said? I've already adjusted it at the Handle and the rod under the humvee, taking up all the slack there. Is there anywhere else I can try to adjust? Assuming not does anyone care to guess the next course of action? Replace the ebrake?

emmado22 · Post by **emmado22** » Mon Mar 05, 2007 12:59 pm

MWO 9-2320-280-35-1 covered changing from the driveline to the "on the brake itself. ALL humvees were supposed to have this and the power steering cooler MWO done

nf6x · Post by **nf6x** » Mon Mar 05, 2007 1:03 pm

My 1986 HMMWV had the power steering cooler upgrade done, but not the parking brake or 3-point seatbelt upgrades. Clearly it was released before they got around to applying those latter two upgrades, but I don't know if it's typical of the USMC "Riverside Auto Auction" trucks.

emmado22 · Post by **emmado22** » Mon Mar 05, 2007 1:10 pm

Mine had the PS cooler and brake MWO's done when it was still with the USMC... Some units got arround to doing them, some didnt.. I did the 3 point seatbelt MWO and reinforcement for the Airdrop bumper done on mine..

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