Severe Brake Fade (1 Viewer)

[OTEP]

I drive an 80 with the front disc and rear drum brake set up. Mild suspension lift and 285 rubber. Other than the TJM bullbar, its basically a stock truck.

After repeated hard stops, my pedal goes spongy and there is a loss of braking power despite flooring the brake pedal. Even during the regular commute home (on mostly flat terrain), the brakes seem to be hotter than normal compared to my other vehicles (the Patrol GU and my ambulance). I tried squirting some water and it instantly turned to steam on contact with the brakes.

When I allow the brakes to cool, braking power and pedal firmness returns.

What could be causing the problem?

I use Bendix Metal King pads up front. I recently had the rear brake shoes replaced with Alba brand stuff. But the brake fade problem was already present prior to this. I also had the rubber gaskets of the right rear wheel brake cylinder replaced with Seiken brand stuff as there was a leak.

However the problem still persists.

After the new shoes were put in and we did some hard stops, I noticed that there was a smell of brake friction material on the left drum brake but not on the right. So could the repair of the right wheel cylinder leak be bad? Also the brake technician couldn't get the parking brake adjusted properly. You need to pull the parking brake lever real high to get it to hold the vehicle while parked.

Should I be looking at the rear load sensing valve also? I'm starting to think that the rear brakes might not be providing enough braking power causing the fronts to overheat.

Inputs are greatly appreciated. Not letting the other family members use the 80 until I sort this out. Thanks.

 

[blkprj80]

How old is the brake fluid? Have you flushed it?

 

[OTEP]

Flushed and replaced a few months ago when the brake master and hydrovac were replaced a few months back as we thought it was causing the spongy brakes.

 

[Qball]

3 things I would suggest:

1. Look into Hawks performance LTS or heavy duty pads
Hawks pads don't fad like factory pads, they like heat and performance is better when they are warmed up.

2. lower the LSPV down an inch
Lower the LSPV will increase rear brake bias or power

3. exercise ABS
Exercise your ABS a dozen or so times should get most of the air out of ABS lines


Those three things helped my brakes a lot.

 

[OTEP]

I don't have ABS. Sorry I missed out on that detail. Will upgrading to slotted rotors help?

Hawk pads arent readily available here. But I will try to source them.

Am i understanding the lspv mod right? Or should I just raise the axle end of the lspv. Sounds easier to do than moving the actual lspv? Most lifted trucks include a longer bracket to lift that end of the lspv.

 

[IronCladLou]

I haven't seen this specifically on Cruisers, but sometimes old brake lines will swell (on the inside) with age. The swelling isn't necessarily visible via visual inspection but can be enough it actually constrict the flow inside the line. What happens then is that the brake pedal force is plenty high enough to force the fluid through and apply the brakes, but it acts like a check valve that keeps some pressure on the pads and so they drag and produce a bunch of heat.

It's a long shot, but if you haven't replaced your stock rubber brake lines it would be something easy to try.

 

[VETTE60]

i would bet it is the LPSV. prolly only the front brakes working.I removed mine along with the ABS ( but I now have a different drivetrain and part time case and the ABS only worked in 4x4 when you dont want it) and like my cruiser much better now.

 

[OTEP]

How about the parking brake adjustment? New rear brake shoes yet the lever pull is still very high. Any tips on this?

 

[Qball]

I don't have ABS. Sorry I missed out on that detail. Will upgrading to slotted rotors help?

Hawk pads arent readily available here. But I will try to source them.

Am i understanding the lspv mod right? Or should I just raise the axle end of the lspv. Sounds easier to do than moving the actual lspv? Most lifted trucks include a longer bracket to lift that end of the lspv.

Hawk pads can be had from amazon or eBay, about 80 for the front.

If you don't have abs then you have a lot less places for bubble to be trapped.

Lower the lspv is easy if yours is not rusted in. Loosen the 2 bolts and then pull the whole thing down and tighten, 5 minutes hub at best.....if yours is rest free.

Quick search in mud should get you instruction with pictures.

One day I will get off my ass to replace the rear pads with haws lts pads sitting in my garage, I am very happy with them and even with them on the front only it still gave me a huge upgrade in braking performance!

 

[jonheld]

Also the brake technician couldn't get the parking brake adjusted properly. You need to pull the parking brake lever real high to get it to hold the vehicle while parked.

None of the suggestions made will fix your issue unless the mechanical adjustment of the rear brakes is correct first.
It sounds like there is a problem with the rear brakes and their adjusters. If the handbrake is not working properly then this could be the root cause of your brake problems.
Rear drum brakes keep their adjustment with the use of the handbrake. If the "technician" couldn't get the handbrake to work properly, then the rear shoes are out of adjustment and essentially you have no rear brakes. The handbrake should pull up 5-7 clicks max.

Drum brakes are pretty low tech and very straight forward. If this guy couldn't figure them out then it's time to find another mechanic.

 

[86tuning]

Fix the rear brakes. A problem with the rear brakes will over work the front brakes and cause excessive nose dive when braking, and all the other symptoms you describe.

Handbrake that doesn't work is a result of your rear brake problem, not the cause.

Check/replace brake cables, adjusters, shoes, drums, hydraulics, whatever it takes. Any qualified technician will be able to diagnose and repair your brakes.

The tech that worked on it may simply need more repair time, or may need to replace parts. If he's really having 'problems adjusting your park brake' then you may need to replace the tech with another one.

Is your truck lifted? If so, an adjustment of your proportioning valve is required. A lifted truck throws the calibration of the LSPV (load-sensing proportioning valve) out of whack because it relies on the rear suspension height to determine the brake proportioning. Raise the static suspension height without re calibrating the valve will also net you the results that you're experiencing.

 

[OTEP]

Thanks for the advice. Went to my usual veteran mechanic today. Adjusted the shoes. Checked the parking brake system. Found a minor ebrake cable issue inside the drums (improper reassembly). No leak in the wheel cylinders. But some diff juice was leaking on the end of the passenger side axle. How easy is this to fix?

Handbrake lever was adjusted from the cabin adjustment on the lever itself. Now at 5 clicks. Also did the lspv adjustment. Lowered it 1/4 inch.

Also checked the bendix metal king front pads and they are worn. Will be putting in Bendix heavy duty pads due to arrive in a day or two. Still going to try the Hawks but shipping time might be a bit long so Im getting the Bendix units first.

Brakes feel better now. But will try it at speed in a safe area soon. The rubber hoses are also on order. Getting longer ones in case I decide to do a 3-4 in lift.

 

[kidglove13]

I use to have really bad brake fade especially offroad

Now that you have the rear drums and brakes adjusted properly it will help but I found that the biggest change in performance was replacing all the braking systems soft lines

It was like night a day difference

My 94 has the same set up discs front drums rear I rebuilt my entire brake system a couple of years back

Remember that the key to keeping the rear drum brakes consistently adjusted is that you must use the ebrake on a regular basis because that is what adjusts your brake shoes in the rear as they wear

 

[jonheld]

Handbrake lever was adjusted from the cabin adjustment on the lever itself.

NO NO NO NO. Adjusting the handbrake cable DOES NOT adjust the shoes correctly. There are shoe adjusters that look like a large threaded bolt with a knurled knob that set the static position of the shoes. These adjusters need to be set correctly when the drums are put back on. There are is a slot on the back of each backing plate toward the top that you are supposed to use to make this adjustment. It is done simply with a flatblade screwdriver.
HOWEVER you need to make sure that the adjusters themselves are free to turn, clean and lubricated during assembly.

Regular use of the handbrake AFTER YOU MANUALLY SET THE SHOES CORRECTLY WHEN THE DRUMS GET PUT BACK ON will keep the shoes adjusted correctly during their lifespan.

This stuff is 1960s technology and is 90% mechanical.

 

[OTEP]

We adjusted the shoes first before the ebrake handle. Previous owner seemed to have had interior work done on the vehicle and prolly messed up the lever adjuster thinking it has to be loosened to remove the handle.

Enrake now holds the vehicle in neutral on hills.

 

[86tuning]

What John said, there should be a tiny bit of freeplay in the handbrake cable when it's in the released position. Otherwise the self adjusting mechanism in the rear drums cannot function.

But your regular veteran tech should know that. I've not looked under a drum-equipped 80 before, but cable freeplay is usually easy to inspect.

 

[86tuning]

And axle oil on rear brakes will lubricate it, obviously the exact opposite of what brakes need. Thankfully rear seals aren't a huge nightmare of a repair unless the axle is bent on the semifloating stuff. Then you need to replace an axle to properly repair it

 

[OTEP]

Funny how the newer techs stare in awe when they see drum brakes. The same look they have upon seeing carbs and distributors.

 

[jvazquez53]

Bleed, Bleed, Bleed! Get a one man bleeder, they are cheap at the parts stores. I had a similar problem and after a good bleeding, problem solved.