Broken brakes (1 Viewer)

[jblueridge]

When I apply the brakes it feels like sonething is binding or blocking and preventing full braking power. If I push harder, I get through that zone and the brakes work almost correctly.
When I force the pedal through whatever it is, I hear a clunk or thump, seemingly from the booster or MC.

By skidding on a dirt road today I established that the rear brakes wont lock even on gravel. I also found that sometmes the brakes pull the truck to the left.

I hope to get some time tomorrow to play around some more. I plan to clamp off the rear brake hose to see the effects.

The booster and MC are from a 1990 80 series. These were rebuilt by brake specialists here in VA. Lifetime warranty doesn't seem so great now. It took 5 weeks for them to do the work the first time.

Any advice?

 

[roscoFJ73]

I found with the rear drum models, getting the rears adjusted as best as possible takes a big load off the front.
I kept the original MC and booster and was quite happy with the brakes. I sometimes feel these booster and MC upgrades are only covering a hidden problem and if you can work out what it is, the upgrade is not needed.

 

[Bob Richards]

I went back to my original booster once I fiixed my vacuum pump and am very happy with it now. I had the adjustment of front to rear braking done professionally and even though I did not like to pay that bill I am happy with the results.

 

[jblueridge]

I had the adjustment of front to rear braking done professionally

Does that mean you deleted your LSPV from the back axle?

 

[Bob Richards]

Nope, I had them adjust it

 

[ALEXY]

[QUOTE="jblueridge, I also found that sometmes the brakes pull the truck to the left.
Any advice?[/QUOTE]

I m challenged by how my brakes feel (hard pedal but not very good braking) and I thought they pull to the right. It came out that there was play on the steering joint , first one that connects to the steering box arm. Might not be your case, but worth considering. eventually I put my truck on mot stand and they said it brakes within limit.

 

[jblueridge]

Alexy, thanks. I will check steering.

 

[jblueridge]

I took the rear drums off and looked around. Nothing interesting. Cleaned out the dust.
I adjusted the shoes after re-fitting drums. I think they were pretty well adjusted before I took them apart.
I am fabbing a bracket to allow for another vac reservoir container.
New LSPV arriving soon.

 

[ALEXY]

what happened with the new lspv?
how did you adjust it?

 

[tornio]

"I also found that sometmes the brakes pull the truck to the left."


Any advice?[/QUOTE]

Good mornig , based on my experience (on j4 but j7 isn't so different) this problem has nothing related to steering box or bad tie rods : if your toy goes straight on paved road even with a lot of steering "free play" when you brake the toy has to brake straight.

I fighted one year to make my toy brake right and straight! (i won my battle with the helps of the forum !) my steering box is more than bad , my steering wheel has a frightening half turn of freeplay but the toy goes straight (paved road) and brakes straight!!

front disk and rear drum i suppose you have , so :

front disk brakes right ? yes ? (check on sand or mud road )

if braking push the toy to one direction you can bet that the rear opposite wheel isn't braking

causes : not correct shoes adjust / a stuck cylinder / air

don't underestimate shoes adjust that if done badly can cause a lot of problems... dont ask me why i know !!! hi

hope it helps

cheers

 

[jblueridge]

Thanks Tornio!
I checked the rear drum brakes a few days ago.
I think they were correct but I re-adjusted them anyway.

I have installed a new LSPV and I will adjust that later this week.

 

[tornio]

Thanks Tornio!
I checked the rear drum brakes a few days ago.
I think they were correct but I re-adjusted them anyway.

I have installed a new LSPV and I will adjust that later this week.
View attachment 1456454

...maybe you still have some air in the rear part of braking circuit... it can be a pain purge the circuit many many time but is mandatory!!
start from the rear wheel opposite the brake pump then the other wheel and then the lspv.

a word on adjusting the shoes : in the begginning i thought that the drum should run free (shoes very close to the drum) but i was wrong
i solved my brake problem only when the shoes made a contact with the drum , wheel ligtly stuck (i was able to turn it by hand but with a light effort).

good luck

 

[jblueridge]

I use a home-made pressure bleeder for my brakes.

Brake shoe adjustment is more likely to be the cause of problems.

 

[tornio]

...probally... also check the cylinder.

good luck

 

[Eric Winkworth]

I know my load sensing proportioning valve is the roughest part of my entire system. sounds like ur drums need a good inspection

 

[jblueridge]

I had some time earlier today so I put most everything back together.
I now have a used 80 series booster, new 80 series MC, new LSPV, and a 2nd vacuum reservoir for brakes.
I adjusted the rear drums and made them maybe one click "tighter" than I normally would.
Things feel much better and I stop easily.
I will try to adjust the LSPV some tomorrow.
Pics later.

 

[jblueridge]

Just to wrap[ this up...
I bought this funky vacuum reservoir off ebay.

I modified the bracket.

I mounted it in the engine bay under the air cleaner.

I put in a tee for the vacuum hoses just before the lines enter the vac pump.
This plastic tee has a check valve in it.

I thought I would be doubling my vacuum reserve but that's not how it worked out in practice.