A BJ40 in Costa Rica - RTV Issues (1 Viewer)

Joined
Jun 7, 2019
Messages
6
Location
Costa Rica
G'Day,

Sorry if this has been posted before and sorry for the long winded story to come. I am having an issue with my left rear brake. As you can see from the subject, its a 79 BJ and for those who dont live in Costa Rica, RTV or Retieve is the annual vehicle corruption...err, inspection.

So a couple years back, engine goes tits and I get it rebuilt. In the process I request other things to be sorted out, specifically a brake flush (I had the clutch, fly wheel, and throw out bearing replaced as well and they didn't flush the clutch). Anyways, the "mechanic" says I need new parts for the brake in question despite having them maintained (all rebuilt pistons) about 4 weeks earlier. I don't have flip flops on the ground to monitor the process so I take their word for it: mistake on my part. Anyhoo, three months go by and I get my beloved back. They had taken it out for about a 40km test run to make sure there were no issues with the rebuild, to which there wasn't (thankfully seeing the block wasn't machined correctly and the crank didn't rotate on the first go around). With that, my daughter and I pick up the battle cruiser and make our way around town getting things done. As I am passing the shop I look over and think "thank f*** I wont be going their again" and BAM the god damn wheel goes flying down the road, damn truck skids to a stop. Tire bounces across the median and two lanes of traffic only being stopped by a fence. Awesome, thankfully it HAPPENED RIGHT IN FRONT OF THE GARAGE I JUST PICKED UP THE TRUCK FROM! My daughter, calmly, looking at me from a height advantage asks "did the tire just come off", "yep", "that tire?" as it bounces down the road. I just look at her and say get out. As I am storming down the road to the garage, two lackeys pop out, see me and sprint to the tire. In process the owner sees me and continues to talk on his phone and ignoring me, yelling at him. So end state, the truck is sitting on the now scored drum, I have no lug nuts (I found one when i was walking back to the bar for a "cool me down" rum), and no patients for BS.

Fast forward to my first RTV with the battle cruiser and I fail. The fail came from that brake and it is because it doesnt brake at the same pressure as the right rear. Now, I adjusted the brakes and no dice. I was thinking maybe the proportion valve however there is one glaring issues: the bottom shoe is not the same as the other shoes on the truck. This shoe is identical in looks however it is missing the centre hole for the retaining pin. Now my physics brain is trying to picture the piston actuating but because there isnt a force (the pin) acting on it, then the pistons efforts negate itself.

So, has anyone run into this brake issue? Sorry, I do not have pics at the moment as the truck is in the process of having the wheels bearings and rear dif rebuilt.

Thanks
 

JohnnyC

Long ago TLCA# 2231
Joined
Jun 17, 2005
Messages
17,027
Location
UpState Ny, Wells Me
Never had that issue ... how do they test the pressures? Metering the outward shoe pressure? Metering the resistance of tire rotation?

I had never had that problem in the states and I had once or twice got tested with a 1/2 frozen caliper and still passed :meh:
 
Joined
Jun 7, 2019
Messages
6
Location
Costa Rica
In CR they use a type of dyno. The vehicle rolls into a cradle so the vehicle can be left in neutral while running. The cradle is run up to say 30km/h and the brakes are applied. The feed back from the wheels stopping is then registered to see the stopping power. There is a threshold for the wheels, anything outside that threshold is a fail. I'm not 100% on numbers. Anyways, I keep failing. Attached is the brakes. The odd ball show without the retaining pin is the left and the other is right. I just noticed today that shoes arent seated correctly either (right). Would this result in too much pressure on the right side?

20200721_093127.jpg


20200721_093332.jpg
 

JohnnyC

Long ago TLCA# 2231
Joined
Jun 17, 2005
Messages
17,027
Location
UpState Ny, Wells Me
Have you turned the drums? Most people do not and it will effect the amount of braking

Did you try giving the one side one or two clicks more and retest it?
 
Joined
Nov 8, 2018
Messages
63
Location
France
hi,
for me different points must be checked:
identify the precise assembly of each shoe ( top/down )
then remove them
open the 4 wheel cylinder and control the seals inside ( no rust inside and no seal sticked , and also presence of the inside spring )
on your picture two outside seals must be changed , one with rip , one other not in place
check also the system of ajustment on each cylinder ( no rust and adjustment easy)
put a few of special grease between the 4 contact point shoe / brake cylinder
make a hole inside the shoe and put in place the system where there is missing tack
reverse one of the long spring , normaly one spring behind the shoe , one spring in front of the shoe

reassemble the assembly and adjust , several times may be necessary for a good adjustment and after drive 200 km ( running in )

other important detail:
The active part of each shoe must be have a double -edged with an identical taper on both sides.
 
Last edited:

John McVicker

SILVER Star
Joined
Jul 11, 2005
Messages
3,372
Location
Big Pine, CA
As @vikor said...you have no brake action on this wheel. The cylinder on the left has a rip, so no pressure for sure. Can’t tell on the one on the right. And you are missing the retaining spring that is supposed to be on each of the rubber cups. And agree...one spring is supposed to be on the inside and one on the outside.

Get the FSM, look at the pictures...easy enough to figure it out. Best to do this yourself and not have to trust a ‘mechanic’.
 
Joined
May 16, 2008
Messages
1,496
Hello,

Maybe I am stating the obvious here.

That brake machine measures each side's braking. Then compares both numbers to get a difference. The intended purpose is to spot a faulty cylinder or a worn shoe. However, often the operators tamper with the machine to produce artificially high differences that will result in a fail. Then they "suggest" a "proper repair" with a "qualified shop" which pays them for every car they send in.

A way to pass is usually replacing the cylinders. Sometimes it is necessary to replace the shoes as well. You never know how bad the tampering is.

How old are the cylinders? How old are the brake shoes?

You may want to replace the cylinders, have the brake system properly purged and then try the inspection.

It is wise to do this step by step, either with the FSM at hand, or with a mechanic you really trust.

Hope this helps.





Juan
 
Joined
Jun 7, 2019
Messages
6
Location
Costa Rica
Well I suck at responding.

So, I passed the damn RTV (inspection) and have been driving the pig like it owes me money. The front was acting up this time but the rear numbers matched one another. To that end, thank you all for the suggestions. As it stands, the fix for this whole mess was putting a retaining pin in the shoe so that physics could do its job. The tear in the dust boot for the one cylinder is just that and doesn't compromise the operation of the cylinder (for now) as the o-rings are still intact.

Again, thanks for all the info.
 

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