- الفرامل الخلفية في سيارتي ضعيفة ولا تفرمل وأحيانا تفرمل.
- هل المشكلة في صمام استشعار الحمل النسبي أم أنه يحتاج إلى وزن فقط؟
- كيف أزنها؟
1991 LC70 PZJ77 (Load sensing for rear brake) (1 Viewer)
- Thread starter Abde
- Start date
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- الفرامل الخلفية في سيارتي ضعيفة ولا تفرمل وأحيانا تفرمل.
- هل المشكلة في صمام استشعار الحمل النسبي أم أنه يحتاج إلى وزن فقط؟
- كيف أزنها؟
- Thread starter
- #2
The rear brakes in my car are weak and do not brake, and sometimes they brake.
-Is the problem with theload sensing proportional valve or does it only need a weight?
- How do I weigh it?
Hi
Brakes must not be corrected with weight. The vehicle must brake properly loaded and unloaded.
First of all: Brakes are all about safety. If you are not familiar with brake jobs, get somebody who has that knowledge to assist.
My suggestion:
- I assume, you did not recently install a lift (changing the distance between axle and body)? A lift requires respective adjustment of the LSPV actuator lever. Sometimes people forget this, causing the rear brakes to basically do nothing.
- Check your rear brakes. Drums, I guess? Take off wheels and drums, check brake cylinder and shoes, -
(!) Adjust brakes properly.
Make sure everything is in good order. Go by the workshop manual.
- Bleed your brakes. Thoroughly. Suck throug at least 150ml, on LSPV (it has a bleeder on it) and per wheel. (Eazibleed or any other bleeding device is a good investment).Make sure you have a firm pedal feeling.
If the issue persists, check the LSPV in more detail:
(Going by your pic: It shows the adjusting mechanism. The LSPV is actually at the other end of that spring arm, at the frame)
Do below test sequence in close timeline.
- Undo the actuator arm from the axle and tie it upwards to the body (mild pressure on the LSPV, but do not bend the arm). This should fully open the LSPV (max braking power to the back). Check function. (CAUTION! This is for testing only. On braking at higher speeds, your rear brakes may lock, causing the back to get out of control (it is the job of an LSPV to prevent this!))
If the issue persists, your LSPV has a more serious issue. Mostly, the actuator pin under the rubber boot is seized.
If you get good brakes in the back now: Well, it works the one direction, but not necessarily the other...
- Now tie the arm down to the axle; more than it would usuall be in its original position. This should shut the LSPV: Almost no braking power to the back now. (CAUTION (obviously)). Check immediately. If it still brakes in the back, at least on 2nd try, your LSPV is seized.
(Braking actually pushes the LSPV back to open, if the actuator arm is not providing resistance, like now, as tied way down)
If in dought, I recommend to check the LSPV actuator pin anyways:
- Remove the rubber boot on the LSPV. (Be warned. It can be put back on with the LSPV in place,but it is a PITA)
- Lower the actuator arm or remove it. Clean the area around the pin thoroughly. Check the actuator pin to move freely. It should be possible to push it up into the LSPV quite easily. (Travel is very little, just about 2-3mm) Ideally, it would also come back out automatically, but latest at a slight tip on the brake pedal (so it gets a bit of brake pressur from the back). Apply penetrating oil and a mild brush to remove grime. Apply a bit of brake fluid for lubrication. Move the pin up and down to free it up, by pressing it in and pushing it out with brake pressure. Do not grab the pin with pliers! It is brass and the surface may get scratched by pliers.
- Once free: Put a bit of grease and reinstall the boot. Make sure the boot is not damaged and seated properly.
- You need to adjust the LSPV now !! No, it can't be done by eyeballing or measuring; 1-2mm on the arm / 1 turn of the adjusting nut on the axle makes a lot of difference.
How to adjust the LSPV is described here:
forum.ih8mud.com
I posted a few more threats on the LSPV. You may want to check my posts, using the search function: Keyword "LSPV" & my username "Felde".
Good luck, be safe.
Ralf
Brakes must not be corrected with weight. The vehicle must brake properly loaded and unloaded.
First of all: Brakes are all about safety. If you are not familiar with brake jobs, get somebody who has that knowledge to assist.
My suggestion:
- I assume, you did not recently install a lift (changing the distance between axle and body)? A lift requires respective adjustment of the LSPV actuator lever. Sometimes people forget this, causing the rear brakes to basically do nothing.
- Check your rear brakes. Drums, I guess? Take off wheels and drums, check brake cylinder and shoes, -
(!) Adjust brakes properly.
Make sure everything is in good order. Go by the workshop manual.
- Bleed your brakes. Thoroughly. Suck throug at least 150ml, on LSPV (it has a bleeder on it) and per wheel. (Eazibleed or any other bleeding device is a good investment).Make sure you have a firm pedal feeling.
If the issue persists, check the LSPV in more detail:
(Going by your pic: It shows the adjusting mechanism. The LSPV is actually at the other end of that spring arm, at the frame)
Do below test sequence in close timeline.
- Undo the actuator arm from the axle and tie it upwards to the body (mild pressure on the LSPV, but do not bend the arm). This should fully open the LSPV (max braking power to the back). Check function. (CAUTION! This is for testing only. On braking at higher speeds, your rear brakes may lock, causing the back to get out of control (it is the job of an LSPV to prevent this!))
If the issue persists, your LSPV has a more serious issue. Mostly, the actuator pin under the rubber boot is seized.
If you get good brakes in the back now: Well, it works the one direction, but not necessarily the other...
- Now tie the arm down to the axle; more than it would usuall be in its original position. This should shut the LSPV: Almost no braking power to the back now. (CAUTION (obviously)). Check immediately. If it still brakes in the back, at least on 2nd try, your LSPV is seized.
(Braking actually pushes the LSPV back to open, if the actuator arm is not providing resistance, like now, as tied way down)
If in dought, I recommend to check the LSPV actuator pin anyways:
- Remove the rubber boot on the LSPV. (Be warned. It can be put back on with the LSPV in place,but it is a PITA)
- Lower the actuator arm or remove it. Clean the area around the pin thoroughly. Check the actuator pin to move freely. It should be possible to push it up into the LSPV quite easily. (Travel is very little, just about 2-3mm) Ideally, it would also come back out automatically, but latest at a slight tip on the brake pedal (so it gets a bit of brake pressur from the back). Apply penetrating oil and a mild brush to remove grime. Apply a bit of brake fluid for lubrication. Move the pin up and down to free it up, by pressing it in and pushing it out with brake pressure. Do not grab the pin with pliers! It is brass and the surface may get scratched by pliers.
- Once free: Put a bit of grease and reinstall the boot. Make sure the boot is not damaged and seated properly.
- You need to adjust the LSPV now !! No, it can't be done by eyeballing or measuring; 1-2mm on the arm / 1 turn of the adjusting nut on the axle makes a lot of difference.
How to adjust the LSPV is described here:
What did you do on your 70 series today?
Those look great! They are so much comfier than the factory seats too, granted the drivers side one had seen better days
forum.ih8mud.com
I posted a few more threats on the LSPV. You may want to check my posts, using the search function: Keyword "LSPV" & my username "Felde".
Good luck, be safe.
Ralf
- Thread starter
- #4
Very happy with your answer.Hi
Brakes must not be corrected with weight. The vehicle must brake properly loaded and unloaded.
First of all: Brakes are all about safety. If you are not familiar with brake jobs, get somebody who has that knowledge to assist.
My suggestion:
- I assume, you did not recently install a lift (changing the distance between axle and body)? A lift requires respective adjustment of the LSPV actuator lever. Sometimes people forget this, causing the rear brakes to basically do nothing.
- Check your rear brakes. Drums, I guess? Take off wheels and drums, check brake cylinder and shoes, -
(!) Adjust brakes properly.
Make sure everything is in good order. Go by the workshop manual.
- Bleed your brakes. Thoroughly. Suck throug at least 150ml, on LSPV (it has a bleeder on it) and per wheel. (Eazibleed or any other bleeding device is a good investment).Make sure you have a firm pedal feeling.
If the issue persists, check the LSPV in more detail:
(Going by your pic: It shows the adjusting mechanism. The LSPV is actually at the other end of that spring arm, at the frame)
Do below test sequence in close timeline.
- Undo the actuator arm from the axle and tie it upwards to the body (mild pressure on the LSPV, but do not bend the arm). This should fully open the LSPV (max braking power to the back). Check function. (CAUTION! This is for testing only. On braking at higher speeds, your rear brakes may lock, causing the back to get out of control (it is the job of an LSPV to prevent this!))
If the issue persists, your LSPV has a more serious issue. Mostly, the actuator pin under the rubber boot is seized.
If you get good brakes in the back now: Well, it works the one direction, but not necessarily the other...
- Now tie the arm down to the axle; more than it would usuall be in its original position. This should shut the LSPV: Almost no braking power to the back now. (CAUTION (obviously)). Check immediately. If it still brakes in the back, at least on 2nd try, your LSPV is seized.
(Braking actually pushes the LSPV back to open, if the actuator arm is not providing resistance, like now, as tied way down)
If in dought, I recommend to check the LSPV actuator pin anyways:
- Remove the rubber boot on the LSPV. (Be warned. It can be put back on with the LSPV in place,but it is a PITA)
- Lower the actuator arm or remove it. Clean the area around the pin thoroughly. Check the actuator pin to move freely. It should be possible to push it up into the LSPV quite easily. (Travel is very little, just about 2-3mm) Ideally, it would also come back out automatically, but latest at a slight tip on the brake pedal (so it gets a bit of brake pressur from the back). Apply penetrating oil and a mild brush to remove grime. Apply a bit of brake fluid for lubrication. Move the pin up and down to free it up, by pressing it in and pushing it out with brake pressure. Do not grab the pin with pliers! It is brass and the surface may get scratched by pliers.
- Once free: Put a bit of grease and reinstall the boot. Make sure the boot is not damaged and seated properly.
- You need to adjust the LSPV now !! No, it can't be done by eyeballing or measuring; 1-2mm on the arm / 1 turn of the adjusting nut on the axle makes a lot of difference.
How to adjust the LSPV is described here:
What did you do on your 70 series today?
Those look great! They are so much comfier than the factory seats too, granted the drivers side one had seen better days
I posted a few more threats on the LSPV. You may want to check my posts, using the search function: Keyword "LSPV" & my username "Felde".
Good luck, be safe.
Ralf
Thank you Ralf for this beautiful answer and your concern for the safety of others.
- Thread starter
- #5
Yes. That's the LSPV.
Note the bleeder on it.
The actuator pin is under the rubber boot.
Clip to remove the boot from the LSPV, bolt to remove the actuator lever.
The mentioned checks can be done by only detaching the other end of the arm from the axle. No need to temper with this for the checks.
Your LSPV actually looks good - from outside.
Check & maintain the brakes first and bleed the system.
Unless the truck hasn't been sitting unused for long, I'd rather suspect the brakes itself to be the problem.
Good Luck Ralf
Note the bleeder on it.
The actuator pin is under the rubber boot.
Clip to remove the boot from the LSPV, bolt to remove the actuator lever.
The mentioned checks can be done by only detaching the other end of the arm from the axle. No need to temper with this for the checks.
Your LSPV actually looks good - from outside.
Check & maintain the brakes first and bleed the system.
Unless the truck hasn't been sitting unused for long, I'd rather suspect the brakes itself to be the problem.
Good Luck Ralf
- Thread starter
- #7
- Brother, thanks are not enough for someone like you.
- I am grateful to you and happy for your help.
By the way, I changed the brake pads about a year ago.
- I will change the brake fluid soon, but I did not check the brake cylinder, which is the remaining part of the system.
- I did not check if the brake cylinder is the problem.
- How do I know if the problem is from it?
- The truck is not stopped.
Check for leaks and the pistons to move free and easy side to side, by moving by hand.
Make sure assembly is all correct, auto-adjuster (actuated by handbrake) works properly and brakes are adjusted properly.
Go by workshop manual.
Ralf
Make sure assembly is all correct, auto-adjuster (actuated by handbrake) works properly and brakes are adjusted properly.
Go by workshop manual.
Ralf
- Thread starter
- #9
Hello, my brother Ralf.
This picture is from replacing the rear brake pads. From your knowledge and experience, is there a leak from the cylinder?
Because I did not know that they check the brake cylinder and because I thought that the weak brakes were due to the brake pads.
Even the engineer did not clean the brakes with a special brake cleaner or put grease in the brake pad friction areas.
He only changed the brake pads only.
Thank you for your answer in advance.
My dear Ralph.
- Thread starter
- #10
I also have a dim brake light, is it due to the brake fluid leaking from the rear brake cylinder?
- Thread starter
- #11
I also have a dim brake light, is it due to the brake fluid leaking from the rear brake cylinder?
Hi
That looks pretty normal. I can't check every detail based on pic, though.
Padding (the rubbing material on the metal brake shoe) appears to be sufficient / not heavily worn. (but I can't exactly see)
Try to move the cylinder by pushing on the pads. There should be some play to move them left to right, but I don't expect that cylinder to be seized.
Lift the rubber boots on the cylinder, at the bottom edge. If leaking, fluid accumulating in the boot would show. But I don't expect that.
A bit of grease (not oil) in the adjuster threads won't hurt, but those don't look seized either.
Was your parking brake working before removing the drum?
Did you have to turn back the adjuster trough the inspection hole in the backing plate?
Should be. If the parking brake was weak and the drum came off easily, without having to back up the adjuster, this may indicate your brake pads were not close enough to the drum. This might happen if the adjuster (actuated by the parking brake) doesn't work.
Check the other side, too.
Check for proper function as per workshop manual, reassemble, and on to the next steps:
Bleed brakes & adjust brakes.
The workshop manual tells how to do it.
Good Luck Ralf
That looks pretty normal. I can't check every detail based on pic, though.
Padding (the rubbing material on the metal brake shoe) appears to be sufficient / not heavily worn. (but I can't exactly see)
Try to move the cylinder by pushing on the pads. There should be some play to move them left to right, but I don't expect that cylinder to be seized.
Lift the rubber boots on the cylinder, at the bottom edge. If leaking, fluid accumulating in the boot would show. But I don't expect that.
A bit of grease (not oil) in the adjuster threads won't hurt, but those don't look seized either.
Was your parking brake working before removing the drum?
Did you have to turn back the adjuster trough the inspection hole in the backing plate?
Should be. If the parking brake was weak and the drum came off easily, without having to back up the adjuster, this may indicate your brake pads were not close enough to the drum. This might happen if the adjuster (actuated by the parking brake) doesn't work.
Check the other side, too.
Check for proper function as per workshop manual, reassemble, and on to the next steps:
Bleed brakes & adjust brakes.
The workshop manual tells how to do it.
Good Luck Ralf
You mean the brakelight in the rear, or do you mean a warning light in the dash?
What means dim? Slightly on, although actually not breaking, or dim (weak) when braking?
In any case: The brake light is not associated to the brake itself.
The rear brakelights is just a switch on the brake pedal.
Means: Either your brake pedal is dislocated, causing the switch to be actuated without actually depressing the pedal, or there is an electric gremlin somwhere in your cables.
Dislocated brake pedal might be caused by a broken spring.
A dim rear lights are usually caused by a bad ground cable or corroded contacts.
A warning light in the dash might be caused by the filling level sensor in the brake fluid reservoir (you check that level when bleeding the brakes ayways), or by a sensor indicating poor vakuum, which affects the brake booster, or by sensors in the front brake pads (which I doubt your rig is equipped with).
The workshop manual has a procedure to test the booster / vakuum as well as spec limits for the pedal travel.
But that test is the last in the test sequence.
Check, reassemble, bleed and adjust the brakes first. Leave that light issue for later now.
Ralf
- Thread starter
- #14
Hi Ralf how are you?
I meant the brake warning light.
You told me that you suspect my car has a (brake sensor). How do I know if my car has a brake sensor or not?
Because I don't know.
I forgot to tell you that the fluid level is good and the brake booster is good.
I think it's because of the low brake fluid light because I disconnected it and the light went out.
Is the problem now with the brake fluid light?
Thanks Ralf, you helped me a lot. I wish you a beautiful life and not just one day.
There you go...
Check / Clean / replace the reservoir sensor as needed. I guess, it is a swimmer that closes a contact for the light to illuminate. Disconnected = no contact = light off.
Good Luck Ralf
- Thread starter
- #16
● Hi Ralf, how are you?
Excuse me for bothering you.
● I fixed the rear cylinder, changed the brake fluid and blew the air out of it, checked the brake pads and tested the LSPV.
● First, I lifted the shackle from the axle to the body of the car and tried the brakes at a speed of 30 km/h on a dirt road and all the tires were locked. On the asphalt, only the right side tires were locked and did not go off the track.
● Second, I returned the shackle to the axle and repeated the test on the same roads and only the front ones were locked.
● Does this indicate that the shackle on the axle needs to be adjusted?
● How do I adjust the fluid pressure ratio correctly?
Thank you for everything. Have a nice day and a happy new year.
Abdulkhaliq
Hi
Happy new year.
First insight from your test: Your LSPV is generally working, but needs adjustment (as to be expected).
Rear drumbrakes are a bit hard to adjust to make them pull equally on both sides, so one side might lock earlier. You might want to fine-tune that a bit. That wouldn't worry me too much though.
If the front didn't lock, that's rather a concern. Front brakes can't be adjusted.
With the lever (shackle, as you call it) up, you want a firm pedal. If not yet the case: Bleed brakes again.
Concerning the LSPV
1. Load your truck with all weight it usually has on it (e.g. winch, toolbox, sparewheel; whatever you carry permanently) + 50% full tank.
2. Mount the lever to the axle and do a pre-adjustment: The lever attaches to a pivot point on the axle, with an adjusting screw with two nuts on it, allowing the lever to be adjusted upwards and downwards by respectively moving the nuts.
When carefully moving the lever manually, you can feel it when the arm touches the actuator pin in the LSPV. Mount the arm in that position, without actually applying upward force on the actuator pin.
You want the mounting point on that adjuster screw on the axle to be roughly in the middle of the adjusting screw, to allow for adjustment in both directions.
If the geometry doesn't work out: The LSPV is mounted to the frame in long holes, so it can be slided up / down a bit to mske it work.
(On vehicles with a lift, this factory geometry doesn't work out any more at all, so the the base of the pivot point on the axle needs to be raised by the amount of the lift, to get back to geometry).
3. Get somebody to help.
4. Go 30km/h on asphalt and do a hard 'emergency'-style stop. Have the other guy standing outside and observe the sequence of wheels locking front - rear from the side.
You want the front to lock first. But also the rear should eventually lock.
Adjust the lever at the adjuster screw as needed. Go by multiple tries in tiny increments (1-2 revolutions of the adjusting nut).
Cases:
- Rear brakes weak / don't lock: Lever up.
- Rear locks first or sametime as front: Lever down.
We are really talking small tolerances in the adjustment here. Depending on how accurate your presetting (1) was, it might take several attempts before the adjustment shows any effect at all. Don't get puzzled, just keep going...
Once you reached the sweet spot, it's about 1 revolution of the adjusting nut that makes an effect already.
(Again, we are balancing front to rear here. This procedure has no effect side to side. If the sides behave differently, that's a different issue and has nothing to do with LSPV at all).
5. Repeat procedure on dirt (packed sand, not loose gravel).
Sometimes the rear locks before the front again. Get that tuned in (front to lock before rear) as described above.
Done.
Good Luck Ralf
Happy new year.
First insight from your test: Your LSPV is generally working, but needs adjustment (as to be expected).
Was that really both right side tires (front and rear), or only the rear?
Rear drumbrakes are a bit hard to adjust to make them pull equally on both sides, so one side might lock earlier. You might want to fine-tune that a bit. That wouldn't worry me too much though.
If the front didn't lock, that's rather a concern. Front brakes can't be adjusted.
With the lever (shackle, as you call it) up, you want a firm pedal. If not yet the case: Bleed brakes again.
Concerning the LSPV
Yes...
1. Load your truck with all weight it usually has on it (e.g. winch, toolbox, sparewheel; whatever you carry permanently) + 50% full tank.
2. Mount the lever to the axle and do a pre-adjustment: The lever attaches to a pivot point on the axle, with an adjusting screw with two nuts on it, allowing the lever to be adjusted upwards and downwards by respectively moving the nuts.
When carefully moving the lever manually, you can feel it when the arm touches the actuator pin in the LSPV. Mount the arm in that position, without actually applying upward force on the actuator pin.
You want the mounting point on that adjuster screw on the axle to be roughly in the middle of the adjusting screw, to allow for adjustment in both directions.
If the geometry doesn't work out: The LSPV is mounted to the frame in long holes, so it can be slided up / down a bit to mske it work.
(On vehicles with a lift, this factory geometry doesn't work out any more at all, so the the base of the pivot point on the axle needs to be raised by the amount of the lift, to get back to geometry).
3. Get somebody to help.
4. Go 30km/h on asphalt and do a hard 'emergency'-style stop. Have the other guy standing outside and observe the sequence of wheels locking front - rear from the side.
You want the front to lock first. But also the rear should eventually lock.
Adjust the lever at the adjuster screw as needed. Go by multiple tries in tiny increments (1-2 revolutions of the adjusting nut).
Cases:
- Rear brakes weak / don't lock: Lever up.
- Rear locks first or sametime as front: Lever down.
We are really talking small tolerances in the adjustment here. Depending on how accurate your presetting (1) was, it might take several attempts before the adjustment shows any effect at all. Don't get puzzled, just keep going...
Once you reached the sweet spot, it's about 1 revolution of the adjusting nut that makes an effect already.
(Again, we are balancing front to rear here. This procedure has no effect side to side. If the sides behave differently, that's a different issue and has nothing to do with LSPV at all).
5. Repeat procedure on dirt (packed sand, not loose gravel).
Sometimes the rear locks before the front again. Get that tuned in (front to lock before rear) as described above.
Done.
Good Luck Ralf
- Thread starter
- #18
1. Yes, the right tires (front and rear) because I saw traces of tire friction with the asphalt, but on the dirt road, the four tires locked and the rear ones were equal (it was not loose gravel, but sandy dirt).
*(When I adjusted the handbrake and tested it on the dirt road, the right rear only locked or locked the right tire earlier than the left tire).
2. When the technician bled the brakes from behind the tires only and did not bled the brakes from the LSPV.
3. Regarding raising the lever, the first time I raised the lever and the rear brakes did not lock, but when I raised the valve body and raised the lever, the rear brakes were locked *Note (Now do I lower the valve body as it was when adjusting the lever upward or not) Now the front brakes lock first and the rear brakes do not lock at the end.
Done.
Thank you very much.
AbdUlkhaleq
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- Thread starter
- #19
Hi Ralf
I have a problem with raising or lowering the valve body.
Does raising the body lower or raise the pressure?
Now the valve body is raised .
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- Thread starter
- #20
Good night
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