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81' Turbo been off the road for many years. A few months ago I refurbished all the calipers , clean, paint , new seals , one new rear piston and new sliding pins. Reassembled with red rubber  grease and silicone on the pins. Pads and discs were as new just needing to remove some rust from discs. System is bleed with new fluid and pedal is hard. Front brakes working on /off and handbrake operating. If I press the pedal hard the back brakes operate but when released the rear hubs are very hard to rotate. I have run the car in gear on axel stands to "bed in" the pads and discs but it is still the same. If I open the bleed nipple to release hydrolic pressure it makes no difference.Sliding pins are moving freely. If I remove the caliper and reset the piston back everything is free until I apply the brakes again. Both sides are the same. Is this likely to be tight new seals and will loosen with a bit of driving ( without overheating the brakes) 

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Not really, the new seals should operate perfectly out of the box. If the pads slide easily and the pistons slide easily, it has to be a handbrake mechanism issue. Has the self adjusting mec

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Its worth checking the handbrake levers on the calipers are retracting fully when the handbrake is off, even if the brakes seem to be releasing. If they are not, the internal mechanism will ratchet when the brakes are applied.

When retracting the piston did you turn it 45 degrees, then afterwards turn it back again?

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8 hours ago, viz139 said:

Is this likely to be tight new seals and will loosen with a bit of driving

If everything is new and functioning as you describe, I would suggest a 5 mile drive,  on a quiet road, with plenty of moderate braking to bed everything in.

When you get home, jack it up and see if things have improved.

Andy.

 

 

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Wheels are away getting refurbished so if I try turning the hub or disc with my hand it won't move. I need to place a large screwdriver (12") between the studs to get leverage to move the hub. Moving it doesn't "release" the pressure, the resistance is consistent so not warped discs. I can apply the brakes and than turn the front hubs by hand. I'll try a few more "miles " on the axel stands and I'll check disc temperature with an infra red thermostat.

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22 hours ago, viz139 said:

Is this likely to be tight new seals

Not really, the new seals should operate perfectly out of the box.

If the pads slide easily and the pistons slide easily, it has to be a handbrake mechanism issue.

Has the self adjusting mechanism been assembled correctly inside the caliper?

Andy.

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On 19/07/2020 at 19:33, viz139 said:

81' Turbo been off the road for many years. A few months ago I refurbished all the calipers , clean, paint , new seals , one new rear piston and new sliding pins. Reassembled with red rubber  grease and silicone on the pins. Pads and discs were as new just needing to remove some rust from discs. System is bleed with new fluid and pedal is hard. Front brakes working on /off and handbrake operating. If I press the pedal hard the back brakes operate but when released the rear hubs are very hard to rotate. I have run the car in gear on axel stands to "bed in" the pads and discs but it is still the same. If I open the bleed nipple to release hydrolic pressure it makes no difference.Sliding pins are moving freely. If I remove the caliper and reset the piston back everything is free until I apply the brakes again. Both sides are the same. Is this likely to be tight new seals and will loosen with a bit of driving ( without overheating the brakes) 

The rubber brake lines on my car were blocked like a bad heart attack. The bores had swollen from old brake fluid contaminated with moisture.

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All Rubber hoses are new and I'm happy that it is not a hydrolic  problem.

The only thing in the back of my mind with regard to the handbrake mechanism is that I replaced one piston. As far as I can find the original pistons are handed, Right SP4064 and Left SP4065  but the one I got from SJ ( SJ089J0011) does both sides. I couldn't any difference in the pistons. The car had a history of sticking calipers ( hence the overhaul) but did operate well before I took it off the road. I found one corroded piston and the sliding pin rubbers had expanded (why can you not buy these rubbers without new pins and there not included in the overhaul kit).Hope to get back to the car tonight.

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Got to run the car again last night on the axle stands. The LH wheel is freer than the right which barely turns  . If I lock the LH handbrake the right wheel turns and without any pressure it is reaching 80 deg C. When I apply pressure to bed it in its reaching 300 degC but still no sign of it loosening up. Think I will strip the caliper at the weekend.

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  • 3 weeks later...
Posted (edited)

So I striped the calipers and everything looks right and moving freely. First time I assembled the calipers with red rubber grease which may have caused some resistance so this time I used only brake fluid  which seemed a bit looser initially . So I took the car for a short drive around the yard and the rears are sticking again. I need somebody to explain the automatic adjustment system to me as it appears to me to be flawed.

When you operate the handbrake the adjuster and piston move in and out together.

When you operate the pedal the adjuster stays put and the piston moves out. If the piston moves more than .8mm it will ratchet on the adjuster and not fully return fully. 

What happens when the piston moves only .8mm , fully engages with the disc and than cannot return.  This is what I think is happening to mine. In the  Lotus manual ( section JB ,page 5) it says "A small amount of lost motion is permitted which prevents over-adjustment,"  but I can't see where this lost motion is.

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Edited by viz139
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55 minutes ago, viz139 said:

I can't see where this lost motion is

Hi Viz,

The lost motion exists as back lash in the ratchet type threads where part A and B interact.

I'm starting to think this issue is due to air in you rear braking circuit.

This would act like a spring in the hydraulics and messes with the auto adjuster's ability to use the essential "lost motion."

Give your entire braking system a really, good bleed and report back.

Andy.

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Unless you are a stickler for originality, you could swap them out for the VAG pattern calipers that are cheap as chips.    I know your fronts are working, but I wouldnt rule out that the master cylinder may also be 'sticky'?

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not sure where you got to with this but have you considered that it could be a hydraulic problem. I know you said all lines were new but perhaps the piston in the master cylinder is not returning far enough to uncover the return to master cylinder reservoir port. Easy way to check would be to crack off the rear bleed screws and see if the rear brakes are still dragging a lot. BTW I have a 84 turbo with new brake setup and I can turn my rear discs by hand pretty easily when the car is on stands.

A small amount of residual pressure in the line can cause a big problem on the road.

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Viz says in his first post, if he opens the bleed nipple while the brakes are stuck, it makes no difference.

That pretty much rules out a master cylinder issue and my air/bleed suggestion.

Got to really be an issue at the caliper.

Are there any anti squeal shims fitted? Are the in good condition, not bent and perfectly flat on the pads?

Failing that, I can't imagine anything but the auto adjuster mechanism being at fault/worn.

Andy.

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My rear brakes came on a few times whilst out driving for seemingly no reason at all - once when being followed home by the RAC van that had just come out when they stuck on an hour or so earlier. I was accelerating down a slip road onto the A10, changed gear and wham, rear brakes were on. RAC chap said he had never seen it before.

Turned out the handbrake cable had frayed and was the cause of the issue. After replacement, not had it happen since.

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1 hour ago, AndyPG said:

Viz says in his first post, if he opens the bleed nipple while the brakes are stuck, it makes no difference.

Thats true, but its odd that both calipers are affected, even after rebuilding them (unless a similar fault exists in both rebuilt calipers).   You could rule out the auto adjuster mecanism , by testing the service brake with the pistons rotatated 45 degrees, with some way to avoid locating the brake pad locator in the piston (angle grind it off some old pads).   

 

 

 

 

 

 

 

 

 

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As said already opening both bleed nipples does not release the pressure. One test I did was to press the pedal gently to bring out the pistons and than operate the handbrake many times. Pads held and released every time. Only locks when pedal is pressed hard . I measured the pawls on the adjuster With a basic calipers and put them at about 0.6mm apart meaning a max gap between each pad and disc of 0.3mm. 

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17 hours ago, viz139 said:

 First time I assembled the calipers with red rubber grease which may have caused some resistance so this time I used only brake fluid  which seemed a bit looser initially .

 

Red rubber grease is something I would not use. Who knows how it would react with brake fluid?

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As you said, like my car your too had been laid up for a long time. I would lay my bets on a block in the system. I had to replace every rubber component on my car, including 2 X part 10 & 2 X part 21.

900939336_Screenshot2020-08-14at10_48_27AM.thumb.png.c5dc13d751f62e9e7e3bb2ad5d077e06.png

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On 14/08/2020 at 04:43, ekwan said:

Red rubber grease is something I would not use. Who knows how it would react with brake fluid?

In over 30 years working with classics this is the first time I have used red rubber grease but by all accounts it is totally compatible with Dot4.  The reason for choosing to use it this time is that I didn't know how long the calipers would be sitting before being fitted so rather than having brake fluid in air causing corrosion I used the grease which doesn't react with air.  I have rebuilt many calipers over the years but this is the first I have done with handbrakes. Fronts are working fine. All rubber hoses are replaced.Heading to the garage now for another look .

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The red rubber grease shouldn't cause any problems. A small sachet of it is often included in brake seal kits.

IMO, if depressurizing the hydraulic system at the offending caliper doesn't release its grip on the disk, the master cylinder, rubber hoses and air etc are all ruled out.

The issue has to be between the auto adjuster and the pads.

  • Check that any anti squeal shims are all flat and correctly located.
  • Try it with the shims removed.
  • Try it with the old pads back in.
  • Make sure the hand brake cable isn't over adjusted.

If this doesn't work, it can surely only be the auto adjusters U/S or incorrectly assembled.

Andy.

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  • 2 months later...

Sorry for delay in update but I have bought an old house which is is even more trouble than the Esprit. I will get back to the Esprit when I need a break from working om the house.

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