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1970 Opel Gt - Purchased July 1972 - Chartreuse - restored - 3000 miles as of 02-16, 2021 -
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Discussion Starter · #1 ·
I have been reading about the rebuilding of the brake calipers and wanted to get some opinions based on the information below.
  • During the beginning of my restoration back in the late 90's I know that I replaced the rubber seals around the outside of the caliper pistons, if memory serves on both sides/both pistons, however I did not remove the pistons. So the car has 21 or so years on it and around 3000 miles since then - and has always been in a garage, at least since 1983. The car has also not been exposed to salt being a southern GT-salt is used on the roads now but not back in the 70's when it was a daily driver
  • The brakes work fine but the car is 50 years old and as stated in the many threads on the subject brakes are pretty important so- based on what I have read I am wondering if I need to do anything else to the calipers besides the seal replacement
  • Can the pistons be lightly sprayed with WD 40 or do they need to be
  • I do not have any leaks and again the calipers appear to work really well
  • I also replaced the rubber brake lines that have been discussed at length and again that was in the late 90's. What is the life expectancy of these lines based on the conditions listed above - should I be replacing them at this point.
  • New Master Cylinder and larger brake booster this year and pads front and back only 3000 miles - no leaks
Your comments are appreciated. Thanks, Carl
 

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Carl. We all have our preferences. This is just my 2 cents.

  • The brakes work fine but the car is 50 years old and as stated in the many threads on the subject brakes are pretty important so- based on what I have read I am wondering if I need to do anything else to the calipers besides the seal replacement
At the very least, you need to flush the brake fluid until you get clean fluid. You mentioned that the brakes work fine. Here is how I would determine if I wanted to go ahead and do a rebuild. BTW rebuild kits are ridiculously cheap, and these calipers, even when slightly pitted in the bore, will not leak as the seals mate to the piston, not the cylinder wall; and they are relatively easy to rebuild. Here is the test: jack the front wheels off the ground. Press the brake firmly. Rotate each of the front wheels. If either drags, even a little bit, you should go ahead and rebuild them. I rebuilt the front calipers on my GT, but then it had been sitting since 74. Lots of rusty looking gunk in there. Pistons cleaned up and looked new. No draggint. I also rebuilt the calipers (ATE similar to the Opel) on my 83 BMW 745i back in 1999. I have faithfully flushed the fluid every two years. Boy, I really miss the old Super Blue ATE brake fluid. Short sighted ignorant beurocrats screwed us over on that deal. It was super easy to see when the new fluid arrived; I just rotated using blue and yellow every two years. So far, after another 220,000 miles, my calipers still do not drag in the least.
  • Can the pistons be lightly sprayed with WD 40 or do they need to be
No. Never put a petroleum product on moving hydraulic brake parts. It is not compatible with the rubber.
  • I do not have any leaks and again the calipers appear to work really well
See above. If the calipers drag at all, rebuild them.
  • I also replaced the rubber brake lines that have been discussed at length and again that was in the late 90's. What is the life expectancy of these lines based on the conditions listed above - should I be replacing them at this point.
I would not be worried about them at all as long as you used an OEM brake line and not a cheap import.

Hope this helps.
 

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Just Some Dude in Jersey
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OGTS has had ALUMINUM reproductions made of our car's ATE brakes and/or the wider vented rotor '77 BMW ones, so the rust worries should be diminished.
 

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Opel Rallier since 1977
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Weeeeell.. aluminum corrodes with moisture as bad or worse than steel/iron rusts. So AL is not a 'free pass' to no problems.

As for the soft brake lines, don't count on more that 20 years use. The inner liner is what degrades and that reaction/degredation occurs due to the fluid's effects, not just from use. And I have had OEM soft lines fail internally right at 20-21 years. So, IMHO, time to replace all 3 if you are doing this well.

'Yes' on the moisture in the fluid as LynnB well discusses. If it were me, I would not hesitate to rebuild everything at this time, especially with this car going to your daughter and wanting it to be as troublefree as reasonably possible. The outer moisture seals at the tops of the pistons are actually very critical, as they keep any road moisture out from above the main piston seal. Probably the biggest problem area for home rebuilding calipers is not getting the grooves for those outer seals fully cleaned out and scraped free from rust, and that allows moisture to seep past and form rust above the main seal.

Inspect all hard lines end-to-end and look for severe rust spots, especialy under clips. A bit of moisture in the inside at a low spot will rust from the inside out, so you cannot spot that; the only way to get around that is just to shotgun replace all the hard lines; I did this on my 45 year old Ascona last year.

FWIW, you could recently buy brand new caliper pistons from RockAuto for cheap, but not sure if that is the case now.
 

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1970 Opel Gt - Purchased July 1972 - Chartreuse - restored - 3000 miles as of 02-16, 2021 -
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Discussion Starter · #5 ·
Carl. We all have our preferences. This is just my 2 cents.

  • The brakes work fine but the car is 50 years old and as stated in the many threads on the subject brakes are pretty important so- based on what I have read I am wondering if I need to do anything else to the calipers besides the seal replacement
At the very least, you need to flush the brake fluid until you get clean fluid. You mentioned that the brakes work fine. Here is how I would determine if I wanted to go ahead and do a rebuild. BTW rebuild kits are ridiculously cheap, and these calipers, even when slightly pitted in the bore, will not leak as the seals mate to the piston, not the cylinder wall; and they are relatively easy to rebuild. Here is the test: jack the front wheels off the ground. Press the brake firmly. Rotate each of the front wheels. If either drags, even a little bit, you should go ahead and rebuild them. I rebuilt the front calipers on my GT, but then it had been sitting since 74. Lots of rusty looking gunk in there. Pistons cleaned up and looked new. No dragging. I also rebuilt the calipers (ATE similar to the Opel) on my 83 BMW 745i back in 1999. I have faithfully flushed the fluid every two years. Boy, I really miss the old Super Blue ATE brake fluid. Short sighted ignorant bureaucrats screwed us over on that deal. It was super easy to see when the new fluid arrived; I just rotated using blue and yellow every two years. So far, after another 220,000 miles, my calipers still do not drag in the least.
  • Can the pistons be lightly sprayed with WD 40 or do they need to be
No. Never put a petroleum product on moving hydraulic brake parts. It is not compatible with the rubber.
  • I do not have any leaks and again the calipers appear to work really well
See above. If the calipers drag at all, rebuild them.
  • I also replaced the rubber brake lines that have been discussed at length and again that was in the late 90's. What is the life expectancy of these lines based on the conditions listed above - should I be replacing them at this point.
I would not be worried about them at all as long as you used an OEM brake line and not a cheap import.

Hope this helps.
Hi Lynn, Thanks for all of the good information. Can you clarify something for me. I don't know what you mean by "Dragging" I mean I do, but I don't, If the car is on jack stands and you apply the brakes I thought that would in fact create "drag" as in the beginning of the braking process. So I know that I must be missing something simple here so please explain further. When all is said and done, I have a feeling that I am going to either rebuild or replace the calipers and based on the comments by Mark the rubber hoses as well. I am also in the process of ordering the copper/nickel brake line by Carlson which I understand is a good USA brand up to OEM standards and I have found,
what appear to be, good stainless steel connectors 10mmX1.0, that are long enough, around 10 to 11 threads to work well at all connections, so I am gearing up to just go ahead and do the whole deal and be done with it. If memory serves and it does not always, I think I replaced the back cylinders/housings but if I did not I know that I replaced the pistons and the seals and the outer rubber caps. Based on the picture they do look new to me, but will check for pitting, etc. I have recently flushed the system so the fluid is good, not that that really matters at this point in time considering my plans. Please let me know about the "dragging" and while It appears the calipers may in fact be easy to rebuild I may in fact take the easy way out, not what I normally do, and just go with the new ones from OGTS, unless there is a reason I should stick with the original calipers and I know that reproductions are not always the best route to go. Thanks again for your and everyone else's assistance. Carl
 

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Carl:

I meant that IF the brakes still drag with no pressure applied to the MC, then there is an issue. It NORMALLY means a build up of rust and crud around the piston so that it doesn't release completely. Disc brakes are designed to move the pad back away from the rotor so that there is no "drag" except when the pedal is applied. Drum brakes have return springs, so there is normally a residual pressure valve in the master cylinder for the rear brake lines, but not the front. Hope that makes sense.

So, with the car up in the air (safely) have someone apply the brake, then let off. The rotor should turn relatively freely.

There will always be a very slight drag. However, the calipers are designed so as to NOT keep any pressure on the pads. In fact, the rubber "O" ring seals on the old GM single piston caliper even had a little bevel built into them (they could be installed backwards) that made the seal roll just a bit in the bore, causing them to roll back when pressure is released, thus moving the pads away from the rotor.
 

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The easiest way to check for drag is to jack the car up, get someone to apply the brakes, put one finger on the tire and attempt to rotate it, release the brakes and the wheel should instantly rotate, if it does not there is an issue.
 

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Detritus Maximus
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Weeeeell.. aluminum corrodes with moisture as bad or worse than steel/iron rusts. So AL is not a 'free pass' to no problems.

As for the soft brake lines, don't count on more that 20 years use. The inner liner is what degrades and that reaction/degredation occurs due to the fluid's effects, not just from use. And I have had OEM soft lines fail internally right at 20-21 years. So, IMHO, time to replace all 3 if you are doing this well.



Inspect all hard lines end-to-end and look for severe rust spots, especialy under clips. A bit of moisture in the inside at a low spot will rust from the inside out, so you cannot spot that; the only way to get around that is just to shotgun replace all the hard lines; I did this on my 45 year old Ascona last year.
My experience is that the old rubber lines are fine until you step on the brakes. The fluid goes thru, the decayed inner liner comes apart and plugs up the line like a one way valve preventing the fluid from moving back, locking that wheel or wheel.

I'm seeing a lot more failed hardlines on cars built after 85. Both Safari vans 86 and 90 (and it's a common problem to have the hardline fail along the fuel tank) and the 97 Protege. Plus a few other cars a I know of. The dirt and mud collects on top or around the chassis clips that hold brake and fuel lines in modern cars. They are more complicated shapes that do not clean out well at the car wash or in heavy rain.
 
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