Calliper leak problems

[Martinshort]

Hi Guys, another can of worms opened. I didn't split last time as I agree with Rob, leave well alone if all is working however fitting the dustcaps was a real mission hence the water ingress. My O-Ring kits came with the O-Rings for joining the two calliper halves so I reckoned to try splitting this time. Upgrading the front brakes on my Capri based kit car to vented discs required fitting a sandwich plate between the two halves of the callipers, worked first time without any drama so far as I recall. Any other opinions on this one?

 

[Martinshort]

Just a thought why go to the trouble of rebuilding I have just bought a set of new O ring calipers for £135 each, no core charge,so no postage to pay on the return. They work perfect

 

[Alben78]

On all the calipers I’ve done they have always been split. It makes it possible to clean up both the bores and the calliper body and for refitting the pistons and seals. In any case the fluid transfer holes are sealed with an o ring which should be replaced every time so the mating surfaces not being completely flat is not a problem. It is worth cleaning them up though. A flat surface (nice worktop?) and some very fine wet & dry usually works. Clean thoroughly and dry off in oven before reassembly.

 

[kentvette]

Just a thought why go to the trouble of rebuilding I have just bought a set of new O ring calipers for £135 each, no core charge,so no postage to pay on the return. They work perfect

That was my point right at the start of this thread. In the general scheme of things a new calliper is not expensive and as Martin says, can be had with no core charge.

Wife June and I have re-built and/or replaced all sorts of bits and pieces on our '78 over 30 years, but regardless of some of the opinions here, I wouldn't be faffing around with something as important as brakes just to save a few pennies.

 

[curious bystander]

I've seen those calipers for £135 on ebay - appear to be a totally unbranded product which may or may not be an issue - but as you say Steve, brakes are quite important. So I'm sticking with those stamped (or approved) by AC Delco

 

[Alben78]

Trouble is that by now almost all the replacement callipers will have been sleeved and re built, maybe a number of times, by goodness knows who with no traceability.

 

[Roscobbc]

I little 'caliper' story for your delectation fella's - seen the Car SOS show where Pete Knodts big block C3 gets a 'make-over'? - yes? there is a whole involved story here which we'll not go into - suffice to say when Pete collected the car following the 'make-over' he experienced brake failure when driving it back home.............the reason? - on one (or both) of the supposedly 'new' replacement front calipers the respective caliper halves hadn't been torqued up sufficiently (if at all!).......resulting in major loss of hydraulic pressure and subsequent brake failure...........
Nipples
Brake caliper nipples that is - if replacing original oem caliper bleed nipples (that have perhaps had the hex's rounded-off) remember if sourcing stainless ones as they will be be far more durable than oem. However there is a temptation if you can't shut them off properly to perhaps over-tighten. They'll take a lot of abuse - far more than the tapped thread in the cast caliper body. A stainless steel bleed nipple will strip the thread in caliper very easily (ask me how I know......)

 

[kentvette]

I've seen those calipers for £135 on ebay - appear to be a totally unbranded product which may or may not be an issue - but as you say Steve, brakes are quite important. So I'm sticking with those stamped (or approved) by AC Delco

Absolutely Bill! Mine came from a "reputable source' and I'd done a bit of homework to decide who I might use - basically only about 4 places stood out based on recommendations. But none were what I'd call expensive, given that we are running "fun" cars that aren't cheap in the first place.

 

[Nosheruk]

Nobody has mentioned runout yet.
If you have excessive runout on your rotors, your calipers will suck in air and leak fluid.
O rings can handle more runout than lip seals, but runout needs to be corrected.

 

[Roscobbc]

Very good point Nosher !

 

[Alan Collins]

Hi Guys, no run out, the disks are good. I decided to go down the O-ring rebuild route of my original AC Delco calipers having seen some of the calipers out there are rather nasty looking aftermarket items. After receiving the rebuild kits I was advised by a mechanic that my bores in my photo look pitted so I have invested in a three legged calipper honner to lightly clean up the sleeves which will also get rid of any high spots mentioned by Rosobbc (Kennedy 4 in 1 which includes the required short stones).

I am working on finishing a weather tight garage area whilst the weather holds and then will rebuild the calipers and let you know the results.

 

[Alben78]

Looks like surface discoloration to me - just be careful. Those I have done which have been stainless steel sleeved only needed a light touch up with very fine cloth backed abrasive.

 

[Nosheruk]

How did you get on?

I have to agree with the point about stainless bleeders.
I will never use them again. Constant weeping.
Swapped back to the original bleeders after a quick rub with 1200 grit and sealed perfectly.

 

[Alan Collins]

Hi all, received an email from Nosheruk asking how I got on. I have postponed the caliper works whilst getting the garage built which was finally completed over the Spring bank weekend save for some detail finishing work. Garage has turned out well but building work takes forever to do. Now itching to get the Vette back on the road so will be doing the callipers ASAP. However, scaffold tower has arrived to paint the front of the house, see photo below, so will need to multi task! Never been so busy since this damn virus arrived.

 

[Roscobbc]

How did you get on?

I have to agree with the point about stainless bleeders.
I will never use them again. Constant weeping.
Swapped back to the original bleeders after a quick rub with 1200 grit and sealed perfectly.

Any of the 'aftermarket' parking brake components available in stainless steel are initially an attractive proposition - and, yes they will resolve the corrosion issues of C3 parking brake components. Unfortunately they DON'T resolve the issues of GM's original poor design where you have components that are insufficiently thick or rigid enough (parking brake shoes?) to do the job properly. Bleed nipples need to be of a relatively 'soft' material to be able to seat properly against the cast iron caliper. Stainless steel nipples will strip the female thread out of the calipers if you are not very careful.

 

[Alan Collins]

Finally started work on the car. Working on front end mechanicals, radiator refurbed, A arms rebushed etc. Brake callipers now honed, rebuilt and refitted, see pictures. Honing is simple to do however we had to strike a balance between how much material we removed and getting out every imperfection. The image shows the drivers calliper which cleaned up easily, we were surprised that the passengers calliper bores were in worse condition despite far less leakage and we had to hone more. Think we have a just tight enough fit with the new O ring seals. I am pretty sure the last failure was due to the dust caps not seating in the callipers properly due to restricted access around the assembled callipers. I would definately recomend splitting the callipers when refurbing to get access to fit the dust caps which we fitted very carefully with a hardwood drift and mallet. I have always been an advocate of repair rather than replace but this experience has shown that Corvette callipers are probably best replaced. Honing showed the condition of mine was far worse than expected with some deep grooves from lip or piston wear and the callipers, although both AC Delco, seemed to be different ages. I will let you know if the car is leak free after testing.

I have a new suspension query which I will post for you all on a new thread.