Rebuilding Front Disk Calipers - Can I Rebuild?

[ct06033]

I had an issue last weekend with my brakes not releasing pressure. I found this out as they overheated and slowed me to a crawl. Made for a really fun drive home. Luckily I guess wind on the highway was enough to keep the brakes cool enough I could keep going. Instead of just finding and replacing the offending part, I decided to just overhaul everything as it was on my list but I kept putting it off.

So after taking off the master cylinder, it seems like the chamber for the rear brakes is blocked (i am not sure how this causes the front brakes to lock up) even though everything looked to be in good condition once apart. I already have a reman 510 master cylinder on order so I will just replace it anyway. (PM me if you would like a master cylinder)

My real issue is what to do with my calipers. Depending on the feedback, i will either just rebuild everything or do the 300zx upgrade. While it is expensive, If i need to replace more than one caliper piston, i will probably just upgrade for piece of mind, and future proofing.

After going over the drivers side, it seems like the rotors were not damaged or warped from the stuck brakes. In fact, It looked like they are fairly new. I ripped open the worst brake caliper (outside drivers) which had been sticking and tried to clean it up but I have no idea if its reusable or not. It was stuck pretty well when I removed it from the car. I had to stand on it to get the piston to move back in. There was not any leaking fluid but the outer boot was ripped. I lightly sanded it with 150 grit then went over everything with 1000 grit, copious amounts of brake cleaner and... I guess it looks okay? I have some pictures below and would love a second opinion before i put it all back together and trust my life with it.



The pic below shows the worst of the pitting but most of it is below the ring?




The rest really looks okay to my untrained eyes I simply have no idea what is "okay".

[mraitch]

resleeve with stainless

[Nissanman]

^^^^^Like he said^^^^^
A good rule of thumb? is the finger nail test.
If you slide your finger nail over the bore and it catches on anything, then you have an issue
Same test for the pistons.

[jamesw]

That pitting shown wouldn't cause your brakes to stick - it would cause them to leak.

The sticking was caused by something else - and has happened to many of us here. My first guess was that the MC piston wasn't able to return all the way after you released the pedal - probably caused by that gunk in the MC you talked about near the rear reservoir.

Second culprit is if you have rubber brake hoses - the insides give out and collapse, not allowing brake fluid to return to the MC/reservoir after you release the brakes.

Now...with all that said, if your brake calipers were not leaking then just replace the rubber rings/seals on the pistons, and the boots and you should be good to go. But on the other hand, from the pix they do look a little pitted.

HTH
James

[notoptoy]

One other cause of sticking, brake backing pads that are too tight. These will stick, or be tough to install, and the problem gets worse when they heat up. Good news is this is readily caught, and remedied, file down the metal pad sides so it fits loosely and smoothly.

[Curtis]

resleeve with stainless

What he said. I did mine and I haven't had to touch them for several years. Plan to do some rears in brass or stainless.

You can do masters as well. The 510 is inexpensive I suppose but don't you need adapters?

[Linda]

Yes. Conversion is documented in the Wiki.
Or you can sleeve your MC and not worry about it again. Doesn't hurt to get a quote
Karp's Power Brake
www.karpspb.com
https://www.311s.org/index.php/resources/vendors/
Linda

[C.Costine]

My brakes are all apart right now. My opinion is that the rust that was in there that did all of that pitting would have caused the pistons to hang up in the cylinders. After all there is high pressure to apply the brakes and very low pressure to release them. If the seals in the cylinders were lip type I would say that yes the walls are too pitted to seal. With the seals being 1/8 inch thick, though, I am of the opinion that the amount of leakage will be insignificant. Far too little to loose any application force, and maybe enough to loose an ounce from your reservoir every 10,000 miles.

[ct06033]

Thanks for all your input! It really helped me decide on a direction to take.

So, a few things, I looked at the resleeve option and all in, it would be around $400 which is half way to a big brake kit. I was hoping to get a bit more life out of what I have but it seems that won't be an option. I have also read that it only staves off the issue, not totally fixes it since there is still exposed steel that will rust in the cylinder.

I decided to go with the 300zx kit since it is close to bolt on (there is a little bit of drilling and the need for a press to modify the caliper which I don't have) also, since the calipers are all aluminum and SS, no issues with corrosion.

I will go ahead and just rebuild the cylinders so I can do some non spirited driving around town while I wait for parts to come in.

As for the 510 master, you do need a metric to sae adaptor but I bought both on Amazon with prime shipping so.they are as readily available as you can expect.

Thanks again for all the input!

[fj20spl311]

Do you already have 15" or 16" wheels?


Usually its the M/C not returning caused by junk or miss adjusted light switch.
It also could be caused by bad brake hoses.

[ct06033]

Do you already have 15" or 16" wheels?


Usually its the M/C not returning caused by junk or miss adjusted light switch.
It also could be caused by bad brake hoses.

I do, I have rota RBs 15x6. I also recently (3 years) bought braided stainless lines. they pass visual still. that doesn't rule out a block in a solid line but fluid seems to be flowing through the system well.

[nismou20]

I am also having to rebuild the calipers due to pitting in the bores. I may take a chance and just install new seals and boots. But, if they do leak there has been suggestions on resleeving the bores with Stainless steel. Is this a matter of a Machine shop boring out the original bores then press fitting a SS sleeve of proper oem bore size?

[Linda]

Tom,
Karp's Power Brake in Upland does it. See link above.
Not aware that machine shops do the work.
My experience 8 yrs ago, price was $60:
viewtopic.php?f=3&t=11825#p85334
Linda

[Nissanman]

From what I understand the parts are bored/honed out to allow a piece of SS stock to be pressed in. All relevant ports are re-drilled and the internal diameter is bore/honed to the original dimension. Gives you a long lasting , reliable, re-buildable hydraulic system.

[mraitch]

It doesn't really matter if there is pitting on the 'base' of the cylinders, what matters is pitting in the walls.

just get is sleeved and say ' done'