Trying to fix brake caliper banjo leak, desperation setting in
 

Of all the foolish things I've done working on my cars over the years, this has to take the cake. Here's how the story begins...

A few months back I got this great idea that my brake calipers on my 930 would look really cool powder coated red. This guy on our local PCA website had published some pictures of other calipers he had done which looked really awesome. He apparently did this for others as a hobby/side business as well, so I contacted him and arranged to give him my calipers. He sounded very confident and competent and as though he had done these many times before. I later realized that his confidence was a result of working on newer cars, with much simpler one-piece calipers. I was nervous when he told me he was going to take them all apart. I should have got suspicious when he told me he wasn't going to assemble the crossover tubes which connect the two sides together, since I would need new copper gaskets, which should be available at a local auto store. Keep in mind if the calipers weren't taken apart, the tubes could have stayed in place. My gut instinct was to tell the guy to give them back in one piece like I gave them, but after weeks of frustration to get the parts back, I didn't care. I figured I could put the tubes on myself.

So I get the parts back, and now the nightmare begins. After I put them back on the car, I notice a leak on one of the calipers at the caliper/banjo joint, see below:

http://forums.pelicanparts.com/uploa...1581920855.JPG

So I disconnect, put a new washer, retry...no luck. Now I'm thinking maybe the guy messed up the mating surface of the caliper with his paint, so I scrape it off and retry. Leak gets worse. More sanding...leak is worse... (keep in mind that each trial involved reattaching brake lines, rebleeding...quite a headache). Now I take sandpaper and really try to polish...leak gets worse...I read that most brake calipers have a groove that the copper gasket is supposed to set into, which made my heart sink thinking I had just polished off the live saving groove. Anyway, after lots of research and going to the Porsche dealership I realized it wasn't the case. My calipers relied just on a smooth surface for the sealing. I get genuine Porsche copper gaskets specific to that joint. No luck.

I researched all kinds of washers. There were many postings about these washers that have an embedded rubber o-ring, stat-o-seals and people swore that this solved their leaking caliper joints. So I ordered all kinds from different manufacturers. The problem is that finding metric sizes was impossible, seems nobody made them. None-the-less, the expert said if I just use the smaller closest standard size it should work. Well they didn't.



At this point I realize that what I was doing wrong was not sanding perfectly perpendicular to the axis of the treaded hole that the banjo screws into. So I had to get the surface flat and perpendicular to the hole, precisely.

http://forums.pelicanparts.com/uploa...1581920896.JPG

So I came up with what I thought was a clever trick. I put a threaded screw with the head cut off into where the banjo fitting hole, and 3-D printed a cylinder with a precise hole exactly perpendicular to a flat surface. I could have machined this part, but I don't have that kind of equipment, and I have access to a 3-D printer. I would paste sandpaper to the flat surface of my tool, put it over the shaft and rotate to sand the surface flat and perpendicular. I could use a drill to attach to the other end.

http://forums.pelicanparts.com/uploa...1581920281.jpg


Ignore the drill press below, Initially I was going to use that to rotate the tool over the shaft, but it was too hard to align. the hand held drill worked much more easily.

http://forums.pelicanparts.com/uploa...1581919159.jpg

This actually worked for a few weeks, until I noticed one of the pistons on the same caliper leaking. In the process of fixing that, I was careful not to touch this joint. I thought I was home free after fixing the piston, only to realize this joint is leaking again!!! After three more tries at sanding, still no fix.

Anyway, I'm desperate for any new ideas. My next step is to just take the banjo joint and put it on the outside half of the caliper, and replumb the incoming line so it would connect to the outside half, and I would connect the short bypass line back into the original banjo hole. It basically moves the banjo mating surface to a new surface. The flare fittings from the lines that rely on sealing at the end of the drilled holes don't have any issues so it shouldn't leak there. But this is a rather hokey fix, which I'm trying to avoid.

Are you sure it is leaking from the banjo bolt? Looks like there is a fitting that goes underneath it as well - seems like you are very thorough with your inspection but just asking incase as I have seen leaking more often from flared brake lines then banjo fittings.

Perhaps there is a hairline crack on the fitting itself? Very strange.

Can you take a few more pics? One of the threads / mating surface of the caliper, and one of the fitting sans banjo - as it sits in the caliper.

I enameled my calipers red and really regretted it. I sent them to PMB and they look soooo good now. Point is, if this was my car, I’d remove them and have Erik strip the powdercoat off and return to the black anodized original finish. Turbo brakes look so cool and proper this way. Explain your problem and maybe he can bench test it. That fthread could be goofed, or rounded out. Replace the lines and banjo there with Porsche parts.

I wish it was the flared fitting, that would be easier to fix. Believe me, I’m about on my 20th trial, I definitely observe and know which joint is leaking. It’s the flat surface of caliper to banjo copper gasket interface.

Try a tinny bit of blue lock tight on the last few threads of the banjo bolt and also apply blue lock tight on both sides of a new copper washer. It may help fix the issue. Other than that I'd take the caliper to a decent machine shop and have the surface redone properly at that fitting.

Could you replace the caliper altogether? At this rate you might spend more on brake fluid than a replacement.

try annealing the copper washers before installing them, just heat them up with a propane torch until they glow then cool them with water, clean them up with some fine sandpaper afterwards and reinstall.... a lot of the copper washers on the market are not annealed and they are really hard and don't seal well right off the shelf

Send it to Eric Shea (PMB Performance) in Salt Lake City.

Install the end setup on another caliper to rule the suspect caliper or the fittings out.....

The best advice I could offer is that you should take your car (on a trailer) to a repair shop that you trust. I can't tell from the discussion and the photos what the issue is. No disrespect to anyone and not to buzz kill, but if you're asking this question to a bunch of strangers on the Internet, you're over your head and risking your own and other people's safety. Some of the suggestions on this thread are pure, dangerous BS.

Stay safe.

Seeing that a new 930 caliper is over $1500, that is not an option (at least not yet).

The seal for a banjo joint is made at the flat mating surfaces, not the thread. That won’t work. Here are a couple of more pics of the surface and banjo, and my method for sanding the surface.

http://forums.pelicanparts.com/uploa...1582078817.jpg

http://forums.pelicanparts.com/uploa...1582078857.jpg

I’ve gotten more BS advice from reputable shops than I have on this forum (I’m talking in general). I trust people who own the same car and have dealt with the same issues over someone who hardly ever sees my car. I can also filter out bad advice from the occasional brilliant idea that people come up with here, so I feel safe and that’s why I’m asking.
Today I went to Napa and found exact ID copper washers that are slightly thicker and bigger OD. Surprisingly the ones I got from Porsche looked thin and warped. I’m feeling optimistic but will see.

This is essentially my last resort, which is to connect to the other port on the caliper.

When i have a banjo fitting that doesn't want to seal i put a very small amount of grease on both sides of the crush washer that is in between the banjo bolt and the banjo. This allows you to get the banjo bolt slightly tighter and usually solves the issue assuming there isn't another flaw causing the leak.

New, thicker crush washer will also help.

yes I would do this. Many have this problem with copper head gaskets on briggs racing engines they must be annealed first

If it were mine, I would use some Permatex 54540 (pneumatic/hydraulic sealant) on both sides of the copper seal at this point.

I'd invest in a few new banjo bolts (screw socket) $10, banjo bolts $20 and all new copper washers. The mating surface looks okay.

This
Annealing copper is the first step. Your surfaces look fine, the copper has to be soft to allow the deformation to occur.
I anneal every copper gasket I install, especially new ones. The manufacturing process can/will work harden the copper, heat treating costs time/money, accountants hate spending money that can be used for hookers and cocaine.

Well, I'm down to my last two resorts. I was very optimistic about the Napa washers, as they were exact size ID of the Porsche ones, but were thicker and larger OD. Tried two different ones, with and without annealing, and dam small seepage could be seen after about a minute under brake pressure. And yes, it is very obvious it is the caliper to banjo interface and specifically the caliper to washer interface. I have that surface smooth as silk. I cannot believe this is happening. It's almost like a curse at this point. There is no way I can get that surface any better. So last two resorts to follow:
1. Permatex sealant suggested by Rawknees Turbo
2. Replumb the lines so that I can put the banjo on the other inlet on the outside half of caliper. (least desirable).