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Street Race Truck More... The Toolbox

Common Causes for Leaky Banjo Fittings and Caliper Issues

9/30/2016

I am currently working on the brakes for my old '29 roadster.  In keeping with the period of the build my car has '40 Ford drum “juice” brakes, but as I burn the midnight oil in my garage memories of customer calls to me on the tech line come streaming back.  Many of the questions we are asked regarding brakes have to do with fairly simple problems.  Usually some quick troubleshooting with our customers puts them back on track getting their old car on the road with updated brakes! In this tech article I will cover a few of the most common questions we help with in hopes that it saves you when in a pinch!

It is not uncommon for someone who has just purchased a vintage car or truck to give us a call looking for a brake kit to convert old drum brakes to disks.  This makes sense given disk brakes are easy to service and if you plan on driving the car frequently the wide availability of replacement parts makes life much easier in the event of a problem on the road.

We have a long list of brake kit designs available through us if you want to get away from the old drums on your car!  Check out our website or give us a call and we can help you determine what will work best for you! Not long ago I used P/N 9106770 on my '69 pickup pictured above and it was a snap!

Once you get a brake kit home, installing is very straight forward. Here are some tips and information to help you! The majority of our kits utilize one of two possible GM mid-size calipers. This is an example of a '69-'77 GM midsize caliper.  These were a great design as they are rugged, light, and easy to service. Our part number is 91031035.

This is an example of a '78-'88 GM caliper, commonly referred to as a “Metric” Caliper, P/N 91031045. This is a very popular caliper and packs a good punch for its relatively small size. It is slightly smaller in dimension in comparison to the earlier caliper above.

Most of our brake kits utilize 7/16 x 20 fittings, so regardless of the style caliper you have in your kit, it will be set up with 7/16 x 20 threads.  We also offer a “Metric” caliper (the '78-'88 GM) with a 10mm thread if you need a caliper to match pre-existing metric fittings. A typical 1” bore master cylinder will be perfect for any brake kit using either of these GM Mid-Size calipers.

It is important to note these calipers are side specific. When installed properly in a vehicle they will point the bleeder screw up to allow air to escape the brake system when bleeding. Most of the time the calipers will have the side designation cast into the caliper body. This side designation is correct if the caliper is situated behind the axle centerline. Remember side designation in a car is relative to the driver in the driver seat looking forward. LH is the driver’s side, and RH is the passenger side.

Some brake kits will mount the calipers in front of the axle center line. Typically this occurs with some vintage cars having a factory bolt on steering arm arrangement that gets in the way of the calipers behind the axle CL. If you need to mount the calipers in front, the performance will be the same because the calipers don’t mind where they clamp down on the rotor.  You will however need to swap the calipers side to side so the bleeders point up.  (Caliper marked LH will be installed on the RH side and vice versa).

Quick note:

There are some cases on rear brake kits ('68-'69 first gen Camaro) where the rear shocks are staggered, so to clear you must run one caliper in front of the axle center, and the other behind. If this is the case you will need to calipers of the same side designation, again so both bleeders both point up.

Sealing

In almost all cases you will attach a banjo style fitting to these calipers to plumb them to your brake system. It is in properly sealing these banjos where the trick comes in. It generates headaches from time to time but in almost all cases there is a simple cause that is very easy to fix.

Before installing the banjo fitting check the mating surfaces. While it is rare, from time to time you might find a small metal burr or other deformity that sticks up too far not allowing the banjo to seat properly. The caliper is usually where we would see an issue if there is one, but it never hurts to look over your banjo fitting too!

Make sure you are using a crush washer on each side of the banjo fitting. I know this seems obvious, but surprisingly enough we have many new builders who attempt using a crush washer on the caliper surface only. You can see grooves on both the banjo bolt head, caliper mating surface, and each side of the banjo to seat down into the softer crush washer.

There are a variety of Crush Washers in the marketplace. Many of our brake kits utilize a solid copper crush washer. These are my favorite but many other styles work just as well. You may also see crush washers of a laminated design which are aluminum with a thin layer of copper on each side. Solid aluminum crush washers are now widely used and work great. If you have a testy sealing surface and have struggled with all metal crush washers there is also something called a stat-o-seal style washer. When I have a customer who just can’t get his crush washers to seal, I send him a set of these and they solve the issue every time. Stat-o-seal washers have a metallic component like a standard crush washer, but they also have an inner o-ring type rubber seal. P/N 6179061 will get you a pair of stat-o-seals in a 7/16 size (same as AN4).

Make sure your banjo fitting seats down on the caliper surface correctly. This is another one that seems obvious but it trips many up. On many rubber hoses available both through us and elsewhere, the banjo fitting is crimped onto the rubber line, and the fitting surface itself is angled. The easy thing to miss on these is most customers will want to keep the line tucked close to the caliper so intuitively angle the line downward. On most metric calipers there will be a relief cut in the casting to clear the crimped portion of the fitting. Sometimes this relief is not cut deep enough and the fitting will bottom out leaving a gap that cannot be filled by the crush washer. The problem is even worse with the earlier calipers ('69-'77) because they do not have a relief cut at all. The correct solution to remedy this is to flip the fitting around so it angles the line away from the caliper and in turn gives the crimped portion of the fitting the space needed.

Correctly Installed Fitting

Clocking the brake lines. Because we use Mid-Size GM calipers on a wide variety of custom applications many customers will want to clock the direction the brake line comes off of the caliper. This is not a problem, but some modification may be needed depending upon the style of fitting you are using. As you can see in the picture below calipers have a raised collar of material that may need chasing to allow the banjo fitting to seat properly. This can easily be done with a die grinder and carbide bur, or file. I cannot stress enough how important it is to seal up the hole to ensure metal filings do not enter the internal cavity of the caliper. A spare banjo bolt with the top wrapped in black tape is what I typically use to keep it plugged.

Anti-Rattle Clip? Many of our calipers come supplied with a small metal clip referred to as an anti-rattle clip. Customers call and ask how it installs. This clip is only used in a stock application and it does not fit most aftermarket brake pads. Hot Rodders simply throw this clip away as it is not needed. It will not fit most pads which are designed to make up for extra clip. Give it a toss and don’t think twice about it!

Hopefully these tips can help you if you run into questions during your disk brake install. Once completed you will have a reliable system that will give you many miles of great, trouble-free service! If you have any questions please feel free to give us a call as we are always happy to help!

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