The Stovebolt Site Forums The Parking Lot Big Bolts Brake Line Hoses

I am replacing the hydrovac on my 1966 GMC 5500 truck and want to change the hydraulic brake line hoses while I am at it. However, I haven't come up with the part numbers and am hoping someone here might be able to help. I have a Maintenance Manual that covers most parts, but refers to another manual for these brake line parts. My truck has the usual two hoses in front and one in the back. The steel lines they connect to look like about 3/16 inch. The Raybestos catalog shows front hoses that might work, but calls for two in the back that I know are too short. Bendix does't list any that I can find. And the local Napa store tells me that their computerized system only goes back to 1970. Any part numbers that I might be able to cross-reference would be greatly appreciated by me and my wallet. I know I can use the old hoses as patterns for making new ones, but I also know from experience that this can be much more expensive.

napa part #UP 4497

sorry that part number might be wrong check out bluedotinc.com for those brake hoses

JRMunn, if you have your old ones off take them back to NAPA or Advance Auto and ask to talk to the COMMERCIAL sales guy there. The commercial sales people or usually quite a bit sharper than the counter folks. Their hoses are usually lined up in boxes in one area. Pull them to you find one the right length/size.
I've done this many times and have seen them do it many times. Our local GIRL here at Advance Auto has been selling parts for over 20 years. Give it another try if someone doesn't have the info here that you need.

3B may see this and chime in. I bet he knows.

EDIT: the Commercial guys, or gals, are usually toward the back of the store but within eye sight!

Hy JRMunn and guys, there appear to be multiple choices for brake hoses on this particular model of truck, I suspect because of the different front axle capacities available on this truck.
Front brake hose with 28" hose Raybestos p/n BH36535 with 23 1/2" hose Raybestos p/n BH36536
Rear brake hose with 16 1/2" hose Raybestos p/n BH33676 with 17 1/2" hose Raybestos p/n BH36563
In most cases to convert Raybestos part numbers to Napa part numbers change the alpha part of the part number from BH to UP, hope that helps.

Thanks to all for the replies and ideas. I will probably need to go to West Sacramento to find parts stores with better selection for medium duty trucks. 3B, I agree with your Raybestos findings for the front hoses that are about 28 inches long, but my rear hose is about 23 inches, which is longer than what Raybestos shows. I am sure my rear axel and differential are original, but truck has a flat, steel dump bed that might have needed a different rear configuration. It is frustrating to have a maintenance manual that shows all the steps of rebuilding a hydrovac and installing brakes at the wheels, but nothing about the lines and hoses in between.

I am finally back to replacing the hydraulic brake line hoses on my 1966 GMC HM5500 truck. It looks like Raybestos makes reasonably priced hoses for the front wheels, but I have another question about the rear brakes hose. Both Raybestos and Bendix catalogs specify two hoses in the back. I only have one hose that goes from a 1/4 inch steel line (originating at the hydrovac) to a splitter that sends 3/16 inch steel lines along the back of the axel to each rear wheel. This single rear hose and its fittings have a total length of 24 inches, and I can't find it in a catalog.

So I have been trying to get the rear hose made. But all of the places I have gone, including truck shops, only carry hydraulic brake line hose with about a 1/8 inch diameter hole and similarly small inlet tubes in the fittings. This seems to be very small compared to the diameter of steel lines that the hose is connecting to, and it must carry the fluid needed for operating brakes on both rear wheels, each of which have two cylinders per wheel. I know that brakes work because of the fluid pressure, but it still seems that the hose needs to move enough fluid to expand four, large wheel cylinders to the point where pressure is applied.

Is this small hose hole size a real problem, or am I just imagining things? Any information about hydraulic brake hose sizes for old medium duty trucks would be greatly appreciated. And if I need a larger diameter hole, I am looking for suggestions about where to get the hose made. Thanks, again, for any help and advice.

Here's a company that will make a custom line for you.

http://brake-hose.com/custom-brake-hoses

Mike B

Hy JRMunn, I have found a hose part number that may do the job for you, Dorman p/n H31669 $17.31 at RockAuto, Raybestos p/n BH31669 $24.79 at RockAuto. Both those hoses have the same specifications, 7/16" X 20 t.p.i. male on one end, 7/16" X 24 t.p.i.female on the other end, looks like a horseshoe clip retension, these hoses are 24 1/4" o.a.l., Hope that helps.

Thank you 3B and Mike B for your very helpful suggestions! 3B, I don't know how you found these hoses. I spent much time looking for the needed length and fittings, but must not know the right way to search. The fittings on these hoses aren't identical to what I have, but they should work fine as long as the 7/16" x 24 t.p.i. female end fits the male inverted flare on my 1/4" steel brake line. This is probably what was used in my truck, but both the Dorman and Raybestos application notes state that two hoses are used (one on the right and one on the left) which still leaves me wondering about supply capacity. I guess the thing to do is to order one, see if it fits, then cut my original hose to check the inside diameter.

I did check the site recommended by Mike B. It has a very long list of fittings, but the only brake hose they show has the small inside diameter hole. But something else might be available if I call to ask.

At this point, I think I should just get parts that fit, put it all together, then see if the truck stops empty and with a load of gravel.

Hy JRMunn, I have never seen a truck with two hoses to supply the rear brakes, but the trucks I know best were built a decade before your truck. The systems I am used to seeing have one hose from the chassis to the top of the differential where there is a tee fitting from which one brake line travels down the rear axle tube to the wheel cylinder connection on either side of the truck. As I said there are older trucks with the system I have described and they have multiple wheel cylinders per side, of the same capacity as yours and the rear axle flexible lines that we are discussing have more than enough capacity to supply to supply those wheel cylinders, hope that helps.

3B - Thank you for the comments. All the trucks I have worked on are just as you describe. I am only repeating what the catalogs say about there being two rear hoses, and am probably showing my concern about mixing newer and older technology. I have noticed that the Stovebolt forum is focused on older trucks, while forums dealing with 1960's trucks are mostly about pickups and lighter trucks. My medium duty truck is a 66 model that was built in 65, and it seems to include some of both years in the engine and drive train, which are very solidly built, while having a new style cab and related wiring that seems to be less well put together and less available. For example, it has the old style tandem brake/clutch master cylinder (showing that older ideas are not always the best) and newer style heater, wiper, and light controls and electrical components - all of which seem to be hard to find parts for. Such are the challenges of keeping older trucks running. But it should work just fine on the ranch if I can ever get finished with what needs fixing.