1976 Cadillac Commercial Chassis Master Cylinder & Hydro-Boost

HydroBoost.jpg

I have traced the source of a power steering leak to the “Hose Pump to Booster” line as shown on Figure 5-69. The poor brake performance was traced to the master cylinder.

CaddyDaddy hose SKU 76PE91566 has the following specs:
Hose End Type 1 - 3/8 inch Male Inverted Flare
Hose End Type 1 Thread Size 5/8 inch - 18
Hose End Type 2 - 7/16 inch Male Inverted Flare
Hose End Type 2 Thread Size 11/16 inch - 18
Approximate hose length - 53 inches

Gates hose #364040 shows the same sizes in decimal form.

The CaddyDaddy ad states to “compare to yours to ensure proper fitment”

Even if I take apart the fittings in my unheated garage, I have no way to confirm thread size and count.

Has anyone used this part and if so, was it a direct replacement?

For the master cylinder, CaddyDaddy SKU TEMNMC M2072-1 is listed for the 1976 Cadillac Commercial Chassis but has the same “compare yours to ensure proper fitment.”

Attributes shown are:
#of line ports: 2
Brake Master Cylinder Bore Size: 1 1/8"
Brake Master Cylinder Line Thread Size: 9/16"-18, 1/2"20
Primary Outlet Thread ½" 20
Secondary Outlet Thread 9/16" 18

Has anyone used this part and if so, was it a direct replacement?

For the master cylinder, rebuilding is not an option as my mechanic lacks space to store the ambulance. That being said, I will retain the old part for a possible future rebuild.
 
The “compare yours to ensure proper fitment.” is a standard statement to keep them from having any liability if the new part fails. Personally, I would call NAPA, O'Reilys, or one of your local auto parts store to see if the part is available. My bet is that they can get the correct part from their supplier without any question as to the fitment. If your master cylinder is leaking internally, if you remove it, your mechanic should be able to rebuild it in his shop. You should be able to purchase the repair kit locally also. It is made by Raybestos, and the part number that I have found is MK-1108, but have the auto parts store verify this in advance. If your mechanic bench bleeds the master cylinder, you should be able to put it back on, and have brakes. The lines will need to be bled also, but it should be safe to drive to your mechanic, if you don't have far to go, and are careful to keep a distance between you and the car in front of you.
You might also need to have your brake booster repaired. I suggest that you contact Booster Dewey for advise. You can find his information in the recommended vendors section of the website.
 
The “compare yours to ensure proper fitment.” is a standard statement to keep them from having any liability if the new part fails. Personally, I would call NAPA, O'Reilys, or one of your local auto parts store to see if the part is available. My bet is that they can get the correct part from their supplier without any question as to the fitment. If your master cylinder is leaking internally, if you remove it, your mechanic should be able to rebuild it in his shop. You should be able to purchase the repair kit locally also. It is made by Raybestos, and the part number that I have found is MK-1108, but have the auto parts store verify this in advance. If your mechanic bench bleeds the master cylinder, you should be able to put it back on, and have brakes. The lines will need to be bled also, but it should be safe to drive to your mechanic, if you don't have far to go, and are careful to keep a distance between you and the car in front of you.
You might also need to have your brake booster repaired. I suggest that you contact Booster Dewey for advise. You can find his information in the recommended vendors section of the website.

I can second this. Even if they cant rebuild it, take it old Master to NAPA and they will likely be able to match it to a part. This is what i did with my 68 a month ago.

Also Dewey did a good job rebuilding my booster as well.
 
If that failes your hoses can be remade using your ends. And shop doing hydraulic hoses can replace the rubber. But if your changing one do them all as they are most liklythe same age.

I doubt if booster dewie will do a hydro boost.
 
Thank you to all who offered suggestions. I did purchase both items from Caddydaddy.com. My mechanic advised that the master cylinder bolted into place perfectly, but he had to remake the lines as my fittings were not the proper size for the new master cylinder. The high pressure hose did fit after it was re-bent some.

This is not a complaint. I just wanted to advise members that some adjustments are required in order to have these parts fit. I am grateful we still can source commercial chassis parts even if some adjustments are required.

The bottom line is that now my ambulance stops and stays stopped when I press on the brake pedal.
 
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