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L85 Hydrovac booster replacement? ISO L model brake parts.

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Howdy everyone,

First off, I dont know all that much about Macks as we (father and I) bought this truck because of its history.

So down to business, we're working on a 1949 L85 firetruck that we've had for a while and I'm finally working on it. It runs and drives but stopping is the current problem. I have a basic understanding of the brake system but it had been modified before we bought the truck. To my understanding the original hydrovac booster wasn't working and the previous owners plumbed the brake lines running from the petal directly to the rear drums via a T fitting, bypassing the booster. We took off the booster and had a buddy of ours who is knowledgeable about Macks try and fix it. Note I said try as he fixed it, then blew up gaskets and diaphragm. So now I'm trying either trying to get that one fixed again or replace it altogether with a new unit if it even exists! We've also bounced around the idea of converting it to air, but seeing as how the old system is mostly still intact I'd like to use it. 

So main questions/concerns:

Is there a way/is it possible to salvage the old unit? I would need to get more info on how bad the old one is.

Is there a rebuilt unit out there that someone is looking to sell?

Are there any new products out there that I can swap in? I'd like to keep it original but I also like stopping when I need to.

Assuming I find a unit or fix the old one, what brake fluid should be ran in it? (where do I find the reservoir might be helpful too)

Anything else I need to check or look into? I haven't got to the actual drums yet as I figured they wouldn't work anyways without a  brake system.


Thanks and any info at all would be helpful for a couple of restoration rookies!

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  • 5 months later...

My department is attempting to restore our 1947 Mack FH Closed Cab Fire Truck.  We also are in need of a Hydrovac Brake booster.  I am attaching a few pic of our truck for reference.   We are a very small rural fire company in western Maryland we are attempting this restore for our 50th Anniversary in April 2017.  If you call hell us please email me at mgs012962@Gmail.com or call me 301 707 5295.  Thank you.




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I used him for the 2 piston booster on my AC Mack. Give him a call. Have the booster part number or other I.D. info and  maker (Bendiz, Moraine, etc. )    Paul




 “Life’s journey is not to arrive at the grave safely, in a well preserved body, but rather to skid in sideways, totally worn out, shouting ‘Holy shit, what a ride!’


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On 11/12/2016 at 9:07 AM, j hancock said:

Good looking fire rig!

Deputy Chief 80:

I agree with j hancock: I always liked the "E" model. This one appears to be a commercial chassis, "EH", with an aftermarket body and separate pump engine (not that there is anything wrong with that !!!!).

Good luck with your restoration, keep us updated on its progress.


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