Hydrovacs

Lar Dowding · #1 16-12-17, 00:54

Just wondering what everyone thinks of hydrovacs? My truck never had one but I have the fitting to fit one, the unit is scrap and thinking of buying a new one. I like the idea of having it just what a few options before I spend out
Ttfn

hrpearce · #2 16-12-17, 03:37

I like them.
I fitted a hydrovac out of a 404 Peugeot into an old 3 speed Nissan patrol and almost halved its stopping distance.

Lynn Eades · #3 16-12-17, 08:29

Lar, are you talking specifically about a (GM) "Hydrovac" or more generally referring to any sort of vacuum booster?

Lar Dowding · #4 16-12-17, 10:23

Talking about an original as fitted to a cmp, thinking of buying the one that lwd has for sale

Lang · #5 16-12-17, 11:07

I would strongly recommend it. I have fitted after market vacuum units to several Dodges (my current WC53 stops better than a brand new Landcruiser) and a number of civilian older commercial vehicles.

Don't know about the GM Hydrovac unit but the generic units are cheap and can be fitted in a couple of hours.

The easiest, cheapest and most practical way to get modern braking on an old vehicle.

Lang

Phil Waterman · #6 16-12-17, 14:29

Hi Lar

Questions before proceeding the original CMP brake booster as used on C60 series has a special linkage which is necessary to make it function.

There are several threads on MLU on the topic which I will try and find and post links. Here is one http://www.mapleleafup.net/forums/sh...ter#post220149

Having said that the booster makes the brakes on both my C60S & C60L have good brakes with out the booster these trucks with a full load would not be safe to drive over 25-30 MPH the stopping distance would be to great above that speed.

Last time I serviced one of my boosters decided to measure the boost at 15 inches of vacuum the mechanical force exerted by the booster was around 325 LBS. Now to figure additional force on the master cylinder you would need to work through all the math of the linkage pivot arms in the linkage.

Cheers Phil

gjamo · #7 16-12-17, 22:14

Here is an alternative practical idea I have seen on a couple of vehicles at Corowa. At least spares will be readily available.

Lynn Eades · #8 16-12-17, 22:51

Lar, If you plan to modify, I would suggest investigating a dual circuit.

Mike Kelly · #9 17-12-17, 01:10

Back in the 70's a few of the club members had fitted those PBR vacuum brake boosters on their WW2 Jeeps. I did the same mod. and the brakes on my Jeep improved by 100% .

One club member reckoned the extra pressure would blow out the wheel cylinders but that never occurred in all the years we were driving Jeeps around.

Phil Waterman · #10 17-12-17, 14:06

Hi All

One thing I don't feel can be over emphasized on CMP is keeping the brakes adjusted. Even for those of us who have been driving and working on these trucks for years, keeping the brakes adjusted is the key to brake performance.

In this day when automatically adjusting brakes are the norm, we get accustomed to never touching the adjustment or even thinking about need for adjustment. But with trucks with only manual adjustment, reading the manual and putting the truck up on jack stands and adjusting buy the book takes on a new importance.

On topic of dual circuit brakes yes it would be nice. But dual or single circuit system one suggestion from a long time CCKW driver (in our MV club) is make it a habit that everytime you start the truck is while you let it warm up, STAND ON THE BRAKE PEDDLE JUST AS HARD AS YOU CAN his logic is it far better to have the peddle go to the floor then.

Cheers Phil