Scary moment today...

Well, just shows what can happen - this was with my international s120 which I use around the property for moving brush taking trash cans to end of drive. Started her up today and went to unload some brush before taking the trash up to the end of the drive 1/4 mile sloping drive.
Went to the lower pasture and wanted to back down to the burn pile - so drove it up a steep slope where I back down and turn to get to pile - started rolling back.....no brakes...not a thing pumping like crazy...nothing - in an instant I was picking up speed going backwards - tried the hand brake - useless - I was going at a fair lick when I realized I was going to back into some heavy brush, brambles etc.....this stopped me but not before I hit a good stump and bent the tailgate.

Whew!!!! got the truck out of there and went and checked the resevoir in the brake master cylinder...dry!!!! Headed back to the garage, got some more brake fluid (old so need to bleed that all out) bled the brakes and got good pressure back.

So that was my bit of excitement for the day - strangely enough I was didnt feel any fear...just said to the dog.....hmmmm this is NOT good!

If this was on a tractor with bad brakes and you were brush hogging or something could be very nasty. My next project is to fix the brakes on the 8N

PS I could not work out for the life of me where that brake fluid had gone!!! No leaks I could see anywhere or stains to indicate a leak.

Good thing about an N-tractor, brakes are mechanical, so total sudden failure is a lot less likely. Of course a big tree limb jammed under both brake pedals can make it difficult to apply the brakes.

No parking brakes?

Could a bad vacuum brake booster (if so equipped) suck some out?

KRS

Is the hydrovac - vacuum brake booster - on the engine side of the dash or is it a seperate unit mounted underneath on the frame of the pickup?
Either way My bet is that the seals in the power brake booster have failed and the missing brake fluid is leaking into the diaphram.
You gotta love them old trucks.
Back in the early 80s a buddy and I drove a 1948
1 1/2 ton Diamond T truck from Utah up the AlCan highway to Alaska. Got up into the St Elias mountains in the Yukon Territories and a seal in the hydrovac failed. 200 miles from nowhere. We stopped and tore it apart but there wasn't much fixing it so we put it back together, bought a couple of gallons of brake fluid and kept on going. On that truck the master cylinder is under the wooden floorboard on the driver's side. Little tin plate to cover it. Lift that tin plate, unscrew the top of the master cyl and add fluid as required.
So we are in the St Elias, twisting road, up and down mountains with an old truck with a pretty good load on it. The leaking seal got so bad that every time I hit the brakes we had to add fluid. So we left the little tin plate off and the cap to the master cyl off and he used a little funnel and added fluid as we drove on down the road. Once in a while the hydrovac would get over full and then the brake fluid would get sucked into the engine's intake manifold. Talk about mosquito control! HUGE plume of white smoke belching from the rear of the truck.
But we kept on trucking and made it into Glenallen and bought more brake fluid. Made it in to Anchorage a day or so later and believe it or not I brought the old hydrovac into a heavy truck brake shop and they had a rebuilt one for it on the shelf. It was dusty from sitting so long but bolted right in and solved the problem permanently.
Sorry about the long post but thoughts of brake boosters conjures up some memories.
So check your booster.

So where you in reverse??? If so why didn't you just turn the key off so as to shut down the engine which would have slowed you down and stopped you??? As for where the fluid went now that it is full you may want to watch for wet spots under it and also next time you have it running smell the exhaust for the smell of burning brake fluid if it has power brakes. Seen more then one brake booster get full of fluid due to a leaking master cylinder and then it gets sucked into the engine and burned

It is quite unlikely the S120 has a power brake unit of any kind. Usually the bigger 1.5 ton and 2 ton trucks had the hydrovac, but the 3/4 ton (120 series) just had a simple single master cylinder, so no backup for a failure. The dual master cylinders did not come out until 1968.

In our northern climate with highly salted winter roads, a brake failure of that type usually means a rusted through brake line, and it is often on the rear axle or along the frame where the steel line passes under a retaining clip. If the leak is small, you won't notice any oil leak as today's brake fluid evaporates slowly and may not get discovered. But with the age of that Binder, the rubber cups in the wheel cylinders are also highly suspect. More likely the ones in the rear axle go first.

The hydraulic brakes of that vintage are highly directional. They give good or adequate braking while going forward, but are almost non existant when backing up. This has to do with the leading edges of the brake shoes and the directional rotation of the brake drums. The brakes on the right side of the vehicle are assembled differently than the brakes on the left side. They are symmetrical if you reference to the rotational direction of the brake drum.

You may get by with just adding fluid and bleeding the wheel cyinders. DOT 3 fluid is fine for this beast, but all brake fluid brands of this type are hydroscopic and absorb water from the air leading to the internal rust of the brake cylinders and the master cylinder. The rust is abrasive to the rubber parts so they eventually leak. Do not put the non hydroscopic silicon fluid (DOT 5) in this system, it is incompatible with what is already there.

Hope you had some clean skivvies in the drawer, they probably were needed.

Paul in MN

Heh heh heh....you know...you have a good point!....I am not sure though...I actually think I might have still been in 1st gear but kept the clutch depressed!!! This truck only has a master cylinder no vacuum booster or anything like that. I will just keep a closer eye on the fluid level from now on!


Great story about the Alaska run!!!


Yeah.... need some strong detergent in the next load of wash!

Shoot if you where in first gear which should be granny you had all the stopping power you needed and then some as long as the drive train held out that is. But funny how once a mistake is done how you can in turn see what you could maybe have done that would have kept it from happening in the first place. LOL