Problem with brake system of dodge t110

serge · #1 15-05-09, 07:32

AMERICAN DODGE T110 or CANADIAN DODGE T110 have a brake system that includes a booster and a valve.
The booster has the shape of a cylinder ; at the rear it is connected at all time to the vacuum of the manifold and in front it is connected to the output of a valve.. Inside, there is a large piston rounded by a rubber and a large spring which pushes the piston forward.

When the motor is running, the vacuum in the manifold sets at the rear of the booster and at the entrance of a valve. The outlet of the valve leads to the same vacuum condition at the front of the booster eading the the piston having the same vacuum pressure on each side as long as the brake pedal is not depressed.

When the brake pedal is depressed the output of the valve leads to applying the atmospheric pressure in front of the booster so the piston is moving to the rear of the booster upgrading the efficiency of braking.

As soon as the brake pedal is released, the output of the valve is switched and leads to applying vacuum pressure in front of the piston which moves towards its first position

The problem encountered is the following : the piston does not return at its normal position when the brake pedal is released.
Using a specific tool I have checked the pressure variation at the output of the valve.
( vacuum at the idle state, atmospheric pressure when brake pedal is depressed , vacuum again when brake pedal is released ).

Once having oiled the rubber ring around the piston the system has been working for 40 miles but became out of order again

IPlease is anyone able to help me to resolve the problem?
Regrads Serge

gordon · #2 15-05-09, 19:27

If the chamber is building vacuum in front of the piston when the pedal is released, then the only thing to do is to polish the inside part of the chamber where the piston runs.

There is a special light oil for vaccum chambers too, so find some of that rather than ordinary oil. Ordinary oil might have damaged the piston rubber?

The other possibility is that the return spring might be weak? or possibly the master cylinder is stiff and the return mechanism there is holding it forward?

Is there anything in the truck manual about this? I don't have a t110L manual here.

Gordon

serge · #3 16-05-09, 13:23

Hello GORDON

I thank you for your answer. I own the technical manual and it is written that the booster should be oiled with the engine oil. I had soon examined the inner of the booster and I had saw that it's surface was in a good state.
Following indication of the technical manual, the return of brake pedal is the result of 3 actions.
1/ Sprng inside Booster
2/ Vacuum in front of the piston of the booster
3/ Pedal pull back spring

Nevertheless the last indication seems to be a mystery because there is no attach for a spring in the rod associated to the master cylinder.
I have to find the kind of oil you have told in you previous post

Regards Serge

serge · #4 16-05-09, 13:25

Here a pic of the rod associated to the master cylinder on DODGE T110

gordon · #5 16-05-09, 13:40

It seems very unusual to me to oil that cylinder with the engine oil, but if that is what the manual says ...

The return spring will be to pull the PEDAL back, not the master cylinder pushrod.

If the return spring is in place, pulling the pedal back, then it comes down to two possibilities;

1. You are not getting full vacuum on the side of the piston when you release the pedal - though you say you have already checked this.

2. The cylinder piston is sticking in the bore.

I would suggest you clean and oil it again, then run it again and see if it sticks again. As long as it is easy to clean I'd do that a few times before I thought of trying anything else.

serge · #6 16-05-09, 19:42

Hello GORDON

Of course there is a pull back piston spring inside the booster. Normaly with it action added to vacuum at the front of the piston of the booster, the brake pedal should return at it idle position after been released.
As showed in my previous pic (and as I saw on an other DODGE T110) there is no pull back pedal spring.

I think that my problem is due to the rubber of the piston. Please,can you give me the name of the specific oil you told in your previous post

Regards Serge

gordon · #7 16-05-09, 21:04

I'd guess you know as much about these cylinders now as anyone you will find on here.

I think the name of the oil is vacuum cylinder oil, or booster cylinder oil, though when I had to service my DUKW hydrovac I used light jack oil (for a hydraulic jack) It has to be quite light and not attack the rubber seals, which a lot of ordinary oils will.

This sort of stuff...

http://cgi.ebay.com/Hydraulic-Jack-O...3286.m20.l1116