2009 at the Hammond Barn

RHClarke · #1 13-05-09, 17:51

Quote:

Originally Posted by Bob Carriere

...Rob did you have any sealer like plumber cement on that bolt thread that went into the block.... maybe the pump is fine and it is just a bolt leaking...Bob C.

Bob, There may have been some silicone on the end of the bolt, but nothing else was added. I suspect you are correct given the rust stain location. I will cut new gaskets and put the goo to the block and gaskets and I will add some of the recommended plumber's dope...

Bob Carriere · #2 13-05-09, 21:09

... we run a tap in the thread and similarly a die with the bolt before we goop them up..... or use new bolts.... and lock washers.....

Lots of proper gasket material around in the barn......

Bob C.

Bob Carriere · #3 13-05-09, 21:19

Last Saturday, being wet, Grant and I jacked up the C15a frame and did a brake adjustment on the beast.

Pedal had gone soft over the Winter. woerked according to the manual by raising all four wheels....... even ran the engine to see if they braked evenly.

Had a persisting problem with the front wheel cylinder not releasing properly...

Off came the wheel.... cylinder removed and checked for rust or dirt..... cleaned and re-installed....... voila.... except the brass junction block kept leaking ever so much..... tried various size and thickness of copper gaskets.... filed some burrs on the brass facings.... in all we assembled and reassembled about 5 times..... last one was lucky and it stopped leaking.....

I now have good brakes ....but.... still require one good pump to get a hard pedal........ I am asking too much of the old CMP......

We adjusted the lower cams and center snail cams on all four wheels and bleed each corner extensively....... why is it soft... I mean why is the brake pedal still soft to the first pump....... ???

We are talking SS sleeved master cyl. .... 4 new wheel cyl... new linings and arced drum to match lining profile....running synthetic brake fluid...

Do we need to bleed again.....?

Comments / suggestions welcomed......

BooBee

Phil Waterman · #4 13-05-09, 21:57

Hi Bob

Don't know what the problem is but none of my trucks have to have the peddle pumped to get peddle. Never have had that problem, peddle is always at the same spot. About 1-2 inch free travel on the HUP and a little bit more for the other two trucks with boosters.

With all the care you have put into braking system it is hard to think of what could be causing the problem. But I'm almost willing to bet in the end it going to be something simple that everybody will say oh of course. Some place I've got some 1930s brake system books I'll try and find them and start thinking simple.

When you say "still require one good pump to get a hard pedal." do you mean each time the brake is applied or only when you first start to drive then it works OK?

Only consistent brake problem I have had is with my HUP after it has sat for a week or so in damp weather, then the left rear wheel will grab. I've pulled the drum a couple of times, the only thing I have ever found is a light rust on the drum face. Now I know to drag the brakes for a moment under power and it goes away. None of the other drums ever do this.

Cheers Phil

Bob Carriere · #5 14-05-09, 19:03

Hi Phil......

It seems that each time I use the brakes it seems to need one fullpump before it starts getting what I would escribe as a good hard feel 1 /1/2 from rest.

In talking with Grant last night...... when we removed and reinstalled the driver's side front wheel cylinder.... we did bleed the front wheels each time.... but ... maybe some air travelled into the rear circuit......

We will have another crack at it this weekend...... Grant as some kind of
"power bleeder" device that we will attempt to fit on the CMP.....

You are right it is probably something very simple...... like an air bubble trapped in high/low section of the circuit that is just moving back and forth but never gets bleed out completely.....

Stay tuned and thanks for all you time and effort....

Bob C

S LATHERON (RIP) · #6 14-05-09, 23:40

Has the MASTER CYLINDER got any adjustment on the pushrod. I had similar problems on a Long Wheelbase Land rover.
Traced the problem to the push rod on the Master Cylinder being to far into the Cylinder. This has the effect of reducing the amount of fluid compressed at first stroke.Stripped Master Cylinder down, Cleaned all moving parts and re assembled making sure that the Piston was as close to the Rubber boot at the back of the Cylinder as possible.
Brake actuation improved greatly having a full charge of the fluid pushed through the whole system at first push.
Also if the Piston is to far forward at the start of its operation there is the danger of it not being fully retracted when you remove your foot from the brake pedal.The Piston covers the return port. The fluid in the system cannot return to the Cylinder Resevoir properley and you can end up with brakes binding and overheating.
Does the Master Cylinder top / filler have a vent hole to let Air into the Reservoir to replace Fluid that has been used.Try brake actuation with the cap OFF and then On see if it makes any difference.
good luck and let us know how you go with this problem.

Walde Libera · #7 14-05-09, 23:52

Bob

Had similar problem on my CGT; with booster and silicon brake fluid.

Leak issues were resolved but I was still not happy with pedal travel, almost hitting the floor. Certainly not safe or comfortable driving it.

So redid all 4 brake shoe adjustments, jacked up each wheel seperately and adjusted as tight as you can go and just enough back to free spin the wheel.
It is easy to get disoriented doing this job, as you are looking at a mirror image from the backing plate side.

The pedal is now hard came right up and is consistanly firm at a mid travel position.

Walde

Bob Carriere · #8 15-05-09, 03:42

Let me first deal with S. comments and suggestions....

I can remember if the CMP Chev Master Cyl. has a screwed adjustment.... remember doing just that on an old car some yeras back..... so you have given me something to look at..... it might also explain the dragging front axle cyl. that did not seem to release..... might explain quite a bit......

Grant to take note for this rainy Saturday....

Master Cyl cover does have a air hole and was placed on loosely just enough to prevent fluid form being squirted up from the reservoir while pumping.... but will check again with a blow gun to make sure it is vented.....

Walde...... yes we did have the truck on 4 axle stand and readjusted all four wheels to slight dragging.....using the small window slot on the brake drum allows to see the tight fit of both brake shoes.....

We may well do the whole process all over again if the rain is just preventing anyother activity......

We actually started the engine and engaged the gears to see the wheels spin.... and noticed that the differentials were working by spinning the less dragging wheel of each axle........ carefully applying the work boot tot he spinning axle usually caused the far side to start spinning.....

I am gambling on push rod adjustment for the moment.... or the overall linkage system for the brakes with all the clevis and adjustments.

BUt..... I also plan to do a full bleeding cycle on all four wheels again..... thank God Grant is very patient and very exacting in such an exercise. He calls it gaining experience for when we do his cab 13.......

Really appreciate your help...... don't be shy to comment.... like Phil said it may be the most simple thing that we have overlooked and need to be reminded.

We are learning all the way.

Boob