Brake fade

[Canadian Gunner]

Hi Guys:

For those who followed the discussion in the newby section of this forum will know that I have been working at turning my 'new' CCKW 352 into a Canadian artillery tractor variant as per Korea 1951-53.

The work is almost complete (removal of the rear bumperettes, painting on the Canadian badges and markings and some minor work on replacing some honking huge modern turn signals) and she has been out to a couple of local events to test her roadworthyness, get used to the shifting, etc.

A sweet truck by all definitions, I am really pleased to have finally added a CCKW to the collection and can be said to be a definite fan of the breed! I love the dsitinctive sound of the 270 pulling away!

Now my headache: she served last with the Norwegian Forces and was converted to silicone brake fluid (theres a bright yellow sticker (in Norwegian) on the master cylinder access panel and the fluid feels and smells right for silicone. She brakes like nobody's business and can lock up all three axles if you stand on the brakes suddenly, however, she is suffering from noticable fading as you keep pushing on the pedal, to the point where a second push is necesary for some stops... its a different feeling from air in the system (one I am very familiar with from constantly bleeding the brakes on my M135) so I don't think it needs to be bled; something I'm going to do this weekend but I suspect the problem will still be there when I'm done.

Que pasa? In the words of my Italian buddy's uncle, are there any "maka da trucka stoppa" experts out there who can help diagnose this problem?

Cheers! Mike

[Barry Churcher]

Hi Mike
The most common fix for your symptom is a master cylinder. Usually the fluid leaks past the seals inside. Never was a fan of silicone fluid but it shouldn't make the pedal fade away like that. There was just a good thread on here about master cylinders.
Cheers,
Barry

[Bill_Wolf]

Mike,

Is there a loss (or consumption) of fluid from the master cylinder or is the level staying the same?

Bill

[Canadian Gunner]

Darn good question, Bill and I should have had an answer ready! I'll check tonight!

Cheers, Mike

[SpookyDad]

Which is the newby section?

Neil

[Canadian Gunner]

Hi Bill:

The level is good so I'm assuming that it is not draining away somewhere.

Hi Neil:

The newby section is the "Welcomes and Introductions" and I have posted a bit of stuff about my beastie here: viewtopic.php?t=3053

By the way, a friend of mine is selling several 'Whermacht' vehicles, including a signals truck, up here in Canada- see: http://www.willysacres.com/

Cheers! Mike

[Bill_Wolf]

Mike,

I am sure you surmised this but for others.

If their is no reduction in the fluid it would, more than likely, be blow by in the Master.

Bill

[dr deuce]

>If their is no reduction in the fluid it would, more than likely, be blow by in the Master. <

OR the booster

[Canadian Gunner]

I'm praying for blowby in the master cylinder 'cause I can get a kit for it easily and do the repair in a hour or so. I hope I don't have to pull the booster out... their a lot of work and a pain to find parts for.

I'll have to post a picture (through Barry) of which booster I have. The truck is an early one (352 40236 B1) but I suspect that it was upgraded at some time in the past as it has the left hand exhaust.

Yippee!

Mike

[Canadian Gunner]

Hi Guys:

I still haven't sorted this problem out. Turns out I have the early style (outside the frame) big rectangular master cylinder. The brake system on my 352 is almost identical to my C60X CMP. The master cylinders are identical except for which side the crank is affixed. My master cylinder has 'Made in France' molded on the inner side so I now know she served in France as well as Norway (or the Norwegians bought surplus French parts!)

I have no idea where to start on the repair of this master cylinder. Are rebuild kits available? (I just spent 40 minutes reveiwing the 107 hits I got on this forum regarding master cylinders and there is nothing on the older models and their repairs).

Rereading my earlier posts, I notice Dr Deuce says that the blow by could be in the booster. I suppose I could block all the lines out of the master cylinder and see if the pedal still fades... that would isolate the problem to one or the other component.

Any ideas and suggestions will be actively pursued as I need to make this machine safe for the road... she stops on a dime but I can't sit on a slope as the pedal drops rapidly to the floor and I have to use the hand brake to hold her. Reminds me of the hilarious Bill Cosby schtick about driving his Volkswagen Beatle in San Francisco..., "Go around, idiot; Go around!!!"

HELP!

Cheers, Mike

[pristus1]

if you dont have any luck with rebuld you could always get m35 master it will work with gmc as i had sim uler problem on ebay your end they was selling for about 50 doll

[Bill_Wolf]

Mike,

The cheapest test would be to get a brass female plug fitting of the proper size and plug off the end of the master to hydrovac line at the hydrovac (as you suggested). It will test as to the whether the master is having internal "blow-by". It is a quick, not labor intensive check. Cost will be the fitting and brake fluid.

It will either tell you if you need a Master or need to pursue other diagnostics.

Make sure you have the Technical Manual, which is available several places on the net for free in pdf.

Bill