front brakes locking up

[The_Handier_Man1]

From: denverguy110  (Original Message)
Sent: 3/22/2005 9:12 PM

The guy from whom I bought my '78 Tiffin Allegro (now with fried alternator field wire) has a '69 Winnie w/ 318... his front brakes are locking up.

He's replaced the master cylinder, the rears are fine, but the fronts are still locking up on him.

Any suggestions for him? He's not online, I will have to relay.



From: Derrek
Sent: 3/23/2005 9:16 AM

I remebered someone saying that installing the wrong master cylinder can cause the front brakes to lock up. I used the message search and found this:

Les, -

Sadly, you have bought the wrong part.

First, SpudBoy has an all drum brake truck using a medium duty type 1.75 inch bore unit - nothing at all like the front disc brake Indian you have.  You purchased a Chevy hydroBOOST unit and your vehicle is equipped with a hydroVAC system, and the dynamics are wholly different.

Second, although the casting numbers match the internal components don't.  It is likely you will shortly be experiencing symptoms like front brake lock up, which is relieved by bleeding off the calipers, only to repeat itself within a short distance.

Or possibly, you won't get a decent pedal at all, blame the unit as a defect, and try again. Or worse still, someone will lead you to the conclusion that the proportioning valve is bad!!  If the unit does not come with a rod preinstalled at the factory, then it is not the right one and you will have problems.

Please contact me at the warehouse and I will be able to supply the correct part, which is new and comes with rod installed, signaling the correct internal configuration. Remember that swapping the rod does not make the unit a correct replacement: only the correct biasing of pressure to the front and rear brakes will do the job safely!


Yours genially,

Geoff
Alretta Truck Parts Inc.

508-788-9409 weekdays 9-5:30



From: brakeparts
Sent: 3/23/2005 9:38 AM

Thanks Derrek for dredging up this letter!

Have your friend call me and we can review his position. It certainly is possible that he purchased the wrong unit. Ask him to have some info on his vehicle to discuss with me? Chassis length, tire size, style of brakes, either vacuum brake or hydrovac, a part number for the unit he purchased, all would be a good start...

Call days 9-5:30 508-788-9409

Geoff
Alretta Truck Parts Inc.



From: Slantsixness
Sent: 3/23/2005 1:58 PM

One other thing, if it's not the "wrong" Master cylinder...

The brake hoses can deteriorate over time and become constricted. This wouldn't tend to "lock" the front brakes, but it would keep them "applied" enough to cause the described condition (what happens is they don't ever release completely). You can determine this by simply bleeding the brakes. With a front bleeder opened, the pedal should go to the floor quickly with a logical amount of brake fluid expelled under pressure, if not, or if the bleeder just trickles or has no pressure behind it, suspect these lines (replace both and consider the rear one(s) too.)

And, it could be the wheel cylinders, too.

Tom



From: denison
Sent: 3/23/2005 2:16 PM

     If it isnt the master cylinder;
      What next comes to my mind is that his wheel cylinders might be starting to leak, the brake fluid running onto the drums and linings, where it turns into a gluey mass when it is heated up to charring and mixed with brake shoe dust. In this case the fix involves removing the front brake drums/hubs, where the leaking brake fluid would be evident  - and clean/adjust/replace/reline everything as necessary.   And lube the front wheel bearings upon re-assembly.
    If this is the reason for his brakes locking up, he should do the “dismantle/inspect/replace" on the rear axle brakes also, unless he has reason to believe such work has been done in the last 6 to 10 years.
  <o:p></o:p>



From: denverguy110
Sent: 3/24/2005 12:31 PM

OK Thanks for the feedback guys... will let you know what happens. I'll give him Geoff's #.

Bruce



From: papamgb1
Sent: 3/27/2005 7:21 AM

not true try replacing the rubber brake line that attaches to the caliper, often the desolve inside and will not let the fluid return.   simple test put them on, when the lock up, open the bleed valve and if the "un-lock" the line is pluged and will not let the fluid return to the reservor...try it .  This was why my locked up, just a simple rubber line    see ya   papa smurf



From: denverguy110
Sent: 7/3/2005 10:22 AM

Well, he got some parts from Geoff and Geoff was really helpful but that wasn't the problem...

He screwed up when he originally replaced the internal brake hardware;  as a model, he looked at the driver side, which as he was facing it had the starwheel on the right, or toward the rear of the vehicle. WHen he went around to the passenger side, he again reassembled the hardware with the star wheel to his right, which was now toward the front of the vehicle, so the brakes self adjusted every time he used the brakes going *forward*.

Thanks to everywone who weighed in with advice.

Bruce



From: Slantsixness
Sent: 7/6/2005 7:02 AM

so... after a couple of traffic lights it wouldn't move at all!?

You're lucky the adjusters were working, forwards or backwards. I put new ones on my rear and did away with the front drums altogather, but for about a minute I was about to put the wrong adjuster on the wrong side of my rear brakes... then I checked the kit part number.... Whew! got lucky that time! Saved by my packing list from Geoff!

Hey, I wonder if this could be Clydesdalekevin's problem.....??

Tom