C30 - grabby power brakes

[ncoonen]

I have a '65 C30 283 4-speed that has a strange behavior. The factory power drum brakes seem to work okay but come on all at once after a long push on the brake pedal. The brakes take almost no effort to lock up. The truck has what looks like the original master and booster.

At some point I will switch to a dual circuit drum system so if the issue with the grabby brakes I have now is the old booster, well now is the time to make that swap. Any tips on that swap would be appreciated also.

Thanks...ned.

[AcampoDave]

When my stock set up did that, I yanked the booster converting to manual and it fixed the problem. Not knowing why it grabbed, I put the booster on the shelf hoping to figure it out later as it looked fairly fresh. After a while, a buddy tried it on his truck and it still grabbed so it went in the trash. Wish I was more help but thought I'd at least relate my experience.

[dtkarst]

I know the master cylinder is less than a year old, but also wasn't driven daily. But sounds like a vacuum booster to me especially being the original one

[ncoonen]

Thanks Dylan and Dave. A faulty booster was my guess but I have not seen this mode of failure before. It's good to know the master is pretty fresh.

...ned.

[ncoonen]

Followup for future thread searchers: a Cardone reman booster #54-73535 solved the problem. Brakes might need some adjustment but the pedal feels pretty good now and you can modulate the brakes to smooth stop. Been a while since I have driven power drum brakes. They have a different feel than modern brakes and I think a majority of the remaining pedal effort would go away if I cleaned and lubed all the linkage bushings! A light touch is all you need.

Thanks oldtruckguys...ned.

[wahl4m]

these old 64-66 power boosters are easy to rebuild ! the tricky part is disengaging the two halves /ive done mine in a press .Twist the two halves in opposite directions then clean & check the insides and rubber diaphram -90 per cent of the time the diaphram is OK.THEN BLAST OR CLEAN UP THE HALVES OR CAD PLATE or powdwer coat them and reinstall with a new boot -which can be bought off e-bay or cheaper at the chevy dealer {using a newer part #} also cleaning up all mounts and the aluminum wedge and lubing all pivoy points /should work as good as new /if cleaned it looks better thaN that off/shore booster kits on evil bay- GOOD LUCK MIKE

[old cool]

Dear ncoonen, I'd like to hop on your post. I have a half ton with a power booster and dual circuit upgrade. It's prob been on there for 5-6 years. The booster appears to be a Cardone. The brakes have a light touch but I got used to it.
A few points for your consideration or input.
1. Did you have to adjust your push rod or did you keep the longer pedal?
2. My brakes are grabby if I need to make an abrupt stop. Otherwise they are ok. Have you made any sudden stops yet?
3. My master cylinder looks contaminated so I plan to change. (awaiting a suggestion as to type of unit to buy- posted a thread yesterday)
4. I learned on this site, and also research, you don't need a proportioning valve with drum-drum brakes. I initially thought that's why they were grabby but apparently not.
5 Lastly, I put a hose up to back of power booster from inside the truck (where push rod enters) and here a faint, continuous hiss. Same air sound whether brake is depressed or left out. Pedal is not hard to push so I'm thinking a little air sound is acceptable. Can you hear a slight air sound from back of booster inside truck?
Since we both have Cardones, I would greatly appreciate some feedback on #1 and #5. Thanks

[ncoonen]

Originally Posted by old cool

Dear ncoonen, I'd like to hop on your post. I have a half ton with a power booster and dual circuit upgrade. It's prob been on there for 5-6 years. The booster appears to be a Cardone. The brakes have a light touch but I got used to it.
A few points for your consideration or input.
1. Did you have to adjust your push rod or did you keep the longer pedal?
2. My brakes are grabby if I need to make an abrupt stop. Otherwise they are ok. Have you made any sudden stops yet?
3. My master cylinder looks contaminated so I plan to change. (awaiting a suggestion as to type of unit to buy- posted a thread yesterday)
4. I learned on this site, and also research, you don't need a proportioning valve with drum-drum brakes. I initially thought that's why they were grabby but apparently not.
5 Lastly, I put a hose up to back of power booster from inside the truck (where push rod enters) and here a faint, continuous hiss. Same air sound whether brake is depressed or left out. Pedal is not hard to push so I'm thinking a little air sound is acceptable. Can you hear a slight air sound from back of booster inside truck?
Since we both have Cardones, I would greatly appreciate some feedback on #1 and #5. Thanks

Okay....

1. I did not adjust the push rod and pedal depth seems okay to me. Before the booster change, the pedal went deep and then grabbed.
2. My truck hasn't been out of the driveway yet due to other issues so I can't comment on real world performance. I based my "success" rating on a couple of back and forth drives on my long driveway. Night and day difference for me.
3. ---
4. drum-drum brakes with a drum-drum master cylinder do not need a proportioning valve.
5. Hmm, this doesn't sound right to me but I can't say for sure that it's bad. I've never tried listening to the booster in the cab.

Good luck!...ned.

[old cool]

Thanks for quick response Ned. If you ever feel so inclined when putzing with your truck, please try the hose method up to the back of the booster @ push rod. I know that a hiss that is heard without a hose is bad, but not sure if you wouldn't hear some air if hose is placed at position I mentioned.
BTW, is your new Cardone taller and slimmer the OE booster? That is why I mentioned push rod adjustment.

[ncoonen]

Originally Posted by old cool

BTW, is your new Cardone taller and slimmer the OE booster? That is why I mentioned push rod adjustment.

The booster I got was exactly like the one that came off. I can't say for sure it was the original but it had great "patina".

Originally Posted by wahl4m

These old 64-66 power boosters are easy to rebuild ! the tricky part is disengaging the two halves /ive done mine in a press .Twist the two halves in opposite directions then clean & check the insides and rubber diaphram -90 per cent of the time the diaphram is OK.THEN BLAST OR CLEAN UP THE HALVES OR CAD PLATE or powdwer coat them and reinstall with a new boot -which can be bought off e-bay or cheaper at the chevy dealer {using a newer part #} also cleaning up all mounts and the aluminum wedge and lubing all pivoy points /should work as good as new /if cleaned it looks better thaN that off/shore booster kits on evil bay- GOOD LUCK MIKE

That's good info Mike. It looks like the rebuilds might be getting harder to find. The core charge just jumped up from $30 to $49 at Rock Auto. This usually means demand exists but the core supply is low.