1958 impala tri-vac brake booster

[Big john]

I recently had my trivac booster rebuilt on my 58 Impala 348. .. bleed the brakes installed it...but I notice there real touchy if I even slightly press it too hard the brakes lock up is there any other adjustment to these booster... thinking about replacing the whole thing with the newer master cylinder and booster things dangerous

 

[ragtp66]

Out of curiosity who did the rebuild? There really are no adjustments to the booster itself. Are you using the correct hose? If your using the wrong hose it can collapse under vacuum. Do you have it hooked up to manifold vacuum with nothing else connected to it? Was it originally a power brake car ? The manual brake pedal and linkage under the dash is completely different then the power brake setup. The go to guy on rebuilding these units is http://www.brakeboosterrebuild.com/

chris

 

[models916]

I would think the pedal linkage for manual brakes has more leverage. Maybe just a pin or rod move. Even so, you could do it yourself to take some pedal advantage out. Move the rod down toward the pedal.

 

[ragtp66]

I would think the pedal linkage for manual brakes has more leverage. Maybe just a pin or rod move. Even so, you could do it yourself to take some pedal advantage out. Move the rod down toward the pedal.

The 58 linkages and pedal assemblies are totally different you cant move the rod like on later cars. Here is a picture of the power brake setup.

 

[models916]

I have a drill bit for cases like this. Move the hole down.

 

[ragtp66]

That will not fix the problem. There is a problem within the booster, send it back and have the rebuilder go through it again or send it to Ed and have it fixed correctly the first time. BoosterDewey who is very well known in the brake booster rebuilding business specifically recommends Ed for the treadle vac both Bendix and Morraine rebuilds. There are parts internally that have not been made for 30+ years that Ed has contracted made for them that nobody else has access to as they are not available in any kit that's currently available. Some things are best left to a specialist, I would not have Joe the handyman perform cardiac surgery but he is fine to repair a hole in the drywall and paint the wall.

 

[models916]

He was asking for an adjustment, not a rebuild.

 

[ragtp66]

He was asking for an adjustment, not a rebuild.

Once again there is nothing to adjust. The booster was not rebuilt properly, it happens more times then it should. Drilling new holes is not an "adjustment". Show me what page of the factory service manual says to re-drill the hole. Your first three words were "I would think", the next sentence starts with "Maybe", so in fact you don't know! Steering and braking are things that should not be taken lightly for the sake of the driver, anyone on the street , or the car itself. Chevrolet built about 1.2 million cars in 1958, General Motors engineers designed the system (whether it is a good system or not is debatable) to not send you through the windshield when you touch the brakes. Since the OP said he recently had the booster rebuilt it seems pretty obvious that the booster itself would be the obvious component to investigate. Bottom line is the issue is in the booster and should be sent back to his original rebuilder to have corrected. My point is if it was a local rebuilder they probably do not have access to the parts or the knowledge of how to properly rebuild one of these. That would be like taking a 58 Rochester fuel injection unit down to the local Pep Boys and letting them have a go at it.

 

[Phil Reed]

Chris..................you said it better than I could have. I personally would not make any adjustments on any part that is part of the braking system.

 

[models916]

I remember the Vega when it comes to infallible GM engineering.