Question about 2006 Buick Grand National

3 Answers

Buick Grand National vacuum brake conversion

I recently changed my '87 Buick " T " over to vacuum brakes, I used a set-up off an '86 Caprice 10 3/4" booster w/master cyl. All the parts bolted up ok but I had to drill and tap the intake plenum in order to get 16.5-17" vacuum. The pedal is pushed all the way back to it's limit installed. Pedal seems Stiff to push, and is Hard then goes down off panic stops. Will not even lock up front brakes on hard stops. This set-up does not work much better than the Powermaster. Whats going on here???? Any help would be greatly appreciated.

Posted by on

3 Answers

  • Level 1:

    An expert who has achieved level 1.


    An expert that got 5 achievements.


    An expert whose answer got voted for 20 times.


    An expert who has answered 20 questions.

  • Contributor
  • 31 Answers

^ Turbo Cars have Lots of Vaccum, Where did you ever get this idea from. I have personally converted 10+ Turbo Buicks to Vac brakes.

Make sure the check valve is okay at the booster. but it does sound like you have a bad booster.
Also, did you change the brake pedal to a Vac brake pedal?
They are not interchangeable.

Also, you should not have drilled the plenum, you can get a vaccum block to replace the plastic one on the top of the plenum with a vac brake port.

Posted on Jan 29, 2009

  • 1 more comment 
  • Bill Jan 07, 2010

    The only time a Turbo car has no Vaccum is under boost.

    This is why we use check valves when converting to Vaccum brakes.

    I have a Boost/ vac gauge on my car and see 17' of vaccum at idle.

    Turbo cars HAVE LOTS of Vaccum because they do not usually have cam shafts that have overlap.

  • billg87 Sep 12, 2010

    i need info on getting the vac block/vac port and any other part needed to change to vac system on buick gn

  • macguyver126 Dec 19, 2010

    please call 803 477-6065 have to covert one myself hope this gets through haveing trouble with this site


  • Level 2:

    An expert who has achieved level 2 by getting 100 points


    An expert that got 5 achievements.


    An expert who has written 20 answers of more than 400 characters.


    An expert who has answered 20 questions.

  • Expert
  • 57 Answers

It sounds like the vaccumn canister is not holding vaccumn.( weak or cracked diaphraim) Also did the swap come with a regulator valve (porposting) to set rear and front psi? Make double sure the system is bled well.. In addition the master cylcinder has a shuttle rod that must be centered up in order to porposition the fluid front and rear.Have a fun day and good luck.

Posted on May 14, 2008

  • Level 3:

    An expert who has achieved level 3 by getting 1000 points


    An expert that got 10 achievements.


    An expert that got 5 achievements.


    An expert whose answer got voted for 500 times.

  • Master
  • 3,113 Answers

Turbo cars do not have enough vac. for a system like that. Get a vac. pump.

Posted on Jan 06, 2009

1 Suggested Answer

  • 2 Answers

SOURCE: I have freestanding Series 8 dishwasher. Lately during the filling cycle water hammer is occurring. How can this be resolved

a 6ya expert can help you resolve that issue over the phone in a minute or two.
best thing about this new service is that you are never placed on hold and get to talk to real repairmen in the US.
the service is completely free and covers almost anything you can think of (from cars to computers, handyman, and even drones).
click here to download the app (for users in the US for now) and get all the help you need.

Posted on Jan 02, 2017

Add Your Answer

Uploading: 0%


Complete. Click "Add" to insert your video. Add



Related Questions:

1 Answer

How to change brake booster

Remove Master Cylinder WITHOUT Removing Lines Set it to the Side or Down Below Booster, Go Inside and remove 4 Nuts/Bolts Mounting it Booster Vacuum Hose and Booster Should Pull Right out ...You May Need to Disconnect From Brake Pedal INSIDE VEHICLE ABS May be Difficult to Work Around At Master Cylinder Side But Feasible

Jun 03, 2015 | 1994 Pontiac Trans Sport

1 Answer

Power booster seems to leak how to fix

These are not rebuild-able, they must be replaced if they leak.
One that leaks will hiss while the engine is running. The hiss is vacuum leaking, not pressure leaking out.
To possibly check it under the hood, be very suspicious of a leaking vacuum line at or near the booster, not the booster itself. It might be bad, but that is pretty rare.
The last one I changed I thought was defective because it hissed when I applied the brakes, but a new one did the same thing! :-(
If you decide to replace it, you will be unbolting the master cylinder from the unit under the hood, and also unbolting the unit under the dashboard.
Of you are really careful, you might not need to disconnect the master cylinder 's brake lines at all, just gently pull/push it out of the way to change the booster.
Be really careful not to kink the brake lines.
The unit is bolted to the car with usually 2 bolts through the firewall behind the brake pedal.

Jan 12, 2013 | 2002 Buick Century

1 Answer

I REPLACED THE BREAKS AND CALIPERS ON MY 97 RAM AND NOW i HAVE NO PRESURE At all. I have no idea what to try next please help

When you open the hydraulic brake line air enters. You will have to bleed the air out before there will be any brake pressure.If the master cylinder is empty there will be air in it to, it is a dual cylinder. Remove both lines at the cylinder you will need a bleeder kit (from auto parts store) or make your own, the way to bleed it is to connect a tube to each port on the cyl. then take both tubes to enter the fluid in the top of the cyl.Slowly work the cyl. till all air is out of the cyl.If the vacuum booster has not had the vacuum released you must do that or the master cyl. will be ruined (with air in the cyl. the booster will drive the piston cups to the end and destroy them) After the master has been bled reattach the lines. Use the tool (from parts house) to hold the apportioning valve open. Keeping the master cyl. full at all times,open the bleeder screws on the calipers one at time and bleed all air out.

Mar 05, 2012 | Cars & Trucks

1 Answer

I am from pakistan and i own a chevrolet caprice classic. i need to replace the brake booster as it has ruptured. there ain't that many mechanics who know how to deal with american cars. need...

The brake booster from most of the GM cars of the same size should fit. To change it you need to unbolt the master cylander from the booster be careful not to kink brake lines disconnect vacum hose from booster unbolt booster from fire wall. Now replace in reverse order. Always be careful of the brake lines.

Sep 07, 2011 | 1988 Chevrolet Caprice

1 Answer

Need to replace brake power booster on 1992 buick limited with AB

Heres a way to save you a lot of time. remove the two bolts that hold the master cylinder to booster, leave all brake lines connected, pull master away as far as it will go, you may have to pull on the line some, next go inside and remove the pin to remove the rod from brake pedal, you can let brake switch stay, back to booster, remove vacuum line from booster, back inside the car remove the 4 nuts that hold the booster to firewall, make sure rood is clear, go out and pull booster out and remove, install new booster make sure rod hooks to pedal before bolting it up, because sometimes the rod may go in the wrong direction, reverse directions to install, when your done theres no need to bleed brake system. hope this helps.

Aug 31, 2010 | 1992 Buick LeSabre

3 Answers

Its a constent hissing from my brakes in my Mazda 2001 tribute. The noise does stop When i press on the brakes but as soon as i let off them the hissing continues. Ive read it could be the brake booster. ...

It is the booster, but it might not be abnormal.

Vacuum from the engine is supplied to the booster, and vented if the brakes are not being applied.

When you step on the pedal, the movement of the pedal blocks the vents, allowing the vacuum to build up. That vacuum then pulls on a diaphragm, assisting you in applying the brakes.

Most people can’t hear that venting, some can.

You should, of course, have it checked out, but it sounds as if this might be normal operation.

The booster is bolted to the firewall, and then the brake master cylinder is bolted to the forward side of the booster.

To replace it you disconnect the brake pedal, remove the master cylinder, take the vacuum line off the booster, unbolt it from the firewall.

Install the new booster by reversing these steps.

But I don't think you need one, from what you say.

Aug 11, 2010 | Mazda Tribute Cars & Trucks

1 Answer

I can't get brakes on my 2001 dakota ,the pedal goes right to the floor with little brakes. I've changed the master cly. and no difference. I've bled the system.there is something wrong with the front...

did you bleed the master cyl. before or during installation? bleed brakes in proper order?RR LR RF LF? does it have a power booster between master cyl.& firewall?check for vacuum to booster.when ABS isn't working you should still have brakes.suspect power booster diaphram.

Sep 21, 2009 | 2001 Dodge Dakota

2 Answers

Brake pedal goes squishy and fluid in the front of the engine on top..not back by the master cylinder

If you look down under the radiator in the area of the power steering pump, nestled in the crossmember you should see some brake lines going in and out of a rectangular steel block. It should also have a single wire going in the top. That is the proportioning valve which adjusts brake pressure to the wheels. One of these lines is likely the source of your leak. Hope this helps.

Sep 07, 2009 | 1997 Buick LeSabre

4 Answers

The brake booster is leaking (hissing sound under dash and diagnosed by Volvo. I am seeking information as how to replace. Can the average person with good mechanical skills and tools do this job in a few...

I have never worked on a Volvo, but they are pretty much the same as everyone else since they are most likely using the same suppliers. The vacuum brake booster is mounted to the firewall on the driver's side and is usually attached by four bolts, and the brake master cylinder is attached to it by four bolts. Start by unbolting the master cylinder from the booster and gently bend the brake lines so the master cylinder is out of your way. Remove the rod that goes between the brake master cylinder and the brake booster and set it aside. Pull the vacuum line off the brake booster, and unbolt the brake booster. Put the replacement booster in place, bolt it back up, put the rod back in place between the booster and master cylinder, bolt the master cylinder back up to the booster, and reconnect the vacuum line. Take the old booster back to the parts shop to get your core charge, and you should be finished. It is usually not very difficult and should not take more than about an hour using normal hand tools. A DIY job should save you about $100-150 in labor costs, and the part will be much cheaper without the mark-up.

Aug 06, 2009 | 2002 Volvo S80

2 Answers

Power brake booster compatibility - 86 crown vic to 83 town car

i think if there is a problem it would be if one had A.B.S. and the other did not, otherwise i can't see any problem. just have to look at it and see if everything lines up. i believe the boosters are the same, if they look the same and bolt up the same i don't see any problem. you might want to chk. with a ford dealer just to see if there is a differance in volume on booster.

Jan 21, 2009 | 1983 Lincoln Town Car

Not finding what you are looking for?
Cars & Trucks Logo

2,312 people viewed this question

Ask a Question

Usually answered in minutes!

Top Buick Experts


Level 3 Expert

70346 Answers

Colin Stickland
Colin Stickland

Level 3 Expert

22041 Answers

Jeff Turcotte
Jeff Turcotte

Level 3 Expert

6869 Answers

Are you a Buick Expert? Answer questions, earn points and help others

Answer questions

Manuals & User Guides