How long to swap brake booster?

[i82much]

I have a 72 K10 with factory disc/drum. I think I might have an intermittent vacuum leak in my booster - engine goes very lean sometimes and I have a hard pedal.

I might just swap in a reman booster tonight after the kids go to bed. But I plow snow with the truck and I don’t want to have it down and not able to use it because we have a storm coming.

So I’m just wondering - how easy of a job is this? Doesn’t look tough at all, but maybe I’m missing something. If there are a lot of little small parts, experience tells me I will lose one and need to order it online, only to find it on the ground a few weeks later!

[geunther]

Give yourself 2 to 3 hours. Only because the pins and clips can fight you a little. It is a little tight of an area for your hands and tools. I assume you will leave master cylinder all hooked up and just move it forward out of the way.

And all of this assumes you have the correct replacement part.

[i82much]

Thank you!

So now I’ve got two choices. Truck is currently functional and capable of plowing my driveway. I have no other way to plow my driveway. I can either:

(a) Keep the truck in service as is until spring, pull the truck into my shop at that time, change out the booster in a nice, dry, well-lit area where I have easy access to all my tools, can take my time, and if I lose any parts they will easy to find on my shop floor. As long as I finish by next November, I’m good to go. Nice, relaxed, easy!

(b) Go outside tonight after the kids go to bed, in the snow with a headlamp on, rip off the brake booster, drop a bunch of little parts in the snow, lay on the ground cursing with a wet butt and completely stressed out and angry because I need to plow snow tomorrow. Realize I also need a new master cylinder and I don’t have anyone to help me bleed the brakes, and also the auto parts store is closed.

For reasons that escape me, I will probably go with option (b).

[geezer#99]

Or leave the booster alone until spring
and splice a vacuum can into the booster line.

[57taskforce]

Wait till spring. Haste makes waste!

[i82much]

Originally Posted by geezer#99

Or leave the booster alone until spring
and splice a vacuum can into the booster line.

that’s a great idea. that would give me an excuse to put a big cam in my old GTO, I mean if I already have a vacuum canister ...

looks like the check valve is leaking, so i am gonna replace that first and see how it goes.

[Mike_The_Grad]

I'd swap the rubber line and the grommet along with the check valve. They are just as old as the valve is. The main thing you dont want is for the master to be leaking into the booster. Brake fluid makes the rubber diaphragm turn to junk real quick. You can troubleshoot the braking system yourself pretty easily. I'm sure someone will fill in any bits I leave out if I mis type. But you should start with everything connected like normal. Engine OFF, put your foot on the brake pedal. You should be able to get at least 1 but more like 2 maybe even 3 pressing of the brake pedal before it stiffens up on you. If not then your booster isn't holding any vacuum. Replace check valve,hose,grommet. In order to verify that the new parts made a difference you gotta turn on the engine. Let it run for about a minute. You can check another area at this time. As the engine is running you should be able to notice if the feel of the pedal has returned. Let say it has, turn the engine off and you should get the 2 or 3 brake pedal presses in before it stiffens up on you. If it does, then hey, things are gettin better. If not, then onto next test.
You got a stiff brake pedal, engine off. Place your foot on the brake pedal as much as you can, then keeping the pressure on the pedal with your foot turn the engine on. You should notice the pedal sink somewhat then immediately return to the position you had it at before you turned on the engine. If the pedal falls and returns you got a booster that is either working fine or has a slow leak. One more test should tell you. If the pedal doesn't return and just stays down until you let up pressure then you booster has a leak. Last part of the test will tell you how bad the leak in the booster is. To do this part turn off the truck. Press the brake pedal til it stiffens up. Take foot off the brake pedal, turn truck on, make sure the pedal travel came back to the pedal. Press the brake pedal a couple of times to make sure it's there. Once you have established pedal travel again let off brakes for 10 seconds or so then press and hold them firmly down. Turn the engine off. All the while still holding pressure on brake pedal. You should be able to hold this position for at least 5-10 seconds with no change in the feel of the pedal and you should be able to release pressure and get at least one full press of the pedal before it stiffens up again. If you notice a difference in pedal feel while you have your foot on the brake while you turned the engine off, then your booster is leaking pretty bad. If you dont notice a difference but cant get the additional pump from the brake pedal then it's got a slow leak. And yes it can be considered a vacuum leak and will lean out your engine. Depending on how bad the leak is. Oh ,and if you for some reason have anything else tied into the same port as your brake booster ( vacuum modulator if automatic trans, or distributor vacuum advance can, or anything else.) It will effect how those items operate. You should have the brake booster connected directly to manifold vacuum in and by itself for best braking performance. If you do, awesome. If not, make it that way.

[i82much]

Originally Posted by Mike_The_Grad

I'd swap the rubber line and the grommet along with the check valve. They are just as old as the valve is. The main thing you dont want is for the master to be leaking into the booster. Brake fluid makes the rubber diaphragm turn to junk real quick. You can troubleshoot the braking system yourself pretty easily. I'm sure someone will fill in any bits I leave out if I mis type. But you should start with everything connected like normal. Engine OFF, put your foot on the brake pedal. You should be able to get at least 1 but more like 2 maybe even 3 pressing of the brake pedal before it stiffens up on you. If not then your booster isn't holding any vacuum. Replace check valve,hose,grommet. In order to verify that the new parts made a difference you gotta turn on the engine. Let it run for about a minute. You can check another area at this time. As the engine is running you should be able to notice if the feel of the pedal has returned. Let say it has, turn the engine off and you should get the 2 or 3 brake pedal presses in before it stiffens up on you. If it does, then hey, things are gettin better. If not, then onto next test.
You got a stiff brake pedal, engine off. Place your foot on the brake pedal as much as you can, then keeping the pressure on the pedal with your foot turn the engine on. You should notice the pedal sink somewhat then immediately return to the position you had it at before you turned on the engine. If the pedal falls and returns you got a booster that is either working fine or has a slow leak. One more test should tell you. If the pedal doesn't return and just stays down until you let up pressure then you booster has a leak. Last part of the test will tell you how bad the leak in the booster is. To do this part turn off the truck. Press the brake pedal til it stiffens up. Take foot off the brake pedal, turn truck on, make sure the pedal travel came back to the pedal. Press the brake pedal a couple of times to make sure it's there. Once you have established pedal travel again let off brakes for 10 seconds or so then press and hold them firmly down. Turn the engine off. All the while still holding pressure on brake pedal. You should be able to hold this position for at least 5-10 seconds with no change in the feel of the pedal and you should be able to release pressure and get at least one full press of the pedal before it stiffens up again. If you notice a difference in pedal feel while you have your foot on the brake while you turned the engine off, then your booster is leaking pretty bad. If you dont notice a difference but cant get the additional pump from the brake pedal then it's got a slow leak. And yes it can be considered a vacuum leak and will lean out your engine. Depending on how bad the leak is. Oh ,and if you for some reason have anything else tied into the same port as your brake booster ( vacuum modulator if automatic trans, or distributor vacuum advance can, or anything else.) It will effect how those items operate. You should have the brake booster connected directly to manifold vacuum in and by itself for best braking performance. If you do, awesome. If not, make it that way.

Lotta good info here, thank you. I replaced the bad check valve and rearranged some vacuum lines as suggested. I haven’t done all of your suggested tests yet, but I did pull the check valve about 30 seconds after engine shutdown and there was still a ton of vacuum in the booster. So maybe I got lucky and it was just the check valve.

[Mike_The_Grad]

That's awesome. You may have fixed the issue with the booster then. Another thing to check for is a bad master cylinder. If you notice the pedal sinks while you are at a stop light then you got a bad master cylinder. That's a little trickier to replace than the booster. The booster is easy to replace. Dont need to disconnect any brake lines or mess with the brake system at all. Just find a way to support the master cylinder. I used a ratchet strap through the hood support cross brace on the drivers side. Disconnect 2 bolts that hold the master to the booster. Slide master cylinder forward a little to give you some room. Pull check valve. And remove 4 bolts on back of booster. Pull booster, careful with the pushrod that goes into the booster. Align pushrod with new booster reinstall 4 bolts. Slide master cylinder back and reinstall 2 bolts. Make sure to use a new gasket if your old one is trashed. Reconnect check valve. Done.

[i82much]

Originally Posted by Mike_The_Grad

That's awesome. You may have fixed the issue with the booster then. Another thing to check for is a bad master cylinder. If you notice the pedal sinks while you are at a stop light then you got a bad master cylinder. That's a little trickier to replace than the booster. The booster is easy to replace. Dont need to disconnect any brake lines or mess with the brake system at all. Just find a way to support the master cylinder. I used a ratchet strap through the hood support cross brace on the drivers side. Disconnect 2 bolts that hold the master to the booster. Slide master cylinder forward a little to give you some room. Pull check valve. And remove 4 bolts on back of booster. Pull booster, careful with the pushrod that goes into the booster. Align pushrod with new booster reinstall 4 bolts. Slide master cylinder back and reinstall 2 bolts. Make sure to use a new gasket if your old one is trashed. Reconnect check valve. Done.

will do! I haven't driven it yet, so can't really say how the brake pedal feel is now that the check valve is fixed. I am playing around with some other tuning issues now that the vacuum lines are better sorted.