question about vacuum boosters.
11-03-2004, 12:34 AM
#1
Pro
Thread Starter
Member Since: Apr 2004
Location: Atascadero Ca
Posts: 687
Likes: 0
Received 0 Likes
on
0 Posts
question about vacuum boosters.
I think i've got a problem with my brake booster. I have a demon carb and i run a line directly from the brake port on my carb to the little check valve on the brake booster. The check valve on the booster is brand new. When i start the motor the brake pedal feels pretty normal for a car with vacuum boost, however when i shut the car off, the pedal immediately becomes solid again. In other words, you don't have to pump it to make the pedal firm again like in a modern car.
Is this normal? or is my vacuum booster leaking?
Is it worth it to replace my factory booster?
What newer and better options are there?
Is hydroboost that good? It looks expensive.
Is there a booster off a modern car that works better and fits our vette's?
Thanks, Mike
Is this normal? or is my vacuum booster leaking?
Is it worth it to replace my factory booster?
What newer and better options are there?
Is hydroboost that good? It looks expensive.
Is there a booster off a modern car that works better and fits our vette's?
Thanks, Mike
11-03-2004, 09:15 AM
#2
Race Director
not sure i'm following the symptons...but ....has this always been like this or did it happen after you replaced the check valve...could you have the check valve in backwards?
11-03-2004, 10:05 AM
#3
Does the check valve isolate the brake port from the lights/accessory port? (I don't know because mine is AWOL) If it doesn't, then it'd be damn near impossible to hold a reserve vacuum in these cars unless everything was in perfect shape. Tank, hoses, relays, actuators ... too damned many things to leak.
11-03-2004, 10:19 AM
#4
Originally Posted by wcsinx
Tank, hoses, relays, actuators ... too damned many things to leak.
11-03-2004, 10:57 AM
#5
Race Director
Originally Posted by wcsinx
Does the check valve isolate the brake port from the lights/accessory port? (I don't know because mine is AWOL) If it doesn't, then it'd be damn near impossible to hold a reserve vacuum in these cars unless everything was in perfect shape. Tank, hoses, relays, actuators ... too damned many things to leak.
11-03-2004, 11:09 AM
#6
Burning Brakes
Originally Posted by i885744
What newer and better options are there?
Is hydroboost that good? It looks expensive.
Is hydroboost that good? It looks expensive.
The hydroboost kit is wonderful. I always was worried about being able to stop with the manual brakes.
After the upgrade, OMG, it is a world of difference.
I highly recomend it.
11-03-2004, 01:10 PM
#7
Originally Posted by bobs77vet
......if its installed correctly it goes "in line" between the vacuum source and the brake booster and is "directional". no other vacuum source is tapped in to it. mine is also AWOL....so i can't really help with the trouble shooting portion...
There's the vacuum feed port on the hidden side, then the brake booster port (big one) on the left and the accessory port on the right. And unless those two ports are isolated, then a leak on other side will bleed vacuum out of the entire system.
11-03-2004, 02:16 PM
#8
Race Director
Originally Posted by wcsinx
All the replacement valves I've seen have 3 total ports. Here's a picture from Zip.
There's the vacuum feed port on the hidden side, then the brake booster port (big one) on the left and the accessory port on the right. And unless those two ports are isolated, then a leak on other side will bleed vacuum out of the entire system.
There's the vacuum feed port on the hidden side, then the brake booster port (big one) on the left and the accessory port on the right. And unless those two ports are isolated, then a leak on other side will bleed vacuum out of the entire system.
not what i'm talking about.... i have one of those and its used for my headlights.. in the picture below the vacuum port on the base of the carb has on some cars a black cannister the size of a fuel filter in line between the vacuum source and brake booster... i believe it is a filter ... it is has a proper way to go on.... on the manifold outlet i have the filter and the 3 port thing that you mention. my car does not have the brake booster filter and i do not know if it has a check valve in it...
11-03-2004, 02:25 PM
#9
Oh yeah, you're right. I was confused. So there's supposed to be a check valve inline between the carb base and booster? 
I don't think I've ever seen that one. The vacuum fitting actually on my booster is a check valve IIRC. And I know you can get aftermarket replacements for that fitting. As luck would have it, I just saw one in the parts store not 2 hours ago on the "HELP" rack.
I don't think I've ever seen that one. The vacuum fitting actually on my booster is a check valve IIRC. And I know you can get aftermarket replacements for that fitting. As luck would have it, I just saw one in the parts store not 2 hours ago on the "HELP" rack.
11-03-2004, 02:33 PM
#10
Race Director
Originally Posted by wcsinx
Oh yeah, you're right. I was confused. So there's supposed to be a check valve inline between the carb base and booster? I don't think I've ever seen that one. The vacuum fitting actually on my booster is a check valve IIRC. And I know you can get aftermarket replacements for that fitting. As luck would have it, I just saw one in the parts store not 2 hours ago on the "HELP" rack.
I don't think I've ever seen that one. The vacuum fitting actually on my booster is a check valve IIRC. And I know you can get aftermarket replacements for that fitting. As luck would have it, I just saw one in the parts store not 2 hours ago on the "HELP" rack.i think its a filter, i know it is directional, don't know if it has a check valve in it, I Know i don't have one...
11-03-2004, 02:51 PM
#11
Race Director
There's supposed to be a check valve plugged into the booster. The hose plugs into the valve and then goes to the carb. If the valve is missing you will have the symptoms you describe.
11-03-2004, 02:59 PM
#12
Instructor
Member Since: Dec 2002
Location: Port Orchard Washington
Posts: 242
Likes: 0
Received 0 Likes
on
0 Posts
The plastic nipple on the brake booster that the vacuum line attaches to is the check valve. Yes, you should still have vacuum assisted braking when the engine is shut off. If you don't, then the check valve is leaking or the diaphram/ internal valve assembly is leaking. The check valve can be replaced separately without rebuilding the booster.
11-03-2004, 04:14 PM
#13
Race Director
Originally Posted by Missileman
The plastic nipple on the brake booster that the vacuum line attaches to is the check valve. Yes, you should still have vacuum assisted braking when the engine is shut off. If you don't, then the check valve is leaking or the diaphram/ internal valve assembly is leaking. The check valve can be replaced separately without rebuilding the booster.
after rereading your original post that started this thread i think what you are saying is that since your replaced the brake check valve the brakes feel different then before.... and yes thats true ...before the brake booster was losing pressure since the check valve was bad and now that its working properly it feels different from before...and thats a good thing!