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Discussion Starter #1
85 Spider.
I am not sure if my brake booster and/or my check valve is bad. I know when I press on the brake, I hear the hissing and my idle goes down. I took off the brake check valve and can fairly easy blow through it both ways. When the check valve is screwed in and I start the car and put my finger over the valve, I do get suction and the car seems to idle higher. Also when I have it all hooked up and start the car, I can punch the booster hose with grips and the idle barely changes, if at all. I know it's a lot of info, but if I am able to avoid buying a booster due to it being good that would be great.

I have a posting on here looking for a brake booster, but I am hoping I only need the check valve. And if that is the case, maybe someone has one they can sell me. Thank you.
 

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I took off the brake check valve and can fairly easy blow through it both ways.
Try sucking both ways. You should not be able to suck any air through it from the booster side.
 

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The valve is there to keep vacuum in the line after the car is turn off. So you can have power brakes for a couple of pedal presses.
 

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If you end up needing a booster. Have your original ATE booster rebuilt. Its not much more then the new aftermarket booster.

But your original booster is a much better quality then the new ones.
 
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Discussion Starter #5
Try sucking both ways. You should not be able to suck any air through it from the booster side.
I can blow through and suck on the valve. But when I took up my bosster, I get a hissing. Could the valve be causing the issue? Thank you. If so, do you have one or know where I can get one?
 

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The check valve is not working. Try cleaning it with carb cleaner.
 

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But Mad North-Northwest
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First, you sure you're checking the right thing? The Spider check valve is the metal valve at the intake manifold, not the elbow on the booster. Replacements are available (I know Classic Alfa carries them) or you can just cut the hose in half and insert a modern inline plastic valve.

Second, if the check valve is bad, all it means is the booster won't hold vacuum if the engine shuts off (as Jim said). If you're getting hissing and dropping idle when you press on the brakes then it sounds almost certain that your booster is leaking and needs repair. The check valve will not cause that.
 

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But Mad North-Northwest
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Here are links to the Alfa part and an example of an aftermarket part that will work if the check valve is bad. But like I said, I don't think that's your main problem


1652181
 

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Discussion Starter #10
First, you sure you're checking the right thing? The Spider check valve is the metal valve at the intake manifold, not the elbow on the booster. Replacements are available (I know Classic Alfa carries them) or you can just cut the hose in half and insert a modern inline plastic valve.

Second, if the check valve is bad, all it means is the booster won't hold vacuum if the engine shuts off (as Jim said). If you're getting hissing and dropping idle when you press on the brakes then it sounds almost certain that your booster is leaking and needs repair. The check valve will not cause that.
Thank you for the info. I was referring to the metal valve screwed into the manifold. But thank you for making sure I was looking at the correct thing. I was just hoping, since I could blow and suck on the valve, that it was the culprit....no such luck..haha.
It sounds like from what I am reading, that i shouldn't be able to blow both ways, so im guessing the valve is still bad correct? Along with the booster.
 

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But Mad North-Northwest
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It sounds like they're both bad, yeah. Sounds like your booster is holding vacuum when closed but is leaking under load.
 

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Replace the check valve first and see what happens. New boosters are more expensive and some of them do not work very well. There are a couple of threads about that.
 

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Discussion Starter #13
It sounds like they're both bad, yeah. Sounds like your booster is holding vacuum when closed but is leaking under load.
Ok. Thanks. Can I just get a universal check valve from a local parts store that I can fit in the hose? And would I just leave the threaded metal valve connected? I'm sure the booster is bad as well, but I would like to check this first since I know it's bad. Maybe I will get lucky..haha.
Thanks again. You guys are wonderful on here.
 

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Discussion Starter #14
Replace the check valve first and see what happens. New boosters are more expensive and some of them do not work very well. There are a couple of threads about that.
Thank you. That is what I'm going to try first. I am hoping to find a universal check valve from a local parts store to just connect into the hose, at least for now to see if that works. Any ideas on what kind of universal check valve would work? I could always get the correct one later if needed. I'm just wanting to see if it, by the off chance, fixing the issue. Thank you again for your help.
 

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But Mad North-Northwest
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I posted one that'll work: search eBay for an ATE or BMW check valve that looks like the one in the picture. If you don't want to cut the hose you can just get another short section of vacuum hose and put it inline. No need to remove the existing metal valve. The plastic one will work fine anywhere on the hose and it's cheap.

Can't hurt to try a new valve, but I'm afraid that if you described the issue properly there's literally no way the check valve can be causing your booster problem. The only point of the valve is to hold vacuum if your engine shuts off so that you still have power brakes for 1-2 stops in an emergency.

So it's only there to keep air from flowing from the plenum to the booster. If your booster is hissing and farking with your idle with the pedal down, then you've got air flowing from the booster to the plenum: check valve doesn't do anything for that.

I don't know about other vendors but the booster I got from Classic Alfa for my GTV worked great.
 

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Discussion Starter #16
I posted one that'll work: search eBay for an ATE or BMW check valve that looks like the one in the picture. If you don't want to cut the hose you can just get another short section of vacuum hose and put it inline. No need to remove the existing metal valve. The plastic one will work fine anywhere on the hose and it's cheap.

Can't hurt to try a new valve, but I'm afraid that if you described the issue properly there's literally no way the check valve can be causing your booster problem. The only point of the valve is to hold vacuum if your engine shuts off so that you still have power brakes for 1-2 stops in an emergency.

So it's only there to keep air from flowing from the plenum to the booster. If your booster is hissing and farking with your idle with the pedal down, then you've got air flowing from the booster to the plenum: check valve doesn't do anything for that.

I don't know about other vendors but the booster I got from Classic Alfa for my GTV worked great.
Ok. Thanks again. I had a feeling I was grasping at straws..lol.
 

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85 Spider.
I am not sure if my brake booster and/or my check valve is bad. I know when I press on the brake, I hear the hissing and my idle goes down. I took off the brake check valve and can fairly easy blow through it both ways. When the check valve is screwed in and I start the car and put my finger over the valve, I do get suction and the car seems to idle higher. Also when I have it all hooked up and start the car, I can punch the booster hose with grips and the idle barely changes, if at all. I know it's a lot of info, but if I am able to avoid buying a booster due to it being good that would be great.

I have a posting on here looking for a brake booster, but I am hoping I only need the check valve. And if that is the case, maybe someone has one they can sell me. Thank you.
Hi. Have this exact problem on my 84 spider. Here's the background. Brake light kept coming on. Filled master cylinder. Fluid leaked inside the car. Replaced the master cylinder, and when i pulled the old one off the booster was full of fluid. Sucked it out, put new cylinder on. After a couple months brakes were hard to press, and i got the hissing sound. So I am replacing the booster. I found this great advice on the forum to replace the booster. Noete: DO NOT follow the shop manual... it's close to impossible. You cannot get to the booster bolts from inside the car. Instead, unbolt the housing the booster is connected to. Two bolts in the engine bay (mine were on the top), two bolts on the inside which are easily accessible with a socket extension. You do have to disconnect and take out the clutch cylinder during this. Once you unbolt the assembly just pull the unit through the firewall, bringing the brake peddle with you Disconnect the nut/bolt connecting the brake peddle to the booster, and using small extension take off the four bolts connecting the booster to the housing. They're easily accessible. Took me a few minutes to manuever the booster so i could get the spring off. Once that's done just pull off the booster. Whoever posted this before saved me a ton of headaches! Ordered a new booster from Vick's. Due today and I'll put it all back together, hoping this fixes my problem.
 
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