Need a vac/boost check valve

David Neibert

SCCoA Admin
Where can I get a check valve to keep from boosting stuff that should only see vacuum ? I've tried looking for generic brake booster check valves, PCV valves and a few other check valves, but the only place I've found one like I want, is from Grainger and you have to buy them in lots of 30 pcs. Looking for something like this to fit a 3/8" hose. But I could make one for a 1/4" or 5/16" hose work too.

http://bwoodyperformance.com/popup_image.php?pID=64&osCsid=c6ac5fcb1119f045cb28594c1c6b543b

This is for my 93 SC (turbocharged v8) and it's for the main vacuum tree supply hose that would normally be attached to the inlet plenum. I've already damaged a vacuum acuator somewhere under the dash and I'm trying to stop anything else from getting screwed up.

David
 
when someone comes home to watch the kids for a few mins. i look and see if i have 1. if i got 1 you can have it as long as i can come see that turboed beast:eek::cool:
 
when someone comes home to watch the kids for a few mins. i look and see if i have 1. if i got 1 you can have it as long as i can come see that turboed beast:eek::cool:

No problem...if the roads are dry we can take it out for a spin.

David
 
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I'd check at the Mazda dealer to see if any of the following part numbers would be useful.
From this page:
http://www.autosportracetech.com/RX-7/faqs.htm
The all White one: N3A1-13-1995 (note: this is a revised p/n and is a very expensive part - $40)
The Black/Green one: N390-13-995A
The Green/White one: HE41-13-995
The Aluminum one: NF01-13-890
I couldn't find the specs for any of these, but they use them in their turbo cars...
 
Thanks guys. I've got check valves at work similar to what DLF posted but those won't work because they have a cracking pressure of about 5 psi which is too high to allow the valve to stay open under most vacuum conditions. I did manage to find a PCV valve at autozone that looks like it will do the job.

David
 
on a turbo car i did few yrs ago i used a vac pump from a olds diesel its small electric and works on brks and acc,
 
on a turbo car i did few yrs ago i used a vac pump from a olds diesel its small electric and works on brks and acc,

Manny,

I don't think I need more vacuum. The only thing that might bennifit from more vacuum is the brakes, but I doubt it, because they were just as weak feeling with the stock SC motor and the stock 5.0 motor that were each pulling around 20 inches at idle. I'm only getting around 11-13 inches at idle with the motor that's in the car now, but it jumps to about 25 inches when quickly letting off the throttle.

Might just be the late model brake system, because even with the 13" Cobra upgrade, the brakes in my 93 feel weaker than the stock brakes on my 91. Come to think of it, I don't recall ever triggering the anti-lock system.

David
 
Manny,

I don't think I need more vacuum. The only thing that might bennifit from more vacuum is the brakes, but I doubt it, because they were just as weak feeling with the stock SC motor and the stock 5.0 motor that were each pulling around 20 inches at idle. I'm only getting around 11-13 inches at idle with the motor that's in the car now, but it jumps to about 25 inches when quickly letting off the throttle.

Might just be the late model brake system, because even with the 13" Cobra upgrade, the brakes in my 93 feel weaker than the stock brakes on my 91. Come to think of it, I don't recall ever triggering the anti-lock system.

David

David, the brakes on that car have always been poor. The 13" brakes should put you through the windshield. I'm thinking something is goofed up. Air in the ABS, a faulty proportioning valve, stuck rear caliper pins, something.
 
David, the brakes on that car have always been poor. The 13" brakes should put you through the windshield. I'm thinking something is goofed up. Air in the ABS, a faulty proportioning valve, stuck rear caliper pins, something.

Rear caliper pins are okay, but I don't have a clue about that other stuff.

David
 
If rear caliper pins freeze up, you usually see high front brake pad wear. If you can't lock up the tires, causing the ABS come on on a 60 to 0 pedal through the floor stop... then something is wrong. I'm gonna guess something in the brake system blocking full pressure from getting all the way to the calipers.
 
I had problems on my '93 SC with the brakes. I didn't have enough vacuum for the power assist, and would run out of assist in stop and go traffic. :eek: I plan to add a vac pump when I put it back together.

Thomas
 
I was puting away parts to day and I found all 3 used stock in working order:eek::cool: I have the stright thrugh big hoses, T big hoses, T big to 2 small. IF you still need it let me know
 
I was puting away parts to day and I found all 3 used stock in working order:eek::cool: I have the stright thrugh big hoses, T big hoses, T big to 2 small. IF you still need it let me know

I installed a PCV/Check valve last night that I think will correct the problem of putting boost into things that should only see vacuum. I still need to track down which vacuum hose is the one with the leaking acuator, that is now causing a vacuum leak. In addition to the leak causing problems with idle and a reduced vacuum signal, it may also be having a negative effect on the brakes.

Please hang onto those check valves for a couple weeks, because I'm not sure the one I installed will be large enough.

Thanks, David
 
David, the brakes on that car have always been poor. The 13" brakes should put you through the windshield. I'm thinking something is goofed up. Air in the ABS, a faulty proportioning valve, stuck rear caliper pins, something.

Dave,

It is possible that the weak brakes could be caused by a leaking/faulty check valve on the brake booster ?

David
 
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