Brake booster check valve ??'s (1 Viewer)

[darwink1]

Ok, Im freaking confused. Specs, 85 cruiser, 91 runner booster (no check valve), 350 ramjet V8.

So ever since I got the 60 Ive had no brake boost with the engine off. I installed a 91 4runner booster last summer when mine went that did nothing to solve the no boost without engine running problem. The runner has a check valve on the firewall and it is not part of the booster so didnt really expect it to.

Heres part one of the question. I cant really get my head around how the whole thing works. I know the engine sucks thereby providing boost for the brakes. With the engine sucking how is a check valve supposed to do anything to keep some vacum in the booster when the engine is shut down? I might be looking at it the wrong way but to me the only way a check valve would work in this situation is if the engine were blowing into the booster and the check valve closed to keep it pressurized after the engine is no longer running.

Part two of the question is this. I ordered a couple different check valves (1 psi to open, good to 125 psi) and both dont seem to provide enough air flow to the booster. With the motor running and vacum line disco'd there is some serious sucking going on. Throw on the check valve and that sucking is seriously restricted. Anyone know what the set up is on a chevy/gm 5.7L booster? Is the check valve part of the booster or is it remote/in line? Im thinking a check valve from the chets would have more flow and resolve my issues.

Any insight would be appreciated. Maybe Im just dense...

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[ntsqd]

The booster is a vacuum reservoir, it stores vacuum on BOTH sides of the booster's diaphragm. When you step on the brakes there is a valve attached to the push-rod that vents atmospheric pressure into the chamber at the rear of the diaphragm. It is that pressure imbalance that boosts the brakes. How far you push the rod determines how much vacuum is vented thereby varying the amount of boost applied.

If the check valve that you're using isn't vacuum specific and oriented correctly it isn't likely to work very well. I'd go get the check valve off the booster's donor & note it's orientation.

 

[ProwlerDriver]

I just put a 4runner booster on my rig to improve the braking, noticed the same restriction issues even with the stock 4 runner check valve... at low rpms my power brakes are non existent.

Im wondering if a vacuum reservoir would help the situation.

 

[TS888]

Does the V8 produce an equal amount of vacuum to the 4Runner stock engine? And likewise the vacuum pump on the Cummins? If you aren't getting enough suck, then you'll get less assist.

I'm pretty happy with the stock brakes on my truck. I did a little maintenance when I did my lift -- all new soft lines (had to replace the axle lines with longer ones anyway), and I disassembled the rears, cleaned and lubricated the adjusters and e-brake parts, and adjusted them properly. Made a big improvement getting the rear brakes working up to spec.

 

[darwink1]

There is no issue with the brakes when the engine is running, I get all kinds of assist and have locked up all 4 tires (40's) on dry pavement.

Having no boost when the engine dies is my only concern. It kind of sucks to stall out on a steep hill in the bush. I have to hammer down on the brake pedal with both feet to keep it from moving until I get the engine started again. It also doesnt help that my driveway has a slope to it, Im reminded of the no boost thing every time I start it.

TS, Im pretty sure the V8 produces more vacuum than either the 2F or the 3slow in the runner. My next move will be to try to find a check valve from a 5.7L equipped chev truck. My buddy looked at his 99? for me and its attached to the booster but its not part of the booster.

Im gonna pm RMP on this site to see what hes running since hes got the ram jet as well.

Thanks for the replies.

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[darwink1]

Threw on a dorman check valve today. Havent started it yet though.

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[Elbert]

Threw on a dorman check valve today. Havent started it yet though.

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What was the result and what part did you use? one of those in-line type check valves?

 

[darwink1]

Yup, just a cheapo plastic 90* lookin fitting with the check valve inside. Put it in between the engine and booster and now the booster actually holds pressure overnight. Its good for about 2 pumps before the pedal goes hard and it makes a huge difference.

Dont have a pn but any parts place that carries doorman products should have it. Pretty sure its called a "universal brake booster check valve" if that helps.
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[Elbert]

http://www.summitracing.com/parts/RNB-80195/

something like the above I presume?

 

[scrapdaddy]

I'll be faced with this, when the motor gets in, but I have a question. What's the difference in the check valves. Does it matter? I went to the link and looked at two, totally different.

Thanks, Ron

 

[darwink1]

Im guessing the diff is what fits your lines. Also some boosters have the valve on the booster itself and not in line so thats something else. Mine has bigger fittings to accept the vacuum lines than the one pictured above.

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[poofyhole]

fj60
I didn't want to start a new thread, and just have a simple question about the 95 4runner booster I had shipped from the salvage yard. Is the felt underneath the rubber boot supposed be oily for some reason. It isn't completely saturated , but it makes me wonder if the MC leaked into the booster when it was on the 4runner. It looks like the felt would be easy enough to replace if it is supposed to be clean.
Also does it look like I'm missing anything on the front besides the gaskets

 

[poofyhole]

Bump....srry Im dumb and need an answer ...anyone but Viperdrhd ....just kidding.

 

[snowboardonsnow]

If you want more then two pumps with the engine off you can add a reservoir, bj's came with them stock. some people use old fire ex's anything that can hold good amount of psi can hold a good vacuum.

 

[Kurtis]

Looks like everything is there. Not sure on the oily felt, sounds like as you said the master leaked. I put that year booster in and was very happy with it.

 

[darwink1]

Should be good but Id be leery of putting in a used unit. Reman or new arent that much cash if i remember right (as long as its not from the stealership). Pretty sure that runner has an in line check valve as well so youll need to splice one in the get boost when the engine is off.

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[LAMBCRUSHER]

runner booster needs an in line check valve. Have not found an aftermarket one that looks like it will work, but I know the dealer can get em for about $40. also not sure on the fluid, but if it boosts without robbing vacuum, then it is working. I priced newly refurbished boosters at over $200, and found the one I'm gunna run for a while at TAP for $35 bucks used. As long as the master is working, even if booster fails, you still have brakes. Depending on your finances, you may just try to run it for now. there are about a half dozen boosters that can be used with our rigs and our masters, and the way I see it, the last component in a braking system that I would worry about being brand spankin new....make sure the wheel cylinders shoes drums brake line and tees, calipers, rotors and pad, master cylinder are up to snuff and stuff in boosters as needed.

 

[LAMBCRUSHER]

Darwin, what was the pn of the check valve you ordered?

 

[darwink1]

Didnt order it, they had it on the rack. Threw out the packaging..... Ill take a clear picture tomorrow.

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[HenryAZ]

On my '74 w/2F, I am running an FJ-80 MC and a mini-truck booster. I hunted through the Toyota parts catalogs for something that looked it was the right vintage, was inline, and still available. I found this one, listed for an '82 1/2 ton pu:

44730-20010

and I've been using it for over a year now. It was $28 or so from the online Toyota order places, and it's a warm fuzzy feeling to have that OEM valve in there