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Booster or check valve


dat620_73

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Ok so I'm pretty sure of what I need, just basically looking for confirmation. I was driving my '73 620 with an all stock braking system today, everything was great, it stopped like normal, until later in my commute when I noticed the pedal was stiffer than usual. So I turned down the radio, pressed the pedal and you guessed it a pshhhh sound from under the dash and a stumble in the rpm. All which leads me to believe the power brake booster. I then second guessed myself, maybe the check valve. I figured if it was a valve i'd loose vacuum all the time not when the pedal is pressed. Right?

Also any ideas on where to get a booster?

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Sounds like the booster went bad, you should not hear hissing when you press on the brake.

One used to be able to get the 1973/74 Datsun 620 brake booster on ebay, but I didn't see anything specifically for it, just stuff that says it will fit without photos, you might try Autozone, I think that was the last place I got one thru ebay, keep in mind that 50 percent of the ones I bought did not work properly out of the box.

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The manual says to pump the brakes to remove any residual vacuum. Then apply the brakes, hold them, and start the engine. What you should see is the pedal drop slightly as the engine vacuum rises.

 

The one way valve prevents the vacuum in the booster from leaking out into the intake when the engine is off.

 

It does sound like the booster. The engine is being disrupted by a vacuum leak.

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You cannot be too picky, that is a 2 year booster, everything after them two years is larger/different so there are a not a lot of that type around, and like I mentioned about 50 percent of the ones I bought didn't last a week or were bad out of the box, if Rockauto has them(rebuilt) they likely have a return policy and you can keep sending them back until you find a good one, if not then I guess I would not buy from them.

When I stepped on the brakes the engine RPM rose slightly when mine went bad(it effected the idle RPM), otherwise I could not tell it went bad at first, but after a day or so it didn't work at all, I had to press hard to get the brakes to work, another one on a truck I sold went bad also, that took a few months of daily driving before the guy contacted me about what booster it was.

 

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1 hour ago, dat620_73 said:

The main problem with rockauto is/and has happened to me, if they send you a wrong part or a defective part, you pay the shipping to return it. Doesn't matter who's fault it is.

 

 

They will pay if it was their error, I recently received a faulty power steering pump for a Ford they provided a pre paid shipping label 

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