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Power steering control unit causing constant buzzing?

'87 NA

Just wondering if anyone has had this problem. I think I have narrowed it down to the control unit or the stepping motor, maybe a short somewhere.
Any hints would be great.

Also spongy breaks, dont hold pressure.
Brand new poly break lines, rebuilt calipers, bled many times.

Master brake cylinder or brake booster?

Any help would also be beneficial.

Welcome to the forum. The search button will become your best friend.

The buzz from the Power steering is fairly common, do a search and you will find the fix. I honestly don't remember what it is off the top of my head but i know it's been covered mutiple times.

If your breaking system is loosing fluid and there is no visiable leak in the lines or at the calipers, the rear seal in the Master is probably shot. Replace it and make sure you empty the brake booster while it is off. If the system is not loosing fluid, they probably just need to be bled.

Quote:

Originally Posted by eric31 (Post 8193161)

'87 NA Just wondering if anyone has had this problem. I think I have narrowed it down to the control unit or the stepping motor, maybe a short somewhere.
Any hints would be great.

Power steering does not make a buzzer. It does nothing or makes beeps that reference the problems.

The things that cause a constant buzzer and not beeping are:
low oil
low coolant
over-rev (exceeding redline)

Quote:

Also spongy breaks, dont hold pressure.
Brand new poly break lines, rebuilt calipers, bled many times.

Master brake cylinder or brake booster?

Brake booster if it is bad will only make the brakes harder too push, not spongy.

So you probably have a bad master or air in the system, or cheap ass brake lines or cheap ass brake pads.

Yes, you are right it is a constant high pitch beep noise. I know it is the power steering because once the CU was unplugged the noise was gone, but now do not have power steering obviously.

Do you know if the P/S CU's often go bad?
I have the diagnosis check, it says with the constant "beep" noise would be the stepping motor (possible short in coil) or the CU itstelf.

Next thing would be to find a spare CU to try it.

As for the brakes, thanks I can now eliminate the booster as the problem child.

Brake pads will not cause a spongy feeling at the pedal regardless if they are "cheap ass".

And no the brake lines are not cheap ass either. Just mentioned those facts to narrow the thought process.

So Im thinkin the master cylinder seal is buggered.

The help is much appreciated, any more hints?!

Quote:

Originally Posted by eric31 (Post 8193827)

The beep will tell you what the problem is. 1 beep pause, 1 beep pause is one thing... 5 beeps pause, 5 beeps pause, 5 beeps is another.

The FAQ for FC sticky thread found at the top of this section covers the beeps and what each set means.

Quote:

As for the brakes, thanks I can now eliminate the booster as the problem child.

Brake pads will not cause a spongy feeling at the pedal regardless if they are "cheap ass".

That would be wrong. Brake pads have a major influence on the feel of stopping.

Switch between a metallic and a ceramic pad and then come back and tell me there is no difference.

Quote:

And no the brake lines are not cheap ass either. Just mentioned those facts to narrow the thought process.

ah, yeah, see I have seen more bad brake lines than anything else, cause a mushy pedal. Particularly if the lines were stainless steel braided or teflon core. Both if improperly crimped will leak internally in the line between the layers. The only way to see this is if the line finally pops, or you have someone press the pedal down hard while you physically touch and check each line for swelling.

So the $100 ebay special stainless steel brake lines are often not worth half the money (hence my cheap ass term) as they have that problem.

Quote:

So Im thinkin the master cylinder seal is buggered.

The help is much appreciated, any more hints?!

The master is pretty easy to replace (maybe an hour if you are slow), so you can try that route too.

Thanks Icemark,

Ok so what is this FC sticky thread?

I went to FAQ at the top and did not return any matches, probably not going where you said.

But like I said, there is no pause...it's constant annoying high pitch beeping. From what I have found, the cause is the CU unit or stepping motor.

I get what you mean between metallic and ceramic pads.
Pedal goes basically right to the floor with no resistance but will stop the car eventually.
I will try the check of each line for swelling next time I get a chance.
I did get the brake lines replaced professionally by a mechanic who used to work for Mazda.
Is there a way to check the master before removing it?

Quote:

Originally Posted by Icemark (Post 8193931)

Could the same thing happen with a stainless steel braided clutch line? my clutch feels like there is air in it but i have no leaks and the clutch still works, i just replaced the master and slave cause my master went bad and was leaking, i added the line at the same time and was expecting the clutch to feel a lot better.

Quote:

Originally Posted by eric31 (Post 8195197)

Thanks Icemark,

Ok so what is this FC sticky thread?

I went to FAQ at the top and did not return any matches, probably not going where you said.

The sticky threads are found at the top of this section, the thread you want is here: https://www.rx7club.com/2nd-generation-specific-1986-1992-17/frequently-asked-questions-2nd-generation-rx-7-faq-fc-494667/

There currently are 4 sticky threads there. They contain all sorts of info including the FAQ for FC, as well as the 10th Anniversary Edition registration, the What did my car come with thread, and the how to use the forum thread.

Quote:

But like I said, there is no pause...it's constant annoying high pitch beeping. From what I have found, the cause is the CU unit or stepping motor.

probably one beep then, which is normally the speed sensor (speedo cable unplugged?)

From the FAQ for FC:

Quote:

Originally Posted by FAQ for FC

I keep hearing a beep beep beep
Probably the power steering computer telling you there is a problem with the system. The number of beeps before pausing will indicate the problem.
1-beep, pause, repeat - in case abnormality of speed sensor signal:
In case broken wires or short circuits occur to sensors or harnesses, the buzzer sounds 60-seconds after the engine speed signal of 2200 rpm continues for 18-seconds.
2-beeps, pause, repeat - in case abnormality of engine speed signal:
The buzzer sounds twice and repeats when the vehicle speed signal is missing input and/or no engine speed signal is found (short circuit, broken wire, etc.)
3-beeps, pause, repeat - in case abnormality of stepping motor signal:
The buzzer sounds when there are broken wires or short circuits in coils or harnesses.
4-beeps, pause, repeat - in case abnormality of the power steering microcomputer:
The buzzer sounds 4 and repeats when there are circuit troubles other than with the micro computer.
5-beeps, pause, repeat - in case abnormality of steering sensor signal: Steering sensor is mis-aligned or failed or steering wheel has been improperly installed.

So are you sure that unplugging the metal box that is the power steering computer, makes the sound stop? Because the only other things that beep are related to airbags/ mouse belts (neither would apply to you as you have a 87), or the door open with the key in, or the door open and the lights on.

So if unplugging the power steering computer does solve the issue of the beep, then you just are not counting or the speedo cable is not hooked up to the speedometer in the dash or the tranny.