How do you adjust the brake pedal??

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ABROCK
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How do you adjust the brake pedal??

Post by ABROCK »

I am having brake issues where the braking is very stiff - to the point where the car is not safe to drive. I can stand on the brake pedal and there is very little movement and very little stopping. NOT soft braking but hard. I've read that the brake pedal may need adjusted if it cannot travel back far enough to release pressure in the master. I've attached a pic of my brake pedal/rod. I cannot see anywhere to adjust the the pedal. Can someone please point me in the right direction? As it stands, my pedal only has about 1.5" of travel when pressed. When depressed there is zero play. Any movement pushes the rod. Any thoughts???

Thank you!!
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Adam
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notoptoy
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Re: How do you adjust the brake pedal??

Post by notoptoy »

Are the clutch and brake pedal at the same height?
If it is hard to press I can only think of few things - Binding in the pedal or master cylinder, or some type of blockage in one or more of the brake lines.
My first bet would be on the mastercylinder - can you post a picture of it? Is it correct for the car or an aftermarket or swap of some sort?
BTW, What is that black cable running in front of the brake pedal, but behind the clutch cable? What ever it is, i'd check the routing, it looks like it could get chaffed or pinched there.
"When all else fails, force prevails!" Ummm, we're gonna need a bigger hammer here.

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ABROCK
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Re: How do you adjust the brake pedal??

Post by ABROCK »

yes, the brake and clutch pedal are the same height. Not sure what the black cable is, I double checked and it is not being pinched. Here is a pic of the master cylinder. It is a dual style. I have not been able to locate any shims for adjustment. I had read in other posts there should be some under the master? I also had the thought the master is clogged or a line pinched. It feels like there is not enough fluid getting through or as mentioned before a lack of pressure being released.
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Adam
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fj20spl311
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Re: How do you adjust the brake pedal??

Post by fj20spl311 »

First, roadsters have a very hard pedal......I am not saying something is not wrong.

The first thing that comes to mind is one or more stuck caliper pistons.

Jack up each wheel and check to see if the pistons are moving.....check for rust on the disc...inside and out ( a bad sign)......Jack up the rear and check the braking in the rear.

My bet would be a stuck pad or caliper piston.....

Does the car pull when the brakes are applied?
Phil
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Re: How do you adjust the brake pedal??

Post by bikermike »

Some master cylinders may have a threaded rod that mates w/ the u shaped "bracket" that the clevis pin goes through to connect w/ the pedal - similar to the clutch master. I just looked under my dash and mine is like yours - no adjustment and looks like your pic. Sorry if I sent you on a wild goose chase in your other post.

Usually a firm pedal is a good thing, but if yours is not actuating the brakes you need to investigate your hydraulics. Does the car pull left or right when braking? That would indicate a failure at one of the corners. If you have poor braking, but even across all wheels, I'd suspect the master or a combination of things going wrong.

You can jack up the car and apply the brakes and see if any of the wheels can be turned by hand when off the ground. You can use broom handle to prop the pedal. Then remove the wheels as Phil suggests and see what the pistons are doing. If you don't have a friend to help watch what is going on or pump the brakes for you, I found it useful to take video w/ my phone of what's happening at each corner as I press the pedal and then play it back.
-Mike
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ABROCK
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Re: How do you adjust the brake pedal??

Post by ABROCK »

Thanks Mike

No worries, I am finding that owning a roadster is an ongoing learning process. The brakes were replaced by the previous owner in November. Even rotors. I have receipts showing the work. Had the wheels off today and pads and calipers all look good.

There is no pulling at all when braking. Only very limited travel on the pedal. Had into Les Schwab today just to check the mechanicals and all looked good. I am leaning toward master cylinder or brake line clogged or pinched. I am not quite confident enough to try rebuilding or replacing the MC. I can tinker with most stuff but brakes are too important to tinker with. Is there a way to test the MC without just buying a new one? They are not cheap!

Thanks all
Adam
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bikermike
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Re: How do you adjust the brake pedal??

Post by bikermike »

I'll defer to others for MC testing. I think you are on the right track. Just curious, have you checked the rear brakes or only the fronts?
-Mike
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ABROCK
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Re: How do you adjust the brake pedal??

Post by ABROCK »

Hi Mike,

Yes, we looked at front and back. Based on the pedal having only about 1.5" of travel, I really think it is a hydraulic issue. I'll need to actually get a mechanic to look at it. We have a Z guy here in town that works on roadsters but he's scheduled out until Oct. 1st!

Anyone know a good Datsun Mechanic in the greater Seattle area???
Adam
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Linda
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Re: How do you adjust the brake pedal??

Post by Linda »

Fish around in the reservoirs to make sure nothing is blocking th bottom hole. I had the foil paper from a bottle of brake fluid fall in there once and it blocked the hole.

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Re: How do you adjust the brake pedal??

Post by fj20spl311 »

Did you have someone press on the pedal while you looked at the calipers and pistons.

Everything sounds pretty normal...might be a pad bedding issue.........

If the calipers are clamping properly (pistons are moving) and not sticking on...its usually not a hydraulic issue.
Bad master cylinder, crimped line, bad hose....If the pistons are moving and the hose were bad, the brakes would stay on....the wheels would lock after one to a few stops...this is not your problem......You can hook up a gauge to check the actual pressure at the caliper....you need 800-1000 psi

You should remove the pads and make sure they are wearing evenly and slide freely in the caliper.

One of the few things you can do about the high pedal pressure is change to higher friction pad.
Phil
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Re: How do you adjust the brake pedal??

Post by raympac »

Hello Adam,
Are you on the DROPS (Datsun Roadster Owners Puget Sound)? If not, get on the list ASAP. There are several good mechanics among the members.
ray (raympac)
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Re: How do you adjust the brake pedal??

Post by Solex68 »

I would go with the above recommendations (you are getting some experts responding BTW) but if all that fails…

You may want to check where the brake pedal rod connects into the master cylinder. In your first photo, from the interior side of the vehicle, slide the rubber cover that covers the rod so you can see the situation from that angle. Press the pedal with your hand to verify that there is no physical binding between the brake rod and the master’s piston.
That is where I was having issues. You can remove the pin that holds the rod to the pedal arm as well, but don’t go that far unless you believe there is an issue with the rod or if you suspect the rod does not come out far enough due to linkage or if the washer on the backside of the master is so thick that is doesn’t allow the master’s piston to retract all the way (that was an issue I encountered when I installed a Different model Datsun mater in my roadster)

There is no adjustment within the rod (unfortunately). I know some people do the math based on the throw needed and re-drill the hole where the rod connects to the brake pedal lever. It may be above or below the current hole depending on the master cylinder installed, original or other Datsun model.
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Re: How do you adjust the brake pedal??

Post by Phred58 »

If there is no adjustment on the pushrod, either for brake or clutch master cylinders, then look for shims between the foot of the master cylinder where it bolts through the firewall. When I rebuilt my brake master about 3 years ago, there were 3 shims there.

I would shim before redrilling the pushrod hole; once drilled, it's done. With shims, you can always add or remove them.
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Re: How do you adjust the brake pedal??

Post by Solex68 »

Phred58 wrote:If there is no adjustment on the pushrod, either for brake or clutch master cylinders, then look for shims between the foot of the master cylinder where it bolts through the firewall. When I rebuilt my brake master about 3 years ago, there were 3 shims there.

I would shim before redrilling the pushrod hole; once drilled, it's done. With shims, you can always add or remove them.
I have seen those shims in pictures. Now that I think about it. That would explain why those dang master cylinder screws into the firwall are so long. I haven't re-drilled my pedal yet. This sounds better. Where can these shims be purchased?
Greg a.k.a SOLEX68 - http://www.datsunvents.com/
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Re: How do you adjust the brake pedal??

Post by fj20spl311 »

Solex68 wrote:
Phred58 wrote:If there is no adjustment on the pushrod, either for brake or clutch master cylinders, then look for shims between the foot of the master cylinder where it bolts through the firewall. When I rebuilt my brake master about 3 years ago, there were 3 shims there.

I would shim before redrilling the pushrod hole; once drilled, it's done. With shims, you can always add or remove them.
I have seen those shims in pictures. Now that I think about it. That would explain why those dang master cylinder screws into the firwall are so long. I haven't re-drilled my pedal yet. This sounds better. Where can these shims be purchased?
You can make them out of thin sheet metal.
The mounting holes should be 2.25 inches apart IIRC and it's either 1 1/2 or 1 3/4 large hole (can not remember)
The original shims are split, but I think that is for ease of installation.
Phil
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