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Brake pedal no feeling and goes right down!


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As usual I am looking for some help from the more experienced on the latest project vehicle I have bought, it is a 200tdi 90 that had a TD5 engine fitted.

It has had vented disks fitted on the front to presumably give an upgrade in stopping performance.

And it does stop, it stops quite well but there is no feel on the pedal at all and only the last inch or so does any braking as such, the pedal is not heavy and does not require lots of effort to brake.

I cannot see any leaks ect but the servo looks like two servos stuck together, so I am wondering (After a quick look on ebay) does that mean that the ABS servo has been fitted to a none ABS car?

And could this be the problem?

Or could it be the vacuum pump has failed.

As you can tell as there's no leaks and nothing obvious I can see like hissing noises or cracks in the servo I really don't know where to start.

Even though it stops really well I feel there is something not right here and I would like to sort it out.

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12 minutes ago, Bowie69 said:

It's more likely you either have air in the system somewhere, or your pedal pushrod needs adjustment/is not suitable. 

Ok thanks I will try bleeding all the calipers tomorrow.

I don't suppose you have any pointers on how to adjust the pedal pushrod?

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Remove the master cylinder, behind it the pushrod is there. You'll see the tip of the pushrod is adjustable by screwing in or out, I have no idea which direction does what.....sorry

How is the color of th brake fluid? I'm wondering if it's too old and needs replacing? A flush and bleeding I think would help.  

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To add, you want a small clearance between pushrod and servo internals, so the brakes don't bind as things warm up. So you need to measure how far the pushrod sticks out of the mounting flange and how deep the receiver in the booster sits. Adjust till you have about 0.5mm clearance.

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Fluid looks a good colour, the brake pipes have been replaced recently by the look of it.

I did bleed the brakes yesterday and a tiny amount of air came out of two calipers.

The pedal felt good after this and was normal.

But after I started it and moved it the pedal went back to exactly as it was before.

I haven't got the time to do it again today but would that suggest that air is getting into the system? Is this possible even though there is no leaks.

I probably used 1/4 of a litre of brake fluid. Did I maybe not do enough even though there was no air in it?

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3 hours ago, steve b said:

Drum or disc on the back?

Clamping the flexi's should give a solid pedal with correct free play at the top, then release one clamp and check pedal , re-clamp and release another and repeat

Steve

It has a disc brake back axle but there is no flexi pipes, every one is either copper pipe or braided hose.

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On 9/3/2023 at 4:07 PM, steve b said:

Does it still have the valve in the rear circuit? - down on the OSF chassis near the footwell.

Steve

I will have to double check this, does it look like a join? I know there is something on the osr but pretty sure there's nothing at the front.

I'm not near it till next week so will check then and take a photo.

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Worth having a m10 female coupling blanked  as a 'dummy' caliper, and switch them fast, the plastic bag helps but if you have a fluid level float use a zip tie or rubber band to hold the bag on, I normally fill the res up first to reduce air.

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