Solid brake pedal

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TallXIII

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42
Location
Scunthorpe
Morning, I've an 02 td5 and my brakes are playing up, after being driven the brakes are fine, but if I use them once the pedal goes solid and won't free up until I've driven a little further or applied some revs. I can usually anticipate it but if I need to brake sharply it can be a hope and a prayer to stop
 
Hi. Seems like servo assistance missbehaviour... check for vacuum leak first of all and if that system is leakless i'm affraid the servo unit is gone
 
TallXIII said:
Morning, I've an 02 td5 and my brakes are playing up, after being driven the brakes are fine, but if I use them once the pedal goes solid and won't free up until I've driven a little further or applied some revs. I can usually anticipate it but if I need to brake sharply it can be a hope and a prayer to stop
Click to expand...
Do you mean that when this happens you have to push like hell to get the brakes to work, but once the car has run a bit it works normally? If so, then the vacuum chamber is not holding vacuum very well, probably a split diaphragm, or, as @sierrafery says, a split hose or a leak somewhere. As you said, in the short term, don't drive off until the engine has ticked over quite a bit, to build up some vacuum, and watch it, leaving plenty of braking distance. Don't forget your handbrake is called an Emergency Brake for a reason! You could use it together with footbrakes in an emergency, but best to get it fixed soon.
 
+1 on probable vacuum problem.
There are black plastic vacuum pipes from the vacuum pump on the back of the alternator to the brake booster / servo, with a T piece for a pipe to the EGR modulator unit.
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Sometimes people remove the EGR control & forget to blank the vacuum pipe to the modulator or blank it with something temporary that falls out.
If no leaks obvious, you can pull the Non Return Valve out of the rubber grommet in the booster & crudely check how strong the vacuum is with your finger on the end of NRV with the engine running. It should have a fairly strong pull on your finger.
If not a strong pull, work your way along the pipes looking for a fault / damage.
When putting the NRV back into the booster rubber grommet, be VERY CAREFUL not to push the grommet into the booster. If necessary, use washing up liquid to lubricate the rubber before pushing the NRV in. If the grommet is pushed inside, your booster is SCRAP as the grommet can't be got out & will unpredictably limit the brake travel.
 
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TallXIII said:
Morning, I've an 02 td5 and my brakes are playing up, after being driven the brakes are fine, but if I use them once the pedal goes solid and won't free up until I've driven a little further or applied some revs. I can usually anticipate it but if I need to brake sharply it can be a hope and a prayer to stop
Click to expand...
You describe the problem as if its been going on for a while...?
 
Like said, it's probably an issue with the vacuum. With engine off, press pedal a few times, then keep pedal down and start engine. The pedal should move further down gradually. Release pedal and wait a few seconds before pressing it a few more times. The pedal resistance should return to normal by now. If not, 99.99% it's the vacuum. If you test with a vacuum gauge, it should read about 0.8 bar, if I'm not mistaken. Otherwise, with the engine running (and assuming you have good idle), remove vacuum pipe and check if you get negative pressure from the pump by putting your finger on it. There's also a non-return valve on the servo which you can test by blowing through it. As for the servo, go for a short drive, stop the engine and wait 15 mins or so. Then remove the vacuum hose. If the servo is working, you should hear a hiss as the vacuum is lost.

As for the emergency handbrake, it's actually a parking brake so I would go very easy on it when the vehicle is in motion to spare yourself from damaging your rear transmission.
 
Re the handbrake, as my MOT tester does not have a rig for testing the brakes on anything other than a 2 wheel drive, when it comes to testing the brakes they take it for a spin with a decelerometer. I did ask if it did any damage to the transmission brake to test it like that and they insisted that was what they had to do and then went on about it being an emergency brake. Have to say the rubber coupling showed no signs of damage on any of my D1s and D2. But I must admit I wouldn't use it for anything other than parking unless I absolutely had to.
Quote from tester's manual.
Using a decelerometer
If the vehicle or system cannot be tested on a roller brake tester, set up the decelerometer in the vehicle as instructed by the equipment manufacturer.

  1. Drive the vehicle on a level road at a steady speed of approximately 20mph (32kph) and progressively apply the parking brake to maximum.
  2. Note the recorded brake efficiency.
Decelerometer brake testingmust always be carried out on suitable roads with as little traffic as possible. A particular public road should not be used for tests so frequently that it could cause complaints from residents. So, yes, only to be used from 70 mph in a dire emergency!
 
NPG said:
As for the emergency handbrake, it's actually a parking brake so I would go very easy on it when the vehicle is in motion to spare yourself from damaging your rear transmission.
Click to expand...
+1^^^, there is a warning for that in the owner's handbook too(what can i do, i've read them all :cool:)

WARNING

DO NOT apply the handbrake while the

vehicle is in motion as this could result in

loss of vehicle control and damage to the

transmission.
 
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@Stanleysteamer - I had the same concern about handbrake testing with the NCT here (which is the equivalent and I'd say based on your MOT) so I made an official enquiry with them. The first response was similar to what you wrote and I quote - "I would like to mention the method of testing the brakes for a four-wheel drive vehicle. With the vehicle on a reasonably level road a decelerometer is placed on the floor of the vehicle and following the manufacturer’s instructions set in the zero position. The vehicle is driven at a speed of approximately 20 – 30 M.P.H. (32 – 48 km/h). The brakes are applied firmly and the reading on the decelerometer is noted. This procedure is repeated for the handbrake."

When I then pointed out LR's caution on the use of the handbrake, they replied as follows - "I can confirm that for your particular make and model of vehicle, the handbrake test is conducted at a lower speed that for other 4 x 4 vehicles. The max speed reached is 5 kilometres per hour." I consider this is within the safety margin for handbrake application and the tests are always carried out accordingly. Have to say that I make certain to show a copy of that email to the tester every time. ;)

So maybe this is something that can be raised and discussed with your MOT administration
 
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