Intermittent brake failure!

Jul 26th, 2006, 02:16

So, I have a 1987 240 DL with heaven only knows how how many miles on it. "The Swede" has always run great, and given me no worries, but in the last two months, I am having very intermittent brake failures.

The brake pedal doesn't travel to the floorboard, and you can't "pump" the pedal to get the brakes to work, like you could if it were a Master Cylinder failure. The pedal stays fully in the position it would be in were the car braking normally, and it is "hard" in that position. There is a kind of moaning sound, but the car doesn't really stop unless I grab the emergency brake and yank it up.

The master cylinder, brake pads, and fluids have all been checked okay. I always thought that if the brake booster failed, it would do so completely, not once or twice every couple of weeks. This may not happen for a month, or a few days, and then it does. It happens sometimes only once, sometimes several times in a row. I took it to a shop, and of course, it performed beautifully every time they test drove it. They don't kniow what to tell me, as they have inspected all the braking system components.

Ideas, anyone???

Jul 26th, 2006, 03:38

Replace Brake bootster & fluid ........ Big $'ss ....... Then you can trust it again .......

No Dealers ..... Lil dude that knows his kit

Clifford Pope · Jul 26th, 2006, 08:21

Could it be the non-return valve on the vacuum pipe to the booster unit? If it sometimes holds vacuum, but sometimes leaks and loses it?
Or a fray in the vacuum pipe caused by rubbing on something, intermittantly losing vacuum as the engine moves?

Alec Dawe · Jul 26th, 2006, 14:56

The vacuum pipe from the manifold to the servo has been known to start to colapse INSIDE, invisible from the poutside, where the pipe looks OK.
As a start, I'd pull the vacuum pipe off, and replace it. Cheap and easy, and at least would eliminate that.
Alec

Jul 27th, 2006, 01:28

From what you say, it sounds like when this problem happens you have more chance of stopping the car with the handbrake than by pushing the footbrake.

Even with servo unassisted brakes you should still be able to push them down although it will be pretty difficult to do. With the engine not running, try pushing down on the brakes and exhaust the servo and then try with no servo assistance: do you get the same feeling as you do when they fail?

I wonder if it is nothing to do with the servo, and is instead an intermittently sticking caliper or some sort of blockage in a brake hose? You may be losing your front brakes almost completely hence it feels easier to stop with the handbrake acting only on the rear brakes.

Pete

Jul 26th, 2006, 02:16	#1
xraytj Guest Location:	Intermittent brake failure! So, I have a 1987 240 DL with heaven only knows how how many miles on it. "The Swede" has always run great, and given me no worries, but in the last two months, I am having very intermittent brake failures. The brake pedal doesn't travel to the floorboard, and you can't "pump" the pedal to get the brakes to work, like you could if it were a Master Cylinder failure. The pedal stays fully in the position it would be in were the car braking normally, and it is "hard" in that position. There is a kind of moaning sound, but the car doesn't really stop unless I grab the emergency brake and yank it up. The master cylinder, brake pads, and fluids have all been checked okay. I always thought that if the brake booster failed, it would do so completely, not once or twice every couple of weeks. This may not happen for a month, or a few days, and then it does. It happens sometimes only once, sometimes several times in a row. I took it to a shop, and of course, it performed beautifully every time they test drove it. They don't kniow what to tell me, as they have inspected all the braking system components. Ideas, anyone???

Jul 26th, 2006, 14:56	#4
Alec Dawe Former Support Team Last Online: Jan 26th, 2024 11:26 Join Date: Jan 2006 Location: Nr Norwich	The vacuum pipe from the manifold to the servo has been known to start to colapse INSIDE, invisible from the poutside, where the pipe looks OK. As a start, I'd pull the vacuum pipe off, and replace it. Cheap and easy, and at least would eliminate that. Alec __________________ Alec. (My other car is a WD 2-10-0)

Jul 26th, 2006, 03:38	#2
J..M Guest Location:	Replace Brake bootster & fluid ........ Big $'ss ....... Then you can trust it again ....... No Dealers ..... Lil dude that knows his kit

Jul 26th, 2006, 08:21	#3
Clifford Pope Not an expert but ... Last Online: Today 08:25 Join Date: Dec 2001 Location: Boncath	Could it be the non-return valve on the vacuum pipe to the booster unit? If it sometimes holds vacuum, but sometimes leaks and loses it? Or a fray in the vacuum pipe caused by rubbing on something, intermittantly losing vacuum as the engine moves?

Jul 27th, 2006, 01:28	#5
peteS40 Guest Location:	From what you say, it sounds like when this problem happens you have more chance of stopping the car with the handbrake than by pushing the footbrake. Even with servo unassisted brakes you should still be able to push them down although it will be pretty difficult to do. With the engine not running, try pushing down on the brakes and exhaust the servo and then try with no servo assistance: do you get the same feeling as you do when they fail? I wonder if it is nothing to do with the servo, and is instead an intermittently sticking caliper or some sort of blockage in a brake hose? You may be losing your front brakes almost completely hence it feels easier to stop with the handbrake acting only on the rear brakes. Pete

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