Brake Servo Hose

[honestjoe]

Hi paul..Thanks for the reply..The fluid would have been changed about four years ago along with a new mc..good point though..cheers hj.

[chesters6]

Originally Posted by honestjoe

Hi..after my interesting trip to oxford and replacing servo hose i have a few symptons which i would like to put forward to you guys..Firstly brakes work fine but to be honest i"m a gentle driver so perhaps something more acute is called for..as clifford suggested start car with foot on pedal and pedal should rise..I have to say mine did not in fact it may have dropped a little?..and while car was ticking over i pressed pedal several times quite firm and this made the engine grunt and lumpy which cleared when pressure was released..finally..i pumped brakes with engine off until brake pedal was at its upper point and firm..then started engine and pedal dropped down to usual position..I"m confident the brakes are working..but how efficient..well i would like to hear your opinions before next move..thanks all..hj.

the lumpy engine could result from a air leak from the hose or a fault or leak from the one way valve on the servo ,if not your servo may have a leak in its diaphragm ,i had the exact same fault on a landy which got so bad it sounded like you had air brakes but without the help of the servo in applying the brakes!
not to bad on a 240 but pant filling on a landy with its ancient pads!

[honestjoe]

Cheers dave..The hose is brand new and volvo geniune part..its funny because as far as i can tell all is fine with the servo but perhaps i"ve never pumped the brakes like that before causing the engine to run lumpy..meaning the servo could have been like this for a long time.. more tests required..hj.

[S40T3]

[QUOTE=..as clifford suggested start car with foot on pedal and pedal should rise..I have to say mine did not in fact it may have dropped a little?.[/QUOTE]

The pedal should depress further when you start the engine! This is because (hopefully!) the servo is pushing with you. It sounds as though your servo is working OK. Not sure about the lumpy running, how long does it persist? The engine will run weak for a second or two as it evacuates the servo, but mine does not noticably alter the engine speed.

[honestjoe]

Hi S40T3..thanks..The lumpy idle is only evident when pumping brake repeatedly while engine ticks over..as soon as you take yor foot off the brake pedal..calm is restored...I"ve never noticed this behaviour before as it is not usual to stamp on brakes while car is stationary..cheers hj.

[BigGreenThing]

Hi HJ,

The exact same set of symptoms has befallen my 240 also. Having read through this thread, did you get to the bottom of why this spluttering on braking was happening?

My rpm drops from around 850-900rpm at normal idle to around 2-300rpm after pumping brakes.

Pulling off a m'way the other day to get some fuel, I applied the brakes (normally) and the car was virtually at stalling point. I had to lift off brake, rev engine whilst holding the handbrake. Not ideal.

I feel it could be the non-return valve, as the pipe seems absolutely fine. Tried the brake pedal test and all seems fine. I don't believe it is the servo.

I'm going to change brake fluid (when it's not raining!), and recheck hoses (again!), but the idea it could be something else is still with me. Is your braking/idling problem now fixed?

Cheers


JG

[chesters6]

Originally Posted by BigGreenThing

Hi HJ,

The exact same set of symptoms has befallen my 240 also. Having read through this thread, did you get to the bottom of why this spluttering on braking was happening?

My rpm drops from around 850-900rpm at normal idle to around 2-300rpm after pumping brakes.

Pulling off a m'way the other day to get some fuel, I applied the brakes (normally) and the car was virtually at stalling point. I had to lift off brake, rev engine whilst holding the handbrake. Not ideal.

I feel it could be the non-return valve, as the pipe seems absolutely fine. Tried the brake pedal test and all seems fine. I don't believe it is the servo.

I'm going to change brake fluid (when it's not raining!), and recheck hoses (again!), but the idea it could be something else is still with me. Is your braking/idling problem now fixed?

Cheers


JG

the one way valve could just be wedged open with a bit of crap ,take off the hose at the servo end and give the valve a good blasting with WD 40 and while your there block the pipe at the servo end and see if the engines still lumpy after running it.
if it is there's no problem with the servo most probably a leak in the pipe itself or inlet manifold connection or the manifold itself
if it isnt theres a problem with the one way valve the pipes connection to it or the servo itself.
pressing on the brake will give a negative pressure in the manifold so it will become a little lumpy but i presume only to the pressure equalises?
when your car is going up the road i guess you wouldn't notice it as the engine is running faster so more/less? pressure.
you could try going up a road (private or dirt track ofcourse) with the pipe blocked at the servo end ,you will need to stand on the brakes to stop but if the engine becomes lumpy the servo has been totally removed from the symptoms

[BigGreenThing]

Originally Posted by chesters6

the one way valve could just be wedged open with a bit of crap ,take off the hose at the servo end and give the valve a good blasting with WD 40 and while your there block the pipe at the servo end and see if the engines still lumpy after running it.
if it is there's no problem with the servo most probably a leak in the pipe itself or inlet manifold connection or the manifold itself
if it isnt theres a problem with the one way valve the pipes connection to it or the servo itself.
pressing on the brake will give a negative pressure in the manifold so it will become a little lumpy but i presume only to the pressure equalises?
when your car is going up the road i guess you wouldn't notice it as the engine is running faster so more/less? pressure.
you could try going up a road (private or dirt track of course) with the pipe blocked at the servo end ,you will need to stand on the brakes to stop but if the engine becomes lumpy the servo has been totally removed from the symptoms

Thanks for your advice chesters6! Lashing down today, so couldn't check conections this eve. Re: releasing brake pressure - yes the engine does ideal as normal afterwards. So your presumption is right. And yes, when the car is running down the road, its fine, and it's fine when I brake at speed also. Soon as the weather lets up I'll start with the least invasive or drastic remedies, and work upwards. Thanks again. Much appreciated.

[Clifford Pope]

Originally Posted by S40T3

The pedal should depress further when you start the engine! This is because (hopefully!) the servo is pushing with you. It sounds as though your servo is working OK.

How very curious! I was convinced mine have always risen when I have done that test, so I have just popped out to try.

What happens is:

If you put your foot on the pedal and then start the engine, the pedal rises.

But if you firstly pump up the pedal so that the movement in all the calipers has been taken up and the pedal hard, and then start the engine, then the pedal falls a bit.

Either way, it seems to indicate the servo is working.

[BigGreenThing]

Well i did the tests. Squirted WD40 down the brake servi non-return valve, sealed up pipe at servo end and the engine didn't run lumpy. It's the non-return valve or perhaps sime kinda diagphram that's perished in the servo. Some kinda air leak.

Any ideas on how much a brake servo cost to replace and have installed?

Gentle braking ok, so now off to Battle for the weekend. Keeping massive braking distances as I cruise!

Just to rub salt in the wound, my perfect dashboard now has a massive crack in it. Gutted!