Vacuum leak on brake booster...........

Dave81 · Post by **Dave81** » Sun Aug 03, 14 8:50 pm

Gents looking for advice on this.......

I've got a vacuum leak on the brakes which is coming from the brake booster. The brakes on the car are woeful and always have been, but this has now also been confirmed by Jim Smith (currently workin on the car).

Brake pedal can sometimes be very hard under foot (not always) and the ability to scrub off speed is verging on dangerous. Add to the fact the engine rpm rises under braking means the car is also pushing under braking!

The booster is the large single diaphragm version with the 'Z' style pushrods at the rear. This has a rubber shroud where it enters the drum, and under braking you can see it deform under vacuum. Jim believes it's defective (and I don't doubt his prognosis)!

Firstly the booster is less that 5 years old I believe and has probably less than 500 miles on it (practically brand new), so no doubt it's been defective from day 1! See below.....
s100.photobucket.com/user/dave81_01/media/My%2072%20Dodge%20Dart%20Swinger/2012-06-23121748.jpg.html]

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Anybody any ideas on this (had similar)......I've searched the net with little luck and replacement is £££......

Has anyone got one hidden away?

I've searched the web and this is the likely replacement (ill do the lot) to solve the issues...
http://www.summitracing.com/int/parts/r ... model/dart

Other than that is turning the car to manual brakes gonna be an issue (it's fitted with Kelsey Hayes 4 pots on the front 11" disc) and drums rear?

Input and advice always welcome.

I may have mentioned this before and had input, but after talking to Jim it's now next priority...... So please bare with me!
I won't dick about with braking or steering, and after driving it first time for 2 years a few weeks ago, I'll not be going far with it as it is..........

Much appreciated!

Mossy68 · Post by **Mossy68** » Sun Aug 03, 14 9:06 pm

Can't you replace diaphragms etc in some boosters ??

Dave81 · Post by **Dave81** » Sun Aug 03, 14 9:17 pm

Mossy68 wrote:Can't you replace diaphragms etc in some boosters ??

Not on these, according to the factory manual! States you should not open the booster.........factory only!
Not sure if doing so loses the seal and renders it useless?

Pete · Post by **Pete** » Sun Aug 03, 14 9:34 pm

I would ditch the booster - you don't need one on a "A" Body and if you have a big cam with a large overlap the booster will not be reliable in any case...........

Mossy68 · Post by **Mossy68** » Sun Aug 03, 14 10:01 pm

Dave81 wrote:
Mossy68 wrote:Can't you replace diaphragms etc in some boosters ??
Not on these, according to the factory manual! States you should not open the booster.........factory only!
Not sure if doing so loses the seal and renders it useless?

Gotcha. Then I think I would do as Pete says.
MC's can be picked up for around fifty quid.

MilesnMiles · Post by **MilesnMiles** » Sun Aug 03, 14 10:56 pm

Dave, when I fitted that booster it was brand new old stock, the guy that sold it to me paid a lot to source it.
My view was that the master cylinder needed bench bleeding and still does. I also agree that the brakes would be fine one day and woeful the next, and I didn't ch k the booster as it was new.
Manual brakes would fix all that but it's a a shame as the m/c and booster were a new matching pair

Johnny Dart · Post by **Johnny Dart** » Mon Aug 04, 14 11:36 am

Dave , this may help http://www.moparuk.com/forums/viewtopic ... highlight=

It shows my midland ross servo in a striped down state.
This servo has no large spring, so doesn't boing apart on your chin when you remove the band

But lots of other make servos have a spring in side, so to be safe ,clamp it to stop it boinging apart

I re glued the control hub on mine , and it only has a slight leak now, and the car is usable.
I have ordered a replacement. But its coming over from the states when my mate brings it back in November. Only the control hub is duff on mine, so if you need parts I will have some available after Nov, but that's probably too late for you.
Mine is quite new, I think whoever fitted it in the states broke it whilst fitting it !

Your Servo looks the same as mine (Midland Ross)
Its available as a Cardone reconditioned unit part number 54-76101

Johnny Dart · Post by **Johnny Dart** » Mon Aug 04, 14 11:45 am

If you pinch the servo hose off, with some grips , while its idling, you will notice a change in engine note if there is an air leak present.
Revs will drop.

Dave81 · Post by **Dave81** » Mon Aug 04, 14 8:07 pm

MilesnMiles wrote:Dave, when I fitted that booster it was brand new old stock, the guy that sold it to me paid a lot to source it.
My view was that the master cylinder needed bench bleeding and still does. I also agree that the brakes would be fine one day and woeful the next, and I didn't ch k the booster as it was new.
Manual brakes would fix all that but it's a a shame as the m/c and booster were a new matching pair

Miles,
I've scoured the net and dug around as much as possible. My findings point at the booster as expected with the symptoms!

If it was an issue with the MC not being bled, I'd expect the pedal would be very spongy, and there would be a possibility of no brakes at all dependant on the amount of air. None of this would lead to a vacuum leak? Just crap brakes!

I've also looked into going manual......nothing's bloody cheap!

So will try and source another booster first, then see if I can investigate the existing one and see if I can fix it/get it fixed!

Thanks for the pointers chaps.......

terryr · Post by **terryr** » Mon Aug 04, 14 8:24 pm

suck on the pipe ,if your tonque sticks in the pipe the booster aint got a hole in it ,old way but simple ,

MilesnMiles · Post by **MilesnMiles** » Mon Aug 04, 14 8:37 pm

I sympathise Dave! pain to be sure. When I got the roadrunner the brakes were crap and the booster was dead. Even so, the brakes wouldn't hold despite having a new M/C. Yet the minute I replaced the booster the whole system came to life and has worked perfectly ever since.
Maybe it is just the booster. Mine was a cardone from Rock Auto. Not very expensive.

Dave81 · Post by **Dave81** » Mon Aug 04, 14 8:58 pm

MilesnMiles wrote:I sympathise Dave! pain to be sure. When I got the roadrunner the brakes were crap and the booster was dead. Even so, the brakes wouldn't hold despite having a new M/C. Yet the minute I replaced the booster the whole system came to life and has worked perfectly ever since.
Maybe it is just the booster. Mine was a cardone from Rock Auto. Not very expensive.

Yes mate.......first port of call! Rest of the system seems good, so no point spending money for no reason!

Terry, when I get the car back I'll see what suction I have.............

challenger · Post by **challenger** » Mon Aug 04, 14 10:34 pm

terryr wrote:suck on the pipe ,if your tonque sticks in the pipe the booster aint got a hole in it ,old way but simple ,

terry, on idle theres nothing leaking servo seals nice but put some foot pressure on here the revs rise a touch and a rock hard pedal which tells me vacuum is leaking past the diaphram you can also hear hissing sound in the servo, ive never had one do this, i,m sure another servo will sort us out