Discussion
Due to go away for a month and guess what? Car throws a wobbly and gives me a job to get on with when I get back. Marvleyous.
The brake servo is hissing reasonably loudly, ie you can hear it whilst sat in the driving seat with the engine running. The actual assistance given and braking power available seems not too have changed at all but clearly something is amiss and it needs sorting.
I have searched the forum for clues, and I have two questions........
1. Anyone hazard a guess as to where the air is leaking into the servo? The hiss seems to be coming from the rear of the servo, where it butts up to the bulkhead.....there's a seal in there somewhere I believe....could this be it, and if so, is it a naus to replace?
2. Is servo replacement difficult? I have heard of servos being sods to remove from the bulkhead even with all the bolts removed. BAH!!!
Thanks in advance guys. I may not be able to reply for a few days due to travel, but I will get back to you sooner or later.
Cheers, chin up
The brake servo is hissing reasonably loudly, ie you can hear it whilst sat in the driving seat with the engine running. The actual assistance given and braking power available seems not too have changed at all but clearly something is amiss and it needs sorting.
I have searched the forum for clues, and I have two questions........
1. Anyone hazard a guess as to where the air is leaking into the servo? The hiss seems to be coming from the rear of the servo, where it butts up to the bulkhead.....there's a seal in there somewhere I believe....could this be it, and if so, is it a naus to replace?
2. Is servo replacement difficult? I have heard of servos being sods to remove from the bulkhead even with all the bolts removed. BAH!!!
Thanks in advance guys. I may not be able to reply for a few days due to travel, but I will get back to you sooner or later.
Cheers, chin up
There is no seal on the servo other than the one way valve rubber seal evident on the front.
Other than that it is a sealed unit with a folded metal edge which is nipped together.
If you are getting a hiss from that unit it is knackered and will need replacing.
The servo itself is not a difficult job to replace. It is held in place by 4 bolts which are in a particular pattern (slightly offset) and will only go into the bulkhead one way.
The servo's are prone to water ingress and the corroding from the inside out. I would check the bottom of the servo and although it may look unbreached the likelyhood is that it will have corroded through.
The servo's themselves are from the Saab 9000 and I would get onto your local scrappy as the position of the servo in the Saab keeps oit very well protected and it is likely to be as good as new.
I would also recommend changing the master cylinder at the same time as if the servo has been knackered for a while the master cylinder will have been overworked and once you get a new servo it tends to upset them.
These are also Saab and I would be new from Partco or such like. They just bolt on the front with 2 bolts.
Take the opportunity to completely bleed the brake system and hey presto 4 hrs later car is sorted again.
Servo from scrappy £20-40
Master Cylinder from Motor Factors £60-80
(from Saab £200 ish)
Brake Fluid (Dot5.1) £10 ish
Not that cheap a job but well worth the effort and time.
Additionally make double sure it is not the one way valve that is leaking as this can be sorted will a good sealant and double check it is performing as a one way valve. Air should only pass from the servo to the plenum and not the other way.
Cheers
Mark
Other than that it is a sealed unit with a folded metal edge which is nipped together.
If you are getting a hiss from that unit it is knackered and will need replacing.
The servo itself is not a difficult job to replace. It is held in place by 4 bolts which are in a particular pattern (slightly offset) and will only go into the bulkhead one way.
The servo's are prone to water ingress and the corroding from the inside out. I would check the bottom of the servo and although it may look unbreached the likelyhood is that it will have corroded through.
The servo's themselves are from the Saab 9000 and I would get onto your local scrappy as the position of the servo in the Saab keeps oit very well protected and it is likely to be as good as new.
I would also recommend changing the master cylinder at the same time as if the servo has been knackered for a while the master cylinder will have been overworked and once you get a new servo it tends to upset them.
These are also Saab and I would be new from Partco or such like. They just bolt on the front with 2 bolts.
Take the opportunity to completely bleed the brake system and hey presto 4 hrs later car is sorted again.
Servo from scrappy £20-40
Master Cylinder from Motor Factors £60-80
(from Saab £200 ish)
Brake Fluid (Dot5.1) £10 ish
Not that cheap a job but well worth the effort and time.
Additionally make double sure it is not the one way valve that is leaking as this can be sorted will a good sealant and double check it is performing as a one way valve. Air should only pass from the servo to the plenum and not the other way.
Cheers
Mark
Great stuff Johno, thanks a lot. Yep, Saab servo and new master cylinder when I get back. I did a 'suck it and see' check on the one-way valve and all is well there. Right then, I'll fix it and try and come along to an 's' meet to see your shiny paint! I was at the first vw meet but have had bad timing for the rest....being away for them. Never mind, cheers for the info,
chin up.
chin up.
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