Brake Servo- Booster air valve spring

[Carlos]

Dear people, first of all excuse my English.
I´m into the final process of fixing the brakes of a 1976 Rover P6 2200 TC, that belongs to a friend of mine.

I´ve made everything:
- rear calipers kit ( late Girlin ) quite complicated but accomplished thanks to Mark Gray´s video.
- front calipers, easy task.
- master cylinder
-complete servo unit kit ( with new diaphragm and slave cylinder kit )

When testing the brakes I found that the front calipers get stuck.
After reading several threads about the subject, I think that the problem could be the air valve.

And now the question: is there any big spring in the air valve ?
Mine doesn't come with it. In the Big Work Manual doesn't exist, but in some threads it does.
I'm attaching a couple of photos to clarify.

I´ll appreciate any help

 

[quattro]

The spring is under the plate marked 'E' in your diagram.

 

[Carlos]

The spring is under the plate marked 'E' in your diagram.

Thanks for your feedback !
The problem is that again, in the Big Workshop Manual ( and in my valve ), the spring doesn't exists. ( see photo )
And there is no spring in the kit.

 

[cobraboy]

 

[cobraboy]

 

[cobraboy]

 

[Carlos]

View attachment 22940

Thanks Cobraboy but I'm talking about a bigger spring that should be under the white cap, between the cap and the rubber diaphragm.

 

[mrtask]

I once had this same issue. I had to fit a spring underneath the big white plastic lid or cap. It was quite a bit larger than the little tiny spring visible in the last photo in the post above this one. I remember thinking it didn't seem to be very strong, but it was obviously strong enough, it fixed the problem of my front brakes sticking on. Hope you find the part you are missing from one of the usual suppliers, such as Mark, Geoff at Winns International or J.R.Wadhams, to name a few.

 

[chrisw]

I've stripped a few lately, and may have a spring.. I'll check when in the garage tonight

 

[cobraboy]

I am 99% certain that the Lockheed remote servo I currently have does not have two springs in the air valve assembly, only the small one I pictured.

 

[Carlos]

I once had this same issue. I had to fit a spring underneath the big white plastic lid or cap. It was quite a bit larger than the little tiny spring visible in the last photo in the post above this one. I remember thinking it didn't seem to be very strong, but it was obviously strong enough, it fixed the problem of my front brakes sticking on. Hope you find the part you are missing from one of the usual suppliers, such as Mark, Geoff at Winns International or J.R.Wadhams, to name a few.

Thanks for your answer.
As you see, some valves have the big spring and some doesn't.
I will try to build one; maybe cutting the soft spring inside the SU carburetors.
With the Brexit, getting parts from England became a little nightmare and takes ages.

 

[Carlos]

I am 99% certain that the Lockheed remote servo I currently have does not have two springs in the air valve assembly, only the small one I pictured.

The same happens with my servo. It comes without the big spring

 

[mikecoombs]

As shown in your first photo there is a spring in there. Unfortunately none of the other drawings are of the same section so you can't see it. There is a kit to service just that part of the servo and it should have a new spring in it but they are a real devil to keep inside the box on the shelf. So these days quite a few kits no longer have them in it...

 

[Carlos]

As shown in your first photo there is a spring in there. Unfortunately none of the other drawings are of the same section so you can't see it. There is a kit to service just that part of the servo and it should have a new spring in it but they are a real devil to keep inside the box on the shelf. So these days quite a few kits no longer have them in it...

When I made the servo, I bought the complete kit: big 7"diaphragm, complete slave cylinder kit, and air valve kit ( white cap, filter, rubber diaphragm but no big spring ). Wins, Wadhams and MGBD doesn't seem to have it.
I will try to build one with a soft spring and see what happens.

 

[colnerov]

Hi, I can remember a few years ago there was a discussion on here about which way up the servo was mounted, air valve up or down. I did some research, or jumping around the internet, and I read an article on I think a Lotus forum about on the hydraulic side of the air valve the piston can be found with 1 or 2 'O' rings. it was pondered that hydraulic pressure can get in between them and lock the piston up and it was suggested to remove one of them and alleviate the problem. Make of that what you will, it was a while ago.

Colin

 

[Carlos]

Hi, I can remember a few years ago there was a discussion on here about which way up the servo was mounted, air valve up or down. I did some research, or jumping around the internet, and I read an article on I think a Lotus forum about on the hydraulic side of the air valve the piston can be found with 1 or 2 'O' rings. it was pondered that hydraulic pressure can get in between them and lock the piston up and it was suggested to remove one of them and alleviate the problem. Make of that what you will, it was a while ago.

Colin

Thanks Colin for your interest.
I read this thread in the Lotus forum and apart the comment about removing one of the o rings, I found a picture where I can see clearly the big spring that I missing.

 

[mrtask]

That's the blighter, Carlos! You've found the photographic proof that I hadn't imagined that. I imagine a Lotus spring will cost more than a Rover spring, eh!?

 

[cobraboy]

Lockheed recommend the air valve be mounted pointing down at something like 45 deg, and the outlet end pointing upward, this is all to aid bleeding.
The point about the little reaction piston having two seals is valid, having two seals can cause the brakes to stick on.

I wonder if the large spring is only fitted to specific applications, dependant on the amount of vacuum generated by a particular vehicle.
I cannot remember if my original, stock servo on my P6 had the large spring, or not, but it was a V8, so not much help anyway.

 

[Carlos]

That's the blighter, Carlos! You've found the photographic proof that I hadn't imagined that. I imagine a Lotus spring will cost more than a Rover spring, eh!?

With Brexit, everything coming from UK costs a lot, money and time...

 

[SydneyRoverP6B]

I am 99% certain that the Lockheed remote servo I currently have does not have two springs in the air valve assembly, only the small one I pictured.

You are right; the brake booster never originally came with a second coil spring beneath the air control housing. Later, a modification spring was installed as it was found that the brakes could remain on, particularly after light brake applications. The inclusion of the modification spring eliminated the problem. The springs could be purchased a few years ago, I recall.

Ron.