Club 80-90 Forums

Hi folks ,first time posting on here (any where) renovating our 2.0 Ltr Air cooled Viking for years ,nearly there  but have a  brake issue that we can't fix ,been to 2 garages still no joy .problem is the brake pedal fades and you have to pump it to get a firm pedal we've replaced servo, master cylinder, calipers,pads ,shoes, drums ,rear cylinders ,springs etc many new pipes  theyve bled them through many times  HELP 
 

Brake vacuum non return perhaps

Hi thanks for that being a complete novice could you tell me what this is and what it does ? Will mention this on to the garage 

chippypaul3 wrote: ↑13 Nov 2021, 20:12 Hi thanks for that being a complete novice could you tell me what this is and what it does ? Will mention this on to the garage 

They should know , it’s near the engine end of the vacuum line for the brake servo

Many thanks

Also worth checking yourself, not sure for your fit but I noticed with mine although working ok the pipe in the engine bay looked a bit rough so as a temporary measure I repaired it with amalgamating tape.  If you read up on "brake servo and vacuum line" it will give you more guidance before you fork out for garage fees. But worth doing properly as it is an important item in the braking system.

This is it. Out of stock at the moment though.https://www.brickwerks.co.uk/t3-parts/b ... t3-lt.html  On Ebay https://www.ebay.co.uk/itm/294260925494

chippypaul3 wrote: ↑13 Nov 2021, 20:12 Hi thanks for that being a complete novice could you tell me what this is and what it does ? Will mention this on to the garage 

 

Thanks all ,just looked at the link will have a good look at it tomorrow .very frustrating ,just when we've got  running great, cant stop it ,although parts needed to be renewed would have been nice to have been resolved ,can been off the road for years so we've not had proper brakes in it yet . 

Can you confirm what you mean by brake fade? Does the pedal gently sink to the floor if you maintain pressure on it whilst the engine is running?
Try pumping the pedal a few times with the engine off, this will remove the vacuum effect. The pedal should now be high and hard (oh nurse!). Holding pressure on the pedal, start the engine, the pedal should sink a little. This shows that the vacuum and servo are working. 
If no leaks are evident, I wonder if the new master cylinder needs a little 'bedding in' time to seat the seals?

When the van has been stood for even a short while and go to use  the pedal will sink to the floor .when you've pumped the pedal 2 or 3 times a I get a firm pedal with good brakes ,continuous driving in traffic and with junctions etc the pedal stays firm ,once you drive 3 -400 meters no pedal use ,then go to brake, pedal then goes to the too and needs pumping to become firm ,I'm getting used to left foot braking but obviously won't to get it sorted ,going out times look for and try the suggestions so far .wish me luck

Not sure on your fit, but are the brake lights controlled via the master brake cylinder and if so do they come on when you put your foot on the brake pedal, including when pumped and when it goes flat to the floor.

It'll have a fluid pressure switch on the master cylinder. Not sure how much pressure it needs to work though, probably not much.

Have checked out the servo non return valve in the engine bay as the Haynes manual suggests and all seems good ,did wonder whether there should have been a jubilee clip fixing it onto the rubber T piece as the hoses did ,so have put one on ,havent had the chance to recheck the yet ,fingers crossed
 

I had a somewhat similar issue after bursting a brake line and Quikfit was able to put a new one in.  What they weren't able to do though was a complete bleed out of the air.  They let me know this and I trialled using the brakes - the pedal went at least halfway down before resistance and the cure was to pump the brake pedal a few time to pressure it up.
The root cause of this was that the bleed nipples on the front calipers had rotted away and couldn't be turned to release the air.
I am wondering if this is the same issue if you haven't replaced your calipers?  Once i replaced the brake lines (tough job) and put new calipers in with new bleed nipples I was able to properly bleed out the air and it works as it should now.

If you have replaced the calipers and nipples then are you getting loss of brake fluid somewhere?

Also, is the brake fluid reservoir letting air escape?

We have replaced the calipers on the front so shouldn't really be a problem there .no signs of fluid leaks anywhere 
your description of brake failure sounds the same as ours ,I'm beginning to think it's an air / servo issue ,so the hunt goes on.