Help with Bedford TK please :)
 

HI, i have recently bought a bedford TK horse lorry (1977 straight six)

When i went to come back the other day from a horse show, i had almost no brakes (eeeekkkk)

The air system seems to be fine, pressure is between 6-7 and only drops if i havent used her for a few days. Handbrake also seems to be un affected, but it was a bit dicey coming home, had to crawl down the hills in 2nd gear cos brakes arent coming on until the pedal is to the floor and even then i have hardly any brakes. Tried pumping the pedal with my foot, but didnt seem to make any difference.

It passed its plating at the beginning of August so this is a very recent problem, could it be something simple?

Any advice would be more than welcome :)

It might be that the brakes need adjusting (or the linings are worn or contaminated with oil).
Maybe the servo is faulty and not operating the hydraulics.

Is it hard to adjust them? As in ... am i able to do that myself?

When i use the hand brake it is still making that hissing noise when the air is released and same when i brake, its just it doesnt seem to slow me down much!

Could they have got hot and melted as to get to the horse show the other day we had to go down a very long and winding hill ... could i have burnt my brakes out doing this... i didnt notice a smell, but the engine smells alot in the cab so maybe i wouldnt have noticed this...

I'd first check the servo and what ever you do get a pro to look the vehicle over, You don't want any mishaps while either you or your horse on-board.

Yes, you really need expert help - it's almost impossible to diagnose remotely - especially if you aren't familiar with how to adjust the brakes.

It's highly probable that you might have 'cooked' the linings descending that steep hill, but it could be a leaking wheel cylinder - which will require rectification by someone who knows what they are doing.

It might be a leaking axle hub oil seal - there's several possibilities that will need the brake drum to be removed in order to diagnose the cause.

Have you checked the fluid level i think you have air/ hydraulic brakes

Your brakes will be air over hydraulic. This means that air from the brake pedal valve will apply a hydraulic master cylinder which applies pressure to the wheel cylinders in the brake drums.
Having air pressure is essential of course, but you need a satisfactory hydraulic system for the brakes to work effectively.

It is possible to boil the brake fluid if you seriously overheat the brakes - especially if the brake fluid is 'old' (it attracts water vapour and it is the water that boils when the fluid gets hot).
This leaves 'air' in the system and the brake system needs bleeding (as a minimum) or, ideally, fresh brake fluid. It is recommended to change the brake fluid every few years (depending on the operating climate).

Alternatively it is possible to 'cook' a wheel cylinder seal if the brakes have been overheated (such as a long downhill descent under load) and subsequently the seal will leak fluid (contaminating the linings) or might 'suck in' air into the system - again requiring bleeding (as well as renewal of the faulty seal(s)!).

Used to drive a N reg TK 7.5t which had an auto lube system fitted below the gear stick and when things like gear change and brakes etc got sticky and did not work to their best a green light came on to indicate the truck needed lubrication and you manually pulled a lever to distribute the lube which had an immediate effect on how things worked it was quite an expensive extra but it worked really well I would think that if this unit was not fitted a manual top up was required but where it was I could not tell you but most likely under one of the side flaps where most top ups were done when we replaced this truck with a TL the system was built in automatically and of course this came with a tilt cab but was not half the truck of the TK as after 4 years it rotted around us and had to be replaced with a Merc

Thanks for all your replies, Its goin to the garage today for the chap to have a look at it.... I will let you know what he says :)

Having re-read your original post, I would strongly recommend that you check the indicator rod that sticks out from the 'black' unit on the sidemember (the air dual-actuator) to see whether your brakes need adjusting.
I know that you have had a mechanic look at things, but you can check yourself if the thin rod is sticking out too far (it should have a red portion) which indicates that it's time to adjust the wheelbrakes.
If the linings are too far from the drums then the hydraulics cannot push far enough (and pumping the pedal won't improve matters as it merely supplies air which pushes the hydraulics). It might be worth getting the brakes adjusted before your mechanic starts work on the servo and master cylinder.

The adjusters on each wheel are simple 'screw in' - turn until the wheel won't turn then unscrew until the wheel spins without binding. You need to jack up the axle to do this properly (and press the pedal with the engine running - or at least with air in the system - to centre the shoes when they are fully against the drum).
Once adjusted push in the thin indicator rod on the air servo and then apply the brakes - the indicator will stick out according to how much travel there is in the hydraulics.

You can adjust the wheelbrakes without jacking up the axles (for example if they are well out of adjustment) but you have to make sure that you 'back off' the adjusters so that the wheels don't bind - which will overheat the brakes - for eample if the indicator rod is along way out it's worth tuning the wheelbrake adjusters a couple of turns and checking the indicator again.

Brakes that are well out of adjustment can give the impression that the hydraulic system is faulty or that the air servo isn't working properly - exactly what your mechanic has diagnosed.

Simply fitting a new master cylinder and new seals in the air servo will not cure brakes which are well out of adjustment.

Just saying.