Rear brakes not working properly. 1983 1.8 GTI tintop

Had a disastrous day and the MOT centre today. After the tester said my rear brakes weren’t really working the car boiled over on the ramp and then the battery was flat 🤬. The tester aborted the mot.
Don’t know why it boiled, it hadn’t overheated, I can only assume the cap wasn’t tight on the expansion tank as everything is fine now. Getting a new battery tomorrow as it’s been on borrowed time for a couple of years so those too issues are sorted.
Ive always had advisories or comments on the rear brakes and every year I help the auto adjusters and the car scrapes through. I’ve gone through the braking system and it works. I don’t know what else to do and the only thing that leaves any doubt in my mind is the load compensating valve. Can anybody explain how it works, if it can be adjusted or overhauled and how I can test it?
im going to book another mot tomorrow and normally the tester is helpful with it when he tests the brakes but it can’t be right if they’re always flagging an issue.
Thanks in advance.

Are your flexi hoses ok?  they can swell and block with age

They are only a few years old but I will check. Thanks.

There is 2 types of rear wheel brake cylinders, 14mm and 17mm so you may have the smaller cylinders.

Not 100% sure what should be fitted to a tin top car but on my 1988 Mk1 cabriolet with the inline rear brake pressure regulator I have to fit the 17mm cylinders and on my 1978 Mk1 Scirocco without any rear brake pressure regulator I've got the 14mm rear cylinders.

Hi Mark, I remember chatting to you on here a couple of years ago about my rear brakes.
I'm sure I have the bigger cylinders, I replaced them 3 years ago and originally ordered the wrong ones and got the 14mm ones. I did have them fitted wrong, which stopped the self adjusting wedge from moving but that is sorted now.
I've always got over it by helping the wedge by poking a screwdriver through the wheel nut hole but surely they shouldn't be an issue every year. Either my mot tester is expecting them to work like a modern car or something is wrong. He's a very reasonable, sensible and helpful guy so I don't think he's expecting modern braking power.

I had an MOT failure on my campaign 3 weeks ago due to rear brake imbalance. I basically bought a set of new brake shoes and spring kit and replaced the whole lot. Gave the drum a good clean and rub with sand paper.



If your cylinders are fairly new, then worth having a look at the master cylinder especially if it's very old as the performance deteriorates over time.

Also check the condition of the brake fluid as mine was contimated on the left rear wheel (dark brown colour). Slightest contaminated can cause issues with brakes. I flushed mine completely with new fluid on all 4 sides. Also check for any obvious air leaks to the brake servo.

When I bought my car, the brake lines were corroded & leaked so I replaced all the pipes (rigid & flexi).

It's a pain removing and installing the springs. I managed to do with a parrot nose, pliers, screwdrivers. After doing the job I decided to invest in spring pliers for future. Hopefully will relief some frustration doing such jobs. Here is the link on eBay but I haven't tested it yet so don't know how good they are.
https://www.ebay.co.uk/itm/402249658351

Remember to push the wedge up so the shoes squeeze inwards before putting the drum on. Also make sure the wedge is in correct orientation, the small round shaped extrusion should face the rear, this stops the wedge slipping through the assembly.

Anyway my car did pass the MOT on retest. I looked at the screen while the brake test was performed and the front brakes do have more pressure than the rear brakes. The tester should not expect a 35 plus year old car to perform the same as a new car.

The only modification to my car is that I have MK2 Golf GTi 8v vented discs and calipers at the front as the vented discs are better for cooling compared to the original non vented discs. I kept the standard rear shoes and did not do the disc conversion, they work well.

Looks like you've done the usual suspect, seized or leaking cylinders and badly adjusted wedge.

Do you do many miles? Are the new shoes bedded in? Has it been bled to 100% to remove any air in the system (start with wheel furtherest from the master cylinder and work forwards)

You might be able to get a bit of adjustment on the threaded rod from the brake pedal to remove any slack in the bonkers bell crank across the bulkhead LHD to RHD bodge that VW came up with.

Thanks for the replies 👍🏻
I've bled them through and everything seems to be working as it should. I checked the load proportioning valve and it wasn't operating. I've adjusted it and things seem a lot better. I just need to take it out on the road and try it. Mot booked for Monday so fingers crossed.
Car usually does about 2k a year but I got divorced last year and the car is currently stored elsewhere so it hasn't been used as much. Hoping to move in the spring so will be able to enjoy it more😎

Thanks again for the tips. Just to let you know that she went back in today and passed with no advisories and the brakes are fine. Probably down to the badly adjusted load proportioning valve.

Saulty said

Thanks again for the tips. Just to let you know that she went back in today and passed with no advisories and the brakes are fine. Probably down to the badly adjusted load proportioning valve.

I hate those things, glad they went with ones off the MC on my Cabriolet.

I had one on a dodge van, and you had to replace the rear leaf spring as it was part of the spring assembly…..so it was a ton of monies….but alas I got one from a breakers for about 50 bucks.