Drum brake cylinders - How to 'bed them in'

thudd

Right, so my car is going in for its fourth (that's right, FOURTH) NCT test on Monday. It has failed everytime on one item, Rear Brake Imbalance - usually of around 50%. Left side reads about 0.950, Right side 1.750. Imbalance should at most be 30% - Its a 99 Honda Civic saloon.

I brought it to a 'reputable' company with many branches in Dublin after it failed the 1st time. They re-filled the brake fluid and re-adjusted everything. Re-test - Fail. Back to these guys, they messed around with it, re-adjusted once more. 2nd Re-test Fail.

I then decided to not have any more dealings with these wasters so I went to another mechanic. He took at look at everything, and once again told me everything was fine. Re-adjusted the brakes to manafacturers settings, and said it should be ok. Full NCT again - Fail.

He didn't charge me that last job of the re-adjustment of the brakes, so I brought it back to him with the results. Asked him to change the brake cylinders as this is what the NCT guys suggested I do. He has now done that and has tested it out on a rolling road to check the results. He has managed to get the imbalance down from 50% to 35%, which is good. But it needs to be under 30%.

He suggested that maybe we should just replace everything - Shoes, Drums etc. I said, if it is guaranteed to work then do it. But now I am being told that the fix of just the cylinders will work, if I just drive my car around the place for the next few days so the drum brake cylinders 'bed-in'.

So, I suppose the question I'm asking is - Does anybody know the best procedure to bed-in drum brakes??

This issue is driving me nuts. Any help would be greatly appreciated.

keithclancy

Bed in ...

Drive with the handbrake slightly on ?

Can't see how that would sort an imbalance though. Maybe one of hoses was kinked or something and now has a bulge in it.

TestTransmission

thudd wrote: »

I brought it to a 'reputable' company with many branches in Dublin after it failed the 1st time.

What company out of a matter of interest?

thudd

They just said to basically drive it into the ground for the weekend to achieve the best results. Very confusing though. Surprised how many different groups of mechanics are struggling with something that seems to be fairly straight forward?

They also said that they checked all hoses, lines, prop valve etc, and all was fine with them.

keithclancy

That seems like very shoddy advice though ... i mean ... EHH YEH I CANT FIND WHATS WRONG .. GO DRIVE THE HOLE OFF IT FOR A FEW DAYS AND COME BACK TO ME.

thudd

@TestTranmission - Dunno if I can name and shame just yet. I want to get on to the management team to see if I can get some of the money I paid for the job back. Give them a chance to redeem themselves a bit

@keithclancy - I know! Not very reassuring advice really. But in fairness, they have corrected the imbalance a fair bit with the change of cylinders (which I suggested). And google tells me that this bedding in stuff is in fact something that needs to be done. Just thought they could do it maybe! Also, they are not charging me a penny until after the NCT also - which is alright. However, if I don't get this bloody thing to pass on Monday coming, I only get 1 years worth of a Cert. They are changing the rules for cars over 10 years old from the 1st of June.

Any other ideas of how I should go about bedding these things in??

n97 mini

The piston is seized on the ditch-side of the car. Very common problem. Just replace the piston, it's not a big or expensive job.

thudd

I see. I informed the mechanic that before a bought the car a year ago, it had been parked up for a while. So I suppose a piston seizing would be fairly obvious - would they have not spotted this though? They say that the wheel is spinning freely enough. I will suggest this to them later though, thanks

n97 mini

thudd wrote: »

I see. I informed the mechanic that before a bought the car a year ago, it had been parked up for a while. So I suppose a piston seizing would be fairly obvious - would they have not spotted this though? They say that the wheel is spinning freely enough. I will suggest this to them later though, thanks

Looking at your NCT report the braking effort is not up to the mark as your piston is seized in the retracted position and therefore not able to extend and exert brake force.

Therefore of course the wheel spins! Stopping it from spinning is the problem!

Plug

I'd say its the cylinders, replace both of them not just the one. They are about 20 quid a part. Also gently rub the inside of the drum with a light grit sand paper and make sure the shoes are clean as well. Use plenty of brake cleaner.

thudd

yep, got them to change both so they'd be symmetrical or whatever. Hopefully they had the know-how to do this sandpaper stuff themselves.

I'll just spin it around for next few days. Will let ye know if it passes on Monday. Just need to get the imbalance down for 35% to 29%! Few breeze blocks in the boot maybe

Plug

30% is a pass. When your bedding them in just brake like you normally do. Don't reddin' the sh!t out of them or you could damage the shoe's. High temperatures are bad for new shoes. Just drive like you normally do.

Nissan doctor

Has anyone tested to see if you are getting the same pressure at both rear cylinders? ie tested the master cylinder?

thudd

Just back from the NCT centre, failed again with the imbalance. Left side way out again, imbalance of 51%. Same as the last test. This was actually the 5th time its been tested and I'm losing my patience with it.

My mechanic told me that when they tested it on Friday that imbalance was down to 34% - it's after taking some jump in 3 days to get back up to 51% eh?

Can anyone recommend a good mechanic in the Tallaght / South Dublin area that can gaurantee a fix for this? The NCT guys keep telling me it shouldnt be that difficult of a job, its just a problem with the left rear side braking system. Every mechanic I have brought it to so far tells me 'We cant gaurantee it will pass, it *should* be ok', not good enough anymore. I'm skint from this.

Preferably the next group of mechanics I take the car to next should have a rolling road thing installed, so they can test it themselves and be able to say 'yes the problem is now resolved' - surely this is not too much to ask!!!!!!!

Plug

Master cylinder could be leaking maybe so, try replacing that. You definetly got the cylinders replaced? Lots of things to consider, it might be as simple as not having the brakes bled properly. Sorry to hear all the sh!t your going though.

vectra

Why dont you head on over to http://www.honda-haven.com/
Some of those lads know the Civics inside out ( and upside down at times )
Seriously though,
There are a few lads there and are always more than willing to sort issues for civic owners.
There might be one of them living near you for all you know.
Worth a shot;)

thudd

Nissan doctor wrote: »

Has anyone tested to see if you are getting the same pressure at both rear cylinders? ie tested the master cylinder?

Mechanic has told me that the Master cylinder has not been tested or changed. He says he does not have the machine needed to test it?? I told him if he thinks changing the master cylinder altogether will fix it, to just do that job. But he has told me that will cost around 600 quid.

If anyone knows a mechanic with the tool to test the master cylinder pressure, let me know.

vectra

thudd wrote: »

Mechanic has told me that the Master cylinder has not been tested or changed. He says he does not have the machine needed to test it?? I told him if he thinks changing the master cylinder altogether will fix it, to just do that job. But he has told me that will cost around 600 quid.

If anyone knows a mechanic with the tool to test the master cylinder pressure, let me know.

As I posted above
you will be better served at Honda-Haven
Plenty of S/H parts available as well there and more than willing guys to help you sort the probelm

Joe 90

Haven't read through the thread but has anyone suggested checking the linings for contamination from leaking seal. Can happen. Used to see it quite often in the days when there were a lot of drum brakes around.

jimmyw

The only way to bed in drums is to lightly sand both the shoes and drum.Saying to run the sh1t out of it is ridiculous.The wheel might be spinning freely, but is the piston actually moving out when the brakes are applied? so they still could be seized or sticking.

Bruthal

I had similar on the front brakes of a brava before. It was the flexible hose actually blocked stopping the drivers side working properly.

n97 mini

Get someone, anyone, to change the piston. It's a €25 part, and the labour's not much more.

And get a new mechanic while you're at it.

I doubt it's the master cylinder as when they fail they tend to fail completely, but if it was you'd pick one up from a fresh, low-mileage car in the scrappy for €20.

mandrax

i know its a bit late, but for other civic users, they might find this useful! i had exactly the same problem, my 96 civic failed twice on rear wheel imbalance, changed shoes, cylinders and it still failed.... after scouring through the civic forums, the last thing to change was the equilizer valve(not proportional valve). this runs directly off the master cylinder, it cost €155 at clonskeigh honda, just back from the test and it dropped from a 48% imbalance to 1%. i also noticed that the braking system as a whole is more responsive. if you dont have the equilizer valve, then it is definately the proportional valve, which is located at the rear of the car and works according to how much weight is applied to the rear and hence forth distributes an equal torque to the braking system.
i hope this helps you and other users.
mandrax...cheers.

mandrax

i know its a bit late, but for other civic users, they might find this useful! i had exactly the same problem, my 96 civic failed twice on rear wheel imbalance, changed shoes, cylinders and it still failed.... after scouring through the civic forums, the last thing to change was the equilizer valve(not proportional valve). this runs directly off the master cylinder, it cost €155 at clonskeigh honda, just back from the test and it dropped from a 48% imbalance to 1%. i also noticed that the braking system as a whole is more responsive. if you dont have the equilizer valve, then it is definately the proportional valve, which is located at the rear of the car and works according to how much weight is applied to the rear and hence forth distributes an equal torque to the braking system.
i hope this helps you and other users.
mandrax...cheers.