Is this master cylinder fubar?

Beta Ray Bill

Hey All

Noticed brakes on car are getting "sticky" after driving in traffic for a while. Gradually gets worse and worse. Feels likes the brakes a r e on even when my foot isnt on the pedal

I don't think its the calipers. Checked master cylinder, and although there are no leaks it is very rusty. See pic below

Im nearly sure this is the issue (opinions?)


G

biko

Impossible to say really.
Just because it's rusty on the outside doesn't mean it's not doing its job.

CJhaughey

Could be sticky calipers, surface rust on a M/C is common, the calipers are more exposed to water and dirt ingress.
Also check the slider pins are moving freely.

biko

Sticking calipers would cause the alloys to heat up.
Are any alloys hotter than the others?

Beta Ray Bill

I should really check Caliper heat shouldn't I?

Need to get a Laser Thermometer.
Anyone know a good place to get one relatively cheap?

Maplin?

Beta Ray Bill

CJhaughey wrote: »

Could be sticky calipers, surface rust on a M/C is common, the calipers are more exposed to water and dirt ingress.
Also check the slider pins are moving freely.

Sorry, dont know a whole lot about "brakes"

Where is the slider pin located?

G.

CJhaughey

When you have the wheel off and the car is safely held on an axle stand.
You will see the wheel hub, disc and caliper that grips the disc.
The caliper will be bolted to the carrier which in turn bolts to the hub.
There will be two pins which hold the caliper to the carrier and these are the slider pins, they are called that because they are supposed to slide to account for wear in the pads/discs and allow both pads to grip the disc evenly.
They usually have small rubber bellows protecting them from Road dirt and water but often water ingress and dirt cause them to seize and when they stick one pad can often stay in contact with the disc surface and cause problems.
The caliper piston can often seize as well causing the pad to stay in contact with the disc.

biko

grahambo wrote: »

I should really check Caliper heat shouldn't I?

Need to get a Laser Thermometer.
Anyone know a good place to get one relatively cheap?

Maplin?

No need for that - the heat from a sticking caliper will spread to the alloy/wheel rim.
After a drive stop and put your hand on the 4 alloys/rims (not the calipers). Is one hotter than the others?

Alun

What biko said. Had this happen to me recently on our MX-5, and it got so bad you could feel the heat coming off it even holding your hand a few cms away from the alloy. Best to nip it in the bud now rather than carry on and have one caliper suddenly seize on you. Been there, done that, changed the underpants (on a different car!)

Beta Ray Bill

CJhaughey wrote: »

When you have the wheel off and the car is safely held on an axle stand.
You will see the wheel hub, disc and caliper that grips the disc.
The caliper will be bolted to the carrier which in turn bolts to the hub.
There will be two pins which hold the caliper to the carrier and these are the slider pins, they are called that because they are supposed to slide to account for wear in the pads/discs and allow both pads to grip the disc evenly.
They usually have small rubber bellows protecting them from Road dirt and water but often water ingress and dirt cause them to seize and when they stick one pad can often stay in contact with the disc surface and cause problems.
The caliper piston can often seize as well causing the pad to stay in contact with the disc.

Cool

So If I were to check this how to I fix?
Is it a simple case of WD40 and elbow grease to clean it?
Or will the mechanism need to be replaced?

I'll check the heat thing tonight.
If I jack up the car 1 wheel at a time (On a flat surface and with stops obviously) and try and turn each wheel I should see noticeable resistance if one of the calipers has an issue right?

Sorry for all the questions, Just want to nip this in the bud before it becomes a serious issue

EDIT: Should have also mentioned in first post that the Peddle becomes stiff as this happens

G.

Hal1

Use something like lithium grease for the slider pins.

CJhaughey

grahambo wrote: »

Cool

So If I were to check this how to I fix?
Is it a simple case of WD40 and elbow grease to clean it?
Or will the mechanism need to be replaced?

I'll check the heat thing tonight.
If I jack up the car 1 wheel at a time (On a flat surface and with stops obviously) and try and turn each wheel I should see noticeable resistance if one of the calipers has an issue right?

Sorry for all the questions, Just want to nip this in the bud before it becomes a serious issue

G.

If its the slider pins then its a case of get them out and clean off and apply a heat resistant grease, not WD40.
I have used LM grease used sparingly on the pins and it seemed to be fine on Toyota's rubber.
I wouldn't go with spray grease its a bit messy, I think its better to coat the pin with a decent smear of grease and then refit.

If its the caliper piston then you need to change the caliper if you can't rebuild it yourself.

Beta Ray Bill

CJhaughey wrote: »

If its the slider pins then its a case of get them out and clean off and apply a heat resistant grease, not WD40.
I have used LM grease used sparingly on the pins and it seemed to be fine on Toyota's rubber.
I wouldn't go with spray grease its a bit messy, I think its better to coat the pin with a decent smear of grease and then refit.

If its the caliper piston then you need to change the caliper if you can't rebuild it yourself.

Copper grease is heat resistant right?

G

Roger Mellie Man on the Telly

Don't use copper grease on the slide pins. It damages the protective rubber boots.

CJhaughey

Copper grease will make the boots soft , silicone grease is good if you have it.

Beta Ray Bill

Hey Guys

Sorry for the late response on this
Dont drive the car that often.

Took it out for a spin the day before yesterday and the issue occured again.
Got it home and jacked it up

Rear wheel movement is good
Front Wheel movement is a bit resticted, a bit more so on front Driver side.

I'll do the slider pins this weekend, but I suspect that that this wont work, as both front wheels feel restricted
This leads me back to original thinking that the master cylinder is busted.

Opinions?

shietpilot

Check the rubber brake line on that corner. If it's restricting the flow of brake fluid it can cause this. When you press the pedal there is enough pressure to overcome the restriction but there is nothing to push the fluid back out after you release the pedal (except for the seal in the brake caliper) and it can make the caliper seem like it's sticking.

Tommyboy40

If you don't know much about cars then brakes are a bad place to start. Shouldn't cost much to get them professionally checked

The Sidewards Man

Tommyboy40 wrote: »

If you don't know much about cars then brakes are a bad place to start. Shouldn't cost much to get them professionally checked

That is nice helpful advice for someone who wants to learn some day car skills.

shietpilot

The Sidewards Man wrote: »

That is nice helpful advice for someone who wants to learn some day car skills.

You would think some people on this forum were born with golden hands the way they tell people to not touch brakes.

If you make a mistake with the braking system you will notice failed brakes the second you roll your car at 5 km/h and press the brake pedal. No need for this "jaaaaaaaaaysus don't be touching the brakes if you don't know what you're at".

fancy pigeon

shietpilot wrote: »

If you make a mistake with the braking system you will notice failed brakes the second you roll your car at 5 km/h and press the brake pedal. No need for this "jaaaaaaaaaysus don't be touching the brakes if you don't know what you're at".

But this isn't always the case. Say a failing servo/one with a water ingress can be intermittent and difficult to diagnose to the inexperienced. Some ABS systems are notoriously difficult to bleed fully and only comes apparent further on down the road. Internally frayed brake hose and a failing master cylinder again is intermittent and will cause brown trousers.

Imagine if someone who did this for the first time went out and crashed. Because I know people who have done this

I ask you this: have you had a brake failure at moderate speeds?

Whilst I wouldn't say don't do your own brakes (because I trust no one else apart from immediate family and a select few to work on my car if I can't) I would say understand how the system works and take your time at it

shietpilot

fancy pigeon wrote: »

But this isn't always the case. Say a failing servo/one with a water ingress can be intermittent and difficult to diagnose to the inexperienced. Some ABS systems are notoriously difficult to bleed fully and only comes apparent further on down the road. Internally frayed brake hose and a failing master cylinder again is intermittent and will cause brown trousers.

Imagine if someone who did this for the first time went out and crashed. Because I know people who have done this

I ask you this: have you had a brake failure at moderate speeds?

Whilst I wouldn't say don't do your own brakes (because I trust no one else apart from immediate family and a select few to work on my car if I can't) I would say understand how the system works and take your time at it

Well obviously you should research what you are doing beforehand to understand how the system works so you have the knowledge on how to put things straight if things go wrong on the job.

I'm not saying he should start removing brake lines and master cylinders but with some research it's doable.

Beta Ray Bill

Lad's I'm fairly hand

Do a lot of work on motorcycle and cars

So don't be worrying lol!

Back on topic, Both front wheels "sticky" Still think it's the slider pins or is it the master cylinder?

Note when the car cools down this is not and issue, Also if it's raining/cold this is not an issue

Issue seems to arise on a warm day with traffic

biko

When were brakes bled last?
Maybe start by doing that and see if it helps.

Change fluid in reservoir and then bleed brakes, keep an eye on the fluid level in reservoir so you don't get air into the system.

Beta Ray Bill

Ok can someone tell me what bolts the slider pins are?

biko

That's a different type of caliper than everyone thought you had.
This design doesn't need slider pins in the same sense.
But in general, take apart and clean properly.
Put a bit if silicone grease or copper grease wherever metal meets metal.

What car is it?

Beta Ray Bill

biko wrote: »

That's a different type of caliper than everyone thought you had.
This design doesn't need slider pins in the same sense.
But in general, take apart and clean properly.
Put a bit if silicone grease or copper grease wherever metal meets metal.

What car is it?

2002 Lotus Elise

Took Calipers off
Was able to push back pistons easy enough with Wrench
Don't think it's the Calipers after all, they don't seem ceased

The fact that it's both Front wheels that were hot leads me to believe what I originally thought, that the master cylinder is fubar (Can't see any leaks mind you)