Braking problems!

[Flying Torquewrench]

Today, my beloved S40 (2.0i 1996) had it's MOT done. It was a first pass but there are some advisory notes.

Measurements:
Brake Advisories: RBT Service Brake Efficiency: 57%, RBT Park Brake Efficiency: 17%

Advisory Items:
001: Service brake. Your vehicle has only just met the required service brake efficiency.

002: Parking brake. Your vehicle has only just met the required park brake efficiency.

005: Park brake effort very close to limit. **DANGEROUS**

In the comments box: Warning: In my opinion, the vehicle is dangerous to drive because of defects marked as such on the failure and/or advisory documents.

Now a few questions:

1) Why does it pass the MOT when the inspector thinks the vehicle is dangerous to drive??

2) Am i correct that the Service brake is your normal brake i.e. footpedal?

3) Whats the likely cause of item 001??

4) Item 002 will be resolved after adjusting the park brake??

FYI: Brake disks and pads are well within limits.

Thanks for your help.

FT

[Gophur]

Mines just done an mot and it failed on a seized caliper on one side, could it be that you've got two seized calipers?

I was under the impression that the handbrake was auto-adjusting on the s40? There is a nut at the handle end though for manual adjustment of the cable, but my handbrake sorted itself out when I fitted new pads/discs.

Hope that's of some use!

[Flying Torquewrench]

Gophur,

You might have a point with regard to the seized calipers. Do you now a quick way to check if they are seized?

According to my Haynes manual you can adjust the handbrake with the nut at the end of the handbrake lever. as you mentioned already.

Rear brake pads have been replaced roughly 4 months ago (by a dealer) so you would assume that they also check the park brake adjustment.

Thanks for your reply.

FT.

[Kerry_T-5R]

I have both of my front calipers for sale if either of you are interested?

Kerry

[ctsracing]

When was your fluid changed adn have you checked all the lines? It maybe that there is a 'bulge' somewhere and so not braking as effectively? What pads are in the front? If they are very soft that could account for poor braking performance?

How does it feel on the road?


Not sure how to check for a seized caliper without taking the pads/disc off though??

[Flying Torquewrench]

Fluid has been changed about 11 months ago. Front brake pads and disks have been changed 14 months ago and the rear brake pads have been changed about 4 months ago. Brake disks and brake pads are original Volvo.

On the road you notice a slight degradation in braking performance. It seems that the ABS kicks in a bit earlier than it used to do.

But maybe the following has something to do with it. The car has not been used for 4.5 weeks and been standing in the parking lot. After this 4.5 week period driven the car for approx. 20 miles in a day before going to the MOT. However the brake disks have a nice clean surface (no surface rust)

[Gophur]

Hmm, personally I'd check for seized calipers by looking at the brake pad wear, if the near side(Wheel side) is much less knackered than the far side (car side, where the piston is) then that would indicate a stiff/seized caliper to me.

If someone else has a better method though?

ABS mine does as well, it's even been known occaionally to give ABS chatter on normal braking and it doesn't bother my - probably grubby sensors.

[jimboynugget]

I recently had an MOT advisory on a 1998 V40 T4 with park brake efficiency of 22%. This was very noticable on steep hills where the handbrake would only just hold the car. You could hear it creaking! There wasn't really a problem driving the car like this, but I guess in your case 17% is enough to be concerning to the examiner. You might not be able to hold the car on a steep hill and could start rolling towards other cars. Go and try it out and see if your happy with it.

My problems we due to worn pads and some rust on the braking surface. New pads and discs solved this, but this doesn't appear to be your problem.

The handbrake works on these cars by operating the rear caliper via a cable, (Rather than separate drum brakes as on some other cars), so the parking brake will probably be fine once the other brake issues are sorted. The cable pulls a lever on the caliper, so it's worth checking that there's no slack at this point. Adjusting the nut at the handbrake end will just dial out the slack, and trying to compensate for the other brake issues by making it tighter than it needs to be probably won't help much. Pull the handbrake slowly without using the button and count the clicks. Should be between 5 and 7.

I agree with the others posting here that seized components are a likely cause. The caliper is held onto the mounting bracket by two bolts. There are two guide pins that the bolts screw into, and these should be free to move once the caliper is off. This allows the whole caliper to move because there's only a single piston on one side of the caliper, so a seized guide pin will cause braking problems.

The pads should also be free to move in the mounting bracket, so check that the bracket is free of rust and dirt where the pads sit. After that we turn our attention to the hydraulic parts of the system, but I'm afraid that where my knowledge starts to run out. Seized brake piston? Worn piston seals? Fluid leaks? Dodgy master cylinder?

[Clan]

It's not uncommon for the PADS ( Not caliper piston) to sieze in the holders , the first step is to take all the wheels off and pads out and make sure they are a loose fit in the caliper holder , if they are stiff then file the brake pad edges where they are held in the caliper bracket until they are clean and smooth and scrape the caliper bracket of rust flakes and dirt . Re assemble then bed the pads in by using the brakes a lot , stopping from 70 a few times , when the brakes have cooled down you will find a remarkable improvment .. The hand brake actualy does self adjust on these calipers ...
The abs working overtime is the front brakes locking due to the rears not doing enough work so you press harder applying the fronts even harder hence they want to lock ..

[Dickymint]

You mention that you have had the rear pads changed by a garage. If I remember correctly, the rear pads need adjusting out before the pads are replaced, there is a small allen slotted flat bolt at the back of the caliper, you first unscrew this, that then gives you access to the smaller allen bolt inside which adjusts the pads when they are being replaced.To renew the pads, the screw needs to be slackened off first, then the caliper removed and the pads changed. Cannot quite remember if you need a rewind tool to get the pistons back in on an S40, but after the pistons are back in, (if they go back, then they are not siezed,) then you can fit the new pads. When the pads have been bolted back up, you need to press the brake pedal to get them somewhere near. Then adjust the small allen screw inside the back of the caliper, to get the pads just to touch the discs and rub but not bind. This sets the correct clearance from pad to disc. Now take it and drive it, see if the brakes are any better. It may be necessary to re-adjust the clearance again. If all is set up correctly, the handbrake will also come back in.
Hope I haven't been rambling.