Seriously weak brakes! Help!

[huw_jenks]

Hi folks, I was driving over to my girlfriends this evening, a distance of about 30 miles. I noticed that when I put the clutch in to change gear, the car would slow down quite a lot, at least more than I think is normal. The revs would drop quite quickly down to idle, but no further. I mention this because although I didn't think it a bit problem, it might be linked to what then happened.

After about 20 miles of driving, and when I was taking a shortcut down some back lanes I hit the brake pedal with another car approaching and the pedal went almost to the floor with little reduction of speed. I pumped the pedal again and the pressure built up, the pedal went about halfway down it's travel and I slowed more, then another pump on the pedal and performance was almost normal.

After a few seconds of driving brake pressure would be lost and for each time I wanted to slow down I would need to pump the brake pedal at least three times.

I'm suspecting a problem with the brake servo, but since I've never actually owned a car with a brake servo before I don't really know how to check it. The fluid reservoir is full, and all of the fluid hoses and vacuum hoses appear to be intact.

Please advise, I need help!

 

[AshLaw]

Have you got any leakage of brake fluid inside the car? aka - from the clutch pedal master cylinder?

 

[huw_jenks]

[post]354133[/post] Have you got any leakage of brake fluid inside the car? aka - from the clutch pedal master cylinder?

No, there's nothing on the matt, on the underside of the pedals. I've had another good poke around inside the bonnet too, there's no fluid leaking and all the vacuum hoses seem secure. Played around with them with the engine running and I nothing happened.

I was cleaning the engine bay today, sprayed quite a lot of cleaning fluid around. Is the brake servo a completely sealed unit, or is it possible that some fluid went inside and has knackered it all?

 

[AshLaw]

As you know - on a Puma the brake fluid reservoir feeds the brakes; the clutch slave cylinder and the clutch pedal master cylinder.

If you were losing brake fluid, then you would have trouble changing gear - specifically getting it into reverse.

It could be a crank sensor problem or the idle control valve.

 

[huw_jenks]

Spent ages last night trying to get my head around this, but I'm with you now. So does the servo amplify the clutch as well? If so then that would rule out the servo being the problem as I'm having no problems selecting gear. I've found a troubleshooting section on the online Puma manual for the servo so I'm going to go through that today.

 

[YOG]

Servo is only for the brakes, nothing to do with the clutch. The fluid reservoir is just a common feed to both brakes and clutch.

 

[coachwhip]

Maybe your brakes are binding and causing the fluid to heat up. Would explain the car slowing more rapidly. Can you smell anything after driving? Anything smell hot?

 

[drmotorsport]

If you can pump the brakes to get some pressure back, then i would suspect bad fluid. How old is the brake fluid and have you bled brakes yet?

 

[huw_jenks]

[post]354169[/post] Maybe your brakes are binding and causing the fluid to heat up. Would explain the car slowing more rapidly. Can you smell anything after driving? Anything smell hot?

That sounds interesting, as I have noticed a dip in fuel economy also. However, I was driving down a big hill yesterday and decided to see how far the car would coast when the clutch was in. The answer was a surprisingly long way! So now I'm not so sure about the brakes binding. If I jack her up and take the wheels off, what would be the evidence of brake binding?

[post]354190[/post] If you can pump the brakes to get some pressure back, then i would suspect bad fluid. How old is the brake fluid and have you bled brakes yet?

I've had the car since March so I don't know how long the fluid has been in there. Haven't bled them but it might be worth a go.

The main problem I've got is that the brakes are now working fine (not really a problem, I know) and so I'm going to find it difficult to investigate what the cause of this problem could be. Is it in anyway possible that it could have been linked to me spraying around a lot of engine cleaner on that day?

 

[moondustka]

[post]354190[/post] If you can pump the brakes to get some pressure back, then i would suspect bad fluid. How old is the brake fluid and have you bled brakes yet?

I would agree with this - also happens when the fluid gets too hot. Very unnerving, as the pedal disappears and then comes back.

If you have no record of when the fluid was last changed, make a conscious effort to make that a priority. These are brakes we are talking about and the only thing that's stopping your ton of metal :wink:

Also I do hope you didn't hold the clutch pedal down when coasting, but took it out of gear and into neutral so the clutch pedal could be relaxed. Much kinder on the release bearing and engine

 

[huw_jenks]

So today I finally got around to changing the brake fluid. Or at least I was going to. The rear O/S bleed nipple is completely rounded off and the rear N/S wont budge! I'm not going to force it incase that just rounds off too. So what the hell do I do now? I can't tell what the bleed nipple is actually connected to, is it the backplate or the brake cylinder? I'm guessing one or the other will need replacing...

 

[oilburner]

The bleed nipple is connected to the wheel cylinder

 

[YOG]

I would use penetrating fluid to soak the bleed nipple threads where they enter the brake cylinders, and leave it to work overnight. You must use a good fitting 6 sided socket to not round the corners off the rear N/S. You may get lucky with either mole-grips, or a pipe wrench for the rounded one.
Worse case is that you'll need to replace the cylinders, and may have trouble unscrewing the brake pipes from the cylinder. There are special brake pipe spanners, which fit over the brake pipe to do this, not sure what size you would need:
http://www.halfords.com/workshop-tools/tools/spanners-wrenches/halfords-professional-flare-spanner

 

[tuonokid]

If the penetrating oil doesn't work take your car to the nearest small garage and have them heat up the bleed nipples with their oxy/ act torch to loosen them off, that always works and it won't cost you a fortune.
Barry

 

[huw_jenks]

A bit of progress! A case of two steps forward one step back at the moment though.

I was having a new tyre put on and the tracking done last week so I asked if they could free up the brake bleed valves for me but they wouldn't touch them just incase they snapped and the car would be stuck there.

I managed to loosesn off all the bleed valves bar one with lots of penetrationg oil and a set of mole grips. I plan to replace the valves as they're all pretty knackered looking. One of the bleed nipples (rear N/S) snapped off so the brake cylinder will need replacing. This means bleeding the whole lot again, but it's a small price for properly functioning brakes!

More importantly, I have come to the conclusion that one of the front brakes is sticking on, I think it's the N/S. I looked at trying to take the caliper off to give it an inspection, and lo and behold, the bolts are rounded off! Brilliant. Any ideas?