Please help , brake pedal to floor
 

Evening all. So first off it’s not my car. It’s the missus. So brake pedal went to floor and suspected master cylinder , replaced and the same. Purchased some blanking plugs and the master cylinder is fine , so is the old one. I’m positive there can’t be air in system as I’ve now run 3 ltrs off fluid through bleeding. An abs light was on that I couldn’t clear and has since had wiring changed to rear o/s sensor ( wiring was broke ) so all good but pedal still goes to floor ? All calipers seem fine and there is zero leaks. Please help as this is really bugging me now. Also there it’s no leaks in booster and vacuum is fine.

many thanks. ( there could be a pint in it if we ever meet ) !!!

Hi , so what car is it , im assuming not a scooby ? Some abs pumps need to be tech 2 to work , if your fluid is running through , but still a pedal to the floor have you checked for a pool of brake fluid somewhere ? What order are you bleeding the brakes ? 👍

Nissan navara , fluid is coming out fine at each nipple , no leaks bleeding sequence is furthest from resovoir to nearest as manufacturer it’s very weird ! I’m wondering if it’s the actual abs module ( valves ) ? What does the slave cylinder do ?

Slave cylinder is the bit in the gearbox that lets you change gear on a manual car , it says disconnect the abs unit electrical supply and disconnect the battery negative supply then bleed it , it's worth a go 👍

out of interest have you had the calipers off?? are they upside down now?
bleed nipples should be at the TOP
Modern Brake systems don't really have a 'slave' as such - there is the "Master" which the pedal operates and then the ABS module.......

I’ll try without abs module connected and neg disconnect but I can’t see it would make any difference as it’s bled with engine off but I’ll try. Calipers haven’t been off and nipples are at top. Could it be rear wheel cylinders maybe ? As before there is no fluid leak or lines bulging ??

Just something some one did on line , I expect battery disconnected will have the same effect , if you do have separate rear calipers for the handbrake that could be throwing up an issue , I take it when you are bleeding it's not got bubbles in the fluid , is the clutch fluid reservoir and brake fluid reservoir sharing a pipe ? Or linked and sucking air in , is it just you bleeding ? I often find the best bleed is two people one pumping one bleeding , is bleeding kit you are using working properly ? 👍

I’ll try it. Two of us bleed. Son pushes pedal down and holds I lock and unlock nipple according. No small bubbles. The rear are drums I’m wondering if the adjuster or peg thing has come off maybe and allowing cylinder to fully expand without contact to the shoes ? I’m lost really.

Has it not snapped yet :norty: Must be pre 2015 if it has drums, Is it a D40 or an NP300 ? If you replaced the master cylinder did you bench bleed it first? The ABS pump will need cycled with the diagnostics to purge any air out of the pump and solenoids. You can pump it all day with your foot your wasting your time. How did this all arise.

its 2007 , has a new chassis on it. How the hell do you do that. If bench bleed means filling and gently priming until fluid comes out then yes I did. So is that a main dealer thing to do abs module ?

It'll be due another one :lol1: Any good diagnostics machine will cycle it.
How did this episode start?

Anyone with an Autel can activate abs for bleeding,
Can you get access to a power bleeder, if not pump and pump the peddle then bleed, rather than the British way we normally do it.

lol it only went on 3 years ago. Brand new galvanised chassis. ! Forgive my ignorance but is a diagnostic machine different from a code reader ?

Also it started just randomly. The brakes were always spongy apparently a Nissan issue.

I'm assuming as per my earlier post that the tech 2 would work and sort the issue , fingers crossed that is , I have a tech 2 but no car that needs the abs pump cycle so never tried it , a can't see a standard code reader sorting it 👍

Take it to a garage and get them to pressure bleed it with a proper diagnostic machine not a code reader. Most cars nowadays are over servoed which gives them the spongy feel. The shoes in the drums will need adjusting too.

sounda a plan ! Just picked up from one garage who re did a wiring issue to rear n/s sensor so abs light is off now finally. He said he thinks it’s still air. Mentioned about the abs and diagnostics he said you can do it by going along the line and cracking nuts on and pump and letting gravity take fluid to that point then doing the two front wheels then topping up and doing rears then back to do front again. ?
might just take it to garage. No point spending £200 + on a diagnostic tool.

If the pedal is going to the floor, you either have air in the system or a leak somewhere in the brake system, stopping it from pressuring. Not cycling the ABS pump will not give a dropped pedal symptom IMO.

He's changed the master cylinder so there has to be air in there.

You really need to cycle the ABS pump and solenoids to achieve a satisfactory result.

True but it should still be drivable without.

thanks chaps. I changed master cylinder because I presumed that was the issue but does it with the same one and old. Both work as I’ve checked with blanks pedal travels an inch and stops dead connect it back up and down it goes. Although there is little braking it pulls quite a bit to left. So maybe air in right hand side ? Thing is I’ve put through 2-3 ltrs of fluid so I’m thinking surely air would be out by now ?

There is a leak somewhere in the system. Check and tighten all connections.

100% not , no fluid leaks on floor and pedal goes solid engine off no nipples open. Just tried again and reversed order and started nearest abs module and also did the load sensing valve , another 1.5 ltrs of fluid no real signs of air only why was between nipple and bottle and still the same.

If you've ABS you shouldn't have a load sensing valve.

well it sure looked like one ? 3 pipes going to it and a spring to the suspension components ? Looked up replacement on net and it looked exactly the same ?

Just double checked and yes it is the load sensing valve.

How many pipes out of the ABS pump and see can you follow them to the rear wheels.

https://cimg4.ibsrv.net/gimg/www.sco...ac65b3184.jpeg

one pipe from mc goes to the brass block the other is front left on top of module.

Does the pedal only go to the floor when the engine is running?