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Other ( non boosted Renault ) Brake bleeding issues

flubber

New Member
Hi All,

First post onTurbo Renault - hope this is in the right place! The car in question is a 1994 Renault 5 Campus Prima, so a late model 5. I would class myself as mechanically competent, but it's a hobby, not a profession, so there are large gaps in my knowledge and experience, but I'll have a go at most things; in the past I've done jobs such as head gasket replacement, so not a novice, but also not an expert. This vehicle was bought as a neo-classic hobby car - the bodywork is in near excellent condition, but it has spent a number of years stored in a garage. I drove it down from Coventry to Kent earlier in the year, but for the last few weeks it's been sitting on my drive whilst I do some re-commissioning work (major internal clean, servicing etc). Daughter #2 has already commandeered it to learn to drive in when she's 17 next year.

My problem relates to brake bleeding. I've replaced a lot of the braking components - the two of the rear pads actually fell off the shoes as I took the drums off. At the rear I have replaced drums, shoes, springs, cylinders and hoses. I've also replaced the front calipers with shiney reconditioned ones, and new hoses there as well. Final job is bleed/flush through with new brake fluid - I have an Eezi bleed for this.

The front offside bleeds fine (you don't do this one first, but I tested it when I started having problems). Neither of the rears bleed; the pedal goes to the floor, and the fluid level doesn't drop in the reservoir. If I disconnect the rear hoses and pump the pedal, fluid comes out; if I disconnect the pipe from the rear cylinder on the back of the drum, fluid comes out. Connect it all up, tighten everything - pedal goes to floor, no fluid comes out of bleed nipple. I've given up with the Eezi-bleed for now as that just sits and does nothing.

I don't understand (a) why the pedal isn't going hard - surely it should do this even if you have air in the system. I've read in the Haynes manual that the later models have pressure relief valves built in to the rear cylinders - which I assume my new replacement cylinders have - could that be something to do with it?

At the moment I'm working with the rear offside, because it's more convenient; however, I have tried working in the correct order (rear nearside, front offside, rear offside, front nearside), but I can't get off the starting blocks with the rears.

This should be simple! I'm also assuming this can't be a specific Renault 5 model issue - as far as I can see, the braking system works on the same principle as other cars.

Thanks in advance,

Phillip
 
Since my post this morning, I've removed the cylinder and checked that - it's fine - so all components are clear:

rear hose
steel line between the hose and the drum/cylinder
cylinder

It's just when you put them all together that nothing comes out. The only think I can think of is the union between the steel line and the cylinder - there must be something wrong with that. So - I'm just going to replace both rear sections of steel line and all unions. Trip out to parts shop is in order....but any other advice is welcome.
 
Have you considered the master cylinder, if the pedal is going to the floor we can assume the master cylinder piston shuttle is moving, however if no fluid is being displaced, then it could be the seals on the piston are bypassing under pressure. If it is the case I would suggest buy a new one rather than a repair kit.
Brake Master Cylinder
 
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To bleed with an eezi bleed (I use one, great bit of kit)

Jack up car and remove wheels, but at the rear you need to support it on the swing arms to load up the rear axle, this open the load bias compensator
Inflate a spare tyre to 30psi
Top up brake res with fluid
Connect EB to res, then to tyre so it pressurises. Make sure its not leaking
Make sure brake pedal is fully UP
Bleed caliper furthest from the master through nearest. If you dont get any fluid coming out of a nipple get someone to prod the brake pedal and see if it shocks some through. Check intermittently for the res fluid level. I dont use the EB bottle to top up the res as it goes, its messy and a pain I only use it for pressurising the res.
Once you bled all the air out, voila!
 
Sounds like the master cylinder needs replacing if it will not bleed up with the eezibleed. Its not uncommon for them to fail when bleeding if its the original.
 
OK - thanks for all your replies on this - I was out on a classic car event with a mate yesterday so wasn't able to do anything - hoping to get some time on it after work.

Is the load bias compensator the same as the pressure regulator - supposed to be connected to the swinging arm via a spring, to reduce risk of rear lock-up under heavy braking? If so, I'm not sure the later models have them, but I will have a look. At the moment its support on the sill on one side and swinging arm on the other (drive is slightly uneven).

Haven't tried reverse bleeding - that sounds a bit messy as I assume the fluid will then come back out of the reservoir. I guess there's no non-return valve anywhere in the system?

Regarding the master cylinder - that sounds like an additional suspect as well. I might just replace that anyway. I had a clutch master cylinder fail in a similar way in a Fiesta - no fluid loss, but no action. So, course of action will currently be:

1. Replace brake lines on swinging arms anyway, because I now have parts and kit to do it, and they are both short, so it's a no brainer.
2. Attempt to Eezi-bleed with rear of car supported on swinging arms; if that works, and if brake pedal travel still continues to floor...
3. then replace master cylinder

note to self - buy lots of brake fluid.....

thanks all.....Phillip
 
Is the load bias compensator the same as the pressure regulator - supposed to be connected to the swinging arm via a spring, to reduce risk of rear lock-up under heavy braking?

Yes, it increases brake force to the rear when there is more weight in the back.

Haven't tried reverse bleeding - that sounds a bit messy as I assume the fluid will then come back out of the reservoir. I guess there's no non-return valve anywhere in the system?

I've never known this work, and pushing old fluid from the system (with god-knows what crap in it) back into the master is a really bad idea!
 
Hi All,

A quick update on this; due to work and other pressures, I didn't manage to get back to the car until yesterday, when my much more knowledgeable mate came and helped me out. Fortunately, it turned out to be nothing I'd done wrong - just lack of experience, and the fact my mate tried something slightly different to diagnose the problem.

The fronts bled fine - it was just the rears. I can confirm there is no separate load bias compensator/pressure regulator on my 5; the Haynes manual says the later model didn't have them, and I couldn't find one. The culprit was the fact the rear cylinders were empty of fluid, and when re-assembled the springs on the shoes pushed the pistons all the way back, thus severely limiting the flow of fluid to the bleed nipple. This problem was solved by removing the shoes, putting a cable tie around the cylinders to stop them popping out, and then bleeding from there. We then replaced the shoes, and bled again.

An additional problem came to light once we had the hydraulic piece sorted out and the shoes were seated normally; even with the handbrake off, the shoes were binding quite badly - even with the self-adjustors backed right-off. This was resolved by careful filing of the bottom pivot points on both shoes, and handbrake arm where the adjuster meets it. In addition, I had already replaced the master cylinder - probably not required, but not expensive to do.

Thanks for all the advice.

Phillip
 
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