Issue with brake bleeding

[NoahR]

Hi All,

Another brake question from me... Nearing the end though (I hope)!

I've spent some time on my 1991 Elan SE Turbo fitting new rear callipers and refurbished the front callipers, alongside replacing some brake lines. This morning though, I went to bleed the brakes using the two-person method, but it doesn't seem to be working.

When we did the traditional two-man brake bleed, initially the pedal straight away pushed to the floor before releasing any bleeder valves, and in turn the fluid level in the MC lowered - I assume this is just the lines filling up with fluid. However, after pressing the pedal 5 or so times, the fluid stopped lowering in the MC and stayed the same, but the pedal kept going to the floor. I then did the classic release the bleeder valve while the pedal was down, and repeated a few times, but fluid never came out. Would this be a result of the pedal already being on the floor before cracking the valve, and therefore, there's no more pressure to push fluid out once the valve is cracked?

Before I started the process, the MC was dry, and little fluid had come out when I had removed brake lines previously; however, I never pressed the brake pedal while the MC was dry, so would the MC still need bleeding?

Not sure where to go from here... Would a vacuum/pressure bleeder help by just sucking the fluid and air out?

Thank you all in advance.

Noah

[dapinky]

Hi Noah,

Whilst a pressure bleeder (Gunsons Ezy-bleed), or a suction pump would help - it is probably not "necessary"..... certainly if you have an assistant - or preferably 2 - on hand.

One thing with the Elan system is that the fluid levels in the master cylinder reservoir don't tell the real picture unless the car is absolutely level - ie, all 4 corners the same height. If you have the rear up in the air, with the front on the ground, it can be difficult to get enough fluid into the rear chamber of the reservoir to bleed the rear brakes..... or, at least, it needs watching carefully as the reservoir appears to be pretty well full when the rear chamber drops, and doesn't refil from the front due to the height of the separating dam.

If you have 2 assistants it can be done with the rear in the air, one to press the pedal steadily, and one to trickle new fluid into the reservoir to keep the levels high enough..... It can be done with one assistant, but needs some athletic endeavour to keep an eye on the rear nipple and the front fluid levels.

So, it is actually a little easier without an assistant to nag at you as to why you are running around and that their leg is getting tired holding the pedal down etc etc.

If you simply attach a clear tube to the rear nipple and open it (other end in a jar) and with the reservoir cap off, just go and have a cup of tea - or push the pedal once if you want, then top up the fluid... gravity will bleed it all for you. Repeat with the other rear, then the front...... or if you have 4 bits of pipe and 4 jars, you can do all 4 corners at the same time - but you need a close eye on the MC levels as it can change quite quickly........ I have left my car overnight before now with the nipple only slightly open to clear an airlock, and it was fine.

In real terms, the 'gravity' system won't shift stubborn trapped air as there is only a slow flow of fluid - but it will fill the pipes enough to give you a pressurised system to do it the traditional way if required.

I understand that the Honda callipers at the rear don't trap air in the same way that the OE ones do, but you may still get a bubble or 2 in the proportioning valves, so tapping them with a spanner whilst bleeding may help.

10-20 minutes of gravity should see fluid emerge from the nipple(s), and is my preferred method of doing the job (because I can sit and drink tea whilst occasionally topping up the fluid ) - but it works because once the pipes are attached, the car can be dropped to the ground to keep it level and make the topping up easier - it is possible to (just about) get to the nipples enough to screw them in and stop the fluid with your fingers, then jack up the corner and get a spanner on them to do it up fully when all 4 corners have finished.

The only real advantage of a pressure system is that it will keep the reservoir topped up for you - and that is worth it's weight in gold really (as long as there is a good seal and you don't get fluid thrown everywhere from a leaking rubber washer) - but a suction system doesn't do that, so I feel, it is of limited value anyway.

[wayne]

After repairing the proportioning valves and front and rear calipers I tried the 2 person method but could never get them to work correctly.

I eventually bought the Gunson Ezibleed kit and after a few tries, it eventually worked and I'm now happy with the brakes.

EEzibleed

I've heard of air being trapped in the rear calipers and some taking them off, rotating them and tapping them with a mallet to get the air out.
The Eezibleed kit finally sorted mine out, I'm sure that there are other options to this 1, I bought it quite a few years ago and not sure if its still available.


Just noticed that dapinkey replied with similar / better info, Hope that you get them sorted out.

[NoahR]

Hi Dave,

Thank you for the information!

Both the front and rear of the car are jacked up; it is relatively level, but the rear is perhaps a little higher. The MC is filled up to the top, and the fluid is no longer going down, even when the pedal goes to the floor, so surely there shouldn't currently be an issue with fluid not reaching the back compartment?

I will attempt the gravity bleed now. Does the tube connected to the bleed valve need to terminate in brake fluid on the other end? Or is the bottle just to stop a big mess from occurring?

I will try tapping the PV with a spanner to release bubbles. From speaking with Jaime, he's mentioned that some people have had issues with the PV valves getting clogged up with debris. - I open the front bleeder screw, though and also couldn't get any fluid to come out of there.

Another thought - given the pedal will go all the way down, but the fluid level isn't changing in the MC, do you think there is a chance the seals in the MC have become damaged and therefore the displaced fluid just goes back to the main reservoir rather than being forced out?

SJ Sports sells a new MC and new PVs for that matter, but rather a large amount to spend.

Thanks

[NoahR]

I've heard of air being trapped in the rear calipers and some taking them off, rotating them and tapping them with a mallet to get the air out.

Thanks Wayne. I have the Honda callipers on from Jami,e but haven't put the car back on the ground since I took the fronts off and refurbished those so hard to pinpoint the issue.

[wayne]

PV's can be cleaned and O rings replaced, I found replacement O rings locally, but don't remember the sizes needed, sorry.
I think I have a spare set somewhere in the shed, I should probably dig them out 1 day and post the sizes on the Wiki

Sorry, I have no experience with the Honda calipers, my car has OEM rears and Hi Spec 4 pot front calipers.

[NoahR]

PV's can be cleaned and O rings replaced

Okay thanks. I have found this http://www.lotusm100.com/manuals/PropValveRebuild.pdf with details, but not sizing. I suppose once apart, I could order the correct sizes.

In terms of just pulling off and testing/cleaning, what would you suggest? Pull them off and clean with brake clean, then test if fluid passes through? Could I, in theory, isolate the issue to the PVs by making a new piece of hard line to bridge where the PVs have been and instead remove them? Then I could confirm if it's PVs, MC or something else.

How challenging/fiddly did you find replacing the o-rings yourself?

[wayne]

Replacing the O rings was quite easy, I gave them to a local company to source and replace the O rings, hence I don't know the size they used.
When I find my spare set I could ask they can give me dimensions or supply more. It's easy to open them up.
They do come apart quite easily and not much inside.

Years ago we had to bypass them to pass the local brake test here, ABS was not understood, Drive between 2 sets of cones at full speed and they wanted to see all 4 wheels lock up.
I would not recommend driving the car without them installed, they are there for a reason.

[NoahR]

Ah thanks for the info.

Interim positive update: I have fluid coming out of the back right calliper after a gravity bleed, moving round the rest of the car now!

[dapinky]

Gravity feed should get it to the point that the pedal will gain pressure to then bleed it fully (if required - it may be fine with just the gravity).

I'm sure you've answered your own question by now, but the jar/pipe is just to collect excess fluid, there is no 'reverse flow' like in a 'normal' bleed as the MC piston doesn't move during this procedure.

I know that lotus claim the prop valves are 'sealed-for-life' and non service items, but I also know people have rebuilt them after a flush/clean. The trick is to use the correct sized 'o' rings, made from a suitable (brake fluid resistant) material - and not just fitting something that is close from a multi-box on the garage shelf.

Personally, I have never bothered, as I sorted out a 'new' system using adjustable prop valves which gives the opportunity for a perfect balance for all circumstances...... I made the decision after the OE units went obsolete, and I was unable to find an 'off the shelf' unit anywhere.

As far as the MC is concerned - many of us have changed to a smaller bore unit (when changing a defective unit) to increase the pedal travel/feel for the same level of braking efficiency....... note that the OE units used by lotus are made from Aluminium, but pretty much all of the now available replacements are steel...... if you do look at replacement, make sure that you are getting what you are paying for - steel units are perfectly fine, and a lot cheaper than an aluminium one.

[NoahR]

Thanks Dave.

Yes I have seen about replacing the MC with a smaller one! Been on a forum deep, deep dive! It's interesting and definitely worth bearing in mind. I hope my MC is okay, given how much of a pain it was to screw in one new brake line, let alone remove the whole thing.

[NoahR]

Did a full bleed today with a new Sealy pressure bleeder, and it's definitely feeling much better, although still a little spongy. I'm hoping the sponginess is down to the 4 new sets of pads on old discs rather than air in the MC, but we shall see once it's got its wheels back on.