free hit
A 'Clack' + This look normal and/or healthy? - Suspension/Brakes/Wheels/Hubs/Steering/Geo - The Lotus Forums Jump to content
Sign in to follow this  

A 'Clack' + This look normal and/or healthy?

Recommended Posts

Now, I am not an expert on this godforsaken Lotus Braking system, but, thought I would investigate this evening a 'clack' at the top of my pedal. If you tap the pedal, there is a 'clack' and freeplay.

Whilst under the bonnet, (after pressing the pedal 40times!) I lifted the cap off the reservoir, and here is what I was faced with; This look normal?

post-9573-050288800 1276622723.jpg

post-9573-025095700 1276622714.jpg

The flash off the camera hasn't changed the look, thats exactly how it is.

Any clues, on either the fluid or indeed the 'clack'?

Share this post

Link to post
Share on other sites
Upgrade today to remove Google ads and support TLF.

Fluid should be crystal clear so it definately needs changing.

That milky colour would suggest to me water contamination. Thats a very bad thing for a number of reasons, first an foremost, it reduces the boiling point of your fluid, thus during heavy braking the fluid can/will boil and introduce air into the system and can render the brakes useless....

Secondly, corrosion internally of all parts of the braking system....

Get it changed!!!

The clack you hear may just be a bit of play in the pin that locates the pedal to the actuator arm of the brake push rod. There should be fee play in the pedal itself but the clacking noise should ideally be identified and rectified...

Share this post

Link to post
Share on other sites

Where are you located might be easier to do all this in 1 go !

You remind me of myself when I got the car - took the thing completely to bits and pit it back together again :)

The fluid is 'normal' for most braking systems of this type.

The setup is a tandem master cylinder with 2 ports for the front and 1 port for the rear. The reservoir is split, front and milkymilky rear.

The front acts like a normal master cyclinder, no big shakes, the rear has all sorts going on inside.

Principally it has the 'boost' hydraulic circuit - cars in the past and present use a vacuum assisted servo to assist your foot to give more powa to the brakes. This system uses a rather rare hydraulic booster which is done by action-pumpo (the bit on the right of the photo with all the red writing ontop of it) and an accumulator which on yours someone has guffed about with and replaced with a non std item - it's probably OK as long as the pressure is right - oh that'd be the silvery thing.

When you pump that pedal like a good-un with the ignition off, you're decompressing the accumulator - all that fluid under 2800 psi (ie...a lot) is decompressing and all the little teeny bubbles are getting bigger and thats what you see in the back chamber...aireated oil.....and we wonder why the hydraulic assisted system never caught on......

The bubbles likely come from a poorly bled system or old skanky oil - remember its hydroscopic and needs changing frequently.

The clack is likely to do with slack in the !extrememly! complex brake master cylinder and abs gubbins in the rear of that master cylinder.

As you press the brakes the high pressure fluid is assisting via a shuttle valve inside which if it has air in it - will simply hit its end stop - it should make zero noise.

Good news is you can get rid of it by clever bleeding - bad news is it's a royal pain in the ass and takes ages - which is why 99% of Delco brake system Esprits (that is a called a Delco Power Master IIIa system btw) have milkymilky brake fluid.

My advice is to pump that mofo and then get a huge cannabis hoticulturist's syringe and suck the airiated fluid out and renew it with good, new stuff....let it settle big time before switching the car on (ie overnight) and then try again.

Thing is if you have 1 bead of air in there under that pressure it will saturate the oil like's a bastard fo sure.

Edited by Jonathan

Share this post

Link to post
Share on other sites

Okey, thanks

So, jonathan, you are saying bleed the rear system by pumping the air into the pot via the pedal and then suck the airated fluid out - repeat as ness until all air is gone? If so, snorted, Il get right on it.

Is this volume of air going to affect my braking performance because, well, to be frank, they are awful compared to cars I have owned previously!

Why is the rear system so effing complicated? Is the braking force aportioned 50/50 on these things??

Edited by USAndretti42
No swearing! This is a family forum

Share this post

Link to post
Share on other sites

You will always get that aerated look when you depress the pedal 40 times and release the pressure in the accumulator. If you check it again in 5 or 10 minutes it will be clear again.

That's not to say you don't need a flush and bleed. Wouldn't hurt to do it as Jonathan suggested as it should be done regularly, at least once a year with our systems.

Share this post

Link to post
Share on other sites

As I say it's 'normal' operation for most cars becuase most cars are not bled propperly becuase it's a right royal pain in the arse to do.

Heres a link to a hig res shot I just took of my fluid 1min after decompresson :

This is new fluid, just been compressed and de-compressed, look how much air is STILL inside the system on the murky fluid.

I'll leave this now for a good few hours before switching the ignition back on, I might even replace it.


[quick foreword]

DONE EVER bleed the rear system dry of oil - nuff sed, you'll be there for days sorting it out if you do.

Mine didnt do that after I spent about 5 days bleeding it down to the last bubble, seriously 5 days I decompressed the accumulator like you did and when my assistant pushed the brakes air was still coming out in micro pockets...incredible.

The only reason why it does it is the fluid has air under extrememly high compression inside - the amount of air is about the size of 2-3 pin heads to cause that.

Take a new coke bottle and shake the bastard and then release it - same difference, that is what is happening here.

The internal worksing of the ABS and boost circuit are very complicated and full of little channels and chambers where air gets stuck in. Once it's in it takes centuries to get it out - it simply gets trapped so bleeding it wont always work.

The only solution is removal.

OK let me explain a bit on how this system works.

Front chamber, ingore it - its simply a twin, master cylinder strapped onto the end of the rear chamber (think of it that way - it is one piece but think of it as sperate), it has 2 ABS hold and release valves which dump the left and right circuits back to the front reservoir if ABS funtion occurs.

Rear Chamber feeds the rear brakes and the 'boost' section. When you switch of and pump all the oil in the accumulator and pressure circuit is damped back to the reservoir which is why we get bubbles (call me bubbles...everybody does)

Most people go "oh thats manky, 'll leave it to settle" but dont realise that these micro bubbles causing that mist will stay inside the oil for ages, some can't even break the surface to vent - this is spent oil, good for jack.

So the liquid ~clears~ and then the switch back on.

The pump winds up and sucks some of that rear reservoir back and compresses all the air again and you'r back to square 1, dont pass go or collect $200

The only way to fully bleed this system is to pump like a bugga with the key off, dont go crazy but firm sharp actions are best,

Then get a drug dealers syringe and suck that oil out of the reservoir and bin it,

Once you're nearly empty (dont let the level go down too much of it'll gulp in air, you can see the drain port in the middle of the tank) fill with new virgin oil - go ahead gently decant it into a glass and then hold it to the light, count the 1000's of air bubbles in it...I've never seen un-airiated oil but you need to get it as clear as possible,

Fill the tank to the fill line and go for a run or watch a movie...let it settle the hell down.

Now switch car on and put the cap on, the oil will be sucked into the system without air,

Now try bleeding the abs valves - switch the car off, put foot on brake, 1/3-1/2 max force - switch the car on - the brake pedal will vibrate, when it stops - switch the car off and repeat 10-12 times (I do this on the fuse to the ABS now becuase the key is getting really pissed off with me)

When you 1st do this leave 2-3 mins between on and offs because air will come out of the ABS valves and back into your reservoir - after 2-3 keys the pump will run and guess what, that air will go back into the system !!!!

This process is the TECH 1 Bleeding proceedure which flutters the ABS valves to clear any air trapped inside the complex gubbins in there.

Once you're happy - let the pump run until it stops (if it hasn't alread) and leave the car for a few hour (overnight is good idea)

Come backto the car and pump like a mad man, open the cover again to the reservoir and have a look.

If the air is foamy - then guess what ? Repeat all those steps :thumbsup:

I managed to get the thing 99% clear the last time I bled the system.

Now, ask yourself.....does the garage do this when you ask him to bleed the brakes ? Do they fu....

Which is why they're all like that sir.

You might find after a 6 month period to a year if you decompress it will go foamy again - dunno why but there really should be no reason to decompress the accumulator unless you're working on the system, so in short - dont do it !

If this is the case you might replace the oil in ther reservoir before you switch back on - it's spent by this time, introducing that much air into it makes it gash.

A final noe, if you really want to clear the rears out then follow this proceedure.

Decompress, suck all the oil out of the front compartment - yes ALL of it

Now crack open the join at the end of the master cyinder to a line that goes to one of the calipers - be ready with an old towel to clean up any mess.

Push the brake down slowly and mop up the mess from the 'leak' at the front.

OK why are you doing this ?

To get a longer stroke on the rear chamber to force any trapped air out.

By relieving the back pressure of the front chamber you can get a much longer stroke on the brake pedal forcing more air out. You can bleed the rear brakes normally like this but be SURE not to let the reservoir go dry at any time.

The reason this is a good idea is that bleeding the rears normally you have the car switched on and the car uses the pump to shift oil - thats fine but there are parts that are not flushed unlike the method above.


Q&A time


Follow what I have said above and you cant go too wrong - yes the brakes are usually shite becuase of this.

Rear system, jsut a design tried at the time - blame GM, not Lotus - it was tried and binned which is why the later cars have the Kelsey Hayes system

Brake balance is more like 70 front 30 rear....if not more bias front.

Jim - yup, it 'usual' for this to happen and most poeple take it that it's OK - if you suck that oil out and look at it though it has so much air still trapped in it - even days after - I kept my old stuff and it's STILL got air in.

Simon - dont be silly, you're right it's contaminated as you say.


Final note, IMO there will always be a quantity of air in the system - it is un-avoidable.

As you decomress the motion of doing so causes small air pockets as the fluid breaks over in the reservoir - so when decompressing be smooth and gentle if you want to preserve the oil and wait before re-compressing.

There's no doubts it's a shit system end of story but it does work if looked after propperly - the battle is knowing what to do, my experience is over 5-10 days bleeding the system with my old man and taking it from a mediocre state to really quite impressive.

Hope it helps.

Edited by Jonathan

Share this post

Link to post
Share on other sites

Fantastic and comprehensive write up Jonathan.

I also have milky brake fluid and will follow your procedure to see if any improvement can be made (by the sounds of it - yes!).

Additionally, often when having been driving for longer periods without any braking, if then applying the brakes lightly - i.e. first 1cm of travel, I get what sounds like a solenoid opening and closing rapidly and a subsequent vibration through the this also a symptom of aerated fluid?



Share this post

Link to post
Share on other sites

Be aware - after the fluid is compressed for sometime it does froth up, I dont know why this is, I did mine with the cap just laying over the reservoir - it's possible with the cap pressed down the air is trapped in the fluid causing the froth ?

All I know is when I bled it for 5 days solid the oil was crystal.

Main thing is by no means decompress the system and then switch it back on - if you decompress the best way to ensure you're safe is to leave the car overnight to clear or to suck out the oil from the rear chamber and just top it up - not a major hardship.

Infact you should NEVER need to decompress that chamber at all, ever, unless working on the pressure system.

When bleeding the brakes - run the front dry and then flush the backs before bleeding the fronts again - that way there is no possible way air can get in.

I think I'll have to write this up again clearly and more concise - it's complicated and knowing what is going on inside is key to avoiding issues.

I was going to ditch the whole system in january this year but we worked really hard at it and got it working the best it has been in ages.

I was doing 100mph stops on the mile straight at Milbrook with good pedal feel and no issues at all for the system.

Andy - possibly, sounds like the ABS is functioning though, try the same thing but disable the ABS and see if it happens.

See here :

Pull ONLY the front and rear solenoid ABS fuses - 30+15amps and test the car on a slow road 1st

I run without ABS on mine now.

Share this post

Link to post
Share on other sites

Good Grief, THANK YOU

Iv read it once, Il let it marinate, and Il read it all again later.

Share this post

Link to post
Share on other sites

Great info Jon.

Just one minor point on the picture posted. That silver capsule which is located infront of the accumlator is standard fit for Car's with Aircon and is something like the reciever drier for the aircon.

Share this post

Link to post
Share on other sites

Now you mention it it does look like a drier, how queer, thats where my Accumulator is !

THe wiring going into it looks like my pressure switch :thumbsup:

Share this post

Link to post
Share on other sites

It is indeed the aircon (has R134a written on the side)

Share this post

Link to post
Share on other sites

Phew, I just didn't want people looking at the picture thinking they had some custom pressure switch setup.

My ABS pressure switch problem is fixed but my brakes are the worse they have ever been. So I'm going to be completing the write up on the pressure switch fix and following Jon instructions to flush through the brake system with plenty of brand new fluid.

I have renewed hope the braking system can be saved since Jon's comments about the improvement hes found by going through the painfully long 'full flush' :thumbsup: process he's documented.

I'll post back how I get on, hopefully this weekend.

Share this post

Link to post
Share on other sites

Go for it Carl, use cheap oil as well, dont waste good stuff on it until you have to change it again.

I went through ~ 5 litres with mine getting things wrong wrong wrong and then right.

Never reuse the old stuff you suck out - as I say if you have good eyes look at it in a jam jar against the light you'll be amazed how contaminated it is even after a few hours.

Share this post

Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Sign in to follow this  

  • Create New...