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Delco-Moraine ABS - what I learnt / problems / solutions - Suspension/Brakes/Wheels/Hubs/Steering/Geo - The Lotus Forums - Official Lotus Community Partner Jump to content


Delco-Moraine ABS - what I learnt / problems / solutions

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Having finally sorted out my brakes in my S4S I just wanted to note a few things that might help others. This is not to discuss how terrible the brakes are ( they might be, but they work!)

 I also want to keep the car as stock as possible and where I live it is very difficult to change brake systems legally - possible but difficult.

I also want to thank Ian Lord et al. for the fine ABS delete servo brake system - I bought the kit as a back up for the future if and when I can no longer keep the original system. It is a very complete and well fabricated unit and part of me is dying to use it!

Being a trusting sort of person and geographical distance found me I buying an S4s off someone who probably was not that honest with the truth - but the relevant part to this post is he had put a small square of black tape over the ABS tell tale - nice!  Whats worse is I paid for a pre-purchase inspection from a very reputable lotus service garage and they did not pick up on this and a lot of other fairly easy to spot common and costly faults......all rectified now gladly.

The ABS was the most frustrating and every time I thought I had it licked the little light would flash on and my heart would sink!

Things I learnt : 

1. Your ABS pump should come one after every 8-9 pumps......maybe 5 at the least.....any less than this and you have a problem

2. Bleed the brakes really, really, really well. And keep bleeding the master cylinder if the pump is running too frequently - Depressurise system, ( ~40 pumps until it goes hard - ooooh!!) and then loosen both nuts until fluid flows (stop it!!) leave the brake depressed and then tighten them back up and then do a few fast hard stabs on the brake. I had to do this a few times after replacing parts. 

3. If still problematic you probably need to replace the pressure switch - this is the most common part failure - I tried to clean mine but it was no help. I bought the replacement unit from lotus marques ...... although its completely different by appearance its bloody good and Steve Taylor is very responsive by email - he also does a fantastic water pump refurbishment . 

4. Next on the list of culprits is the accumulator ( the bastard black bulb) I bought a land rover one STC2784 - although its half the price and it works (sort of) save your money as the neck on it is different and with out modification you get a slow fluid leak..... get the lotus part. 

I don't know how long until it gets kooky again but hopefully not for a while.

I just bought a V8 also so I will compare the brakes on that to the S4S..........




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  • 2 weeks later...
  • 1 year later...

Sorry, I'm a bit late to this convorsation.   I'm about to tackly changing out my accumulator as well.  But I'm still a bit of a noob and not a seasoned mechanic.   Do I need to bleed my brake lines to depressurize that accumulator?  The shop manual just mentiones pumping the brakes hard 40+ times with th eignition off to depressurise the system.  I'm affraid the just pump the brakes 40 times and try to take off a pressurized tank.  Is that all I have to do?

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  • Gold FFM

By pressing the brakes until they go hard (max 40 times) you effectively release all the pressure in the system, which is why the pedal goes hard: no more pressure to assist. So no need to worry taking off the accumulator. Brake fluid can sill drip out of it, so do have some rags ready and rinse with plenty of water if you do get some on the car.

Straightforward job, you'll do fine! 😉


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I have made many mistakes in my life. Buying a multiple Lotus is not one of them.


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The accumulator might be a bit hard to unscrew though (in the end it was not that tightened but the allow mounting it's attached to has nowhere to put a spanner properly, so ... I used a big adjustable wrench to hold the alloy mounting)

Edited by Giniw
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  • 3 weeks later...

I just replaced the accumulator tank (the holy hand grenade) on my S4 (still has original Delco ABS).  The process was quick and far easier than I expected. I'm not a hard core wrench turner so all those pressure warning stickers on the system gave me pause.  But everything worked perfectly.  HOWEVER, I did notice that the fluid coming from the original replaced tank had quite a bit of debris in it.  The fluid in the brake reservoir still looks quiet clean and debris free.  Is this debris an issue?


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It only seemed to be in the accumulator so far that I can find.  The accumulator was bad so I'm hoping it was contained there.  I have bled the brakes about 3-4 months ago and the fluid was free of any particles at that time.  so Im' hoping that it sjust that accumulator.  Fingers crossed.  Brakes seem to be functioning perfectly too. no issues in function.

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  • 1 month later...
  • Replaced accumulator.  
  • Installed Lotus Marques' ABS pressue switch replacement. Pretty easy installation.
  • No leaks
  • sufficient brake fluid in res.
  • turned key to on position (without cranking engine) I can hear the pump pressurizing
  • ABS light is still on - so there's an issue 
  • When I crank engine and depress brake pedal, I hear the accumulator pump working each time.  IS that normal?  I thought the accumulator held pressure for a while and the pump was NOT supposed to have to work each time.  Is this the case?  Or is this normal operation?  My suspicion now is that pressure is not building up sufficiently somehow/somewhere.

Any thoughts or things to check would be most helpful.  Should I get a pressure meter? 

Anybody with experience in this?

Thanks in advance gentlemen!


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11 minutes ago, DigiTiki said:
  • When I crank engine and depress brake pedal, I hear the accumulator pump working each time.  IS THAT NORMAL?  

No, the motor should only need to repressurise after 10 to 15 (I think) pedal presses.

There is a very long thread on here somewhere on diagnosing & fixing problems with the ABS unit, try the search facility.  Also, I think the Espritmon diagnostic tool reports faults with the ABS unit :thumbup:

Edited by jonwat
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John W

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