Retaining Delco brakes

[PaulEspritGT3]

I’ve been having some trouble with the ABS on my Delco brakes lately, and I’ve found the “Calling All Brake Gurus” thread very useful but it has become rather unmanageable and difficult to use (14 pages long and started nearly 3 years ago) so I suggest that we start a new thread dedicated to keeping the original Delco brakes.

I know some people have replaced the braking system completely, and I may be forced to in time!, but for the time being I want to keep the Delco system for these reasons,

1) Although the brakes are not as good as modern supercars when they were new they were capable of 1.3g deceleration which is adequate.

2) I would like to keep ABS (which it isn’t really feasible to replace).

3) I’m concerned about possible MoT and insurance issues.

4) The value of the car is probably less.

Is anybody else interested in doing all we can to keep the old Delco system on their Esprit??

I have spent a lot of time in the last week trying to understand how the system works, how to test it, which components are likely to fail, which cars have similar systems and alternative parts sources (as Lotus seem to have discontinued virtually all the parts).

I’d be happy to put what I’ve found out in this thread if there is interest (and summarise the “Calling All Brake Gurus” thread content). .

Paul.

[dodge1979]

Im intetested, as currently im trying to ensure my abs works all the time..although at the moment it seems to choose itself when it fancies working or not! Also, sometimes when it is working the pedal feel is acceptable, other times its scary and is better without the system!.

[lotus4s]

Yes Paul,

Definitely post whatever info you've been able to dig up as it will surely help others in the future.

[philip600]

Hi,

Count me in.

My S4S brakes where terrible when I bought the car but Ive cleaned the sensors & that improved things but pedal travel & 'feel' was inconsistent & did not give me much confidence in them.

Since then I unplugged all three solonoids to try them without the ABS but although the pedal felt better the brakes were still inadequate.

Strangely when I plugged it all back they seemed to be better.

I decided to have another go the other day & bled the master cylinder as decribed on here ( pump pedal 40 times, have cup of tea etc & then pedal half way down while turning ignition on ) the pedal is now much firmer. They still don't work too good though so this weekend I am going to flush through some new fluid & bleed them all as I suspect the back ones are not working as well as they should, will let you know how this goes but definately interested in any info you have as I too you prefer to keep my car standard.

I was reading a car mag from 1995 with a full test of the S4S & they commented how good the brakes where, so they did work well when new.

Regards, Phil.

[PaulEspritGT3]

I started investigating this because I got an error code of A062 (Low accumulator Pre-charge).

Below is my understanding of how the ABS control works, if anybody knows any of this is wrong please let me know.

These comments only apply faults with the Pump/Accumulator/Switch unit.

The tests you can try ....

1) Depressurise the system (40 presses on the brake pedal with the ignition off), then switch the ignition on and the pump should run for 30 to 40 seconds.

2) Press the pedal several times until the pump cuts in again, and time how long the pump runs for. The pump should start after 5 or 6 presses and run for 4 or 5 seconds. If the pump runs for less than 1.4 seconds the ABS light flashes.

(mine takes 15 secs for test 1) and in 2) the pump comes on for less than a second every time I press the pedal.)

The cause of this is usually a faulty Pressure switch (Lotus # B082J6137S).

What the pressure switch does .......

1) Switches the pump on (via a relay) if the pressure is less than approximately 2200 psi and then switches it off when the pressure gets to approximately 2700 psi, and

2) via a second set of contacts if the pressure drops below approximately 1800 psi it switches on the red Brake tell tale (via the “Lamp driver module”) which means there may not be enough pressure to enable power assistance to the brakes – which is obviously for more serious than no ABS).

The ABS warning light starts to flash not when the pressure has fallen too far, but when the pump runs for less than 1.4 seconds which the ABS controller interprets as not enough time to build up enough pressure.

My understanding is that even if the ABS light is on it is unlikely that this will lead to failure of power assistance (but of course it could).

On my car I used Espritmon to identify the fault code, which is A062 Low accumulator Pre-charge.

Possible sources of supply for a new switch.....

The safest source is obviously Lotus themselves but the part is not currently available.

Lotus have said (on 21st Sept 2011) ......

“The Engineering work on the replacement pressure switch is complete.

We are just going to do the checks on the sample production parts.

As soon as that is complete our Aftersales Group will get the production parts in stock.”

Can I ask Bibs to let us know via his contacts at Lotus when the part is actually on the shelf please?.

One other possibility I’m investigating is a similar switch from another car – it seems that the Buick Reatta has a similar one which is available for $110.

[philip600]

Hi,

I'm no expert but what you describe above is my understanding of how they should work.

Update on mine - today I flushed about 1 litre of fluid through to each of the back brakes to put new fluid in the system & ensure there is no air left. ( after bleeding the master cylinder, see above post )

Been out for road test tonight & at last my brakes work

On a dry road I can now get the anti-lock to operate where as before they would never work enough for it to be needed.

There is much more feel there now & initial bite is much improved.

The feel of the brakes isn't as good as most modern cars & I'm running green stuff pads all round & I'm not sure how these normally feel but I now have confidence to drive the car knowing that it will stop quickly if needed.

I'm happy now

Regards, Phil.

[sailorbob]

I personally don't advocate de-pressurising the accumulator and then turning the ignition on straight away. The act of de-pressurising aerates the brake fluid a lot which takes a long time to settle out. I wait until the fluid is clear before energising the pump.

[Rich H]

Something I noticed when bleeding the brakes was I struggled to bleed the back brakes as the front brakes prevented movement of the MC

The way I got round it was to bleed the fronts at the same time. Very fiddly but it was the only way to get the rears to bleed.

I put pipes on the front nipples backed them off a touch so they just weeped fluid then bled the rears using the old school pedal push method.

Once that was done the fronts are much easier to bleed as they shunt much more fluid per pedal push.

Much improved brakes all round.

Rich

[G_Reaper]

I would just like to point out from the original post.

1) There are no MOT issues with removing the ABS. The car must obviously pass the mot on the power of brakes. The car must show no obvious signs of the ABS system such as ABS pump and ABS tell tale lamp on the instrument pod. (Remember not all cars came fitted with ABS. Some cars at the time of the Esprit production ABS was an expensive optional extra).

2) There are no insurance issues as long as you inform them the brakes have been modified and the car has passed an MOT.

3) I am running my S4s with an SE Esprit master cylinder and servo, the feel is superb and the power is spot on, I would not go back to the Delco set up too much to go go wrong too old and out of date. In fact the Delco system was almost out of date when first fitted to the Esprit.

However I wish you good luck in trying to keep your cars going with the original set up.

Cheers Mike

[lotus4s]

Rich,

The way to bleed the rears is to turn the ignition switch on, depress the pedal about half way and then open the bleed screw. The abs pump will pump as much fluid as you want out the rears.

The Delco brakes are actually pretty decent and you can get a firm pedal if you do two things. Flush plenty of fluid through the whole system to make sure it's all fresh and no air, and as Derek mentioned, keep depressurizing the accumulator and letting the air bubbles clear in the reservoir before turning the key back on and filling it back up. You may have to depressurize 4 or 5 times until it comes out with no bubbles but eventually it will. This is assuming all other parts are in good working order of course.

Part of the bleeding procedure in the manual is also to use the bleeders at the master cylinder. Follow the bleeding instructions in the manual and you should have good working brakes.

Philip, just an opinion, I ran Green Stuff pads for a while in my S4s and thought they were crap. I switched to Porterfield R4s and braking was greatly improved. Others have had good success with other brands as well. The Yellow Stuff pads are better suited than the green for the Esprit, IMHO.

[Rich H]

OK ta, didn't think of turning on the ignition.

[dodge1979]

Well in preparation for sundays jaunt round wales with a few other esprits, ive rebled tye brakes this week to try and improve the wooden feel ive had. My abs doesnt work all the time, but when it does it doesnt instill confidence...now, ive had the pressure switch out, sprayed it up in releasing fluid to make sure there is no crap in the hole on the.end, reinstalled and rebled. Pedal feel with abs working is shocking still. However, a I have a fault on it, out of shape abs ring on front hub, it soon turns itself off and onto normal assisted braking. Which, on a quick test run tonight, appears to be far better. Before I wasnt impressed with the feel and bite of yellowstuff pads, but it appears now the pedal feels more.like a normal servo'd brake with a sharper bite...

The test wil be sunday really, im going to disable the abs I think for good, I just dont like the inconsistent pedal.everything appears to work as it should, just that interferes.

On another note, anyone else fancy joining the trip out? Theres 8 pf us.so far!

[dodge1979]

Well, abs disabled...wales trip done to test them.so much better...whilst not the same sharp feel as a modern brake, but definately much sharper...so, it would be interesting to see the pressure my system is producing currently to compare it to the figures it would have been new..

[davevr6car]

Hi Mike,

I also have an S4s and I'm not happy with the standard of the brakes. I have fitted the s350 ap brakes all round including calipers and wanted to remove the ABS Delco system. Where are you getting your vacuum from to feed your SE servo?

Was the SE servo a straight fit / what was involved in the conversion?

Cheers in advance for any info / help on the above.

Dave