Calling All Brake Gurus

[Dasar7]

It actually requires a, wait for it............. 39mm (1 1/2 inch) deep socket to get off. I'm about to do this myself.

Cheers

[ramjet]

I have to go through this as well now. My ABS light is flashing. Pretty much all the time. I do know that sometimes my brake lights do not extinguish when I lift off the brakes, so that will be the first adjustment. I have also been told by a Lotus mechanic in Melbourne that the ABS fuse is the same fuse as the heated rear screen and if that circuit is faulty, it can cause a flashing ABS light. However, I can't find a circuit diagram for my car that shows this.

Here is a thought though as an option to fix this. The pressure switch serves two functions - low pressure switching and high pressure switching. How hard would it be to use two separate switches on a tee piece and separate the wiring from the connector and attach to the respective switch? If it would work, it might be a bit tight to fit it in where the switch is, but there would be nothing to stop us piping it to a more accessible point. The pressures required would overcome any loss through a pipe extension.

I'm going to run this past some of the engineers where I work to see if it is a viable option.

Michael.

[DanR]

If you're lucky it will be due to the brake light staying on. Easy fix.

[ramjet]

Oh dear. Pump cycles on every press of the brake pedal. Two presses at most...

[Paul93Lotus]

If it comes on every press of the brakes then it could also be your accumulator. It is possible that the brake pressure switch is working fine, its just that the accumulator is not storing the pressure due to the diaphragm being compromised within it, and then the brake pressure switch keeps turning on the pump to replenish the pressure within the system....something near 1600 psi or more?

Edited April 18, 2009 by Paul93Lotus

[Dasar7]

Michael

It must be our Southern Hemisphere - mine's doing the same thing..... pump running every 1-2 presses. Hopefully it is the Accumulator, not the pressure switch.

Paul (or anybody else) are the Accumulators still available & rough idea how much?

Cheers

David

[ramjet]

David,

Process of elimination and circuit testing the switch seems to say mine is the accumulator. I only get the flashing light once I have pressed the brake for a second time and the pump runs up. Pump runs so can't be that. Pump runs for awhile and then cuts out. Comes on again after next press. This says to me that the switch is cutting in and out on pressure and circuit testing across the switch went closed circuit after pressing the pedal so it's not that. Don't get a flashing light when I am driving and have not braked so that eliminates the passive wheel sensors. Only thing left is the accumulator which does fit in with it being faulty and not holding pressure in the system. The ABS computer must register pump runs versus pedal presses which might trigger the light. The shell of my accumulator is also corroded where the accumulator screws into the housing and it looks like fluid has leaked there. It's not serious corrosion and I think the accumulator would be quite thick due to the pressure so I doubt the corrosion plays any part but I do think everything else points to the accumulator.

If someone thinks I'm off on the wrong track, let us know.

Thanks,

Michael.

[bzguy]

your statement makes sense Michael, seems like a leaking accumulator ? So pressure cannot be held, so pump is running more often than it should be ...

Having similar problems : pump was running fine but ABS light on, then I checked everything (couldn't disconnect the pressure switch though), pump was then running constantly, the checked again,, all was normal again, and now pump is running constantly again :S (which could mean accumulator is dada)

Guess I'll just disable that crappy ABS ... found a page (Mark Wien's) how to disable ABS but keeping the ABS tell tale light in function

[fflyingdog]

Hans

Be carefull about disabling your abs you may invalidate your insurance,i would also point again to the abs pressure switch and not the accumulator in your case.................sorry mate !

Nick S4s

[bzguy]

I'll disable the ABS for the time being since I need the car on 1st of May (so running short on time) but will have it investigated on my next service @ Lotus garage ; it's real pain to remove the pressure switch, tried it and it's very hard to access (and no way to find the right size of 'pot' to remove it)

thanx for the info Nick

[bzguy]

Just back from Lotus specialist, have it checked out : it's the ABS PUMP RELAY (luckily, it's a lot cheaper than a pressure switch)

They put a spare in, a new one is not available for the moment @ Lotus.

Any one knows if there is some other source to get it from ? Lotus PN A082M6493S (Denso 056700-8420)

Edited April 24, 2009 by bzguy

[davevr6car]

Hi folks,

just read down thru this very interesting topic.

Now, I'm no brake guru..... I might be stupid by suggesting:

Can the electric vacumn pump system fitted to our esprits not be replaced with a mechanical system used on lots of other modern cars.

Alot of cars have the vacumn pump built into the alternator...like this bosch type fitted to a 2005 opel combo.

Would it be possible to find a similiar alternator to whats on the lotus at the moment and replace it with this type.

It might mean making up a new bracket. From this pump, run a vacumn pipe to the servo with a non return valve.

Another idea was to use the mechanical chargecooler pump drive, to power a vacumn pump?

Appollogies if this idea is a bit stupid...I'm no expert.

cheers

Dave

[ramjet]

Question for someone that might know.

If the Delco Moraine Powermaster III system on the S4 is the same as off other cars, is the module identical or has it been tweaked by Lotus? I am trying to find a way that I can get my system read so that I can get closer to the fault. (Lotus dealer over here is a long drive away and charges like a wounded bull).

After reading the ABS manual (section JF) it may not be the accumulator, there are a bunch of scenarios that could give what I am seeing. Building myself a pressure test rig should not be difficult so that is one thing on the list.

The couple of mechanics that I contacted today all said that even though they have equipment that will hook up to the ABS module, their machines would not have the correct software to read the module. i.e. Lotus would not be in the vehicle list in their gear. Could the codes be read if another model vehicle is in their system that had the same ABS system?

Basically, is there anyway to read the fault codes without a Tech 1 tool?

Thanks,

Michael.

[bzguy]

trouble's there again ... pump is okay now (sticky relay), but now it's the 'anti lock' light blinking/steady again.

Managed to remove the vacuum 'bomb', and got the pressure switch off with a water wrench, cleaned it with some brake fluid (spray) and some air ; seems not to bee too much to clean though ... put it back in but 'anti lock' light still on, guess I need to top up the brake fluid first (lost a little when removing the pressure switch)

Where are the solenoids near the wheels ? I'd like to clean them with some WD40 ...

[ramjet]

Well I spoke at length with Steve Taylor at the Elan Factory and told him my thought process. He reckons based on that it's the accumulator as well. So I'll be sending off my $260 to get a new one.

Just checked the SJ website as one of the guys over here said they were pretty good. Is the price correct that I found on their website?

Edited May 5, 2009 by ramjet

[Dasar7]

Michael

Let me know how you go - as my symptoms mirror yours. I am also looking for local (cheaper) sources - as I saw the S&J price too.

Cheers

David

[ramjet]

Everyone,

I have found this on the net. Is there anyone in the good ol' US of A that is close to these guys (maybe even with an S4) to see if they possibly have a pressure switch that would suffice our needs? The info on page 1 shows one of the units that they build running from 1500~2500 psi which is really close to the Powermaster IIIa operating pressures. I am still looking into the idea of using two pressure switches via a tee piece to do the job of the one switch but can't find a source for switches yet. It's a work in progress.

clicky

Just a thought.

Michael

[fjmuurling]

Maybe the following link pressure switches is an idea.

Freek

[Paul93Lotus]

Michael -

There is no special "Lotus software" when it comes to the Delco Morraine Powermaster III abs system used in the Esprit...any diagnostic application that can talk to the PMIII for GM 88-91 Buick Regal, Oldsmobile Cutlass and Pontiac Grand Prix Turbo will work on it. You just need to connect to the correct three pins on the Lotus diagnostic connector. If you have the revised harness car, it would be the Orange White wire, the orange wire and the black wire as seen going into the ALDL connector. The Orange White is the serial data wire, the orange is a "switch", and the black a ground. One thing I noticed is the the standard "GM" plug on most diagnostic scanners do not match the Esprit's...it is different...so you might have to rig up a jumper set up to the proper pins on the Lotus plug.

There are some abs scan tools that work that are sold over here...one is made by OTC and the other is a Matco, and they look very familiar which leads me to believe they are one and the same unit.

If you had a Tech 1 with the proper GM Tech 1 cartridge W 88-89 ABS TKO 3030 you could talk to your Lotus and perform all the handy tests, live data monitoring, etc. The connector would be the only hurdle....as I believe there was a Lotus specific connector for the Tech 1.

I just got one of these ABS scan tools, and it had no problems talking to my Lotus...and it had all the functionality of the Tech 1 with a Lotus cartridge. I just ran the powerbleed function on my Esprit the other day, and it noticeably improved the pedal feel as I must have had some air trapped somewhere in the system....it did not take away what I suppose some people describe as "wooden", but I think that is common in any brake system that has an accumulator and a pump instead of a vacuum booster.

I have also looked at the SnapOn scan tool number MT2500 with the MT2500-2794 cartridge and believe this may work as well...but you would have the same connector issue.

I have the Delco Morraine Antilock Brake System III factory manual and one of these days I will scan it into pdf format and post it...a lot is in the Lotus manual as well, but there is a better operation description in the DM book. I also have the pages from the GM OEM factory manual for the Olds, and all the respective ABS pages.

Per this DM manual (and I believe also the Lotus brake manual), the pressure switch grounds below 2200 psi, and open 2700 psi turning the pump off. So a similar spec switch would be needed.

Edited May 25, 2009 by Paul93Lotus

[Jonathan]

We need to summarise this thread - it's so huge now.

I'm gonna do some more work on the brakes soon, but we should all get together and make a wiki for this as it is a problem most cars will suffer from.

Most of my ino is all in a PC folder somewhere so I need to find it but I'll try and do some real test with is as well.

[ramjet]

A quick update for anyone that's interested.

Steve Taylor from the Elan Factory in Melbourne looks like he has split the pressure switch system into two sides. i.e. a low pressure and a high pressure switch mounted on a tee piece. He is looking to get engineering approval from the relevant authorities here in Australia. Don't know what that means as far as approval goes in other countries.

Not sure if the system he is proposing also runs an inline pressure gauge to help with on line diagnostics. If not, I know he has been able to source the parts to make a pressure test rig.

Will let the forum know more as I find out.

[fflyingdog]

Look forward to the results

[ramjet]

Hi everyone.

Here we go again. I have replaced my accumulator which has given me three presses between pump runs versus the one press I had. However, the test rig I have also shows the switch consistently switching the pump on at about 13,500 kpa (1,960 psi) and off at 16,500 kpa (2,400 psi). The system should be switching the pump off at about 19,000 kpa (2,750 psi). The ABS manual section JF actually shows these ranges:

Switch on between 11,700 and 13,100 kpa

Switch off between 17,900 and 20,000 kpa

(That's the ranges Nick (flyingdog) was looking for. Are the PVL guys still an option Nick?)

I am going to attempt to clean my switch as others have done, but I believe while I am getting three presses now between pump runs, my pressure switch has gone soft on the high side so basically I am never getting to the full operating pressure.

When I think about this system and read the manual, the way we get feedback with this system is via the system pressure pushing on a piston and forcing the pedal back against your foot. So essentially, each brake press lowers the system pressure so the amount of feedback force alters each time. Not really a wonder that people report inconsistent pedal feel.

Oh and Steve Taylor has had his dual switch system passed. He is putting a price together and will let me know as I'm up for one.

Not sure if anyone has ever looked, but for reference numbers on my switch are as follows: 92 04 18016950. Which don't look like anything that anyone has ever posted. The maker stamp on it is - wait for it - GE as in General Electric. It is definitely not GM.

Michael.

Edited September 29, 2009 by ramjet

[esprits4de]

GE produced these for GM / DELCO..... Not to be found at any GE distributer, so far....

[ramjet]

Oh ok Olaf. Still though, I can not confirm the operating pressures of the switch in my car.