Calling All Brake Gurus

[Paul93Lotus]

Nick

Yes, I can turn igniton on without engine running & press pedal a few times & get abs light to flash. (BTW pump comes on either every 3 times, but more often than not every 2 times). I think you're right, its most likely the pressure switch. Brakes still seem to perfom fine though, just that the light always comes on.

Don't believe I'm losing any brake performance, it's just that I don't like these sort of problems especially when it comes to brakes.

Cheers

David

Could also be your accumulator. If it is not holding enough pressure (if the diaphragm is ruptured)...then your pressure switch will see low pressure and keep telling the pump to kick on.

GM made a special tool that goes in line between the accumulator so you can determine if the accumulator is holding enough pressure, and also to see what pressure the abs pressure switch is turning on at. Surprisingly, it is not listed in the lotus manual as one of the special tools. I have one, and all it is is a pressure gauge, but one that can hold the 1000+ psi. If you can get a pressure gauge in between there that can go to the higher pressures, you could determine which is to blame without "part swapping" in order to fix it.

[fflyingdog]

Good point Paul although i have to say all his symptons seem to point towards a presure switch ,i suppose you could try giving the accumulator a technical wack with a hammer just in case its stuck or corroded(more likely),these dam pressure switches just seem to be designed to fail !

What he could try doing is the ignition off test,pump brake pedal untill it goes hard (ie .no travel),now i think off the top of my head it should give around 35-40 brake applications,so if he gets this amount or close to i think this would prove the accumulator as being good (cos as we know the accumulator provides backup pressure as well as smoothing the pumps pulses).Now if he turns the ignition to the on postion his pump should run for around 30 seconds (again not exactly sure) and the pressure switch feels the upper pressure of its parameters and commands the pump off (the modified presure switch is coloured grey and the old one is black).and obviously the switch after normal brake applications senses the pressure drop and commands pump on again,i think it should command the pump after around 3-4 brake applications.Someone on the forum i forget who, but he was going to take the switch apart and see if it would be possible ro fix it ,it may be soething stupid as sticky contacts burnt together with the amperage the pumps drawing(unless it commands a relay?) it wouldnt surprise me if this was part of the problem.Has anyone got a schematic /wiring diagram of the system it would be usefull to have a look and seeif anything can be done???

Cheers

Nick S4s

[Dasar7]

Nick & Paul

I've been through the ignition off pump the pedal process, & all seems within spec - i.e. pedal goes hard after 40 pumps, turn ignition on & pump runs for the relevant time - I think around 30-40 seconds sounds about right. (My mechanic did the same thing & said everything was in spec also).

As I said, brakes seem to perfom fine, just stupid light keeps coming on!

If I learn anymore, I'll update.

Cheers

David

[fflyingdog]

Nick & Paul

I've been through the ignition off pump the pedal process, & all seems within spec - i.e. pedal goes hard after 40 pumps, turn ignition on & pump runs for the relevant time - I think around 30-40 seconds sounds about right. (My mechanic did the same thing & said everything was in spec also).

As I said, brakes seem to perfom fine, just stupid light keeps coming on!

If I learn anymore, I'll update.

Cheers

David

Hi David

What colour is your pressure switch? To my thinking if you are getting the flashing abs light on without actually moving just through stationary brake application then i would definitely err towards a dodgy pressure switch,your symptoms are the exact same as i had a few years back all attributable to the switch,tell you what if you change it and it doesnt fix your snag i will buy the new switch off you ! cash on delivery of course .

I have just been doing some research and found this ,now if someone has got the exact parameters that the switch operates on we may have something to work on http://www.pvl.co.uk/pressure_switches.htm

Nick S4s

Edited February 25, 2008 by fflyingdog

[Dasar7]

Thanks for the offer Nick. Bit loath to buy anything yet, but I'll look up the colour & report back. (Might not be until Thursday my time, as I won't have email access tonight or tomorrow.

Cheers

David

[karluk29]

i "think" there grey.

does this company make to order? in theory can we send them a pressure switch and they make a copy?

[fflyingdog]

i "think" there grey.

does this company make to order? in theory can we send them a pressure switch and they make a copy?

I have emailed the company today with the parameters that we are looking for (1700/1900 psi low and 2600/2900/high),i"m not exactly sure what the thread size is though anybody know??

Nick S4s

UPDATE!

Had a intresting phone conversation with a really helpfull chap at PVL,i gave him the details for this switch and i think we may have a solution ,they can supply the switch within our operating parameters,1/4 BSP parallel thread,zinc plated for around

1023___PSM___PSP.pdf

Edited February 26, 2008 by fflyingdog

[sanj]

I hope you made it clear that it will be used with brake fluids, I'd hate to see the diaphragm melt.

[fflyingdog]

I hope you made it clear that it will be used with brake fluids, I'd hate to see the diaphragm melt.

Yeah i had a very detailed conversation with the guy in the tech department,but what i could really do with is an old switch for him to have a good look at to confirm that we order the correct part,he seemed to think that they could indeed supply a correct part to sort our problems,so come on guys someone must have an old switch that we can send to him???

Nick S4s

Edited February 27, 2008 by fflyingdog

[lemoncurd]

Having been through this one before, I know what a nightmare it is...

Thought I would have a look and see if I could find my old one... would this be what we are looking for?

Like I said, it is the old one that caused all my problems so it probably isn't much use as a working example, but I am happy to donate it in order to help us all out by finding a replacement for the little b**ger if it is of use.

Having said that, given the age of the rest of the system, if any engineers or race mechanics feel like tackling the physics needed to set up a dual master cylinder replacement I suspect they would be treading a very useful path for the rest of us.

Ben

Edited February 27, 2008 by lemoncurd

[fflyingdog]

Having been through this one before, I know what a nightmare it is...

Thought I would have a look and see if I could find my old one... would this be what we are looking for?

Like I said, it is the old one that caused all my problems so it probably isn't much use as a working example, but I am happy to donate it in order to help us all out by finding a replacement for the little b**ger if it is of use.

Having said that, given the age of the rest of the system, if any engineers or race mechanics feel like tackling the physics needed to set up a dual master cylinder replacement I suspect they would be treading a very useful path for the rest of us.

Ben

That would be great Ben,could you send it to me ??

Nick S4s

[Dasar7]

Well done Nick.

Let's hope this works out.

[karluk29]

hi guys

sorry only just come back on the thread, i only have the one on the car and at present i cant get it off as im using the car to go to work in, i have frigged a emergency push button under the dash to manually pump up the system to get me to work.

looks like ben has sorted you out anyway (nice one). fingers crossed, this could be a life safer and the company could possibly supply lotus if it works and they approve

[karluk29]

hi guys

was there any luck on the pressure switch company?

[fflyingdog]

hi guys

was there any luck on the pressure switch company?

Yes they recieved the switch today so hopefully will have some news later this week.

Nick S4s

[Dasar7]

Well done Nick.

I think we're all waiting anxiously.

[karluk29]

thats wicked news, nice one matey

[t70]

Well.. I was thinking this morning... about the brake pressure switch and the fact that it's a GM part. So I checked out what GM car the system was from (1991 Buick Regal apparently) and found the brake pressure switch... $325 from GM. I may be able to get a better price.... but does anybody have a part number from the stock one on the lotus that I can make sure is the correct part?

[fmxa]

I believe all this data is in the parts cross-reference guide

[t70]

Yes.. the year, make and model of the car that has the brake system is in the x-reference on www.espritfactfile.com but nobody here seems to be ordering from GM or any other local parts place to get this part. So, I thought I'd put in my 2 cents. And... if it's cheaper than from Lotus... why not get it from GM?

[fflyingdog]

I am still waiting for a response from Pvl ,will keep all posted when i know .

Cheers

Nick S4s

[karluk29]

if you get it from gm its the same price i hear, plus GM dont make the part anymore, lotus are saying that the profit they make on the switch is under

[greekmix]

We all know many esprits some time during their life will produce a ABS fault.

Most comment parts to go is the accumulator or the pressure switch or both.

I was lucky enough to source the switch some time last year however this time I have a feeling it will be impossible to find as the GM and ACDELCO are not produced any more.

Lotus for more than a year is trying to find a supplier with no luck, in the main time some vehicles may stay off road due to luck of parts.

If anyone know where about we can find these parts showing below it will be a help to those whos cars are parked on the driveway.

Someone out there must have some old new or second hand stock .. if so please let us know!!

PART to search for ABS PRESSURE SWITCH

Lotus PN B082J6137S or A082J6137S

GM PN 88927270

ACDELCO 18M873

[Bibs]

Topics merged.

[Paul93Lotus]

You should try www.priorreman.com

They rebuild the complete abs assembly for about $750...they must get their pressure switches from somewhere. Maybe they will sell them individually...

I know they work as I have their pressure switch from the assembly I bought.

The only caveat is that you would have to send your complete assembly if you need it rebuilt as there IS a difference between the Lotus unit and the OEM GM one where the push rod comes into contact with the master cylinder. (Don't ask me how I know this )