Calling All Brake Gurus

[Atle]

Darn! $xx6@

[lemoncurd]

Nick,

I was wondering if you had heard a response from PVL yet - did they have any luck with the switch?

-Ben

[fflyingdog]

Nick,

I was wondering if you had heard a response from PVL yet - did they have any luck with the switch?

-Ben

I have heard from PVL and they have sent me an adjustable switch, they have kindly sent it to me on a sale or return basis.Now all i need is someone who has a knackered system to try it out on?? I dont know how much it is ,but what i could do with knowing (if someone has a workshop manual) is the exact switching pressures.I am abroad working untill the 6 May,so cant have a proper look at the switch untill i get home.

Cheers

Nick S4s

[fflyingdog]

I have in my sweaty hands a pressure switch from the guys i have been chasing,i shall bring it along on saturday ,if anyone is intersted ?

Nick S4s

Edited May 23, 2008 by fflyingdog

[DanR]

Any developments or still unobtainable?

[fflyingdog]

Hi Dan

Yes i have the switch from PVL ,i need to double check the parameters that it was set to,has anyone got written down in black and white what the parameters should be? I have ben in contact with Lotus and they dont know,i am ii the States for a couple weeks (Its not raining in Atlanta) so if anyone has any info i would really appreciate it,the later limits (ie. the grey moulding switch) i need to be sure that PVL has set the switch properly.

Cheers

Nick S4s

[t70]

Any luck yet on the switch nick? I have not been able to locate an alternative here as of yet..

Well.. I found a source for the pressure switch.. it's $325 plus tax... So... I would really like to know if there's a cheaper alternative yet.

[t70]

I've had a breakthrough! I don't think we need to be replacing the pressure switch at all. It appears that it just gets gummed up over time. I took it out today, and used brake clean to clean out the gunk and I also used high pressure air to make the piston on the pressure switch move back and forth. What I was doing was blowing into the switch... then banging it (so that the piston falls back to the bottom) and then using brake cleaner and then repeat. Once I had done that about 50 times... I switched from using brake cleaner to using "Chem Loose" (a very potent penetrating oil that is similar to "Nut Buster") and I let it sit in the switch for longer periods than the brake cleaner. After about 25 repetitions of this technique.. I sprayed one last bit of penetrating oil on the switch and re-installed it. BINGO! The ABS light doesn't even flash anymore. I've got great pump response and the brakes themselves are consistant again. So.... why spend $350 or so when you can use about $3 in chemical and some compressed air?

[aerobat]

Ah Mark..... you are the Master.

We give thanks to all the Lotus gods that you live nearby....

B)

[DanR]

Brilliant

[t70]

Let's just hope it stays working now... I suspect it will... but there's always that slight chance that this isn't a miracle cure.

[fflyingdog]

Great news Mark,have you any pictures? how did you disasemble the switch ? As far as the switch that i sourced from PVL i still need the exact operating parameters if anyone can help out??? I would be more than happy for someone to try it,if they are stuck.

Cheers

Nick S4s

Edited July 21, 2008 by fflyingdog

[t70]

Nick.. I didn't disassemble the switch at all.. as far as I can tell, it appears that the switch would be dependant on the clearances etc.. so switch disassembly would be a very bad idea. If you look at the tip of the switch itself, there are 4 points that are "hammered" in from the outside to keep the "guts" in the centre bore of the switch. One would have to grind those "hammer marks" away and take it apart and then put it back in and re-hammer it back into place with the right clearance... This is something that I'm not willing to try without a backup part. So... all I did was spray the brake cleaner and penetrating lubricant into the hole where the pressure piston resides.. and use the compressed air to make the switch go in and out. I left penetrating lubricant on it for the final installation in the hope that it keeps lubricating it for a long time to come. We will see how long this works for... However, as it is a fairly easy job to do, one could do it several times before it equates to the same cost as a new one.

[Dasar7]

Well done Mark!!!

Fingers crossed.

[fflyingdog]

Hi Mark

Yeah makes sense ,i was wondering how the switch would come apart especially bearing in mind the pressure it reads (would make somewhat of a mess !),so hopefully as you say the switch has just been gummed up,i have a spare old switch so will gve it a blast.

Cheers

Nick S4s

[t70]

Just a brief update... the brake light has not even flashed yet... The only complaint i have left is that the break jumps back at me slower than it used to... i'm guessing it's the nitrogen capsule... or maybe the system needs a bit of a flush

[lotus4s]

Nice work Mark! I think I have a defective one in the shop I'll have to try that on.

[Paul93Lotus]

This kind of makes sense....since most Loti spend a lot of time sitting, the brake fluid absorbs moisture and turns bad...since the system is under extreme pressures, any contamination in the lines can potentially get pushed into the pressure switch. This in turn can possibly cause the internals in the switch to bind. Probably the same scenario with oil pressure switches for the motor. Sludge can cause a slow or inaccurate reading.

Probably the biggest culprit is the lack of fluid changes / lack of use when it comes to the demise of the brake pressure switch.

Everyone should keep in mind that the accumulator can fail as a result of constant "de-pressurizing" from servicing the system. The bladder within it can separate or develop a leak from the stress of pressure loss. I believe it is mentioned in the service manual itself.

Edited July 29, 2008 by Paul93Lotus

[t70]

I think I would have to agree with you Paul.. I suspect that's why the brake pedal is quite delayed now too...

[t70]

well... it's been 3 weeks... and still no problems with the brake pressure switch... i know it's early... and i'll have to knock on some wood... but... it appears to be a success!

[t70]

Update! I would say we can call this method a total success... it's now been 3 months and no relapse of brake light or other brake issues at all!!!

[Bibs]

Very good news, great work Mark

[fflyingdog]

Great news Mark ,maybe that is one barrel that we are getting bent over that can removed !

Nick S4s

[bzguy]

I've had a breakthrough! I don't think we need to be replacing the pressure switch at all. It appears that it just gets gummed up over time. I took it out today, and used brake clean to clean out the gunk and I also used high pressure air to make the piston on the pressure switch move back and forth. What I was doing was blowing into the switch... then banging it (so that the piston falls back to the bottom) and then using brake cleaner and then repeat. Once I had done that about 50 times... I switched from using brake cleaner to using "Chem Loose" (a very potent penetrating oil that is similar to "Nut Buster") and I let it sit in the switch for longer periods than the brake cleaner. After about 25 repetitions of this technique.. I sprayed one last bit of penetrating oil on the switch and re-installed it. BINGO! The ABS light doesn't even flash anymore. I've got great pump response and the brakes themselves are consistant again. So.... why spend $350 or so when you can use about $3 in chemical and some compressed air?

where is the pressure switch located ? (on an S4 ?) I do have a similar problem (sometimes off, sometimesflashing, sometimes steady on)

[t70]

I'm hoping somebody has a picture out there... but it's under the plastic panel (where the relays and fuses are located) in the front of the car on the drivers side. Once you've removed the plastic panel (big black thing with two "thumb nuts") then you will find a black steel bulb attached to what looks like a second master cylinder. when looking down at the bulb... to it's left you will find the pressure switch... it has a plastic wire connector attached to it...

Now.. once you've located it... get in the car and with the ignition off... repeatedly depress the brake pedal (40 times is normal amount) in order to depressurize the system.... Once the pedal becomes very very hard to push... the system is depressurized... now disconnect the wire connector and remove the pressure switch (the pressure switch I think requires a 30mm wrench or something equally as enormous)