In need for new brake pump for Delco ABS IIIA (Lotus Esprit S4 1994)

[Karl lambrechts 2]

Hi guys,

This problem is a hard one: already 4 years...

I follow the bleeding procedure, and the car brakes perfectly. But after a while ( variable 1 week - 1 month), there is always air in the system, and also in the accumulator. I presume some air is sucked in by the brake pump. I tightened the clamps around the hose (reservoir-accumulator assembly) , later I replaced the hose , but the phenomena stays.

I can only imagine something goes wrong in the pump. Any ideas? Any experience?

Is a seal kit available for this pump? Where can I buy a complete pump? Brand?

Thanks in advance.

 

[ramjet 892]

Welcome to TLF Karl.  

You should duck over to the Introductions area and say hi in there as well.

If you do a Goole search on the ABS system name, it was used in a bunch of different types of vehicles. Possibly that may help you. What do you mean by the statement that there is air in the accumulator? It is a reservoir that is under pressure internally to keep the system pressure at a level so that the system still works.

Some other people on here may suggest scrapping the system for another option. I am not sure what you can and can't legally do in Belgium though.

There is lots of info in this very subforum on deleting the system and replacing it. Link for example.

[DanR 57]

That's a hard one. I just did the bleeding procedure on mine today and what a convoluted procedure. I was about to do the road test BUT while refitting the wheels I discovered both rear wheel bearings need to be replaced. They're off now so that's tomorrow's job.

When I fitted the new accumulator, I used the Land Rover one, 200bar, I wasn't happy with the size of the O ring seal. I replaced it with one of thicker section. If there is no brake fluid at any of the other points of connection or bleed nipples but there is where the accumulator screws on maybe yours need to be checked for an air leak in there?

[Chillidoggy 3,419]

46 minutes ago, DanR said:

That's a hard one. I just did the bleeding procedure on mine today and what a convoluted procedure. I was about to do the road test BUT while refitting the wheels I discovered both rear wheel bearings need to be replaced. They're off now so that's tomorrow's job.

When I fitted the new accumulator, I used the Land Rover one, 200bar, I wasn't happy with the size of the O ring seal. I replaced it with one of thicker section. If there is no brake fluid at any of the other points of connection or bleed nipples but there is where the accumulator screws on maybe yours need to be checked for an air leak in there?

 

I didn't have any problems bleeding my brakes, but it did take quite a while to remove the air due to me having fitted new calipers.

I do wonder, given the complicated internals of the master cylinder, whether it can accumulate sludge over the years. Pete at PNM has stripped and cleaned them in the past, but it's a four hour labour cost.

[Richard123 8]

It's an odd braking system that is sometimes difficult to troubleshoot.  The accumulator and the pressure switch are common problems.  I haven't heard much for actual pump problems, which is surprising since in many cases the pump cycles quite frequently! 

 

How many "presses" of the brake pedal do you get before the pump turns on?  If the pump runs every press, then your switch, relay or accumulator have completely failed.  If it's every couple presses, it may be a weak accumulator or air in the brakes.  If it's every 5 or 6+, then your hydraulic system is good.

 

Best to test with key on but engine not started, window down and front bonnet open so you can hear the pump easily.     

[Karl lambrechts 2]

Hi,

After some years of intensive search, the system is not that odd anymore... :-)

I hear the pump, it runs normal. Every 3(-4) presses of the brake pedal it switches on ( 3-5 is normal according the servica manual)- the accumulator is ca 2 years old- and even straight after the replacement I had the same thing. Pressure is ok, switch is ok. Really everything is ok (even with the diagnostics), except that after a while there is again air in the system. I checked the aeration (with rubber membrane) of the reservoir ( so there will be no underpressure) that is ok.

A next test i will do is  uncouple the high pressure side, and guide it with a transparent hose back to the reservoir: I expect to see very tiny bubbles. But a consideration is that they may be that small I cannot see them...)

[Richard123 8]

It does get more familiar the more you have to work with it, unfortunately!   

I'm curious.  How do you know when you get air in the system?  The number of presses goes down?  Or does the braking "feel" change?  Do you bleed each caliper to get the air out, or just depressurize the accumulator?     

[Karl lambrechts 2]

Hi Richard,

There are several ways:

1/Push the brake pedal, and switch the contact on (that is the way to bleed the recirculation valves from the abs). You will feel the ABS test ( and bleeding) in the pedal. Do that 4-5 times and look into the reservoir: If you have a milky fluid, that are tiny air bubbles.

2/Just depressurize the accumulator, and look again in the reservoir. If you see a difference in colour between both reservoirs, that is suspicious....

3/Bleed the rear brakes (1 is enough- I always take the left and push the pedal with a long stick), you will see passing an air bubble.

Afterwards, the brakes feel different (better), the 'pushing back' of the brake pedal is less, and the rear brakes (and the servo of the brakes) are acting faster. ( Rear brakes and servo action are fed by the same valve in the main brake cylinder). Only this circuit is affected.

I'am almost sure that cars where the brake pedal pushes clearly back are affected by this phenomena: the spool valve is very small, and to compress the air ( after the spool valve), it will take up to 3-6 sec before pressure is building up ( and before you get proper rear braking and servo action  = the pushing back of the pedal)

The number of presses does not change.

 

Please , let me know what you see in the reservoir.

[Richard123 8]

Karl,

 

I've always gotten that milky look in the reservoir when emptying the accumulator.  I was told (by posters here or another Lotus specific site) that it is normal (cannot verify).

I've also had that brake pedal that pushes back, which is definitely not normal.  However when I had that happen, it coincided with a pump that would run on every pedal push.  

[Karl lambrechts 2]

Hi Richard,

Milky look = very small airbubbles. It can be that it happens with a lot of cars, but it is not normal: air in the high pressure side of the brake circuit is not ok 1/ for braking, and 2/ the humidity of the air will absorbed by the brake fluid.

But it strenghten my idea that a lot of cars have this problem.

Thanks for that info

[DanR 57]

I don't know if you read my recent post about the Delco system?

I now believe that a lot of problems are due to in-correct or short cuts with the bleeding procedure. It's complicated. There's a proper sequence  and doing the isolation valves on the master cylinder is not easy, especially the one hidden under the relays. Allow a few hours to do it.

Here's the bleeding procedure (available from many sources) http://www.lotusesprit.com.au/docs/bleeding brakes.pdf

Takes a bit of time to understand but well worth it.

[ramjet 892]

I have had to bleed my S4 brakes after a fluid change some years back and I will do them again shortly.

Other than my accumulator failing (new one installed) I have had no issues with my brakes and I, like Danny, think they are fine as well.