Having a very odd problem with my 89 328 and am close to losing my patience here. (car has ABS) When I start the car, I hear the booster pump in the brake system charge the system. Problem is that I only get that initial charge up. It doesn't kick back on when the system pressure goes down from using the brakes....which results in weak/no brakes after 10 minutes of driving. Any ideas or suggestion. Already bled the brake lines at all 4 corners, changed all relays and cleaned electrical connections. Is there a sensor someplace that reads pressure and directs the booster pump to turn on?
I had a similar experience with my '89 328; i thought air was in the system but turned out that the brake fluid had to be drained and changed because it was contaminated with moisture.
Yes, the pressure switch controls the running of the pump when the key is on. It keeps the accumulator charged within the designed pressures. It is the round piece screwed into the body of the pump assembly just below where the accumulator screws in. It has a typical Bosch electrical connector (like on the fuel injectors). The signal from this switch goes to the ECU. The ECU then runs the pump motor through the pump motor relay. This relay should be pointed out in your owner's manual. I believe this relay is also fused.
I don't think it's that issue Wang because I bled new fluid through the whole system and still same problem. Any other ideas? I'm pulling my hair out chasing this down and hoping it's not the ECU.
The connector on the pressure switch is 5 pin. It does look like the pump motor relay is activated directly by this switch, without going through the ECU.
Yes. Both the ABS and Brake Failure lights come on simultaneously. The odd thing is that I have normal feeling brakes for 10 minutes. When I try and cycle the pump with the engine off and key to on position, after that initial "pump up" I don't get the pump kicking back on when the pressure drops from pushing the pedal many times.
I had a problem with a soft pedal on a non ABS 328, and the tech replaced a "check valve" somewhere in the system, which brought back the proper operation.
I wish it was that easy! ABS system doesn't use engine vacuum pressure. If some one has a photo or clearer description of the pressure switch on the pump, I'll check that next. Time to go to the garage and jack up the front end!
Yes, the pressure switch is replaceable. I think that it is even available. Most of this Teves stuff is hard to find or breathtakingly expensive. I think that I would try to test the switch with a meter or try to test the relay function to get a better idea of where the problem lies. Are you able to get any codes out of the ECU?
No codes out of ECU. Solid ABS light and Brake Failure light. I still can't seem to find the pressure switch on any diagrams......hmmm...
The pressure switch is #3 in the attached picture. I think that pin 1 on the pressure switch is ground. The pump relay is activated by connecting pin 4 on the pressure switch to pin 1. That is, there should be continuity pin 1 to pin 4. Pin 1 should be to ground and pin 4 goes to one side of the pull down coil in the relay. The other side of the pull down coil in the relay is supplied with 12V. hardtop: The 328 ABS ECU does have some self test function. The codes are read from the flashes of the ABS light. Image Unavailable, Please Login
That assembly looks very much like what Jaguar used in the 90's, switches might interchange, still very expensive. I have replaced a few of those in the past. Wrecking yard?
Thanks for the pic. sowest Wow, that's a $1000 part. DAMN!!! Here is a dumb question: I want to test and clean the contacts but can't get the connector off. Is this a normal Bosch spring loaded connector like i'd find at the injectors? It's so tight under there that I'm feeling around trying to get it off. Also, if I do end up having to change this switch, will I have to drain the brake fluid from the reservoir and pump? Hoping I won't......
Dan, you might try these folks for some support in case your ABS pump needs to be rebuilt/checked: http://www.bba-reman.com/content.aspx?content=remanufactured_abs_controllers_pumps_and_modulators_from_bba_reman_bosch_teves_lucas_and_all_other_types They're in the UK. And, this looks like the same ABS pressure sensor: http://cgi.ebay.com/ebaymotors/ABS-sensor-Jaguar-booster-Brake-pump-used-warranty-/260414993796?cmd=ViewItem&pt=Motors_Car_Truck_Parts_Accessories&hash=item3ca1f17584
If you do replace the switch, be sure to pump the brake pedal - with the key OFF - 40 or 50 times to deplete all the pressure and put a rag around the threaded area. Brake fluid spraying 20 feet will give you a unique paint job.
danman: Yes, the connector on the pressure switch is like the ones on the fuel injectors with the fine spring wire clip. When these connectors have been in place for some time, they can be very uncooperative about coming off. I try to pry off the spring clip first and then try to pull the connector apart. Perhaps you can side step the whole issue by doing the test from the relay instead. Pin 1 goes to chassis ground. Pin 4 goes to the pump motor relay (#85 at the relay, I think). The other pull down coil terminal at the relay (#86) will be the 12V supply. You could pull out the relay and do the continuity check from there without even worrying about getting the plug off the pressure switch. But...... I have been thinking about this a little today and am beginning to wonder if the pressure switch is even suspect. I don't believe that there is any other circuit that runs the pump motor when the key is turned to the "run" position. If the pump charges the system when the key is turned on then it should also run when the pressure in the system falls below the threshold. Why would the pressure switch fail just because the key is on? Well, if you can get some continuity checks for pins 1 and 4 in both the charged and discharged state, it will be helpful. Here is another thought. Sometimes the main control valve will not be energized and the system will charge up normally when the key is turned on, but will give symptoms similar to what you describe when the brakes are used. The evidence for this is a pretty violent swirling action of the brake fluid in the reservoir when the brake pedal is pushed because the inoperative control valve is allowing the high pressure fluid to go back to the reservoir. Can you have have an assistant watch the fluid reservoir as you push on the pedal? eurogt4 is absolutely right. Make sure that you deplete all system pressure before anything is opened up. These systems operate a very high pressures. This basic Teves system is was used on a lot of cars. British, German, American, Italian. A lot of the parts seem to be physically identical. I simply do not know if there are any differences in operating parameters. For instance, a Jaguar or GM pressure switch may fit right in, but the pressure settings may be different. I found a GM master cylinder assembly that looked the same as a Ferrari unit, except that it was a mirror image. Just to be clear. You did ground pin 26 on the ECU by inserting the fuse and received no error code? Well, some food for thought.
The function of the pump check you hear when you start the car isn't to build pressure in the brake system which you would deplete by stopping. It's only supposed to run when you start the car. If you've got a soft pedal problem, it's either related to the foundation brakes, or you could have a valving problem in the ABS module, I suppose. I haven't heard of the latter, but that doesn't mean it doesn't happen. Disconnect the battery and see if the ABS light comes on right away or not until the pump check occurs, or after you start driving. Both lights on indicate a significant error condition has been detected. I doubt that ABS systems 30 years ago had no diagnostics, but have no idea how to access them.
I will be able to test the pressure switch from the relay tomorrow or Friday and will get back to you all. THANK YOU. don_xvi - The ABS light (and brake failure light) will come on immediately when the key is turned to on. They go both go out (first ABS and then a few seconds later brake failure) after the pump test where the system pressurizes. This clearly pressurizes the system because I feel it in brake response. What's not happening is additional pressure being added to the system after the initial charge-up is depleted. Yes, there is a way to pull the codes and yes I have done it previously. but this time, no codes. Just solid lights when I ground the diagnostic diode. this is all very frustrating because car is out of commission....
Do you think he's interested in meeting an Ottowa Asian escort? I'm sure he'll make contact directly rather than discussing details with them/her publicly through the site here....
What I'm trying to tell you is that the pump is energized at startup, and only supposed to run, potentially, during an ABS event. It doesn't run as a matter of course during operation. The lights coming on as you describe is normal, we call that "bulb check" it will be described in your manual. The fact that no codes are reported when you query the system goes along with the fact that there are no further lights as the system has no faults. I don't understand the basis for you statement that the brake system doesn't use a vacuum booster. ABS doesn't remove the need for a power booster for brakes, and 3x8s have had one since day one. Unless there was a significant change to the foundation brake design from that point to the 328 with ABS, I'd be confident that you have vacuum brakes. I see that you described the symptom as "weak/no brakes". Does that mean that you have a hard pedal and it's hard to stop the car, or perhaps the pedal goes to the floor with little decel? You need to be looking at your brake fundamentals, the presence of ABS on your car isn't the cause of your issue.
Check the parts listed in these diagrams, they're your vacuum booster elements: http://www.ricambiamerica.com/parts_catalogs.php?M=FE&P=&V=diag&I=2481 1 120233 1 Pipe, vacum servo to check valve - For RHD use no. 129230 call 2 101538 1 Check valve - After exhaustion use no. 128435 call 3 107982 1 Pipe, check valve to manifold 5 133569 1 Vacuum servo - From car no. 72029 http://www.ricambiamerica.com/parts_catalogs.php?M=FE&P=&V=diag&I=2464 #11 Rubber hose for servo-brake depression Failure here will cause a hard pedal.
