Question about 1990 Oldsmobile Toronado

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1990 Trofeo .. brakes pedal goes hard .. loss of power brakes. Fluid is up and I can't find any leaks

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There are two things to look for regarding this problem. You have the "teves" ABS system, as do I in my 1989 trofeo. They were NOT that good, and tend to be somewhat trouble--prone. I DID have the same problem you do, mine was the ABS pump relay. There are two brake system relays mounted on the firewall of our cars, near the center, above the A/C blower motor. One is for the pump--the other one is for the whole brake system. If the pump relay goes bad(due to it running too much, from a "bad acumulator" which I DID have--and you probably do too..), it will not turn on the brake pump, and if the acumulator is either bad, or will NOT get ANY power assist at ALL!! Our cars do NOT use vacuum brake assist--it is ALL done by the hydraulic pressure, stored in the accumulator. The relays are only about 10 each, and not hard to get. Another somewhat possible problem is the brake pressure switch, which triggers the pump relay, and it sometimes goes bad. If so, it causes the same problem as the relay. It is on the brake master cylinder assembly, and has about 4 wires or so on it may have a bad accumulator. This is the ball--shaped thing on top of the master cylinder.It stores brake pressure, between pump runs. If it goes bad but the pump still WILL have brakes, but SOMETIMES...the pedal will be hard at first, and then work. They go bad after some years of use, and mine was bad. A new one is available from GM, for about 150.

Once these "sore spots" are taken care of...the Teves system DOES work nice, and stop quick. Just have someone check these things that knows what they are doing. Good luck with your Trofeo--I love mine.


Posted on Oct 10, 2009

  • Makinbacon May 10, 2011

    The best way and the cheapest idea that i have found is a conversion to a standard non-abs master cylinder with a vacuum booster. The engine is configured for a vacuum booster. You will have to visit the salvage yard for parts. This is the hardest search to find info on. I did have better luck on searching the Buick Reatta. It has the same brake system. The Teves 2 is a one of a kind compact abs system as the Teves Mark 4 which is used on some of the newer vehicles and is more reliable since the entire brake system doesn't rely on it . The Mark 4 consists of a conventional master cylinder and vacuum booster with lines routing through the abs system and is mounted separately. Where as the cost of the Teves Mark 2 cost an unbelievable $1500 for the replacement of the more expensive parts and wont work with out proper functionality the and the all-in-one design makes it hard to deal with. The The mark4 the brakes will operate with a malfunctioning abs unit in most cases. The mark 2 was a bad idea from the start. The issue usually starts with a leaky accumulator as explained in the main post. If the pump runs for more than 60 seconds at a time it could fail by over heating. That is an $800 replacement. in most cases just replace the relay and the O-ring seal on the accumulator and it should be ok. One thing to know about brake fluid is that its slightly corrosive it will deteriorate seals, corrode and rust metal, and eat paint over time. Hope this helps...


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Vacuum failure -check for faulty vacuum check valve,vacuum hose plugged loose,cracked,also check for leak between vacuum power cylinder[power brake booster] /and master cylinder or leak in booster

Posted on Sep 29, 2009


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1 Answer

My problem is related to the brake pedal the first few times i have pressure if you insist always pressing the pedal loses pressure and goes to the bottom gearbox automatically stops responding and it

if when you push the brake peddle and it is hard at first then starts to fade towards the floor and you have no visible fluid leaks or noticeable fluid loss then your master cylinder is bypassing internally and needs replaced

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Are there vacuum hose on the brakes hydraulic system?

NO. the vacuum is used to make the brake pedal easy to push, power brakes. the pedal would be hard without vacuum, that is why the pedal gets hard with the key off and engine not running. the problem you are having is more of a hydraulic problem.
Have the brakes checked asap. the brake system may have a leak causing the pedal to go low. check the fluid level and if it is low or empty then there is a problem, could be a rotted brake line leaking or a wheel cylinder leaking.

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I would strongly recommend checking your trucks R.A.B.S. (Rear Antilock Brake System) valve . It is located on the left frame rail just under where your left foot would rest . They can leak internally and exhibit the problems you are describing (loss of pedal , with no fluid loss) .
It is highly unlikely that a power booster would cause this , as a failed booster will show itself in these ways . 1) a hissing sound when you apply the brakes (indicates a vacumm leak) 2) rough engine idle/stalling when brakes applied (also indicates a vacumm leak) or 3) No power assist (brake pedal hard to push) .
If you do discover your hydraulic problem is in your RABS valve , don't forget to bleed it ,(there is a bleeder valve on it) and the rear brakes again after you replace it .
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check your brake booster vacuum pipe for leaks otherwise it sounds like your brake booster has failed

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