hello again, im planning on doing a brake flush/bleed. does anyone know what fluid is good to use? in the book it says do not use dot 5, but i have heard conflicting stories on this. the book recomends dot 3, so does that also mean you cant use dot 4 or can you??

also, does anyone know where the vacum lines run for the abs unit? what side of car, and where does it feed from in engine bay.

thanks again.

 

I use Valvoline Syntech in everything I own.

 

Any good quality DOT3 fluid will work fine as will DOT4. Unless you use the car for track days, the DOT3 fluid will suffice. As to the DOT5 fluid (silicone based), it should not be used in an ABS brake system. This fluid will cause cavitation in the ABS pump and can introduce bubbles intot he lines. DOT5.1 is a synthetic fluid and it can be used.

The ABS unit does not have any "vacuum" lines. There are steel brake lines that run from the master cylinder down under the car along the driver's side at the inside edge of the lower body panel. The lines go up to the cargo comaprtment behind the driver's seat. You will be able to see them under the car just in front of the left rear wheel well.

From the ABS unit, the individual lines then go out to each of the calipers.

The ABS unit does not really need to be bled as the system perfoms a self-test everytime you start the engine and move the car forward through 3-4 MPH. Fluid from the pump briefly circulates between the ABS pump and the MC. You may hear a soft buzzing sound behind the driver's seat.

IF the ABS pump really has to be bled due to something like installing a new pump, you will need a GM Tech-1 scan tool with the brake module. There is no bleed screw on the ABS pump housing so it can get pretty messy if the pump has to be bled.

 

Valvoline Syntech/synpower has been discontinued and is difficult to find anywhere - there is a thread to this effect. Castrol LMA or (even harder to find) ATE SuperBlue is a good fluid - just what I've read on the forum. Personally, I used Valvoline Synpower at my last brake bleed and luckily bought some extra bottles.

Jonathan

 

Another good DOT3 fluid to use is the Ford Motorsports HD fluid. You can get it at any Ford dealer and it comes in the small 1/2 pint bottles so you don't have a large 1qt bottle laying around opened.

ATE Super Blue is a decent DOT4 fluid and it is available easily through various websites. Their TYP200 is the same fluid but just a different color (golden) . You can alternate them to make sure a flush has cleaned out the old fluid simply be looking at the color as it comes out the bleed valve.

 

 

I have some left too. There is still some around.

 

excellent advice, thanks all. the reason i think it needs bleading is because every time i start the car, it does the wirring noise as it should a few seconds, but then as i apply the brakes a couple of times as ive pulled away, the pedal goes hard and the wirring starts again, then shortly after the service abs light comes on and disables abs. does any one know what this could be?? bit concerned! thanks

 

anyone?? :-)

 

If the ABS pump runs more than once per ignition cycle and the Service ABS light comes on, there is more likely something wrong with the pump itself or the electronics rather than just a need to re-bleed the pump. A hard pedal can be indicative of a failing power brake booster.

If the Service ABS light came on and stayed on as long as the ignition switch stayed on, then there should be some ABS error codes stored.

Hopefully, somebody with a 90 FSM can chime in and help with diagnostics and retrieving error codes.

In the meantime, check all of the electrical connectors at the ABS pump to make sure they are snapped in place and check to make sure all of the individual wires are secure in the connectors.