Unusual Brake problem
This morning on my way to work my brakes started to malfunction.I would breifly touch the brakes and they would almost "lock up",then they would be all "Spongy" and the brake warning light would come on.
This is in a 1990 Chev Suburban 6.2 Diesel 2500.I checked the Brake fluid level and it is fine.Also I checked the hoses for any leaks,again all in order.The Brake Fluid is quite dirty,I will flush the system this weekend.
I was wondering if there is a load sensor on the system that might be problematic.Somthing that increases your Braking power when you are towing for example?When the brakes are vauge the limited brakeing power seems well distibuted around the car.So my guess is its a technical fault rather than a mechanical one?
All input is appreciated.
There was a RABS (rear ABS) system in 1990, and that might be your culprit. There is a way to check the RABS computer codes. It's shorting out a different pin in the OBD connector to ground and then counting the flashes. Sadly, I don't remember which wire it was off-hand. It could be that something's going wrong with the RABS and the computer for it's just giving up and shutting down. Make sure you get this issue resolved before taking it back out on the road.
I had an issue similar to yours but only after I'd let the thing sit for 2 weeks When I started to drive it the brakes were dangerously sensitive and hard to gauge and then became spongy. This continued for about a half a block and went away. I used a code reader and nothing came up so I took it to the brake shop and they couldn't find the cause nor dupicate the condition. It hasn't occured since and I've experienced no other problems. Please post an update if you find the cause.
the abs system is a good starting point the rear brakes set the pedal height try a mighty vac brake bleed and flush it out might clear up