!st Gen ABS Problem

[AMatsonIII]

Have a 93 2WD auto diesel. The truck has been acting up lately. When you press on the brakes they work fine. Then all of a sudden the ABS and Brake lights light up on the info board. At that time the brakes become real hard and don't want to stop. any help or insite would be great

Thanx

Alex III

 

[paccool]

Sounds like you may have a booster problem. If the vacume assist goes away, it is real hard to stop the truck and those lights will come on. Check the pump output first to be sure it is working. If you have good vacume there, I'd look at the booster. There could also be a master cylinder problem.



Does the cruise control still work alright? It also uses vacume.



Have you done a search yet? There is a lot of info there. If you can't find anthing, let us know.

 

[sparks57]

Yep, sounds like a vacuum leak. Take all your vacuum hoses off and give 'em a suck and stick your tongue on the end of the hose... if it lets your tongue go, then it's bad and needs replacement.



That would be the most likely culprit. Try that and see what happens.

 

[AMatsonIII]

Thanks guys. The cruise does work but it will not excellerate when you try to do it with the cruise. I will check that out. thanx again

 

[phillips5]

I raplased a booster for the same exact problem. To check the pump you have to isolate it because a vacuum leak will make you think the pump is bad. My 90 has a bad booster there is very little asist and its been that way for 200,00 miles. I just drive acordingly. NOBODY ELSE DO THAT PLEASE ! If I set at a light for to long my break light will come on I think that booster is going bad now. I will fix that one. I think it is common for the booster's to go bad on the 1st gen's

 

[phillips5]

That last part of the last post refers to my 93.

 

[sparks57]

I have the same problem. My assist fades on me, and my brake lights come on after a few second at a light.



I still need to figure out the problem... if it's a boost leak, a bad booster, or what.

 

[hdm48]

The best way to test a vacuum booster is to start the engine, let it bring up the vacuum, shut off the engine, slowly press the brake, listen for a leak. Normally a booster will loose the seal at the brake rod and you should be able to hear it in the cab.

One other thing you should check is the "one-way valve" at the booster. It is a simple device that is often overlooked.

 

[paccool]

Per the manual, there should also be enough vacuum held for three applications of the brake pedal with the engine off. You can tell if all three are assisted or if the vacuum goes away.



Stan

 

[CGauthier]

I dont think my ABS works at all, even though the light doesn't stay on

 

[prototech]

Hey guys,

I just got done fixing this same problem on my truck. After getting some help from this marvelous forum, I changed all of my vacuum lines and the checkvalve on the booster. upon inspecting my old vacuum line(the 3/8" one from the pump)I found that the line was really spongy and soft and was probably colapsing when I applied the brakes. Also be very careful when removing the brake line from the vacuum sensor on the fender well as the nipple will break if you do not slice the old vacuum line before removing it ( I learned this the hard way! and created a whole other problem!) the other thing I did was to put a tee in the line and run a line into the cab and connect a vacuum gauge temporarilly, this was a very effective troubleshooting tool because I was able to monitor the vacuum pressure while I was driving. good luck! hope this helps!

Proto

 

[JLEONARD]

connect a vacuum gauge temporarilly, this was a very effective troubleshooting tool because I was able to monitor the vacuum pressure while I was driving

Great idea... . then cap it off later.



CB... . did you see this? Another gage you can buy.



Jay