Brake problem on my 1998 Chevy K3500.

[wtd]

About three weeks ago while driving to a Doctor's appointment, I lost brakes on this truck. I discovered the line running from the front of the truck to the rear cracked.

I just installed a new line and bled the rear brakes and still have no pedal. It sinks to the floor. The Master cylinder never went empty or even got close when I lost the brakes.

I'm going to try bleeding the front brakes when I can get the bleeders broke free but I'm not sure that will help. I'm sure that the three weeks that the truck sat with the cracked line must have allowed air to travel up to the master cylinder.

This truck has the hydroboost braking system as well as front ABS. I'm not very familiar with this setup.

Does anyone have any tips to correctly bleed this system. This is the first vehicle in all of my years of bleeding brakes that I cannot get to work. Thanks.

Wayne

 

[The_Eric]

May need a scan tool for the automated bleed function to activate the ABS unit.

 

[eljefino]

Do you have the Delco VI ABS? There's a method that involves the two nipples on the unit as well. Those are a bear to bleed right.

I drove a diesel 3/4 ton GM of about that vintage and equipment (likely hydroboost; diesels have no vacuum) and for whatever reason I could stand on the pedal and it would slowly sink. I thought it was weird but could be an ABS "feature". It stopped fine with decent pedal in real life.

 

[wtd]

The brakes worked fine until the line broke. I'm not sure what version of ABS this truck uses. I have been told that you have to have a scanner to bleed the ABS system and if this is the case, then I'm going to have to take it somewhere to get it fixed since I don't have a scanner that will do this.

 

[George7941]

Air should have infiltrated only into the rear circuit, so it is surprising that you don't have some pedal from a working front brake circuit.

Since you don't have rear ABS, I don't see air crossing over from the rear circuit to the front at the ABS unit.

 

[Lubener]

Try tapping on the distrubution block, then re bleed the rear brakes.Don't press the pedal all the way to the floor when bleeding.If the master cylinder is original, it's possible that when the pedal was repeatedely pressed to the floor, the piston seals in the bore of the master cylinder traveled onto virgin metal on the bore where a ridge developed and got damaged traveling over this ridge.A new master cylinder may be needed. Last month, I had to replace my rear lines, I did not have to bleed the fronts.

 

[artificialist]

Originally Posted By: Lubener
Try tapping on the distrubution block, then re bleed the rear brakes.Don't press the pedal all the way to the floor when bleeding.If the master cylinder is original, it's possible that when the pedal was repeatedely pressed to the floor, the piston seals in the bore of the master cylinder traveled onto virgin metal on the bore where a ridge developed and got damaged traveling over this ridge.A new master cylinder may be needed. Last month, I had to replace my rear lines, I did not have to bleed the fronts.

I also suspect a failed master cylinder.

I sometimes encounter them after something else in the brake system develops a leak. I always thought that happened because there wasn't enough fluid in the master cylinder to lubricate all the components.

 

[wtd]

I believe the master cylinder to be the original one but I don't know for sure since I bought the truck used in 2007 with 94,000 miles on it and the master cylinder didn't look new when I bought it. Truck now has about 107,000 miles on it.

It is possible that the master cylinder went out while trying to get the truck back to the house as I had to press the brakes pretty hard to get the truck to stop.

It didn't feel like I had any brakes so I'm not sure about the front brakes not being compromised from the rear brake line leaking.

 

[wtd]

I finally got the brakes fixed. Did the old fashioned method of bleeding by having someone press the brake pedal while I operated the rear bleeders. I did this with the truck off and then did it with the truck running. Brakes work better than they ever have in the almost eight years I've had it. I'm just glad it's fixed.

Wayne

 

[Yup]

Buy a Mighty Vac. Makes brake bleeding a piece of cake.

 

[wtd]

Originally Posted By: Yup
Buy a Mighty Vac. Makes brake bleeding a piece of cake.


I already have one and is what I used prior to using the method I finally did to get the brakes bled. For some reason, the Mighty Vac would not work and I bled the brakes for awhile until I saw no signs of air in the lines.

Wayne

 

[DoubleWasp]

I've noticed that vacuum bleeding doesn't work as well as pressure bleeding. This is why I use a pressure bleeder on everything now. One-man job, and bleed with no pumping.

 

[wtd]

Originally Posted By: DoubleWasp
I've noticed that vacuum bleeding doesn't work as well as pressure bleeding. This is why I use a pressure bleeder on everything now. One-man job, and bleed with no pumping.


What kind of pressure bleeder do you use?

Wayne