2nd Gen Non-Engine/Transmission Brake bleeding issues...again

[FHerault]

Hello,

I think I've red all the topics about brakes issues on the second gen... If not I've tried....before posting. Perhaps toomuch information !
Four weeks ago I had to replace the brake line that goes to the rear brakes, it was very rusted and was leaking. I decided to go with the cunifer piping, since I am fed up with changing the lines every 3 years or so (bad and long winters here...).
Since I was not able to finish the job at time, I have let the project sitting for two weeks. When I had been able to find some time (and I need the truck...) I decided to change the pads and caliper hardware (I had alittle right pull when braking). The left caliper was frozen (it has only 1 1/2 year and less than 15000 mi !). The piston was rusted. So after changing the caliper, I had to bleed.
I've started with a vacuum hand pump, then I switched to the 2 persons method that has always given me good results for decades...
Now, after several bleeding attempts, I have eratic brakes. Sometimes the truck brakes with light pressure, sometimes the pedal goes to the floor, another time the pedal is very spongy but if you pump it 2 or 3 times it becomes hard and brakes strong.
I have no bubbles at the wheels when bleeding. I've found no leaks on the new tubing. The pedal is very firm when the engine is off.
Should I suspect a faulty master-cylinder ? or a problem with the hydroboost ? or perhaps I should continue to bleed until next spring ?:{

Your inputs are welcome !

 

[jelag]

I have a couple of thoughts for a place to start... first make sure that the bleeder on the caliper you replaced is at the top of the caliper and not at the bottom... calipers can be switched from side to side... and the calipers will not bleed correctly if upside down... if you bought a set.... do you have them on the correct side.... or if you purchased a single caliper, did they supply you with the correct one?

I can't tell by your post what you did about the rust damage to the piston.... some can be cleaned and returned to service, some must be replaced (pistons) and at times its just easier to get a replacement caliper...

Over the years I've owned a small fleet of these trucks (4-5 at one time) and we've kept the trucks for 350K miles in an area where a lot of chemicals are used on the road in the winter... I've never replaced a brake line... so this part is a first for me...

So I suggest you go back to basics... make sure the bleeder is correct... go back to the vacuum pump and bleed out at least one qt to 1 1/2qts... and than recheck... I assume your using a jar with two tubes in the jar so you can see of when you use the vacuum bleeder how much air is bubbling up into the jar as you draw the brake fluid...

If after the back to basics checks and you still have an issue.... I'd replace the master...

I've owned a small fleet of these trucks and we've always been able to easily bleed them with a vacuum bleeder...

 

[FHerault]

Thank you for the reply Jim.

I can bring some precisions :

I have a couple of thoughts for a place to start... first make sure that the bleeder on the caliper you replaced is at the top of the caliper and not at the bottom... calipers can be switched from side to side... and the calipers will not bleed correctly if upside down... if you bought a set.... do you have them on the correct side.... or if you purchased a single caliper, did they supply you with the correct one? I've heard about that so I have checked at the store twice, and the bleeder is at the right place.

I can't tell by your post what you did about the rust damage to the piston.... some can be cleaned and returned to service, some must be replaced (pistons) and at times its just easier to get a replacement caliper... I've changed the caliper,it was less time consuming.

Over the years I've owned a small fleet of these trucks (4-5 at one time) and we've kept the trucks for 350K miles in an area where a lot of chemicals are used on the road in the winter... I've never replaced a brake line... so this part is a first for me... I think the number of winters is perhaps more important than mileage, and my truck is now 20 years old Some of the lines were changed few years ago by very cheap ones that have rusted very quickly...

So I suggest you go back to basics... make sure the bleeder is correct... go back to the vacuum pump and bleed out at least one qt to 1 1/2qts... and than recheck... I assume your using a jar with two tubes in the jar so you can see of when you use the vacuum bleeder how much air is bubbling up into the jar as you draw the brake fluid... I will bleed again just to be sure, but since I have no bubbles at all, I was suspecting something else was wrong.

If after the back to basics checks and you still have an issue.... I'd replace the master...

I've owned a small fleet of these trucks and we've always been able to easily bleed them with a vacuum bleeder... I've never had issues like this when bleeding the brakes on the dozens vehicles I've owned, so that is comforting the idea that it is not bled enough ?

Thank you again for your input.