Front caliper pistons aren't extending

C-ya

Well-Known Member
Had a dragging left front caliper on my '05 EXT so I replaced it today while swapping from snow tires to all seasons. I can't get the brakes back to normal as the pistons aren't extending in the reman'd caliper. I get good fluid from the caliper when I'm bleeding but the pistons aren't moving.

I had trouble with the copper washers so fluid was dripping for a while. At one point, the fluid stopped so I added more fluid to the reservoir and it immediately started dripping again. Did I get air somewhere that is hard to get out? I do have a TechII in case I need to do anything with the ABS.

Help!
 
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MRRSM

Lifetime VIP Supporter
The Original Copper Washers get "crushed" into the concentric sealing rings in the orbits around the Brake Line Fittings against the face of each Brake Cylinder and cannot be re-used. Using Brand New Copper Washers is essential to getting the Brakes Line Fitting solidly and safely mated to the Brake Cylinders .

In the absence of achieving Perfect Seals... it is possible that when the Brake Pedal is Depressed and the Master Cylinder attempts to draw in Fresh Fluid, that Air can get vacuumed into the Piston Chambers around the Leaking Copper Washers and cause the Brakes to Fail.

This is due to the fact that the presence of any Air or Gas inside of any Hydraulic Line or System will compress under pressure as the Brake Pedal is depressed and the free fluid in the Brake Line will squeeze down on the Air Bubble as the Pedal travels freely towards the Floor. Hydraulic Systems can only function properly in the presence of Nothing But In-compressible Fluids inside of the Brake Lines and filling all of the the Brake Cylinders, purged of Air.

On the positive side... as long as you did not perform this "Brake Pedaling" effort too often...then the in-dwelling Gas Bubble is unlikely to have traveled all the way up and into either the ABS Manifold or make it as far as the Master Cylinder.

If you failed to lubricate the Caliper Pins with Fresh Brake Pin Grease and Cleaned and Installed the Silicone Sealing Weather Cups tightly around the Attachment Bolts... then the Caliper Brackets will find it difficult to completely withdraw and relieve the direct contact between the two Ceramic Pads and the two faces of the Brake Disk Platter. This symptom can also occur if the Cylinders-Calipers are installed upside down which, believe it or not, is entirely possible to do.

You will be able to eliminate or confirm that this problem has occurred if you can see that the Bleed Valves are located on the BOTTOM where they would be rendered absolutely useless to Bleed the Brakes... instead of being located on the TOP of the Brake Cylinders where the in-dwelling Air Bubbles can Float up to the Top of the Fluid and get expelled under pressure. The way this can happen is when the Left Caliper-Cylinder Set accidentally gets installed on the Right Wheel... or Vice-Versa.
 
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OP
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C-ya

C-ya

Well-Known Member
The reman'd caliper came with new crush washers on a new banjo bolt that were larger than the ones that were on the original banjo bolt. I tried to tighten it down but it would not stop leaking - just the drip from gravity. I ended up going back to the parts house and finding the size that were on the truck and those tightened down and stopped leaking. That is why the drip went on for so long. I have worked on autos and motorcycles since I was a teen. I have rebuilt a few calipers (car and bike), and replaced many more than that. I always use new crush washers on the lines/banjo bolts.

I did some searching and found a procedure for bleeding the brakes if you get air into the valve body - presumably of the ABS module. It says to bleed all 4 corners, starting with the right rear. The problem with that is that both of my rear calipers have the bleeders sheared off. So, I guess I'll be replacing the rear calipers and bleeding all 4. There is just no pedal.

I guess to round out the fun factor, I might as well replace the front right caliper so they are all "new". I'm sure the bleeder on that caliper is rusted shut and will most likely shear off as well.
 

Mooseman

Moderator
Just as a test, pinch off all the hoses and see if the master cylinder builds and holds pressure just in case that's the problem.
 
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C-ya

C-ya

Well-Known Member
Might be a good test, but I was not having any brake issues other than a dragging caliper. I don't think it is a master cylinder problem.
 

Expeditor

Member
I just had a issue with my 03 Silverado. Brake dragging, changed all the calipers, pads and rotors, they were needed. After all that still had brake drag. Come to find out it was the hose, it would fill the piston but take its time releasing. Piston would drag for a couple of minutes until fluid would slowly release inside collapsed hose. Replaced that hose and all is well. Just bought all hoses to replace all of them.
 

MRRSM

Lifetime VIP Supporter
We have all been there... and the need for having the Peace of Mind probably prompted each of us to go the Replacement Route... just to be safe and be able to Step on The Brakes... without having any doubts creeping in our minds that the vehicle will reliably STOP.

I like your decision very much... with added suggestion that whenever replacing Brake Components of ANY kind...whatever you do to the Left Side... you should also do to the Right Side. Brakes can be replaced in Pairs... either at the Front or the Rear...but never on any single wheel. :>) And if your Brakes have never been Bleed... One of our GMTN Members produced this Excellent Instructional Video so your Brake Job really is Complete:


How to Make a Brake Bleeder:

 
OP
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C-ya

C-ya

Well-Known Member
I always do things by axle. Yesterday was a "get it back on the road today" decision and get the other side replaced in a week or 2. Now I get to do it all this week after work when the weather is decent. Yesterday was 55, today is 35 and rain/snow. Tuesday looks decent at the moment.

I was going to flush the brake fluid a couple of years ago. That's when I discovered having no bleeders in the rear. I figured I would ride those calipers until I had to do something major and then replace them. Now is that time, I reckon.

I have my bike in the garage so the truck is outside on jackstands. The bike is getting ready to get the front brake master cylinder rebuilt, front calipers rebuilt, new fork seals, and a fuel pump gasket. I may do the front brake MC today and ride it to work for the next few days until I get the brakes done on the TB.

@Expeditor , that thought crossed my mind. I dealt with collapsed hoses on my Type 3 VW. Once replaced and the calipers rebuilt, she stopped great. The reason I went with the caliper on this side was the fact I couldn't compress it with a C clamp. I think with enough force, I should have been able to override the hose restriction.
 
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Expeditor

Member
I always do things by axle. Yesterday was a "get it back on the road today" decision and get the other side replaced in a week or 2. Now I get to do it all this week after work when the weather is decent. Yesterday was 55, today is 35 and rain/snow. Tuesday looks decent at the moment.

I was going to flush the brake fluid a couple of years ago. That's when I discovered having no bleeders in the rear. I figured I would ride those calipers until I had to do something major and then replace them. Now is that time, I reckon.

I have my bike in the garage so the truck is outside on jackstands. The bike is getting ready to get the front brake master cylinder rebuilt, front calipers rebuilt, new fork seals, and a fuel pump gasket. I may do the front brake MC today and ride it to work for the next few days until I get the brakes done on the TB.

@Expeditor , that thought crossed my mind. I dealt with collapsed hoses on my Type 3 VW. Once replaced and the calipers rebuilt, she stopped great. The reason I went with the caliper on this side was the fact I couldn't compress it with a C clamp. I think with enough force, I should have been able to override the hose restriction.
one way to find out if its the caliper or hose is to apply brakes with wheel in air. Try to move wheel, rotor by hand, if it is hard or you cant, then rotor is stuck. With wheel locked up and in air try to bleed fluid from caliper thru bleeder screw. If caliper releases then most likely its a collapse hose. If after bleeding brake caliper still wont release most likely bad caliper. Hope this helps. This is the first time I ran into a bad brake hose, there is always a first time, I guess......

I think most of us have been in the situation where we can only do just enough to get us back on road. The rest gets done when we have more time or money. Just saying.
 
OP
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C-ya

C-ya

Well-Known Member
I talked to my mechanic buddy about my situation and he said to bleed the other front caliper. Our system isn't criss-crossed like the older brake systems were. On ours, per the manual, front is one system with each wheel/caliper controlled individually (two circuits once past the MC) and rear is another from the MC (single circuit controls both calipers as one). I'll try that this afternoon and see what happens. He mentioned, and I have seen elsewhere, about finding a gravel or dirt road to activate the ABS, and then rebleed. I have my Tech II, so I may try that rather than driving somewhere to get the ABS to activate. Of course, playing in a gravel parking lot is always fun. I could have done it in the snow yesterday if I had had it back together and had a decent pedal.
 

MRRSM

Lifetime VIP Supporter
FWIW... At the very bottom of Post #9 in this Thread... DrShock uses an After-Market Brake Bleed Pressurizer and his "GYMKO" Tech 2 Clone to show and perform this "GM Dealership Quality ABS System Automated Brake Bleeding Procedure" on this Video:


 
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OP
OP
C-ya

C-ya

Well-Known Member
FWIW... At the very bottom of Post #9 in this Thread... DrShock uses an After-Market Brake Bleed Pressurizer and his "GYMKO" Tech 2 Clone to show and perform this "GM Dealership Quality ABS System Automated Brake Bleeding Procedure" on this Video:
I found that video but didn't watch it all the way through. I'll go back and watch it all this time and see what he does.
 

northcreek

Well-Known Member
@Expeditor , that thought crossed my mind. I dealt with collapsed hoses on my Type 3 VW. Once replaced and the calipers rebuilt, she stopped great. The reason I went with the caliper on this side was the fact I couldn't compress it with a C clamp. I think with enough force, I should have been able to override the hose restriction.
A collapsing brake hose can restrict in both directions so you won't be able to compress the piston. I recently when through this on my Chevy G30 van, after replacing both calipers, it was a $8 hose. I'm thinking you have the same problem.
 
OP
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C-ya

C-ya

Well-Known Member
A collapsing brake hose can restrict in both directions so you won't be able to compress the piston. I recently when through this on my Chevy G30 van, after replacing both calipers, it was a $8 hose. I'm thinking you have the same problem.
Thankfully not. I got the power bleeder hooked up and bled the front calipers. Passenger side had a bubble or 3 but the driver's side had a fairly long stream of bubbles. I have brakes now but I think I will bleed all 4 corners when I replace the rear calipers when the weather warms up more and I have some more time. That will also accomplish a flush of the entire system.

Thanks for all the ideas and links/videos. Seeing the guy in the video MRRSM posted helped me make sure I was using the bleeder correctly with the Tech II.
 

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