intermittent spongy brakes

[eelvan]

1985 LE van 172,000
Brakes seem fine for a while. Then all of a sudden to the floor. A pump or 2 and they are solid again. So I'm in the habit of always pumping.
I may go all day with no problem. Then to the floor. No leaks, res is full.
I did the rear shoes and cylinders(AutoZone), and replaced the master cylinder(rebuilt O'Reileys). I have bled and re-bled flushing the system. Still the same. So I got some new calipers(AutoZone reman) and am about to change them.
Any thoughts on this?

[timsrv]

Try bleeding from the LSP & BV bleeder port.

[eelvan]

I think I did that, it was about 6 months ago.
Could a sticky caliper be the culprit? The pads still have some life even though they have 50K on them.
They are not to the squeel indicator yet.

[timsrv]

Yes, these vans do have a tendency to seize slider pins. If that happens, most of the braking pressure will occur on one side and the piston(s) get pushed back into the caliper after braking. This will typically make the brakes spongy on the 1st pump, but they will usually firm up on the 2nd. When things get too far out of alignment, it's not unusual for the pins to slide abruptly. When that happens, there's usually a loud snap from that caliper and the brakes will work better until more pad wear occurs.

I used to never replace calipers, but after experiencing this a couple times I started replacing the calipers for every 2nd or 3rd set of pads. Since I started doing that I haven't had any issues. Tim

PS: Whenever you work on the front brakes, it's a good idea to lube the slider pins up with a silicone grease.

[bushcat]

Yes, these vans do have a tendency to seize slider pins. If that happens, most of the braking pressure will occur on one side and the piston(s) get pushed back into the caliper after braking. This will typically make the brakes spongy on the 1st pump, but they will usually firm up on the 2nd. When things get too far out of alignment, it's not unusual for the pins to slide abruptly. When that happens, there's usually a loud snap from that caliper and the brakes will work better until more pad wear occurs.

I used to never replace calipers, but after experiencing this a couple times I started replacing the calipers for every 2nd or 3rd set of pads. Since I started doing that I haven't had any issues. Tim

PS: Whenever you work on the front brakes, it's a good idea to lube the slider pins up with a silicone grease.


This is exactly what's happening with me. Soft on the first push usually, then the second pump it firms up. I'm wondering if I should just wait it out until I hear that loud snap or replace the caliper ASAP. Is it a tough job? Do you recommend replacing the pads as well if they are of unknown age?

[llamavan]

Having to double-pump brakes sometimes but not others can also result from wheel bearings that are adjusted a bit too loose (an embarrassing lesson I learned the hard way).

Replacing the flexible caliper hoses and the flexible hose for the LSP & BV (http://www.toyotavantech.com/forum/showthread.php?127-Load-Sensing-Proportioning-Valve-and-Bypass-Valve) on vans this age is a wise choice when brakes aren't nice and tight. The caliper hoses may have been replaced with the calipers at some point in a van's life, but because the LSP & BV (http://www.toyotavantech.com/forum/showthread.php?127-Load-Sensing-Proportioning-Valve-and-Bypass-Valve) often gets ignored, that hose can get in scary condition.

Calipers aren't that hard to replace, but because brakes are so critical, it is ideal to have someone knowledgeable on hand to walk you through things. You'll need a second person to help bleed after installation anyway. If you can't get knowledgeable help, pay to have it done right, and safely.

I replace pads when they are worn. That does not require bleeding, so no helper required — but again, brakes are critical, so if you aren't sure, then get help or pay to have it done. Be particularly aware that new brake pads initially have a long stopping distance (google "bed in new brake pads" BEFORE you go anywhere with new brake pads)!!!

Gwen

[bushcat]

Having to double-pump brakes sometimes but not others can also result from wheel bearings that are adjusted a bit too loose (an embarrassing lesson I learned the hard way).

Replacing the flexible caliper hoses and the flexible hose for the LSP & BV (http://www.toyotavantech.com/forum/showthread.php?127-Load-Sensing-Proportioning-Valve-and-Bypass-Valve) on vans this age is a wise choice when brakes aren't nice and tight. The caliper hoses may have been replaced with the calipers at some point in a van's life, but because the LSP & BV (http://www.toyotavantech.com/forum/showthread.php?127-Load-Sensing-Proportioning-Valve-and-Bypass-Valve) often gets ignored, that hose can get in scary condition.

Calipers aren't that hard to replace, but because brakes are so critical, it is ideal to have someone knowledgeable on hand to walk you through things. You'll need a second person to help bleed after installation anyway. If you can't get knowledgeable help, pay to have it done right, and safely.

I replace pads when they are worn. That does not require bleeding, so no helper required — but again, brakes are critical, so if you aren't sure, then get help or pay to have it done. Be particularly aware that new brake pads initially have a long stopping distance (google "bed in new brake pads" BEFORE you go anywhere with new brake pads)!!!

Gwen
Hi Gwen,
Do you have part numbers for the flexible caliper hoses and flexible hose for the LSP and BV? I have a 1985 toyota 2wd. I've done some brake hose replacement in the past. Is there a certain brake bleed kit that you like?

Thanks for your help.

[llamavan]

Do you have part numbers for the flexible caliper hoses and flexible hose for the LSP and BV? I have a 1985 toyota 2wd.

I've used aftermarket hoses from RockAuto (Raybestos). Use their catalog to drill down for your van (by year) and see what they currently have available.


Is there a certain brake bleed kit that you like?

Yep. Spousal Unit. Not for sale (unless he misbehaves badly). But Tim has covered what he uses somewhere. Here's how to best search the forum (http://www.toyotavantech.com/forum/showthread.php?5323-Searching-TVT-successfully-and-posting-new-threads) to find out.

Gwen

[bushcat]

I wanted to update this post with the fix that helped me. Auto shop quoted for me for a bad brake booster but I went ahead with the advice on another thread about changing the master brake cylinder because the brake booster rarely fails. I had a mechanic swap the master brake cylinder and bleed the brakes and the intermittent spongy brakes went away and haven't return in the few months I've been driving it. Hopefully this helps someone else out.