Constant Air in LSPV brake line, 96 LX450

[Cattledog]

Hey guys,

I was over at Landtank's house over the weekend bleeding my brakes. Let me start off with that the brakes work fine and I can kick in the ABS without any problem.

I was interested in bleeding the line because after driving Landtank's truck he had brake drag within an inch of petal travel. Comparitvly my brakes had a drag after about 1.5" or so.

So, Landtank and I said what the hell and cracked open a couple of beers and went to town. In the end I had no air in any of the lines but one... We were not able to bleed the LSPV free of air even after 1.5 quarts of fluid... The truck is rust free for a northeast truck at 145K, and without a lift. The hard and soft lines look perfect. Any one have a diagram of the 80 ABS brake system or the LSPV? The one in the OEM manual sucks.

I will be ordering a female/female soft line to isolate the problem unit/line... I searched the forum and have seen a couple of other people with the same issue. Every one ended up using a pressure bleeder to remove the air, so one is being shipped.

 

[landtank]

As I told Dave, I don't think the pressure bleeder is the answer. While it will likely bleed the system of all the air it won't fix the problem or identify the problem. It seems to me that the same thing I was fighting on my brakes is happening here. Using the standard bleeding method the up travel of brake pedal draws in some air. Then the subsequent push moves the air back out of the system resulting in that soft feeling.

If you read back in my thread I had it pressure bleed by a dealer and the brakes were great until I had used them enough to re-introduce the air and then it was another complete failure.

IMO, until we can bleed the brakes properly using the standard method we haven't located the problem and should keep looking. But it's Dave's truck and I'll help him do what he wants.

 

[Cattledog]

Rick, We will isolate the problem leak by vacuum/2 person bleeding, no problem there. I just have no desire to bleed the system for a couple of hours after I/we find and fix the leak. The pressue bleeder should make short work of properly bleeding the abs unit and lines if the ABS unit is the problem.

 

[landtank]

Rick, We will isolate the problem leak by vacuum/2 person bleeding, no problem there. I just have no desire to bleed the system for a couple of hours after I/we find and fix the leak. The pressue bleeder should make short work of properly bleeding the abs unit and lines if the ABS unit is the problem.

I think you are missing my point. I think the only way to be sure that the problem is fixed is to do a traditional bleed on the system and by then the need to power bleed the system is negated.

Maybe once I see this thing in action I'll change my mind.

 

[turbocruiser]

I dunno; I've tried the vacuum bleeder but I did not like it as it constantly pulled air in around the actual hose especially when the screw was closed so bleeding was basically impossible without sucking some super small air bubble in ... then I tried the pressure bleeder but on our rigs where the brake fluid reservoir cap does not screw down, you have to really tighten the top to get an adequate seal and then even then I am convinced that concentrating all that pressure 35+ psi into the brake fluid reservoir is the wrong way to do it. IMO, This is truly one of those things where the wife is the best thing around - she's getting really good at taking some trashy novel into the seat and going through the motions to bleed the system. We've tried it both ways (engine off and engine on) and it seems to work either which way we try although engine on is indeed the fastest and most forceful for bleeding the system. Ohh, one more thing to mention, I've found that with either way you really want to pause a super long second after the pump, pump, pump with your foot and really put some pressure and some pause on the brake pedal before you open the screw - for whatever reason, I've noticed that tends to force whatever air is in the system into its own little pocket - a bigger burp instead of all sorts of smaller bubbles. HTH.