LPSV Bypass Problems (1 Viewer)

[1973Guppie]

here's another pic from jcardona's write up, I have hooked everything up the same, #2 to the back of the MC direct line. The only difference between his setup and mine is I did not use a prop valve so #1 port on the abs unit never got removed on my truck. The only one I had to remove was #2 and then reuse a line direct to the rear of the MC.

I can't see how I did the routing wrong? It is basically as stock is except for deletion of lspv, sensing lines and unions.

 

[Dave 2000]

really? I have never heard of this happening. I usually just use the pump method and it works fine. The MC is original I think so it is old.

Very common on older vehicles, the piston moves only a fraction most of its life, this creates a small ridge in the master cylinder. Then you start to bleed and push the piston and seal over this ridge, it is not much but often enough to distort the seal, often breaking tiny particles off 20 year old rubber.

Whenever working on old systems I put a block of wood under the pedal to limit its travel, it works.

Regards

Dave

 

[1973Guppie]

Very common on older vehicles, the piston moves only a fraction most of its life, this creates a small ridge in the master cylinder. Then you start to bleed and push the piston and seal over this ridge, it is not much but often enough to distort the seal, often breaking tiny particles off 20 year old rubber.

Whenever working on old systems I put a block of wood under the pedal to limit its travel, it works.

Regards

Dave

huh, learn something every day, worked on 40's and older trucks for years but never have seen this happen in person.

 

[nukegoat]

If you really f'd up the master cylinder then you can verify by simply leaving the truck off, pumping the pedal a few times to get rid of the vacuum reservoir, and then press and hold the pedal for a while and see if it slowly leaks down. If not, I sort of doubt you have mc issues.

 

[Dave 2000]

@1973Guppie I am unsure if this is due to less lubricity in newer fluids DOT4 versus DOT 3 for example, I see vehicle's from all year's so don't take any chances.

Once pressure is built in the cylinder the seals may hold if pressing hard, when pressing very lightly on the other hand you might find the pedal falls as the fluid slips past damaged seals.

Regards

Dave

 

[2fpower]

I know what @Dave 2000 is talking about; however, it typically will not bleed good at all four corners if your MC front/rear valving is messed up, typically you get front or rear, but not both. My point is if you can bleed all four corners, it is not the MC.

 

[2fpower]

here is a good example of what I have seen when MC goes bad.

At the end of my rope... bleeding brakes

 

[1973Guppie]

If you really f'd up the master cylinder then you can verify by simply leaving the truck off, pumping the pedal a few times to get rid of the vacuum reservoir, and then press and hold the pedal for a while and see if it slowly leaks down. If not, I sort of doubt you have mc issues.

well just tried this and it is holding pressure with the engine off.

 

[1973Guppie]

just went for a drive in the neighborhood, gassed it over a speed bump and got the abs to engage really well 4 times in a panic stop. Probably bedded in the new pads during the process as well. Going to try to bleed them again and see what happens. My wife is gonna hate me.

 

[nukegoat]

just went for a drive in the neighborhood, gassed it over a speed bump and got the abs to engage really well 4 times in a panic stop. Probably bedded in the new pads during the process as well. Going to try to bleed them again and see what happens. My wife is gonna hate me.

Either you're going to come back with "the fluid was still clear, no change" or "i think i saw some little tiny air bubbles, and it's a little better, but still way too mushy"

I look forward to this

 

[Red Merle]

I am considering it at this point. If I can't get the abs to actuate to get the air out I really have no choice. What is the reasonable lifespan for these abs units? Are there internal components that degrade over time? Just wondering if these wear out similar to a master cylinder or other component.

I am not experienced enough to know what the reasonable lifespan of the ABS units are, but I can tell you that I was concerned about my insurance covering me in the event of an accident if I deleted it, so I called my agent to ask about it. He told me that with the earlier iterations of ABS like we have in our 20+ year old rigs, the underwriters actually consider them a slight liability. My premium went down when I deleted it and I believe the truck is now safer without it. The truck used to have very marginal brakes and the ABS used to kick in at times when I didn't think it was warranted. I have all new calipers, rotors, MC, booster and pads now and the truck stops on a dime with very good pedal feel.

Just my $0.02.

 

[2fpower]

Either you're going to come back with "the fluid was still clear, no change" or "i think i saw some little tiny air bubbles, and it's a little better, but still way too mushy"

I look forward to this

Agree with this comment. I will say it again, took me a good 4 times of cycling the ABS/bleeding to get mine done.

The one thing I did not mention, was that I got it to about 90% of what I thought was as good as my other rig, and then my son drove it for about 2k miles. I went to bleed it again, and it did not need it. Not sure what happened, but it improved somehow.

 

[2fpower]

I am not experienced enough to know what the reasonable lifespan of the ABS units are, but I can tell you that I was concerned about my insurance covering me in the event of an accident if I deleted it, so I called my agent to ask about it. He told me that with the earlier iterations of ABS like we have in our 20+ year old rigs, the underwriters actually consider them a slight liability. My premium went down when I deleted it and I believe the truck is now safer without it. The truck used to have very marginal brakes and the ABS used to kick in at times when I didn't think it was warranted. I have all new calipers, rotors, MC, booster and pads now and the truck stops on a dime with very good pedal feel.

Just my $0.02.

very interesting.... Good info.

 

[1973Guppie]

Either you're going to come back with "the fluid was still clear, no change" or "i think i saw some little tiny air bubbles, and it's a little better, but still way too mushy"

I look forward to this

I'm glad you enjoy my pain Nukegoat, lol

I also ordered a motive power bleeder, should be here same day, amazon is crazy, they are taking over the world. I didn't want to deal with the roll of eyes from my wife asking her to bleed the brakes again.

 

[1973Guppie]

I am not experienced enough to know what the reasonable lifespan of the ABS units are, but I can tell you that I was concerned about my insurance covering me in the event of an accident if I deleted it, so I called my agent to ask about it. He told me that with the earlier iterations of ABS like we have in our 20+ year old rigs, the underwriters actually consider them a slight liability. My premium went down when I deleted it and I believe the truck is now safer without it. The truck used to have very marginal brakes and the ABS used to kick in at times when I didn't think it was warranted. I have all new calipers, rotors, MC, booster and pads now and the truck stops on a dime with very good pedal feel.

Just my $0.02.

that is very interesting good info, thx for that. To your point when I recently took it for a spin when I slammed on the brakes I got the tires to start locking up. Makes me wonder about the viability of these old abs systems and whether they really do anything after age and deteroration comes into play, bigger tires, mods, etc.

I am still considering removing the abs. I figure I am into it now so we will see. I have a 2005 toyota echo I drive for work all over sd county and it does not have abs. I figured that out the other day on the freeway when I locked the tires up. But it is a light little car, easy to do. I am more aware about it now than I was before. I guess my point is no system is really going to keep you from an accident ultimately.

I am not spending weeks bleeding this godamn truck. I am going to give it another go with the power bleeder and if that does not work to my satisfaction out the abs comes.

 

[Red Merle]

very interesting.... Good info.

That was with Allstate and I now have Safeco because they gave me an agreed value policy. I would just double check with your carrier to be sure they see it the same way.

 

[1973Guppie]

That was with Allstate and I now have Safeco because they gave me an agreed value policy. I would just double check with your carrier to be sure they see it the same way.

honestly I kinda chuckle when I hear guys mention the dangers of removing the abs unit, I get the risk but when you look at our trucks they are just one big risk, you can get sued for anything these days. I have gas cans hanging off the rear of my truck for god sakes. Bigger tires, armor, all the mods, etc. If it's not one thing it is the other you will get sued for or be held as "at fault" for. I have been in accidents before and was amazed whom was dealt "at fault" randomly for seemingly mundane reasons that a police officer handed down his opinion.

 

[Red Merle]

honestly I kinda chuckle when I hear guys mention the dangers of removing the abs unit, I get the risk but when you look at our trucks they are just one big risk, you can get sued for anything these days. I have gas cans hanging off the rear of my truck for god sakes. Bigger tires, armor, all the mods, etc. If it's not one thing it is the other you will get sued for or be held as "at fault" for. I have been in accidents before and was amazed whom was dealt "at fault" randomly for seemingly mundane reasons that a police officer handed down his opinion.

I was thinking more along the lines of an insurance claims adjuster noting that you removed some of the "safety equipment" which they then decide is what caused the accident and thus refuse to cover your loss or those of the other driver. But yes, I agree, if someone wants to sue, they will find something to sue over. My truck doesn't have airbags either since it is a '94 but i am sure someone could try to sue me if they were riding in the car and something happened. I was just offering a friendly piece of advice for anyone that wants to delete the ABS and is concerned about the insurance implications of doing so.

 

[1973Guppie]

tonight when in the truck I noticed that I heard a hissing when the brake pedal was depressed, I am thinking maybe the brake master is going out, I think I will remove the master from the booster to see if there is any fluid seeping through. It's a fairly mushy pedal and am thinking maybe it is going out slowly. I believe it is the original unit to the truck.

 

[1973Guppie]

hooked up the power bleeder tonight, got a lot of air coming out on the rear two calipers, and a little from the front pass side caliper. Went to bleed the drivers side rebuilt caliper (the one that I thought looked fishy with the tiny 8mm bleed screw) and got nothing coming out of it even with 20 psi on the power bleeder. I mean nothing, no fluid was flowing out of the bleeder screw whatsoever even when I removed it. I am guessing it is just a bad part. Ugh. Going to pull the tire tomm and crack the banjo, if I get fluid from there I know it is the caliper and will need to return it.

So a few days and hopefully the new caliper and another bleed will solve things. I may bleed the whole system 2x after reactivating the ABS again as that really seemed to dislodge some air. it is easy enough to do now with the power bleeder. It might also be the fact that I am using a power bleeder now as well rather than the pump method.

I forgot how nice these units are to have. Only problem in my experience is they really don't last long. It would be nice to find a higher quality one that lasts. I seem to only get about a dozen uses out of them, at least my old one. The brake fluid just seems to corrode them. Hopefully this one will last longer.

Will update in a few days. I wish I had gotten toyota reman's now.