[jung4x4]

Hey guys, I'm in some desperate need of help. I installed the ProComp extended steel braided lines on the front of my 95.5 Tacoma and shortly thereafter is when the problem began. The problem is inconsistancy in the brake pedal. Sometimes (most often just after starting the truck) the pedal is stiff and has minimal travel. Other times (after minimal brake usage while driving) the pedal will be soft and travel almost all the way to the floor. I doubt the ProComp lines have anything to do with my troubles, but after installation is when the problem started.

I have bled the system (in proper sequence, to include the LSPV) numerous times. The master cylinder has been replaced with a brand new (not remanufactured) OEM unit, and the original brake lines were reinstalled at one point. After all that, the problem has remained. Also, it has not gotten any worse. It is exactly the same since a couple days after the install of the ProComp lines.

The problem seems to be magnified when the truck is in 4 Lo. The pedal will go ALL the way to the floor nearly 100% of the time.

Today I disconnected the vacuum line from the brake booster and plugged it and drove it around a bit. The brakes were extremely firm and difficult to depress, but the pedal pressure was consistant. Perhaps the booster is applying too much vacuum sometimes causing inconsistant travel? I don't know if my theory is physically possible but I can't come up with anything else.

Please throw all suggestions and previous experiences out there. I cannot figure this one out, nor can anyone else I've talked to.

Thanks in advance.

-Adam
NMTTORA

 

[TacoCrazy]

The first thing I would do is put the stock hoses back on it and see if the problem goes away..Not likely the fix, but you may chase your ass forever if you don't..Put it back like it was when it had no problem and see..A booster is not likely to cause inconsistent travel, only a hard pedal when it loses it's vacuum source..Have you pressure bled it?? Some don't take well to gravity bleeds..

 

[jung4x4]

I already did that, and them bled them too. The problem remained, no better, no worse.

-Adam
NMTTORA

 

[TacoCrazy]

I already did that, and them bled them too. The problem remained, no better, no worse.

-Adam
NMTTORA

See my edited post above..Pressure bleed??

 

[jung4x4]

If by "pressure bleeding" you mean back or reverse bleeding, then yes. I failed to mention that in my original post. I used a Phoenix pressure bleeder and forced the fluid from the calipers back up to the master cylinder. Same result as all the other attempts, no better, no worse.

-Adam
NMTTORA

 

[TacoCrazy]

If by "pressure bleeding" you mean back or reverse bleeding, then yes. I failed to mention that in my original post. I used a Phoenix pressure bleeder and forced the fluid from the calipers back up to the master cylinder. Same result as all the other attempts, no better, no worse.

-Adam
NMTTORA

Pressure bleeding, meaning a pressurized fluid filled container on the master cylinder used to bleed the brakes..You can't go from the calipers back to the M/C..That in itself would cause an air pocket..The pressurized fluid source must be on top of the M/C..Then starting with the wheel farthest from the M/C, open each bleeder until an airless stream of fluid appears..Doing the LSPV last..

 

[TacoCrazy]

If you don't have the means to do it, take it to someone who does..Trapped air can be a real bitch sometimes..A pressurized bleeder will aleviate the air..

 

[jung4x4]

In that case, no, I haven't pressure bled. Nor do I think I've even heard of it. Can you explain it to me or post a link to a write up? BTW, thatnks for your help.

-Adam
NMTTORA

 

[TacoCrazy]

In that case, no, I haven't pressure bled. Nor do I think I've even heard of it. Can you explain it to me or post a link to a write up? BTW, thatnks for your help.

-Adam
NMTTORA

Here's a link to one so you can see..
http://www.motiveproducts.com/
Pressure bleeding uses a pressurized container filled with several liters of brake fluid..It screws to your master cyl cap..You connect an air source to it which pressurizes the container and your fluid reservoir..By doing this you force the air out under pressure..Many vehicles will only bleed with such a device..If you have not done it I would really suggest you find a local shop that can do it and get it done..The issue with typical gravity bleeding is if the air is trapped a good way up the line and you don't bleed long enough you won't make it to the air pocket..Your problem is air in the lines if there are no external leaks..Did you bench bleed the M/C before installing it??

 

[jung4x4]

OK, thanks. I did a search on Google for "pressure bleeding brakes" as well. You've been very helpful. Hopefully I can get this done and it will solve the problem.

The master cylinder was installed by a mechanic I know and trust. I did not ask him if it was bench bled, but I assume that it was. Also, I'm not sure how he bled the brakes after completing the job. It seems that he would have pressure bled them. I'll have to ask him.

-Adam
NMTTORA

 

[TacoCrazy]

Not all use it, some still rely on the ole' gravity bleed..Be sure and tell whoever pressure bleeds them the problem you are having, so they might leave that bleeder screw open a tad longer than normal, give the trapped air time to reach the outside..Best of luck..

 

[jung4x4]

I'll do that. Thanks again. But, just in case this doesn't work....any other suggestions?

BTW, I love your rear bumper.

-Adam
NMTTORA

 

[not2XS]

Well, when I read your initial post I was thinking of two things. One is that I had similar symptoms when a rust spot nicked a piston seal in the master cylinder from pumping the brakes to bleed them. You say you have a new master cylinder so that should rule that out. The second thing that came to mind is the brake booster. When you disconnected it, did it feel like the times when they are stiff? If the booster is working intermittently, that may explain the variations in feel you are getting, but are you getting a loss or increase of stopping power when the pedal feels softer?

Also, have you checked very carefully if your fluid level is dropping? You may be getting a leak somewhere only under pressure (or only when fittings are flexed a certain way). Sometimes when it leaks the fluid will find its way to the strangest places and not be at all visible.

 

[knoxtaco]

If by "pressure bleeding" you mean back or reverse bleeding, then yes. I failed to mention that in my original post. I used a Phoenix pressure bleeder and forced the fluid from the calipers back up to the master cylinder. Same result as all the other attempts, no better, no worse.

-Adam
NMTTORA

I have a vacuum bleeder that you attatch to the bleeder screws and it sucks the fluid out. I have seen the phoenix system and always though it was a bad idea to flush the old dirty fluid and contaminates back through the system and into the master cylinder. It is possible you may be picking up some debris from bleeding this way and it is causing the seals in the master cylinder to have an intermittient seal. Mightyvac and others have a cheap vacuum pump and bleeder kit. the one that i use at my shop is a model 7200.

 

[GoodyearMTR]

I used to be a mechanic, and went to several Goodyear ABS schools, we were always told never to depress brake pedal all the way to floor while bleeding for that exact reason!!

 

[jung4x4]

Good info. Thanks.

-Adam
NMTTORA

 

[jung4x4]

When the booster was disconnected the brake pedal was way stiffer than it was at any other point, however, it was consistant. As far as stopping power goes, it is more difficult to stop the further the pedal travels. It definately FEELS like a pressure problem but I've bled them so many times it it kinda hard to believe.

I have checked all the lines and I've been keeping an eye on the fluid level at the master cylinder. There does not appear to be a fluid leak anywhere in the system.

-Adam
NMTTORA

 

[TacoCrazy]

Well, when I read your initial post I was thinking of two things. One is that I had similar symptoms when a rust spot nicked a piston seal in the master cylinder from pumping the brakes to bleed them. You say you have a new master cylinder so that should rule that out. The second thing that came to mind is the brake booster. When you disconnected it, did it feel like the times when they are stiff? If the booster is working intermittently, that may explain the variations in feel you are getting, but are you getting a loss or increase of stopping power when the pedal feels softer?

Also, have you checked very carefully if your fluid level is dropping? You may be getting a leak somewhere only under pressure (or only when fittings are flexed a certain way). Sometimes when it leaks the fluid will find its way to the strangest places and not be at all visible.

The booster would not cause the pedal going all the way to the floor as he mentioned though..It could vary pedal pressure but not to the floor..In order for the pedal to go there it either has a leak, internally (the fluid is bypassing a defective seal) or externally, or it needs to be bled properly, not "back" bleeding, but pressure bleeding from the M/C..

 

[TacoCrazy]

I have a vacuum bleeder that you attatch to the bleeder screws and it sucks the fluid out. I have seen the phoenix system and always though it was a bad idea to flush the old dirty fluid and contaminates back through the system and into the master cylinder. It is possible you may be picking up some debris from bleeding this way and it is causing the seals in the master cylinder to have an intermittient seal. Mightyvac and others have a cheap vacuum pump and bleeder kit. the one that i use at my shop is a model 7200.

You are absolutely correct about the Phoenix type, although the vacuum type is prone to issues if the connection at the bleeder screw is not totally air tight, which can be tough..Pressure bleeding from the master cylinder with the appropriate equiptment is really the only sure-fire way to eliminate those variables..If the seal is not tight at the M/C it will bleed off the air pressure on the tank, maaking it obvious..

 

[jung4x4]

In order for the pedal to go there it either has a leak, internally (the fluid is bypassing a defective seal) ..

Where in the system could fluid bypass a seal other than the master cylinder? The rear wheel cylinders? Front calipers (both are about 18 months old)? LSPV?

-Adam
NMTTORA