Need help re. brakes, brake fluid, pressure, and stuff

I drive a 1989 Isuzu pickup. (Sorry, ladies, I’m taken.) This morning I noticed that I had to push the brake pedal waaay down to get any braking power. The truck still stopped fine, but I had to push the pedal almost all the way down to the floor.

I asked a few friends about it, and one suggested I check the brake fluid. I did, and there was no fluid at all; none visible in there, anyway. So I got some brake fluid, topped off the master cylinder, and… nothing.

It’s still exactly the same; I still have to push the pedal almost all the way to the floor to stop the thing. After a short test-jaunt around the neighborhood, I think it may be getting slowly worse (not sure about that, though).

I’m planning to take it to the mechanic around the corner in the morning; they’re generally pretty honest there and don’t seem to overcharge me too badly. Actually, if it’s something like removing a nail from my tire and patching it, they don’t charge me anything.

Any suggestions as to what I might tell the mechanic? Anything I should remind them to check if they forget? Anything I should check before I take it in there?

As you may have gathered, I don’t know much about cars or the maintenance of same (I had to consult my trusty Haynes manual to check/fill the brake fluid), but I like to have some stuff to throw out there that makes the mechanic think I might not be an idiot.

Thanks in advance; I hope someone on the board knows a bit more (or a lot more) about this stuff than I do.

Tell them exactly what you told us.
I suspect that either the master cylinder has gotten so low, air has been introduced into the system, or your rear brakes are somehow got way, way, way, way out of adjustment (this is very unlikely)
I suspect that there is a leak somewhere in the system, either the master cylinder or a wheel cylinder that caused the fluid level drop.
This could easily be to be a multi-hundred dollar repair depending on the fault.

I’m just a shade tree mechanic, but i’ll share my “wisdom.” Brake fluid is designed to be practically uncompressable so that pressure on the pedal is transfered to the brake, once you get air into the system you have a problem, as air is much more compressable than brake fluid. If you’ve ever heard the expression “bleeding the brakes,” it refers to getting air out of the line.

So, if there was no fluid in the master cylinder then you have air in the system, that’s why your pedal feels slack. You need to have the mech bleed the brakes at least. The next question is WHY was there no fluid? If you just haven’t checked it since the vehicle was new that’s probably reason enough, but you want to see if there’s a leak somewhere. If it’s a slow leak it may take awhile to find, if it’s a major leak it’s easier to find, but more dangerous to drive. When you get to the shop, check and see if the master cylinder fluid level has dropped visibly. If not, and there’s no obvious leak you’re PROBABLY ok to bleed and go. If so, start checking the level on a regular basis, also get in the habit of checking for a fluid on the ground as you pull out of parking spaces, good luck.

Going to a mechanic is like going to a doctor. The best thing, the most helpful thing, is to describe the symptom(s). Let the expert determine what testing and inspection is called for, and let him make the diagnosis. If the practitioner you’re going to knows what he’s doing, he won’t need hints or reminders of what to check. If he doesn’t know what he’s doing, you’re much better served going elsewhere than trying to guide him.

That said, it’s a virtual certainty that you’ve sprung a leak in the rear brake hydraulic system, either a wheel cylinder, a rubber hose, or a steel line. The loss of fluid from the leak has emptied the reservoir and caused the long pedal travel. The rear brakes are not operating. The vehicle still stops reasonably well because the front brakes, still working, typically provide 2/3 or more of the total stopping power. Adding fluid didn’t change the pedal feel because there’s air in the lines, and because the new fluid leaks right out under pressure, just like the old fluid did.

If it is a leaking wheel cylinder, which is the most common cause of the symptoms described, the proper repair involves replacing both (left and right) cylinders. It’s also possible, likely actually, that the cylinder has leaked onto the brake shoes. This contaminates the linings and requires brake shoe replacement, again both sides.

Just remember to drive slowly and judiciously and not allow a situation that might call for a panic stop. Also keep in mind that the parking brake can be used to supplement the service brake.

Good info all around, folks; thanks. This all jibes with what I’ve been told in the meantime at a friend’s house (where I went in my wife’s car). I’m hoping it won’t be terribly expensive; if the estimates are high, I may have some serious thinking to do regarding the cost-effectiveness of repairing an 18-year-old truck.

ah, it’s the brakes. if you don’t repair it you could be on the wrong end of a very expensive law suit when you hit someone.

Nitpick: “re” is not an abbreviation. It’s Latin for “in the matter of”.

And you’ll be lucky if that’s all you end up with. I had the brakes go completely out on me one time and was damned lucky to not get killed before I was able to get the car stopped.

The cost is going to vary with what the problem is. Simple stuff, like a loose line, is going to be cheap. Replacing the wheel cylinders or master cylinder is going to be more expensive. I’ve no idea what the going rate for brake repairs is, since I do my own, but I know that my father paid $300 to have the front brakes redone on his car, which seems high to me (of course, I don’t know what all he had to have done, it might have been more than simple pad and rotor replacement).

If you decide to get rid of the truck rather than fix it. Scrap it! Don’t try to sell it to someone unless you get it in writing that they know it needs to have it’s brakes replaced. That way, if they decide to drive it around, rather than getting the brakes fixed, they can’t come back and sue you claiming that they didn’t know the brakes were bad.

Also do not try to use the parking brake as an “emergency” brake. That’s not what it’s designed for, and the chances of you being able to bring the vehicle reliably to a stop (assuming the parking brake still works, which often it doesn’t) are exactly nil. It’s worth grabbing in an “Oh shit! We’re going to die!” situation, but you’ll still wind up crashing into something.

OK, I’ve taken the truck to the mechanic and left it there. He said if it’s the master cylinder there won’t be anything they can do, because the truck’s so old and not a common make/model. They can bleed the brakelines, though, so I asked him to check out what he could and get back to me.

Dangit, I really don’t want that truck to die. For one thing, I’ve enjoyed driving it for seven trouble-free years, and for another, I’ve got about three months left in law school and I’m up to my ears in debt already; this is not a good time for me to need a new vehicle.

I don’t know the exact model, but a cursory search at a couple of online parts stores reveal master cylinders for 1989 Isuzu trucks. They are available with little to no problem (other than costing ~$150 or more). If your mechanic can’t find a part for a non-antique big brand automobile, you need a new mechanic.

This worries me. I wasn’t there to hear exactly what was said, but as related it sends up red flags. First, brake master cylinders (both new and rebuilt) are available for the vehicle. I cannot imagine why someone would say they couldn’t do anything if that’s what it needs (and while it’s possible, I believe it’s unlikely that’s what it needs). Second, bleeding won’t solve the problem. If there’s air in the lines, it’s because of a leak, and the leak will have to be fixed. This report just has me wondering about the shop’s competence.

Yeah, it’s not that uncommon. It’s not like Isuzu went out and made some unobtainium-plated master brake cylinder for their truck or anything; this is likely a standard OEM part used on several makes and models which Isuzu has just slapped their own unique part number on. If nothing else, there should be rebuild kits available, or in worst case, you can backfit and mount a different master cylinder, which any competent brake technician should be able to do.

It sounds like your mechanic might be a bit over his head; I’d look around for a good brake shop and ask them about it. It should go without saying that, if the brakes are totally compromised, you should go ahead and pay to have it towed, which will be much cheaper than an accident resulting from total failure of the braking system.


The mechanic may have meant there’s not much he can do but replace it.

Rick and Gary T, you disappoint me! :stuck_out_tongue:

There doesn’t need to be any leak for the brake fluid to drop. The fluid drops as the brake pads (and rotors) wear down and the slave cylinders are pushed outwards. When the fluid drops below a certain level in the reservoir, you start drawing air.

If there is no leak after all, this means that the rotors are paper thin and the brake pads are mostly metal.
And a piece of advice on bleeding. Normally the manual way of bleeding (ie. having someone push the brake pedal while you unscrew the bleeding nipple) is the most effective for removing air from the system. But this method should be avoided for poorly maintained cars. This is because unless the brake fluid is changed regularly, the innermost part of the master cylinder gets rusty; when bleeding, the brake pedal goes all the way in and the rusty parts of the cylinder rub against the o-rings and damage them.

I’ll grant that that is possible, but it’s extremely unlikely. If the fluid level is full when pads are new (which is almost always the case), it will only drop to approximately the minimum mark when the pads are worn out and grinding the rotors. It would take a heck of a lot of further wear to empty the reservoir, and it’s incredible that this would occur without other symptoms.

If this did happen, adding fluid would almost always improve the pedal feel somewhat, as some of the air would bleed out into the reservoir with each pedal application (up to a point). But in this case, there was not only no improvement, but it seemed to get worse. I would be very surprised if there’s not a leak here.

OK, I talked to the mechanic.

Let me preface this: He’s not going to do any work on it at all; I’m going to pick up the truck in an hour or so, and he’ll give me a big printout of what all is wrong with it. He’s not charging me anything for the assessment, and he’s not recommending me to anyone else.

I say all this to emphasize that I think he’s honest. I’ve gone in there three or four times for some minor stuff over the last few years (nail in tire, etc.), and he’s never charged me a penny for any of it.

The diagnosis: The master cylinder is shot. The brake pads are almost completely worn out, and the rotors are rusted beyond salvage. There’s so much rust and corrosion on the underbody that screws are rusted through and he’s afraid they’ll break off if he tries to do anything to them. I should mention that I bought this truck in Iowa, where they salt the roads.

He didn’t give me a price estimate on any of this, nor did I ask for one. I suspect, though, that it’s time to call this truck “dead.” The Blue Book value is $575, and I feel pretty certain all these repairs would greatly exceed that figure. (I’ll get an estimate, of course.)

I’m trying to look on the bright side. I bought it in June 1999 for $2000, making for a yearly cost of about $266. So I definitely got my money’s worth.