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Car Forum / Driving, Maintenance, Tuning / Maintenance and Repair / May 2006leaking brake line
1989 Toyota Pickup Truck, rear-wheel drive. Front disc brakes, rear drum brakes. I use this vehicle on my property for hauling tools and dirt etc. Last week, one of the brake lines sprung a leak, and I lost most of the fluid in the master cylinder. I still have some braking, but the pedal goes most of the way to the floor and is spongy. There seem to be TWO brake lines, running side-by-side going to the rear of the vehicle. It is one of these lines that sprung the leak. Both of these lines go into some sort of small device at the rear of the vehicle. One line comes out of this device and goes to a second device. There are two lines coming out of the second device; one goes to each rear wheel. What is the purpose of this arrangement? Can I simply crimp the bad line upstream of the leak, to prevent loss of fluid and retain full function of the front disc brakes? I believe you are describing proportional check-valves for the braking system, not good to bypass them. Just get replace metal tubes, a cheap tube-bender, drop the original lines, bend the new to shape, compression fitting and nut, good to go.  SignatureKnifeblade_03 http://www.automotiveforums.com > 1989 Toyota Pickup Truck, rear-wheel drive. > [quoted text clipped - 15 lines] > Can I simply crimp the bad line upstream of the leak, to prevent loss > of fluid and retain full function of the front disc brakes? I have heard of others crimpint radiator tubes and brake lines, but my experience has never been successful at it. Brake fluid is very thin and slippery. I suppose a guy could try to solder it closes at the crimp, but why. Fixing it is quicker. that is a valve used to very the braking force in proportion to the weight in the bed of the truck. dont bypass anything just replace the lines autozone and checkers sell brake line with fittings in various lengths and sizes just take the leaker off buy one thats close bend install and go.. Why are there 2 brake lines going to the rear of the vehicle? Is this for redundancy, or do they serve different purposes? Why not trace them back and see if each goes to a separate reservoir on the master? <<Why not trace them back and see if each goes to a separate reservoir on the master?>> I tried, but I don't have a visual the whole way. I'd have to take a bunch of rusted-on stuff off to see where they go. What I need is a hydraulic schematic of this vehicle's brake system. I had an old Haynes manual laying around and looked in that, but all it says is that the front and rear brakes are serviced by separate hydraulic circuits. I googled around quite a bit looking for a website with a hydraulic schematic but couldn't find a thing. If anyone out there has a manual for this model and year truck and would be willing to answer a few questions about the brake hydraulics it would be much appreciated. > <<Why not trace them back and see if each goes to a separate reservoir > on the master?>> [quoted text clipped - 3 lines] > > What I need is a hydraulic schematic of this vehicle's brake system. I can't find a map of the lines, but the first "device" at the back is apparently called a "load sensing proportioning and bypass valve". Bottom of page: http://www.autozone.com/servlet/UiBroker?ForwardPage=/az/cds/en_us/0900823d/80/1 6/24/1a/0900823d8016241a.jsp Here's a big picture of what you probably see under there: http://www.autozone.com/images/cds/gif/medium/0900823d8016241e.gif The second "device" is likely just a standard T-union to run the rear brakes after the proportioner decides how much pressure they need. << I can't find a map of the lines, but the first "device" at the back is apparently called a "load sensing proportioning and bypass valve". >> Yup, that looks like it. And there's a linkage (steel rod) going from it to a smaller pivot arm mounted to the differential. So when the truck bed gets loaded down, the linkage moves. Now, since it's called a *bypass* valve, I gotta assume there's some bypassing going on, yes? and if so, there's gotta be some place for the "bypassed" fluid to go. I assume that's what the second brake line is for... I bought the parts I needed but when I crawled under the truck (on ramps) I quickly became discouraged. This is no easy job. A large section of the lines is inaccessible (tucked between the frame and the gas tank - yikes), with immobilizing clamps nestled in there. The nuts retaining the lines going into the "load sensing proportioning and bypass valve" are completely rusted over. They are not going to succumb easily. There is one section (foreward of the gas tank and upstream of the leak) where the lines are accessible. I'm very tempted to just crimp them shut to stop the leak. Not sure what sort of tool to use though. That is the line for both rear brakes then. The valve varies the pressure with the truck's load. If you crimp off that line, you will have no rear brakes. Jeep pickups have the same thing. Mike 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's Canadian Off Road Trips Photos: Non members can still view! Jan/06 http://www.imagestation.com/album/pictures.html?id=2115147590 (More Off Road album links at bottom of the view page) > << I can't find a map of the lines, but the first "device" at the back > is apparently [quoted text clipped - 20 lines] > leak) where the lines are accessible. I'm very tempted to just crimp > them shut to stop the leak. Not sure what sort of tool to use though. > << I can't find a map of the lines, but the first "device" at the back > is apparently [quoted text clipped - 16 lines] > bypass valve" are completely rusted over. They are not going to > succumb easily. You are planning to replace the line that leaks? right? All you need is to get at both ends of the line you are going to replace. The old corroded line can be left right where it is if it is too difficult to remove. To remove the compression nuts on the end of the lines cut the old line with a side cutter right next to the nut and use a 6 sided socket to remove the nut (do not use an open end wrench and round it off). Make sure to route the new brake line so that it is protected. You can use nylon tie straps to hold it in position if the old retainers are too far gone to be used. -jim > There is one section (foreward of the gas tank and upstream of the > leak) where the lines are accessible. I'm very tempted to just crimp > them shut to stop the leak. Not sure what sort of tool to use though. <<use a 6 sided socket to remove the nut>> I think it's going to take more than that, like an impact wrench or an air hammer or something (which I don't have). I've fought battles with rusted bolts&nuts before, and lost. This one is caked with rust. I find myself wanting just to limp down to an auto repair place and handing it over and saying "here, you do it". What's holding me back is cynical visions of them using a torch on the nut to loosen it, and ruining the valve in the process. If you can get a good grip on it it will come apart. Failure will come from chewing the nut up to the point where there's nothing left to grip. Its rusted badly only on the outside not on the inside like an exhaust bolt. jim > <<use a 6 sided socket to remove the nut>> > [quoted text clipped - 9 lines] > What's holding me back is cynical visions of them using a torch on the > nut to loosen it, and ruining the valve in the process. |
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