Brake system work



I am fairly adapt at doing my own work, and recently bought a 1991 Firebird so I could expand my automotive skills. One of my projects is to replace the brake hoses (and possibly brake lines) throughout the car.

Having said that, most manuals I have read state to use a “line wrench” or “flare nut wrench” to remove the lines. Fair enough. However, I would like to know ahead of time what others recommend when removing the lines. Flare wrenches are not cheap, and I don’t want to buy both an SAE and Metric set – is there a way to find out which one this particular car uses? In addition, is there any other speciality tools I should know about before I jump in?

Thanks in advance for any help!


Flare nut wrenches, or line wrenches as they’re called, are precisely the same as a regular open ended wrench, except they are almost a complete circle, like a box wrench. They’re the same size as their open end or box counterpart.

Just put a regular open ended wrench on the line fitting you’re interested in. Whatever size open ended wrench fits will be the correct size for the line wrench.


Have a look in the front of a Haynes repair manual for that vehicle. It will tell you what tools you need.


i don’t recommended NOT using them. you will find that brake lines in particular are always a little undersized (due to rust, and decay) and the regular wrench will round them off almost every time.

think of it like this… a regular wrench only bears on two corners of ANY thing you are trying to undo.

a flarenut wrench bears on three or four sides at once. and they almost always get the fitting off.

you can get by without it, but they are not that expensive, and since you are attempting to get into fixing up an OLD car i am guessing you will really find them useful.

a set of them cost around $35. so it is recommended to get a set, that way you are covered no matter which size you find.


Flare nut wrenches aren’t essential, but they reduce the risk of rounding off these fittings. That’s because the fittings are usually made from a soft metal. So they have a tendancy to round off easier than say the head of a bolt.

Also, before you get into this job, soak all the fittings with a penetrating oil and let the oil work for a couple of days. If you do run into a stuborn fitting, heat it good with a propane torch and then let it cool back down. Doing this sometimes breaks the bond at the fitting threads and fitting to tube.



Thanks everyone and thanks for the tip Tester!

I bought this car with the intention of it being the one I “learn the ropes” on. I chose it because of the availability of parts and the “fun” factor to it. I’ve done some mechanical work in the past, but this will be the first time I really tear into anything. I just got tired of relying on the mechanics and such to do the work. I figure that I’d never learn if I didn’t try.



Tester is right, carefully applied heat will be helpful but I never waited for it to cool down. When it is hot the fitting has expanded and should pop lose easily so why wait for it to cool and contract? If you have the money and time using this toy to learn is great!!