Hello: Mine name is Cindy, and my car is a 1986 Firebird, 8 cyl, 305, carb'ed. I have posted on the Tech/General Engine forum several times as we were reinstalling the car's original carb and intake manifold. Now we are onto the brakes. We have rebuilt both rear drum brakes with all new parts--shoes, springs, drums and cylinders.

The problem is we can't get the wheel cylinders to stop leaking from the connection at the brake line. Tried tightening several times, and still leaked. Today we apparently stripped the fittings and have now ordered new rear brake lines. Will put them on when they come, but wanted to ask for any suggestions or thoughts on why they would keep leaking, and how best to seat them. The fittings appear to have double flare ends, and appear to be metric. I did have the rear brake lines replaced a couple of years ago, and again believe the fittings are metric but unsure as to how to confirm that.

The wheel cylinders I bought were ACDelco, metric. They have a concave bottom at the brake line connection. One of the cylinders does appear to have been replaced, probably a couple of years ago, and that one appears different. First it is smaller in size--width wise, and has a raised nipple, instead of a concave bottom. Does this indicate SAE thread? Anyhow probably wasn't the right cylinder bc of its size--width wise.

Any help would be most appreciated.

 

One more question. Any suggestions on how to plug the brake lines for a couple of days until the new brake lines come in. Thanks again.

 

I am wondering if the auto parts store gave you the wrong wheel cylinders, pre-85 cars had SAE fittings, and late '84 onward had metric fittings. The only other thing I can think of is the fittings being cross-threaded when you put the lines back on.
You could probably slip some Zip-Lok back over the ends of the lines with zip-ties or rubber bands to temporarily seal them off...

 

My best guess for the leaking is a parts mismatch of some variety. You can clamp the soft lines closed with vise grips, try to apply the minimum amount of force needed to stop the flow so you don't crush the rubber. Otherwise you can slip a rubber hose around a hardline and clamp that.

 

Normally, such brake line connections are rarely a problem. You've been sold the wrong parts (probably the wheel cylinders), not an unusual occurrence when buying parts for a 37-year-old car.

 

Golf tees (or similar) work.

As for which fittings, see the picture. The metric are bubble flare, which have a concave section in the wheel cylinder. The SAE are double flared and have the raised cone in the wheel cylinder.

The key to which is which is in the threads, note the SAE start right at the tip of the tube nut. whereas the metric bubble flare has a short section with no threads.

As previously posted, IIRC, '85 was the cross-over year from SAE to metric for the brake lines/fittings.


RBob.

 

I know, never read about a problem seating the brake line fitting to the wheel cylinder. Thought once we had gotten the clamp onto the back of the wheel cylinder we were good to go. No problems installing the shoes or springs, or the rest of the hardware.

I don't think I got the wrong wheel cylinders. I ordered them rom RA, and they are ACDelco 18E1279.

Mismatch is what I was thinking. But how do I confirm that. Tried a SAE threaded wheel cylinder on line and it didn't seem to fit (of course this was after we had stripped the fitting--so maybe that is why it didn't fit). As I said, the front to rear brake line was replaced, not by us, about three years ago, along with the trailing hard brake lines to each drum, and the middle rubber hose. They said they had bent the lines them selves, so I guess one possibility is the wrong flares, or just bad flares. I think that is all they replaced at that time. I followed the brake line to the front, where it goes into the valve and that was not replaced by them.

I also think the rear pass side wheel cylinder was replaced after that. As I said in first post, it was smaller in size and had a different seating bottom for the brake fitting (like a raised nipple) than the wheel cylinder on the rear driver's side (had a concave seating for brake line) that looked ancient---been there a long time. The only other thing we noticed was that there were two different bolt sizes for the brake line fittings. One side was 3/8 and the other was 11 mm (however both sides leaked so I am not sure that is very helpful--but certainly odd).

My problem now is worrying that when we get the new metric rear brake lines, with new wheel cylinders (so one would think that will solve the mismatch btw the brake line and wheel cylinder), and try and screw them into the middle rubber hose, that's going to be a mismatch.

Any suggestions. I guess one of my questions is how close are the SAE threaded lines and metric lines. Is it possible to screw say a SAE threaded brake line to a metric threaded wheel cylinder, and it feel right, or would you immediately know the threads don't match. Also, I hate to go there, but thought maybe I should replace the whole thing. I have the rear brake lines on their way, and could go ahead and get the front to rear line. How hard is that to do. Keep in mind I am a newbie at jacking a car up, and putting it on stands (though we have accomplished that) but have no desire to now crawl under the car and start wrenching. Maybe one day I will get the courage up for that, but considering how things are going wrong at every turn, I am most reluctant.

Thanks for the initial responses.

 

Thanks RBob--the pics are helpful, as was well as you confirming the seat bottoms of the SAE and metric wheel cylinders.

 

Ok, the mystery is solved. Well, at least part of the mystery. Per what Rbob offered, prior to us doing any brake work, the passenger side had a metric fitting on a SAE wheel cylinder, and on the drivers side there was a SAE fitting on a metric wheel cylinder. Yes, mismatch everywhere. We also noticed that on the new brake lines we got (haven't put them on yet), it is a bubble flare (and I believe that is correct), and the fitting does not go beyond the bubble flare (whereas on the old set up the fitting slid right over the flare). So we have new brake lines, new wheel cylinders (thinking that when we stripped the fittings we probably also messed up the threads on the wheel cylinder) and a new middle hose (just in case those funky fittings that were on the line also messed up threads at the junction box. I am hopeful.

 

Glad you got it figured out. My first guess was a mis-match...

 

Thanks T. L. You've been a lot of help

 

out of curiosity, where did you get the new brake lines from?

 

I got them from Classic Industries. Very nice lines. Good bubble flares. The drivers side fit perfectly. The passenger side we had to bend the end a bit more towards the wheel cylinder, but we also had trouble figuring out exactly how the line was supposed to run around the pumpkin. Think we got it pretty close but that bend we had to do may have been bc it was a little off. We paid extra for two day shipping, and lo and behold 48 hrs after we ordered it from California it was delivered to me on the East Coast. I would also consider Classic Tube (got my fuel line from there--very nice) and Inline Tube--first rate operation. Hope that was helpful.