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I have the fuel tank out (replacing) and see an opportunity to access and replace the rear brake lines and rear brake hose assembly on my '70 Cutlass Conv't. Looking for some experienced feedback on whether I should go ahead and "fix it even though it ain't broke." The rear brake lines on the axle appear easy enough to remove and replace. However, the rear brake hose connection to the main rear brake line is the one that concerns me. Is the rear brake hose and main brake line connection likely to be an issue? The car has dual exhausts and the frame clip and connection is tucked up above the muffler and is a little crusty. The rear brake hose does not appear to be dry-rotted. (The car has been garaged for the last 40 yrs.)
Anyone who has experience with this specific connection I'd appreciate your input. Thank you in advance.
You don't need to replace all the lines, just the hose, it can be bought at your local parts store. Break the connection at the line on the body side, then remove the clip. Then break the 2 connections on the rear end and remove the line (there is a bolt that needs to be removed to get the rubber line off the bracket). I use a crescent wrench on the hose side to keep everything from twisting. Reassemble following the steps in reverse. Do not use antiseize, thread compound or teflon tape on any of the connections. I recommend getting an inexpensive set of line wrenches for the job.
You can get these at Loews for around $20.
The biggest problem you will have is if the flare nut is rusted to the tube on that main line. If you try to unscrew it and the tube starts twisting, immediately stop. What I do in that situation is to pull the clip that holds the fitting on the hose into the frame. You can usually push the hose fitting (with hard line still attached) back out of the indexed hole enough to clear the flats that keep it from rotating. Now you can hold the flare nut with a wrench and spin the hose, loosening it. The trick here is to break the hose loose from the flare nut and back it off enough so that you can use penetrating oil in between the flare nut and the tube to break loose the rust holding them together. This may take some effort, but the alternative is replacing that entire main brake line. If the flare nut won't budge, you can thread the new hose onto it the same way, but it is highly likely that the flats on the end fitting won't line up with the hole in the frame. I DO start the flare nut in the hose before I push the hose fitting into the frame hole, however. This eliminates the chance of cross-threading.
By the way, I've done this same thing when replacing wheel cylinders. Frequently the flare nut on the hard line is rusted to the line. Unbolt the wheel cylinder and pull it outboard from the backing plate just enough so you can hold the flare nut and spin the wheel cylinder to loosen it.
My concern is exactly as you state, Joe - the rusted connection at the main line. The alternative - replacing the entire main brake line - is not appealing and frankly unnecessary. I'm just trying to do preventative maintenance by replacing the 50-year old brake hose, and the crusty rear axle-mounted brake lines, but I don't want to cause a main brake line replacement.
I have line wrenches. I would use penetrating oil (PB Blaster). If I get in a jam, is using a little heat on that brake line connection a no-no?
I've avoided heat on brake lines. I've found that once you get the flare nut unscrewed from the fitting, you can usually break the rust loose between the flare nut and the tube with some care.
I've been surprised more times than not that the connections come apart with no trouble. Then again, most of the cars I work on are southern ones, my car is from Washington state and had little to no corrosion.
I've been surprised more times than not that the connections come apart with no trouble. Then again, most of the cars I work on are southern ones, my car is from Washington state and had little to no corrosion.
I've similarly been lucky specifically with the connection from the hard line to the rear brake hose, possibly because that one is somewhat protected.
This is great input guys. I'll order the brake hose and hose clip, and apply penetrating oil to start. Appreciate your sharing knowledge and experience.
The flare nut on the hard brake line to the rear axle brake hose is rusted such that it is no longer size 7/16". After clearing off the surface rust on the hard brake line nut, the 7/16" line wrench has too much play to even try to loosen the connection - it would strip the nut for sure. The 3/8" wrench is too small for the nut. Not to be deterred, I'm going to get metric line wrenches, perhaps an 11 mm or even 10 mm, which are slightly smaller than 7/16" but larger than 3/8". Failing that, my only choice short of complete hard brake line replacement is Joe's method of moving the hard line into the rear space and use vice grips on both the nut and the hose end connection.
Last edited by Toms cutlass; March 17th, 2020 at 12:38 PM.
Yes, I've had to use the 10MM wrench before. And I've nearly always had to pull the wheel cylinder outward when that happens. Of course, if the flare nut is rusted that much, you're dangerously close to replacing the whole line. You may want to bend up the retainer on the axle housing closest to the wheel to put a little slack in the hard line before pulling the wheel cylinder away from the backing plate.
Joe, remember this is the connection of the main hard brake line to the flexible axle hose line on the driver's side up above the muffler through the frame, not the connection at the wheel cylinder.
Joe, remember this is the connection of the main hard brake line to the flexible axle hose line on the driver's side up above the muffler through the frame, not the connection at the wheel cylinder.
Sorry, I forgot that. Yeah, pull the clip, use a vice grips. On my 67 I had to unbolt the first couple of clips on the hard line.
If the flare nut is that rotted, it seems silly to continue to use it.
Cut the tube about ten--twelve inches back from the flare nut. Examine the inside and the outside of the cut section. If the inside of the tube isn't rusty, buy a one-foot, pre-flared section of brake tube, an inverted-flare union, and an extra flare nut at any real parts store. Double-flare the cut end of the main tube, use the inverted flare union to connect the original tube to the foot-long section you just bought. Now the flare nuts are brand new, the flares are new, and the NEXT time you need to service the brakes, they won't be rotted. Flush the brake fluid until it's new-looking at all four wheel cylinders.
If the inside of the cut section of tube IS rusted, you need to replace the entire tube, perhaps all the way back to the master cylinder.
For the record, I do use anti-seize on the outside of the tube and the threads of the flare nut(s). Might as well make the next time easier. As long as you don't get anti-seize in the brake fluid, you're fine.
Last edited by Schurkey; March 17th, 2020 at 07:43 PM.
Good point, Schurkey, I was thinking about splicing a section, what it would involve, etc. Thank you for your input. I'd be uncomfortable with a splice, especially having no experience flaring the line. If I go to all that effort, I'd rather just replace the whole front-to-rear brake line. I started looking at that option tonight, for the reason you mentioned (flare nut eroded). I replaced a front-to-rear brake line many, many years ago on a '70 Cutlass coupe, and I did the line bending.
Now with extra time available, I may just replace the whole main brake line, rear axle lines and rear brake hose. Anyone with experience / tips on installing the long, pre-bent brake line, threading it through the chassis?
I'm removing old & installing a new rear main hard brake line. I want to replace the brake line clips as well. I will replace the line clip (part #3952717) near the rear upper control arm bolt. Then there are 3 other clips along the inside of the frame rail leading up to the front of the driver's side wheel opening to hold the line to the front connection at the proportioning valve. Can anyone confirm that these 3 frame rail clips are push-in type line clips? The Assembly Manual shows a sketch of the face of the clip only with part #1380949. (The Assembly Manual notes this clip was Lansing plant only - where the convertible was built.) There are 2 types of these frame clips; push-in and rivet. I don't want to remove the brake line clips and discover they are riveted onto the frame. Thank you.
Last edited by Toms cutlass; April 28th, 2020 at 02:15 PM.
I wanted to replace the entire rear brake line front-to-rear. The chance you could take is replacing the rear hose and rear axle lines on a rusty main line only to have the main line fail - as you apply the brakes on the road. (See Schurkey's post #14 above.)
My442, when you replaced the main line to the rear, did you re-use the old, crusty frame brake line clips? My question: If you replaced the clips, were the frame brake line clips push-in or riveted?
March 10th, 2020, 02:58 PM
I'll try the metric 'trick' first ... thanks again Joe.
