Brake Flush (1 Viewer)

My '97 with 116,000 miles is showing signs of a brake fluid leak, and after topping up the reservoir it looks to have some air in the system now. When the leak is found and repaired (I have not been able to find a leak yet?) is it as well to drain the system and add all new fluid, or is likely to get more air trapped and be unnecessary?

Michael

Brake bleed

I just did a full bleed on my 94 LC last weekend, very simple. I could walk you through the procedure if you need. I changed the front pads and bled the entire system in about an hour (with helper pumping brake pedal). I would start with a bleed first, you might just find your leak at one of the bleed points.

Riley

If the fluid is less than a year old, just bleed until the air is gone and the pedal is firm. If the fluid is older than a year, flush the entire system until no dirty fluid appears at the calipers. You should do this every two years anyway, so get it done now and be happy.

John Davies
Spokane WA

John E Davies said:

If the fluid is less than a year old, just bleed until the air is gone and the pedal is firm. If the fluid is older than a year, flush the entire system until no dirty fluid appears at the calipers. You should do this every two years anyway, so get it done now and be happy.

John Davies
Spokane WA

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Agree! I recently bought a bleeder kit so I could do it alone. Best $50 ever spent. Screw on to you master cylinder fluid tank and pump it up. As you bleed the brakes it adds new fluid to your tank. So damn easy. I switched to a Valvoline synthetic brake fluid that exceeds dot 3 and 4. My LC is next up for a flush.

Driley said:

I just did a full bleed on my 94 LC last weekend, very simple. I could walk you through the procedure if you need. I changed the front pads and bled the entire system in about an hour (with helper pumping brake pedal). I would start with a bleed first, you might just find your leak at one of the bleed points.

Riley

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I'm about ready to change my front brake pads. If you can provide a small walk through (Write-up) on the bleeding procedure, it would be appreciated.

Are you sure it's leaking fluid? The pads may be worn.

Dan: I got new pads from you less that 9,000 miles ago so I doubt it but will check when I bleed. The reservoir was about 25% down a few weeks ago but since filling up it has not dropped again, even thought break efficiency is getting worse. It now requires one down push to prime system before brakes work. Booster is air tight.

Michael

Walk Through

Ok, I hope I do not leave anything out. Open hood and remove the brake fluid reservoir cap and place a collection pan (I just used a cut down milk jug) to catch any spilled brake fluid (might not be necessary, but when you compress the caliper pistons, fluid level may rise).

Loosen lug nuts then jack up front end (use good quality jack stands at each end of the axle-before the knuckle). I just jacked up both sides and put stands under the axle and positioned the jack at the center of axle for peace of mind. Remove the wheels (have a breaker bar or long lug nut bar - mine were obviously too tight - just had new tires installed at Tire Factory 2 months ago).

I started on the USPS. Looking at the rotor, the brake caliper is on the left. Get a good light and examine the back side (left) of the brake caliper. You will see a thin little bent wire clip holding 2 guide pins (each pin approximately 4" long) that hold the pads in. Do not pull the clip out of the guide pins just yet. Using a pair of needle nose pliers, I pushed the middle of the bent clip out of the hole at the center rear of the caliper gently. You will have to flex the clip a little-just be gentle! Once it is out of the hole, use the needle nose plyers to pull the clip out of each pin, again gently (I had read that if this breaks, you need to replace before driving - after looking at it, I would think that 2 cotter pins (1 per guide pin) would also work. With the bent wire clip out and placed in a safe place, put your hand on the flat metal spring clip that holds onto both the upper and lower guide pin shafts. Slowly pull the upper guide pin out and catch the flat metal spring clip (it will pop out if you do not have your hand on it. Remove and replace 1 pad at a time. I started with the outer pad. I then used 2 channel lock pliers and slowly squeezed the brake pad watching both pistons on that side slide into the caliper housing. Once the pad is loose, you can remove it and then compress the pistons until you can get the new pad back in. Mine went in very smoothly and I did not have to apply too much force. I was able to use the original shims (they have little tabs that help them stay on). If you do not have them, use the ones that came with whatever pads you bought (I used Napa pads until I do the front axle service and put new rotors in and then go with the 100 series pads). After compressing the pistons and inserting the new pad with shims, I inserted the guide pins back just enough to hold the new pad in place while I change the inner pad. Once you have done the same procedure with the inner pad, slide the lower guide pin all of the way through to hold the bottom of both pads then put the flat metal spring back on the lower guide pin and hold it in as you slide the upper guide pin all the way in. Reinstall the bent wire clip carefully. You are done with that side! Do the other side the same way.

I have not changed the rear pads yet (still pretty good condition), but I assume it is pretty straight forward like the front.

Now for the bleed procedure. Make sure that you have at least a full quart of dot 3 of better fluid ready. Have about 2 feet of 1/4" clear tubing. Make sure that the brake fluid reservoir is full then lay down under the PS rear, right in front of the tire and look back at the axle/brake area. You should see the bleed nipple poking out towards the top of the caliper (my back ones had the little dust caps on them. Clean the nipple off and put the box end of a 10mm combination wrench on the nipple. Slip the 1/4" clear tubing on the nipple and put the other end of the tube into a container (at least a quart size unless you want to dump during the procedure). I had a little dot 3 fluid from another container and poured it into the catch container and held the tubing in the fluid to minimize the risk of sucking air back into the nipple. Have an assistant pump the brake pedal until it is stiff and then with verbal commands, have the assistant press on the pedal as you open the bleed nipple. Once the pedal is almost down to the bottom, close the nipple. Only a few tablespoons (about half of a 2' length of 1/4" tubing) come out at a time, but flow was smooth and predictable. Have the assistant constantly check the level at the reservoir and refill when necessary. Repeat this procedure as many times as necessary until the fluid that comes out of the nipple is clear (mine was dark green at the start, then clear). It took about 30 cycles (press on brake pedal/open nipple/fluid out/close nipple) to get all of the fresh fluid to come out.

Move to the DS rear and repeat procedure (it should take fewer cycles to get the old out).

Move to the the LSPV (it is located directly forward of the DS rear axle, mounted to the frame/body). Some of these will be corroded (I had looked at a 92 LC before buying my 94 and the LSPV (did not know what it was at the time) was just a hunk of rust! I did get air out of this, so spend some time and cycle as many times as necessary.

Move to the PS front and then to the DS. The whole idea is the start at the farthest bleed point from the master cylinder and work your way home. All in all, it was a very easy procedure and took about an hour to change front pads and bleed the whole system. The brakes were spongy for about a day after, but stiffened up after that.

I went through about the whole quart of dot 3. I was scared to attempt this without the FSM, but just read every post I could find and dived in!

I hope this helps and please let me know if I left anything out. I know that there are some short cuts, but just wanted to do it slow and get it right for a newbie!

Riley

Thanks Driley!

Yeah, thanks!

Hurry up and do the rear brakes so you can write that up too!

You don't mention bleeding the master cylinder. And what is LSPV as in when you say "Move to the the LSPV (it is located directly forward of the DS rear axle, mounted to the frame/body"?

LSPV = Load Sensing Proportioning Valve, which senses rear suspension compression by means of a mechanical arm to adjust an internal valve that splits brake force front to rear. Take a look at the brake lines in the area described (rear axle on driver's side - follow brake lines) and you'll see the arm and a box. The box has a bleeder valve on it just like the 4 calipers.

DougM

Thanks Doug, I was just looking for the old post that had the definition.

Reply to MH_Stevens: I really did not want to mess with the master cylinder. Maybe someone more knowledgeable than me could post up the procedure.

IdahoDoug said:

LSPV = Load Sensing Proportioning Valve, which senses rear suspension compression by means of a mechanical arm to adjust an internal valve that splits brake force front to rear. Take a look at the brake lines in the area described (rear axle on driver's side - follow brake lines) and you'll see the arm and a box. The box has a bleeder valve on it just like the 4 calipers.

DougM

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Don't forget to re-pack the LSPV bearing!