Ready to bleed brakes from dry-any tips?

[kings1527]

I don't follow. If the brake master sits level while in the car, how is it going to be a benefit if you bench bleed it while it's level outside of the car?

[Trstno1]

So, I allowed my brake master to run dry when I took the rear suspension apart. When I put everything back together, I filled up my motive bleeder and pumped it up to 15psi. It of course filled the brake reservoir with fluid. I then bled the rr, rl, fr, then fl last. Everything seemed fine until I pressed on the pedal. The pedal seemed more spongy than normal and made a click noise at the end of the brake pedal press. I do have brakes, they just seem a little weak, and of course now I have a notable click noise at the end of the brake pedal press. I assumed I still had air in the system. Then I started wondering if I should have started the bleeding process by bleeding the master brake cylinder first somehow. I just figured I would throw it around the forum prior to opening things back up and attempting to bleed again. Last year I replaced the brake booster, brake master cylinder, and all calipers. My brakes were awesome then. No so much now..... hopefully I didn’t screw up any of the parts I replaced by bleeding the brakes improperly. Any ideas?

[DMC-81]

Hi there, I think you still have some air in the system. When I bled both the brake and clutch systems after replacing components I had to do it a couple times to get a hard pedal feel.

[Trstno1]

Hi there, I think you still have some air in the system. When I bled both the brake and clutch systems after replacing components I had to do it a couple times to get a hard pedal feel.

Yeah, that's what I thought. Ill do it again. Thanks!

[hippieman9]

I would recommend bench bleeding the Master Cylinder, as others have said. Then once you install it, Start at the rear of the car with the Caliper that is furthest away from the master cylinder. Then work your way towards the master cylinder. So start with Right rear, Then left rear, then Right Front, then Left front. Making sure to top off the master cylinder between each caliper. Just don't let it run dry and you should be good.

[DMC-Ron]

We've seen a couple opposing recommendations for the order of bleeding when using a pressure system. One has us bleeding from the caliper closest to the master then proceeding in order to the furthest caliper. The other just the opposite from furthest to closest. Does anyone know the reasoning for one verses the other when using a pressure bleeder?

Ron

[David T]

Having done it all different ways, on a Delorean it really doesn't matter all that much. What does seem to matter the most is to bench-bleed the master cylinder before all else if starting "dry". Next important thing is to NEVER allow the master cylinder to run dry during the bleeding process so refill after bleeding each wheel and bleed the system twice. Choose whatever order you like but be consistent so you don't skip a wheel. Do not assume this advice to be universal, other make cars are very specific about the bleeding order, especially if they have ABS. Other important things to consider are;
Don't spill brake fluid, it works great at removing paint
Never reuse brake fluid
Dispose of used brake fluid properly
Only use Castrol DOT 4
Replace any missing or damaged bleeder caps
When bleeding a 5-speed don't forget to do the clutch too.
Should be done at least every 2 years
If using a pressure bleeder use the least pressure necessary so you don't blow up anything, the reservoir was not meant to have ANY pressure on it.
Test the level switch to make sure it will warn you of a low level. Too many Deloreans don't even have the wiring plugged into the switch!

[Ron]

Even with a pressure bleeder it is probably a good idea to bench-bleed the Master before trying to do the whole system. My method is to bench-bleed and then, using a "One Man Bleeder" I do the L/F, the R/F then the L/R and finally the R/R

The fact that it sits almost level allows a bubble to sometimes get stuck in the nipple coming out of the plastic reservoir. A pressure bleeder *should* be able to handle that. I don't use a pressure bleeder so that is maybe why I have to bench-bleed the thing.

I suspect the reason you have to bench bleed is because you aren't following the sequence that the manual says "MUST" be followed. (See Below)

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I've had sever different power bleeders and the instructions always said to use the factory recommended sequence. For a D, the manual says, "When bleeding the brake system it is important to start with the longest length of hydraulic line first." It continues, stressing the point with, "...the following sequence MUST be followed:", and calls out RR, LR, RF, LF (like most cars).
All of this (including using a power bleeder) is in the WS Manual L:11:01.

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Ron,
There are several reasons to do the longest line first [per hydraulic circuit]. It gets the most air out of the lines and MC the quickest. (With manual bleeding, this makes the pedal strokes more productive too, since air compresses...) But mainly, it reduces the amount of air passing junction points leading to previously bled branches, reducing the potential for air to float or be pushed into a line previously bled. Now, if there is only one junction in the circuit, this still applies because the longer line potentially holds more air to be pushed back beyond the junction when the pressure is released and the air expands (which fluid doesn't do...).

[David T]

The length of the lines running to the rear are about the same so does it really matter which side you do first? And what difference would the order make to the master cylinder as far as bleeding it? As I said, I have tried bleeding several different ways, they all work once the master cylinder is bled. Another point to make, if you are flushing and bleeding a car that has not been done in a long time, if you stroke the master cylinder ALL the way to the floor you will be pushing the seals into an area of the bore that they don't normally reach. It that area is all corroded you tear up the seals and the master cylinder will start to leak. If you think that will happen use a block of wood under the pedal so you can't push it all the way down. If the car sat a LONG time the pistons in the calipers will be all corroded and once you start driving and wearing the brakes, the seals will start leaking when they move over the corroded area of the pistons. Bottom line, if you have a car that sat a LONG time, flushing is not going to help you anymore. If the old brake fluid is dark, thick and nasty you will be rebuilding the WHOLE brake system. If a 5-speed the clutch system too.

[Ron]

The length of the lines running to the rear are about the same so does it really matter which side you do first?

Regardless of line lengths, it matters because the order given in the manual is stressed, twice.
(See above)

And what difference would the order make to the master cylinder as far as bleeding it?

Probably none IF the first one you do purges the master cylinder.
(The longest will -- Always has for me.)
BUT, if you bleed it, you need to bleed all of the calipers...That's where their reasoning takes over...
(See above.)

It that area is all corroded you tear up the seals and the master cylinder will start to leak.If you think that will happen use a block of wood under the pedal so you can't push it all the way down.

If I think that is going to happen, the master cylinder is coming off!