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240 Manual brake bleeding taking forever and fluid/air going back in?

ogamer777

ogamer777

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Joined
May 22, 2016
Location
New North Winchestersonville (PNW 425 gang)
1984 242

I purchased and installed remanufactured front calipers, pads and rotors. I also went ahead and purged the brake fluid system and attempted to replace it. Well here lies my problem.

I do not own a power bleeder so I went with the manual bleeding method. I followed the correct order in which to bleed calipers. So as we are bleeding the rear driver side caliper, very little fluid is coming out. I am using a power bleeder bottle to catch the fluid. https://www.ipdusa.com/products/4679/111342-motive-power-brake-bleeder-catch-bottle-1820

What I am experiencing is the fluid/air will go towards the bottle, then once I close the bleeder screw, the fluid and air mixture will still go back into the caliper somehow. What is going on here? I have never experienced this while manually bleeding the brakes. When I have the hose detached, the fluid comes out and I cannot tell if any air is getting in through the bleeder valve. Fluid is going down in the reservoir. We ended up trying to bleed it for long time, like 45 minutes. At one point, it seemed like air was just coming through the hose but like I said before, the air would just go right back where it came from.

What am I doing wrong? This is my first time bleeding brakes on a 240.
 
The Creek Is Rising.

When replacing calipers always install one caliper at a time starting with the fronts and immediately bleed the freshly installed caliper starting with the top bleeder since air rises.

Continue swapping calipers [or lines] until they are all swapped and bled one at a time and no bubbles are coming out.

Then bleed again at least once in the recommended order since that uses the least amount of fluid but it is not magic in and of itself.

Lord help you if you have the front open and bleed the rear sending air out back to be trapped in the proportioning valves.
 
Last edited:
Redwood Chair said:
When replacing calipers always install one caliper at a time starting with the fronts and immediately bleed the freshly installed caliper starting with the top bleeder since air rises.

Continue swapping calipers [or lines] until they are all swapped and bled one at a time and no bubbles are coming out.

Then bleed again at least once in the recommended order since that uses the least amount of fluid but it is not magic in and of itself.

Lord help you if you have the front open and bleed the rear sending air out back to be trapped in the proportioning valves.
Click to expand...


Thanks, Ken. So what should I do if I had lots of air in the system beforehand? I think I tried expelling the fluid out long ago when the brake lines were disconnected.

When I was bleeding the rear driver caliper, all other bleeder screws were closed.
 
It might be a pain but if [ you might need a helper] you open the bleeder, press the pedal down, close bleeder, release the pedal, repeat. this way you don't compress the fluid and trap air. Think of stop and go traffic ,verses an open road.
 
ogamer777 said:
Thanks, Ken. So what should I do if I had lots of air in the system beforehand? I think I tried expelling the fluid out long ago when the brake lines were disconnected.

When I was bleeding the rear driver caliper, all other bleeder screws were closed.
Click to expand...

Always bleed until there is a good pedal before proceeding in any way.



283SD said:
It might be a pain but if [ you might need a helper] you open the bleeder, press the pedal down, close bleeder, release the pedal, repeat. this way you don't compress the fluid and trap air. Think of stop and go traffic ,verses an open road.
Click to expand...

Stone age buy a Motive power bleeder.
 
I used to do this manually on my 240 series. But it always is a long protracted process when doing this manually with a helper. Even when I would be successful. It would still take going around the car three or four times. One tip that helps a lot is to use a small hammer to gently tap the lines and proportioning valve, warning light valve and various bends and areas that can trap air. This will help push the bubbles to the end of the line. Another thing to do is only use the part of the master cylinder that was being used to brake with. Otherwise you may tear a seal and you need a new master cylinder. Also I've had success with bleeding the front calipers first and after both front calipers are working then go around in the standard order.

I alleviated all this work by buying a Motive power bleeder which has served me well for about 15 years. One of the tools that has paid itself back innumerable times.
 
dl242gt said:
I used to do this manually on my 240 series. But it always is a long protracted process when doing this manually with a helper. Even when I would be successful. It would still take going around the car three or four times. One tip that helps a lot is to use a small hammer to gently tap the lines and proportioning valve, warning light valve and various bends and areas that can trap air. This will help push the bubbles to the end of the line. Another thing to do is only use the part of the master cylinder that was being used to brake with. Otherwise you may tear a seal and you need a new master cylinder. Also I've had success with bleeding the front calipers first and after both front calipers are working then go around in the standard order.

I alleviated all this work by buying a Motive power bleeder which has served me well for about 15 years. One of the tools that has paid itself back innumerable times.
Click to expand...

Are you talking about the motive power bleeder with the pressure gauge on it and you just pump it by hand? I think I read you need 20psi to go through the brake lines?
 
ogamer777 said:
Are you talking about the motive power bleeder with the pressure gauge on it and you just pump it by hand? I think I read you need 20psi to go through the brake lines?
Click to expand...

No gravity bleeding works too and is helpful for some things like removing excess air when changing the lines and calipers but for getting a good flow and a timely job the Motive is the right tool.

Also don't forget Art's brake stick when you have the system open to fiddle with things.
 
Redwood Chair said:
No gravity bleeding works too and is helpful for some things like removing excess air when changing the lines and calipers but for getting a good flow and a timely job the Motive is the right tool.

Also don't forget Art's brake stick when you have the system open to fiddle with things.
Click to expand...

Thanks again, Ken. What is this brake stick you speak of?

Would this be the power bleeder you guys have used: Motive Products, European Power Brake Bleeder, 0100, Hand Pump Pressure Tank with Adapter https://www.amazon.com/dp/B0002KM5L0/ref=cm_sw_r_cp_api_i_jc1aFbHAR43HH
 
Yes IPD has the motive too.

https://forums.turbobricks.com/showpost.php?p=6073280&postcount=14

brake48.jpg
 
Oh and if you do get air trapped in the rear proportioning valves get the back end of the car as high as you can safely and tap on them with the plastic handle of a screwdriver while the fluid is running so you don't completely destroy the undercoating.
 
Yes, I was referring to that model of Motive. Also I use about 15psi to bleed. I used to use 20psi but it works better with the lower pressure.
 
Does the same thing happen with all four? Are you sure the new calipers aren't defective? Bleed screw not sealing? I had sooo many issues with the ones I got from FCP and had to replace them again to get the car to bleed.
Or is it just so full of air that manual bleeding isn't pushing fluid to the calipers?

I pulled all four at the same time, replaced them, bled them, drove for a week, bled again, and they were ok. That said I still have a weak pedal, so maybe some air is still in there somewhere 10 years later. Didn't know to only do one at a time to avoid air entrapment.

Motive bleeder is worth the money if you don't always have a helper.
 
Did you replace your old brake hoses?

I have bled numerous brake systems with one helper and pedal pushing method. Never followed bleeding sequences, just go around a few times and its done. With a clear hose it is visible how bubbly the fluid that comes through, and also can be heard nicely if the environment noise is low.
My technique to avoid air going back into the caliper is pretty simple, i just ask my helper to say with simple words when does he/she actually started to push the pedal and then stopped. This way i can close the valve exactly when fluid is actually coming out.
Never had any problem with this stone age technique, every car passed with great numbers at inspection stations.

As for the master cylinder failure (during pushing it all the way in), I think if its that far done (wear or sludge buildup) then its a good time to change it anyway...
Before pouring in new fluid, i often remove the reservoir completely, wash it with hot water and throw it back in.
 
If you are doing the manual bleeding process and are replacing the master cylinder. Be sure to bench bleed the master cylinder before installation. It is extremely difficult to get the air out of the master cylinder if you don't.
 
neptune said:
Does the same thing happen with all four? Are you sure the new calipers aren't defective? Bleed screw not sealing? I had sooo many issues with the ones I got from FCP and had to replace them again to get the car to bleed.
Or is it just so full of air that manual bleeding isn't pushing fluid to the calipers?

I pulled all four at the same time, replaced them, bled them, drove for a week, bled again, and they were ok. That said I still have a weak pedal, so maybe some air is still in there somewhere 10 years later. Didn't know to only do one at a time to avoid air entrapment.

Motive bleeder is worth the money if you don't always have a helper.
Click to expand...


I threw in the towel after the weirdness with the driver side rear caliper. It sure does seem like the bleeder screw is not sealing.

I got the power bleeder that was recommended, so when it isn't raining I will put it to the test.
 
petiww said:
Did you replace your old brake hoses?

I have bled numerous brake systems with one helper and pedal pushing method. Never followed bleeding sequences, just go around a few times and its done. With a clear hose it is visible how bubbly the fluid that comes through, and also can be heard nicely if the environment noise is low.
My technique to avoid air going back into the caliper is pretty simple, i just ask my helper to say with simple words when does he/she actually started to push the pedal and then stopped. This way i can close the valve exactly when fluid is actually coming out.
Never had any problem with this stone age technique, every car passed with great numbers at inspection stations.

As for the master cylinder failure (during pushing it all the way in), I think if its that far done (wear or sludge buildup) then its a good time to change it anyway...
Before pouring in new fluid, i often remove the reservoir completely, wash it with hot water and throw it back in.
Click to expand...

I did replace the front rubber hoses for some stainless braided hoses. I have the two replacements for the rears that go aft of the proportioning valves, too.

One thing I did forget to mention was I replace one of the hardlines that goes from the octopus (brake distribution block) to the passenger side front caliper, the aft one, with a used line. I wouldn't think that would matter but worth mentioning.

I did the same technique as you described...for close to 45 minutes...
 
I never heard of the replace one, bleed one method. It was probably covering some other problem, and that's what we have here.


If the OP actually observes that the air bubbles move backwards toward the caliper even after the bleeder valve is closed, then he has a faulty bleeder valve OR his bleeder hose is not sealing tight enough around the valve. Obviously, the end of the bleeder hose must be immersed in brake fluid, not just hanging in the air. I used a pretty cool and simple method for years using the spare tire for "power bleeding". Then I got the cool IPD unit. Even then you might have to struggle with the master cylinder sometimes. Be sure to observe the correct bleeding order: RR, LR, RF, LF on American cars.



I have a TSB somewhere that states that problems arise if bleeding is not performed after a brake pad replacement. It claims that pushing the pistons open forces dirt into the brake lines. Just a thought.



-L
 
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