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Bleeding Dot 5 brakes

Moss Motors
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catlotion Avatar
catlotion Toby M
Leeds, West Yorkshire, UK   GBR
I was getting to that point too. My problems were twofold - the first being a slight weeping leak on the crimp on the rear flexible hose to the axle. It was barely noticeable on inspection but caused micro-bubbles when bleeding the rears. I made the mistake (not for the first time) of assuming that new parts were perfect and couldn't possibly be the problem...

have you definitely checked every union, hose and cylinder? could be a cylinder leaking into the drums perhaps?

My other issue was general agitation of the fluid. This was my fault too and not really believing the experiences of other people to be careful when working with silicone fluid. Because I was being tight and not buying enough fluid I ended up trying to recycle it during initial bleed, which probably aerated the fluid and made the whole job harder.

In the end I've got a good pedal (although quite low) and doesn't need pumping up. Managed to bleed the clutch by using the caliper to reverse bleed. That worked straight away after hours of cursing and even suspecting a faulty master cylinder...

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bobs77vet Avatar
bobs77vet bob K.
northern Va, Va, USA   USA
In reply to # 3535427 by DEklof I haven't tried gravity bleeding, but nothing else has worked to gett good pedal on my A. When I took it out of storage after 25 years I replaced all hoses, the wheel cylinders, master cylinder, clutch slave cylinder and rebuilt the calipers with new pistons and seals (all from Moss). I am using DOT 5 silicon fluid.

After thorough bleeding I still had to pump the pedal to get firm brakes.

I called Moss, they told me to replace the new Master cylinder (under warranty). I did. I have bled the system until my wife threatens to divorce me if she has to spend one more hour pumping pedals. I still can't get a firm pedal without a pump, and the clutch needs to be pumped after the car sits for a few days.

I plan to try gravity bleeding next, if that does not work I may consider switching back to DOT 3. Anyone had any experience flushing the system and starting over with DOT 3?

Dennis

do you have free play at the MC where the push rod goes into the MC?

Blueosprey90 Avatar
Blueosprey90 Jeff Sienkiewicz
New Milford, CT, USA   USA
Toby, now going back to post #24 ...

My Morgan friend, Chris T., throws out a multi-colored parachute when he needs to come to a complete stop. But he has one of those light, three wheel Morgans, and throwing out a parachute to stop the MGA seems like far too much work for the application. Plus you need to watch out for the guy behind, so you don't get the parachute in his face. So maybe not so good in the emergency. But a proper boat anchor for when the brakes fail. You're a savant! But I don't think you said what was the best boat anchor to use? smileys with beer



Firm brakes, but low pedal. The best official way to deal with that is by adjusting the rear brakes. Turn the adjuster nut all the way to the right until the wheels lock up. Then one click to the left. It may help somewhat. I also made some new master cylinder pushrods, maybe 5/8" longer than stock. My stock pushrods were extended so far out that they held on by only a couple of threads. I'm not sure my new pushrods extend out any further, but they are treaded on sufficiently so I don't need to worry about them falling out/off.

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bobs77vet Avatar
bobs77vet bob K.
northern Va, Va, USA   USA
In reply to # 3535434 by catlotion

In the end I've got a good pedal (although quite low) and doesn't need pumping up. Managed to bleed the clutch by using the caliper to reverse bleed. That worked straight away after hours of cursing and even suspecting a faulty master cylinder...
good news on the bleeding....what a low pedal says to me.. check the pushrod up top at the MC and set for less the 1/16" back lash or free play just enough to have free play but no more. and check all brakes for proper adjustment so there is just the slightest evidence of drag

Don MGA 1600 Avatar
Don MGA 1600 Silver Member Don Tremblay
Rutland, Rutland, USA   USA
1960 MG MGA "My Oldest Friend"
1962 Jaguar E-Type "Rich Bitch"
I just finished an extensive front end rebuild and as such and since no one was around to help me, I chose the gravity method of bleeding the brakes.

This will be my 34th year of using DOT 5 with all original Lockheed components.

After bleeding, I had a firm pedal and I didn't have to pump the brakes a single time during the sequence.

I started with a rough bleeding of the two forward caliper's since they were part of the rebuild and I wanted to get some fluid back into the empty lines and caliper. After the rough bleed of the calipers, I followed the conventional sequence of left rear, right rear and back to the left front and right front calipers

The trick was to add a vertical loop (higher than the bleed screw being addressed) coming out of the bleed hose for the bubbles to collect in before descending down into the collection vessel. I also used a fluid tight funnel to monitor the fluid and provide a visual reservoir.

Once I collected the components all I had to do was to crack open the bleed screw and go do something else until the bubbles in the loop were pushed over the top of the loop into the catch container while keeping an eye on the funnel and then move on to the next bleed screw.

Simple and very effective.

Don



Edited 1 time(s). Last edit at 2017-06-19 08:46 PM by Don MGA 1600.


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jonathan in mass jonathan eagle
weston, ma, USA   USA
Don,
Wow, the MGA sits on an oriental rug. Pretty classy. My MGA would be jealous.
How did you get the funnel to seal?
Not sure I see where the following is.
"The trick was to add a vertical loop (higher than the bleed screw being addressed) coming out of the bleed hose for the bubbles to collect in before descending down into the collection vessel. I also used a fluid tight funnel to monitor the fluid and provide a visual reservoir. "
Great photos as usual.
Jonathan

Don MGA 1600 Avatar
Don MGA 1600 Silver Member Don Tremblay
Rutland, Rutland, USA   USA
1960 MG MGA "My Oldest Friend"
1962 Jaguar E-Type "Rich Bitch"
Jon,

The fancy oriental rug was courtesy of a cat we use to have that left its calling card on the rug rendering it useless and thus relegated to the garage as an excellent vapor barrier.

As far as the funnel sealing off: It is simply a run of the mill polyethylene funnel with a tapered snout. I simply pushed it in until the taper matched the ID of the filler neck and it sealed perfectly.

Regarding the hose configuration. Think of the hose confgured as a reverse sink trap. If the loop in the hose is higher than the bleeder screw, but lower than the reservoir, the air bubbles will form in the ascending portion of the loop and eventually be pushed over the top of the loop once they are displaced by the brake fluid. Once this happens, you know that that particular bleeder is air free since the ascending loop is now all fluid and no air.

I am making sense?

Don

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catlotion Avatar
catlotion Toby M
Leeds, West Yorkshire, UK   GBR
I'm liking the carpentry clamp to hold the bottle stable. The amount of fluid I've knocked over on my drive is beyond a joke!

jonathan in mass jonathan eagle
weston, ma, USA   USA
Like this ?

In reply to # 3536275 by Don MGA 1600 Jon,

The fancy oriental rug was courtesy of a cat we use to have that left its calling card on the rug rendering it useless and thus relegated to the garage as an excellent vapor barrier.

As far as the funnel sealing off: It is simply a run of the mill polyethylene funnel with a tapered snout. I simply pushed it in until the taper matched the ID of the filler neck and it sealed perfectly.

Regarding the hose configuration. Think of the hose confgured as a reverse sink trap. If the loop in the hose is higher than the bleeder screw, but lower than the reservoir, the air bubbles will form in the ascending portion of the loop and eventually be pushed over the top of the loop once they are displaced by the brake fluid. Once this happens, you know that that particular bleeder is air free since the ascending loop is now all fluid and no air.

I am making sense?

Don

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Don MGA 1600 Avatar
Don MGA 1600 Silver Member Don Tremblay
Rutland, Rutland, USA   USA
1960 MG MGA "My Oldest Friend"
1962 Jaguar E-Type "Rich Bitch"
Excellent Grasshopper!

RJBrown Avatar
RJBrown Randy Brown
Queen Creek, Arizona, USA   USA
MGAs are a bit more difficult than other cars according to some. The only part I found more difficult was the clutch.
5 MGAs since 1985 and all used DOT5. Quit blaming the fluid. Going to another won't help your technic. SLOW down and do it properly no problem, it is easy. Count 2 seconds for each stroke. When you thrash the brakes you waste your time and piss off the helper. Allowing the small MC reservoir to get empty is a easy and frustrating mistake to make. If it weren't for the internet I would never have realized how hard this job really is.

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