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Bleeding Dot 5 brakes

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catlotion Avatar
catlotion Toby M
Leeds, West Yorkshire, UK   GBR
Can anyone recommend a good way to get a firm pedal with dot 5 please?

We've sorted the clutch out (eventually, after connecting to caliper bleed) but just can't get the brakes right. The first press goes to the floor almost but then it hardens up in subsequent strokes indicating air somewhere.

I've adjusted the rear cylinders so they touched drum then backed them off slightly until free. Handbrake cable is slack.

We've been round the system a few times now and even tried an eezibleed tonight but still the same... Quite a lot of bubbles were coming through rear bleed...

Getting tempted to flush out now and go to dot 4!

The whole system is new btw...

Edited 1 time(s). Last edit at 2017-05-19 01:54 AM by catlotion.

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Aridgerunner Avatar
Aridgerunner Silver Member Bill Bussler
Montoursville, PA, USA   USA
1956 MG MGA 1500 "The A"
1959 Triumph TR3A "The Mistress"
Try the gravity method. A friend of mine swears by it. Fill your master cylinder and let it sit over night with the cap off or loose. The next day open one bleed screw and let the fluid run out watching for air. Close that one and move on to the next one, etc., etc. Do not touch the brake peddle until you have done all four. Make sure the cylinder stays full. Then slowly depress the pedal and slowly release it.

I hope this helps. Personally I 've never had problem bleeding dot 5. I must be lucky.


bobs77vet Avatar
bobs77vet bob K.
northern Va, VA, USA   USA
corvette C3 guys use gravity bleeding all the time.

I used a motive pressure bleeder, its probably best not to recycle the fluid as you do it, the bubbles seem to stay in the fluid for a while. just keep doing it, if you see bubbles its not from the fluid its from trapped air.

you can also let the fluid sit for a day or two and then continue, i read accounts of people thinking that this was the success to their bleeding, their thoughts are there are micro bubbles and letting them sit overnight lets the bubbles accumulate together. I dont know if thats true or not but many people seem to think so.

the only real issue is that the fluid is expensive so you hate to throw out clean fluid that you pass through the system in bleeding it. hang in there and keep doing it.

Edited 1 time(s). Last edit at 2017-05-18 07:15 PM by bobs77vet.

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GILMGA Silver Member Gil Dupre
1962 MG MGA
1974 MG MGB GT
I use the vaccumn method It takes a while to get all the air out of a new system. You have to be careful not to shake dot 5 when pouring in the resevore


copernicus Avatar
copernicus Nick Kopernik
Toby, nothing wrong with silicone brake fluid (many have used it successfully for years; I've been using it for 30+ years), but it is susceptible to bubbles & needs to be used & handles a bit differently from glycol based fluids. Here's a good article from Moss Motors about silicone fluid and bleeding brakes:

perfectpitch Avatar
perfectpitch Charles Windsor (Disabled)
Disabled Account, Antarctica   ATA
Only way to do it is either gravity method or by use of a Mityvac type professional bleeder that hooks up to compressed air line, and sucks on the circuit when trigger squeezed and bleed nipple cracked. Pressure vacuum will be more (over gravity method) likely to knock out air bubbles clinging to brake lines at bends, etc. When using two person way to bleed you end up stroking MC piston under zero pressure (nipple cracked) and that causes more bubbles to form there. When the MC piston is being used to create pressure on the fluid in normal use, no bubbles are getting formed. Bleeding a different matter, and a problem in Dot5 but not other type.

gary s Avatar
gary s Gary Starr
N Illnois, USA   USA
I didn't have any trouble bleeding it either,I used a gunson ez bleed. I wonder if it can be rigged up backwards ie push fluid up from the wheel cylinders to the master cylinder to help any bubbles rise?

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RJBrown Avatar
RJBrown Randy Brown
Queen Creek, AZ, USA   USA
I have never had any issues bleeding brakes. It is the clutch that is tough.
Once filled with brake fluid you can't change from 5 to 4 or 4 to 5. Flushing out is not enough.

catlotion Avatar
catlotion Toby M
Leeds, West Yorkshire, UK   GBR
Thanks everyone. Will try gravity method I think. How does it push it out though? Particularly out of top caliper bleed?

We tried normal two person method first so have probably introduced lots of micro bubbles. We did talk about reverse bleed with eezibleed but thought that would push air up into system initially. Has anyone tried this method?

Edited 1 time(s). Last edit at 2017-05-19 01:53 AM by catlotion.

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bobs77vet Avatar
bobs77vet bob K.
northern Va, VA, USA   USA
gravity. ....basically all the fluid on top of the system is the weight that wants to move to lower territory. and nature does the rest just don't let the MC run dry

jonathan in mass jonathan eagle
weston, MA, USA   USA
I use the gunson ez bleed as well and silicone. My brakes seem good, although not as good as a modern car.
I knew there could be bubbles, but probably more sensitized to it after reading this thread. I'll have to be more careful.

Look at videos on utube.
Bleeding hydrolic clutch mg midget.
There are many good videos that will help.

Gary E Avatar
Gary E Silver Member Gary Edwards
Kernersville, ,N.C., USA   USA
X2 or 5 on Ezi bleed , no problem.


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"

Silicone DOT 5 has many advantages over normal brake fluid, but requires as others have mentioned judicious bleeding and a little forethought.

BTW: I have been using it for over 30 years with zero problems.

A few recommendations.

* I prefer the gravity method. First go out and buy yourself a funnel that between the normal reservoir and the funnel itself will contain a pint of fluid.
* Make sure that funnel you choose has a taper in the stem to provide a leak free fit into the normal fill opening.
* Gently decant the fluid into the reservoir and filling the funnel
* Start by bleeding the rear left, followed with rear right, the front left and finally the front right.
* Any fluid that goes through the system cannot be used for a least a few days to expel micro-bubbles, Instead, buy and extra pint so that the fluid that is introduced into the .funnel is free of bubbles.


catlotion Avatar
catlotion Toby M
Leeds, West Yorkshire, UK   GBR
Thanks Don. Will give that a try. We have returned fluid to master cylinder after bleeding so it's probably full of micro bubbles. It's full now but I've got a new bottle so is it best to bleed the 'old' aerated fluid all out by pumping first do your think?

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