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Hyrdaulic Brake Help

9K views 11 replies 7 participants last post by  derekR 
#1 ·
Hey Guys,

I was down at the LHS toying with my fg and noticed several air bubbles in my front right brake line contained in the bend of the tubing heading along the front right arm to the front right calliper.. Anyway I took the car for a quick run down the street and noticed that I had lost 95% of my front braking and a dramatic increase in bubbles which were now half way down to the main cylinder.

I am running FG Magura hydraulic brakes front and rear.

I have never had any dealings with hydraulic brakes any suggestions on what could be the cause of the air bubbles? From the front main cylinder I have individual hydraulic lines to each calliper. Any ideas on causes/fixes? Any info on proper bleeding/refilling/oil types to use to refill would be much appreciated or links to such info would be appreciated. I rang Kellets and was pointed in the direction of Castrol dot 5 to use to refill, no idea what is currently in the lines at the moment as the car was bought second hand.

I have not had any sever impacts on that side but did notice that the outside of the line was oily all along the length of the front arm.
 
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#2 ·
Not trying to state the obvious but you have a leak???? Clean it up, refill and apply max brake pressure until you find the line or fitting to replace.

I run dot 5 in my track bike 1:1 and have braided lines, can you get braided lines for your set up as they stop flex on standard rubber lines when the oil heats up..

Dot 5 is overkill if you cant because it is made to handle high temp... eg twin cbr1000 metal disc brakes..
 
#3 ·
I know its leaking but what components could it be leaking from? Where should i be looking? I havent disassembled a hydraulic brake system before ( and dont have any manuals showing components/exploded views) so i have no idea what i could be looking for to spot the leak? It not visibly dripping out of any part, the line istself is just oily to the touch.
 
#4 ·
If you refill it with no bubbles and really apply pressure with a light viscous oil you will find the starting point and there is no better education than dissasembling and inspecting yourself. Just make a list of how you dissasembled so as to make it easier to re assemble.

Once dissasembled it will soon become obvious what is damaged then post some pics so we can guide you in the right direction..

have fun
cheers
 
#5 · (Edited)
You will need syringe and two bits of tube. One for the end of the syringe to goto the caliper and one to catch the excess from the master. You have to bleed them backwards. Fill the syringe up squeeze air out then fit to the caliper, crack nipples at both ends then squeeze fluid in until all bubbles disapear. Then lock them both up and your right to go. If it's only a couple of bubbles I wouldn't worry to much.
You may have a loose nipple or even the t piece Kellitts sell them.
 
#7 ·
The Hydraulics I have use hydraulic fluid not brake fluid.

There was a notice attached to the kit when it arrived to remind the user that there is apparently a difference, I am using hydraulic compressor oil, which is supposed to have a higher boiling point.

Brake fluid like the hydraulic fluid used in 1:1 cars is claimed to damage the working components of the master cylinder on RC brakes. Not being a chemist I am unsure what the difference is, but have followed the supplied instructions with hopes that the info was correct.

I am guessing that the hydraulic compressor oil doesnt have the same corrosive properties that brake fluid has.
 
#8 ·
Under no circumstances use automotive type brake fluid, it will destroy the o-rings and seals in the master cylinder and calipers. You can use a good quality light machine oil such as singer sewing machine oil or preferably go to http://www.chequeredflagracing.com.au/ and give Colin a call, he's a top guy and knows FG like no other.

If Colin hasn't got the oil or can't offer a substitue then go to http://rc-car-online-shop.de/shop/en/products/fg_9452-9452-fg-hydraulic-oil-50ml-1pce-.html and order a bottle of the genuine FG fluid. If you are in a hurry then PM me and I can sell you one of my spare bottles as I have a few extras and I can replace it next month when I order a few other parts from them.
A few small bubbles are actually desirable as they allow the fluid to expand with heat, without them the fluid can get hot and expand forcing the pads to drag. I thought this a bit strange when I first heard it sine generally air in brakes is a bad thing but automotive systems have an air pocket in the resovoir to compensate for fluid expansion.
Regards
Brett
 
#10 ·
I never saw this thread earlier. Easiest thing to get is the fg fluid from CFR. The other option is to get the fluid that the Citeron's use in their cars with the sit down hydraulic suspension - it has green in its name. It doesn't affect the rubber o-rings like normal brake fluid does.

You don't want any air in the lines , it creates uneven braking, poor release of brakes, loss of brakeing pressure. You can catch and reuse the fluid over and over. At around $35 / 50ml it is worth it. Just let it sit for a while so any contaminants settle to the bottom.
 
#11 ·
Supercheap have heaps of Hydraulic oil, it is Gulf Western brand and comes in 1 litre bottle for around $20 per litre.

I sent an email to the makers of my brake system and they said it would be fine.

Brake fluid has corrosive properties but the Fluid used in Hydraulic Jacks is fine.
 
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