New Brake Fluid Reservoir / Expansion Tank

[Patrick]

Recently tried to flush the brake fluid with a pressure bleeder. It uses a chain to hold a top on the fluid reservoir/expansion tank. That doens’t work at all well, didn’t hold well, brake fluid went everywhere. On the other cars I look after there’s a screw on cap type that works really well with the pressure bleeder.

The reservoir that’s been on the car since building it was from Marlin, I don’t know what car it’s from but I can’t find an adapter for the pressure bleeder. So the next best thing was to change the tank for an OE BMW one that works with the bleeder.

The new part is from a 1972 BMW E21 BMW Part 34321112399 – ATE Part 03.3508-5851.3. It doesn’t come with a level sensor, for that I used a newer part from an E9X BMW part 34336774451. I had to modify the expansion take slightly to allow clearance for the sensor. It is about 0.5cm longer than there is room in the expansion tank, just meant chopping a small amount of the wall between the front/rear fluid chambers. There is a sensor specifically for the E21 tank 34321153157 but I wasn’t able to get one.



Removed this one, set it aside so the system remained closed while creating the mount for the new one.



Cut out an aluminium plate and added some riv nuts in the top to bolt the the tank to. Made sure the tank is level fron to back.



The rear bottom is the same mount as the old one, drilled a hole for the front riv nut.



Transferred the clutch and two pipes over from the old tank to the new one. Added some clips to be sure they’ll stay there under pressure.



Added a new plug on the end of the level sensor wire, this one is off ebay from an E46. Could figure out the part numbers for the plus so that was the easiest way to get one.



Clearance check for battery.



Battery back in, lots of clearance for the bonnet.



View through the louvers



Fluid change should be relatively clean and easy next time!

[Ye Ol Ripper]

Re: New Brake Fluid Reservoir / Expansion Tank

Hi Patrick.

Were you aware that you had another option to changing the brake fluid reservoir?

I mention this purely to assist others that may face a similar problem in the future .

I have used a device similar to the following to bleed clutches and brakes on other vehicles and motorcycles .
It works by vacuum and sucks the fluid through the bleed nipple .
Here's an example and they are very useful if you are working on your car without an assistant.
https://www.ebay.co.uk/itm/324088092...kAAOSw~KxeWmb3

[jon_wilkinson]

Re: New Brake Fluid Reservoir / Expansion Tank

Thanks for the heads up Ye Ol Ripper. I wasn't aware of these and will now be acquiring one as my brake fluid is overdue replacement.

[Tony Stott]

Re: New Brake Fluid Reservoir / Expansion Tank

+1 ^^

[Patrick]

Re: New Brake Fluid Reservoir / Expansion Tank

That's a nice bit of kit, I'd not seen that one before. Good choice for anyone that doesn't want to change the tank.

I've been through 3 brake bleeders over the years (including one suction type that goes on the compressor, that just didn't work well at all for bleed but its good for emptying fluids out of containers) and found the one that fits on the BMW style tank worked very well so I decided to standardise the tank rather than find and buy another bleeder.

I like the athletics better on the new tank so it wasn't just a functional change.

The bleeder I have that works well for me now is the Sealey VS820 - the cap it comes with works great, the universal adpater with the chains you can get for it doesn't work at all well not worth buying.

[Ye Ol Ripper]

Re: New Brake Fluid Reservoir / Expansion Tank

I first used my recommended vacuum bleeder on a MK1 Toyota MR2 approx 20 years ago that has the engine and gearbox at the rear of the car. I had replaced the clutch slave cylinder and that setup being so far away from the clutch pedal was impossible to bleed by conventional methods of pumping the pedal with the help of an assistant.

We had spent over 1 1/2 hours ,so I borrowed one of these off a motorcycle mechanic. ( many clutch reservoirs are rectangular on Bikes with 4 screws , so all the usual kits such out there wouldn't fit).

The device worked well and there is minimal waste fluid whilst bleeding and no chance of spraying your paintwork from a pressurised bleeding device.

Another useful tip of mine that you all will find beneficial is to remove the bleed nipple and wrap white plumbers ptfe tape around the threads. Then ensure you haven't blocked off the bleeding hole at the pointed end . If you have poke through with a pin. Refit your nipple to the cylinder.
The purpose of this is it prevents the bleed nipple from seizing up as this seals the thread from water/salt ingress causing corrosion.

If you use this method you won't shear off anymore brake nipples in the future. I also use the white Ptfe tape on the threads of brake pipes and hoses fitted into:
wheel cylinders ,Calipers, clutch slave cylinders , brake and clutch master cylinders etc.

By the way, you won't find this info in any workshop manual ; but I can assure you it works.

[Patrick]

Re: New Brake Fluid Reservoir / Expansion Tank

Thank you, that's an really useful tip - you're right never seen that one in a manual