Pressure Bleeding Brakes Via Master Cylinder

[rager]

Has anyone successfully bled their x40 using this method?

I have a pressure tank with tubing attached to a brass fitting which I have screwed into an extra master cylinder cap.

Unfortunately, my cylinder won't hold any pressure?

The moment I start pumping air in it leaks out... Its hard to tell but it looks like it is coming out from around the o-ring connection between the plastic reservoir which holds fluid and the actual metal cylinder.

Any ideas? I have pressure bled other cars with zero issues....

[ww1dm1]

I tried and failed, technically I'm still working on it. The pressure leaks between the cap and and the reservoir (mostly through the two cutouts at the opposite sides). That was a surprise to me, as there is a rubber insert in the cap that suggests the reservoir is airtight. It could be that only the part below the rubber insert is airtight when you screw the cap on. And since I cut a hole in the middle of the insert (still wondering if that was a good idea), it won't seal.

The only solution here is sealing the cap. I used some silicone sealant on the inside of the cap and it definitely helped, but it still leaks a bit, so I plan to simply keep repeating that until it stops leaking.

[druid]

I think it might have been PeireMcalpine (sp sorry dude) that solved it.

[Musicus]

I've got the same problem. Made a pressure bleeder myself but the reservoir is leaking. Don't think it's the 0-ring connection, because then you got brake fluid all over the place.

(sorry for my bad writing, i'm dutch)

[pierremcalpine]

I cobbled together a pressure bleeder that has worked really well for me. Some have accused me of over-engineering though...

I used the reservoir cap itself for air pressure delivery. I got myself a spare cap and drilled a hole through the middle and carefully screwed in a compressor quick-connect adapter (male/male). I was careful to drill the hole just a tad too small so that I could screw the compressor adapter in nice and tight. One important detail about the cap though: it is designed to have some sort of pressure release via the rubber insert. To eliminate the "feature" you have to pull the insert out, cut out the "hat" and keep the "donut" (to be used as a washer). Then you have to seal the channel that exists on the inside edge of the cap itself. I think I used some JB Weld to seal the channel and then I used some permatex for good measure all the way around the washer to get a good seal.

I then got some attachments and a see-through hose and connected the other end to a garden sprayer (which I happened to have sitting around). The garden sprayer is nice because it has two outlets in addition to a pump handle: I used one for the delivery hose to the cap and the second for a combo pressure gauge and schrader valve using a t-fitting from the plumbing store..

Feel free to ping me if you want some pics.

[ww1dm1]

Originally Posted by pierremcalpine

I cobbled together a pressure bleeder that has worked really well for me. Some have accused me of over-engineering though...

I used the reservoir cap itself for air pressure delivery. I got myself a spare cap and drilled a hole through the middle and carefully screwed in a compressor quick-connect adapter (male/male). I was careful to drill the hole just a tad too small so that I could screw the compressor adapter in nice and tight. One important detail about the cap though: it is designed to have some sort of pressure release via the rubber insert. To eliminate the "feature" you have to pull the insert out, cut out the "hat" and keep the "donut" (to be used as a washer). Then you have to seal the channel that exists on the inside edge of the cap itself. I think I used some JB Weld to seal the channel and then I used some permatex for good measure all the way around the washer to get a good seal.

I then got some attachments and a see-through hose and connected the other end to a garden sprayer (which I happened to have sitting around). The garden sprayer is nice because it has two outlets in addition to a pump handle: I used one for the delivery hose to the cap and the second for a combo pressure gauge and schrader valve using a t-fitting from the plumbing store..

Feel free to ping me if you want some pics.

That is pretty much exactly what I did. Wouldn't call it overengineering, just a proper home made pressure bleeder. Only difference is that I didn't fit a pressure gauge. I have one lying around, but it just doesn't seem that useful, my garden sprayer can't accumulate enormous pressures.

Good to know that sealing the cap properly will work. Did you get that mythical rock-hard brake pedal?

[pierremcalpine]

Originally Posted by ww1dm1

Good to know that sealing the cap properly will work. Did you get that mythical rock-hard brake pedal?

Not sure about rock hard but good and solid for sure! the pressure gauge was helpful as I was able to hook up a small compressor to the Schrader end - didn't want to put too much pressure through.

[rager]

Appreciate all the replies!

Managed to get a successful seal using a Motive power bleeder drilled into the cap. Sealed inside of cap using the cut donut method combined with Sikaflex construction sealant, its what I had laying around. Sealed under the donut with sealant and around the lip in the cap. Once i put the cap on I also smeared the sealant around the outside of the reservoir on the portion of the threads where the is a gap, there are 3 sections and it seems like the air always leaks out of one of them. I didnt wait for it to dry just left it smeared while I bled the brakes.

I pressurized to 7psi and the flow at each caliper was strong. I ran a LOT of fresh brake fluid through since my brakes were garbage even though I had all new hardware except hoses.

After two drive/bleed cycles my brakes are GREAT! Not as firm as a 2005 Acura MDX I drove recently but their performance when braking hard is the best I can remember. Very confident braking heavily and repeatedly at highway speeds and I have poor snow tires on. Really pleased that I finally got this to work... Recently had car at the mechanic to look at brakes and all he had for me was pretty much "yeah your pedal feels a little soft and has some extra travel but I can't find anything wrong..." Not sure why he didn't try bleeding... I literally doubled my braking power/ability by pressure bleeding.

[Musicus]

Thanks pierremcalpine!

Problem is solved. I removed the rubber seal and applied some silicone instead. Now i've got an nice seal and the container holds the pressure. I went to 10Psi and thats enough to bleed the brakes.

Here some pics.

Pressure bleeder with a cap for a V40 and one for a S60



Pressure gauge from Aliexpress



The silicone for a nice seal

[pierremcalpine]

Nice work. Mine takes up some valuable room in my small utility shed but every time I have to use it I'm reminded on how painless the brake bleeding is with that contraption on hand!