Brake pedal Squishy and needs to be pumped after bleeding.

2001 VFR800 (no abs), 55,000mi

Hello friends, long time lurker, first time poster. I'd like to start by saying I know 100% this topic has been covered before, but I do not have the usual symptoms in the rear brake. I have a full dealers book and have followed the bleeding steps to a "T" and I have watched multiple videos as well as read multiple posts about bleeding the linked system.

We did the usual procedure following the steps for the fronts (lever) and had no issues. Fronts feel great.

We did the steps as follows for the rear (pedal):

1. bleed right middle
2. bleed left middle
3. remove left front caliper and hold at an angle, use smc to bleed rear mc via pcv valve under tank
4. bleed rear center
5. bleed rear outer

Rears now have to be pumped before pressure is felt on pedal.

I thought I must have miffed something so the next day, after reading several forums here and elsewhere, as well as rereading the dealers book and watching videos, I attempted it again. The second time I was much more thorough with the bleeding between the smc and pcv, and still the result is the same. The pedal is completely soft and will bottom out for 1-3 pumps, then will have pressure like it should. I hear a noise at the smc for the first couple pumps, which tells me that it is "building pressure" but it goes away within minutes.

I do NOT have the rear brake lockup that most people write about. This tells me that the smc is good and the rear mc return is not clogged.

Please let me know if there is something that I have overlooked, I'm at a loss here. I've worked on lots of brake systems before but nothing linked like this. I am unsure of what to look at next.

I appreciate your time reading this. Thank you in advance

 

I feel your pain and have had a similar results after working on my brakes.

You don't say if you changed the back pads, but I know from personal experience that it is possible to insert a pad badly and catch it on the edge of the pad spring; the spring flexes enough to push the pad away from the disc and you need to pump the brake a few times to push the pad back to the disc.

Actually bleeding the SMC is also challenging and I enlisted a helper (my wife) as I did not have the required three hands and extra long arms. What we did was:
1. Press and hold the pedal
2. Press on the SMC and hold it in, as you release pressure through the PCV bleeder
3. Close the bleeder, release the pedal and repressurise/extend the SMC with the pedal
and back to 2, repeat as needed

I also have the ST1300 with a similar linked brake system, released a few years later. The bleed sequence for that is slightly different:
1. Remove and tilt the SMC up
2. Bleed through the PCV
3. Bleed the rear calliper (direct line from master)
4. Bleed the front right, then front left centre pistons
5. Bleed the rear (line from SMC)

What I find is that very little fluid will draw through the PCV bleed or the related rear bleed unless the pedal is also pressed; just using a vacuum bleeder is ineffective on its own.

 

Thank you for the reply, the process we used for the smc was to tilt it up 15-20deg and push the pedal down until it fully extends the smc, then open the nipple on the PCV while simultaneously still holdig the brake pedal down and depressing the smc, close the nipple on the pcv as soon as the smc is fully depressed and reset the system. We did this 15ish times both days. The result has been the same. Each time we bled the complete sequence starting with the front right center nipple and working all the way back.

I must be missing air in the system, I just don't know how

 

Ok, it sounds like we did basically the same procedure. Did you change your back pads as well? It is unfortunately fairly easy to do as I described if you do it with the calliper installed on the disc.

For some other inspiration take a look at the ST1300 article. Basically the same brake system except at the back caliper the SMC activates the outer pistons but on the VFR it is the centre piston. https://www.st-owners.com/forums/threads/st1300-brake-maintenance-avoiding-the-pitfalls.135125/

 

Thanks for your reply again! It is funny that you bring up the rear pads - no I did not replace them. Between your last reply and now I was on the phone with a shop in town that said if you bleed these brakes you pretty much always want to do rear pads. This is the first I'm hearing of this, but hearing it twice in like 45 minutes tells me that I should probably do pads as well.. haha. I am thinking Galfer pads. Any opinion?

 

I would not say that you need to do rear pads just because you bled the brakes. My comment was that you can end up with the same symptoms if the pads get badly installed. Personally I like EBC HH pads but the back brake is much less critical than the front.

I forgot to ask, why did you do the brake bleed in the first place?

 

the brake fluid was chestnut color and had particles in it

 

Brake bleeds don't go bad unless you get air in the system. The link that I sent (from the St1300 page) has a few tips on chasing air out of the system.

https://www.st-owners.com/forums/th...g-all-the-air-out-of-the-brake-system.156754/

 

This is the most relevant file.

 

when other things make no improvement, i try a syringe reverse-bleed from the right side front brake bleed nipple up to the mc. [cover any paint and make allowance for excess fluid.] i almost always remove mc from bar and hold it vertically from the lever letting it hang and tapping lightly at the banjo bolt.

i imagine a bleed or full system fill on a linked-brake model would be difficult and slow.

 

if it tears down it's getting de-linked

 

I did that (delink) on my previous 5th gen and Mellow did it before me. I fitted CBR600F4i forks and front brakes and was happy with the outcome, but when they are working well, the LBS is a great system, just a bit unforgiving for maintenance.

 

I just know that the pcv is unavailable now so it will either need to be rebuilt or cleaned and pray that it works, OR I can just de-link. I also know that the smc can have an issue where it "locks" or gets stuck in position and basically removes the usefulness of the system anyways?

I really don't care what system I use, but I don't want to go through this every couple years.

Also I checked out the EBC brakes and will order a full set since I have a 2,000 mile trip soon and new pads is not a bad idea regardless

 

The SMC can get corroded if the rubber boot gets degraded. There is also a one-way check valve and a compensation port in the SMC that can block if the fluid is not regularly replaced. Doesn't seem to be so common on the VFR but the ST1300s (which probably do much greater all-weather mileage) seem to have the seizing SMC and locked brake more often. TBH any brake system will be rubbish if it is not properly maintained, the LBS is just a bit more unforgiving.

I'm not sure I've ever heard of the PCV failing. I have (for S&G) diassembled the delay valve on the front fork; that one is easy enough to clean if you needed to.