HPP PRX Se pedal problem

[Kek700]

I have some HPP PRX pedals, I really wanted to see if all the positive reviews are justified about hydraulic pedals.
Unfortunatly mine have a lot of initial stiction, you could say a notch‘y start.
After that they are rather good, but every time I press them I have to go through a notch‘y start.
This is very annoying, it spoils their overall affect.
Has anyone got an answer, I have tried silicon spray, i just put it on the master and slave push shafts to some affect, soon back to that notch’y start.
Sorted.

 

[Kek700]

There is a passage that feeds the sensor.
Long shot it may be but it is not impossible that some crude has got in there..

 

[Kek700]

Just to report, no air, very easy to bleed, used mobile1 0W40, second race just done, pedal whilst racing has very low initial stiction, so low, I now do not notice it at all.

 

[Jrehm]

New sensor and wiring should be here tomorrow.
using the pressure bleeder/syringe that blaze talked about was the perfect way to bleed i think. i no longer have 0 movement in the pedal before hydraulics engaged. much much better.

Still looking for a clutch pedal if anyone is willing to sell theres

 

[Neilski]

The pivot on the brake pedal travels on an arc, in this case on the picture it will go down slightly when depressing the brake.
So then the pushrod should exact a downward force on the piston and cylinder wall.
I guess thats why HPP redesigned the cylinder assembly and put it on a swivel so it can stay straight to the movement of the pushrod al the time.

Oh wow, that's a serious "ouch" to look at. What would possess someone to build this and not put the cylinder on a pivot??

 

[Kek700]

I checked that and found that it is at the optimum location in an attempt to eradicate , or should I say limit misaligned due to movement of the piston rod to the master cylinder.
But there will always be some misalignment, but as the rod movement is so small the end result is not significant enough to cause a problem.
My bores were in perfect condition, his latest pedals have a pivot to the master cylinder.
So perhaps heavily used pedals can be problematic for this, but it is most likely that he is just aiming for mechanical perfection in his latest pedal design.
As I have said before you do not need a syringe to bleed these pedals, it takes me two minutes to bleed these as the master cylinder and slave are next to one another, I have bleed them 5 or 6 times with motor oil and brake fluid with no problems at all with air in the system.
My advice is use motor oil, or thin 3 in 1 oil if you must, but 0W30 is perfectly okay , if you get a leak it will not cause any damage, either cosmetic or cause problems to pets and kids.

 

[stigs2cousin]

I checked that and found that it is at the optimum location in an attempt to eradicate , or should I say limit misaligned due to movement of the piston rod to the master cylinder.
But there will always be some misalignment, but as the rod movement is so small the end result is not significant enough to cause a problem.

So possibly the users who experienced problems where on the optional "soft pedal" rubbers?
If the rod travels a longer distance because the resistance rubbers have more give the misalignment would be greater too?

MFG Carsten

 

[Chris Dawson]

As I have said before you do not need a syringe to bleed these pedals, it takes me two minutes to bleed these as the master cylinder and slave are next to one another, I have bleed them 5 or 6 times with motor oil and brake fluid with no problems at all with air in the system.
My advice is use motor oil, or thin 3 in 1 oil if you must, but 0W30 is perfectly okay , if you get a leak it will not cause any damage, either cosmetic or cause problems to pets and kids.

@Kek700 Would you be able to give me some pointers on how to bleed these pedals, with some images? I have partially disassembled them and can't see how to fill the master cylinder and get it to bleed:

If I take the four bolts out of the plate on top of the master there is a reservoir. I have filled this with oil and replaced the plate, opened the bleed nipple, and held the assembly vertical so that the bleed is below the reservoir and the pedal shaft is facing upwards, but no oil flows through. Or do I somehow need to extract the master cylinder piston that the pedal shaft pushes against and fill from there?

Thanks for any assistance!

 

[Kek700]

I did not use the master cylinder reservoir to do any of the bleeding, just removed it, ie the four bolts and plate that you mentioned.

If you have a syringe and tube to fit over the bleed nipple, making sure there is no air in the syringe you can reverse bleed back into the master cylinder reservoir by pumping the oil via the syringe in to the bleed nipple with the unit in its horizontal position..
I did not do this because I was going to strip and inspect the whole assembly anyway.

I cannot do a photo shoot as all is in place, and you really need a garage to do this. Over the kitchen sink or outside is possible Into a container.

You have removed the two bolts and piston push rod from the master cylinder whilst the whole assembled is vertical. ( I lubricated the end of the push rod with silicon grease after bleeding and reassembling the unit )

Remove the bleed screw

Now pull the master cylinder piston out with its spring.
( I carefully did this with pliers and protected the piston with a rag, I am sure there must be a safer way to do this as you do not want to score the piston )

Now check for scoring in the cylinder, should be none. Check the master cylinder seal for scoring too.

Clean, then tip the unit so that the master cylinder is vertical , making sure to pre lubricate the bore with a low viscosity oil, I used 0W30 mobile1.

( I disassembled the slave cylinder as well by removing its four bolts to clean the cylinder and check for scores. Oil the bore and seal, reassemble )

This is what you are going to use, not brake fluid.

With the bleed nipple removed, fill the master cylinder with oil. ( to the very top )
It will virtually bleed itself, when you see no bubbles replace bleed nipple making sure that the master cylinder is still if full of oil.

Push the master cylinder in as you now release the bleed nipple slightly and with the piston push the fluid through doubly making sure all the air has expelled.

With this final part of the process oil will shoot out of the master cylinder reservoir hole, I put some rag over it to catch the oil, or stick your finger over the hole to stop the oil flying out.
Use this with the bleed nipple done up to get the piston into its correct position.
you will notice that at a certain point the seal seems to pass the reservoir hole.
This has always been a confusion, when it does any oil in the master cylinders reservoir will bleed onto the back of the piston and out of the push rod onto the floor.
I noticed with my reservoir oil has all but gone. Most of it ended up on the floor.
My advice is to just leave a thin layer of oil in the reservoir.

Tighten the bleed screw.

The master cylinder piston should be about flush with the master cylinder housing, bolt it back and you are good to go.
If your bores are scored, the above is of no use, you can buy honing stone for this bore diameter from eBay.

 

[Chris Dawson]

Thanks @Kek700 much appreciated!

I'll grab a syringe and some tubing and have a go bleeding though the nipple with the system laid flat, as that seems to be the easiest approach!

 

[Kek700]

The reason for all the faff is that there is a reason why you need to bleed your brake assembly.
It is very good practice to clean and inspect the whole assembly both master and slave cylinders and sealing rubbers.
I cleaned all the muck out that had accumulated with use.

 

[LyD-]

Picked up a set used. There's some kind of metal-on-metal rubbing or binding going on with the brake pedal, and it's not smooth at all. I can feel the vibration through the pedal. Quite loud actually: https://streamable.com/qxwr9q

Seems like it's coming from the cylinder assembly (not the pedal or levers). The seller offered to take the pedals back if I wasn't happy, and said his other set is doing the same thing but not as bad. I'd like to fix them if possible.

Already sent a message to HPP about it, but anyone here have ideas?

 

[metalnwood]

Picked up a set used. There's some kind of metal-on-metal rubbing or binding going on with the brake pedal, and it's not smooth at all. I can feel the vibration through the pedal. Quite loud actually: https://streamable.com/qxwr9q

Seems like it's coming from the cylinder assembly (not the pedal or levers). The seller offered to take the pedals back if I wasn't happy, and said his other set is doing the same thing but not as bad. I'd like to fix them if possible.

Already sent a message to HPP about it, but anyone here have ideas?

Its going to cost you, from memory 250-300 for hpp to redo them. It would all be at your own risk if you take them apart and try and do something yourself.

I would suggest, if you are not happy with HPP's cost to fix then you should give them back. imo.

 

[LyD-]

Its going to cost you, from memory 250-300 for hpp to redo them. It would all be at your own risk if you take them apart and try and do something yourself.

I would suggest, if you are not happy with HPP's cost to fix then you should give them back. imo.

Ouch, that's painful. These pedals were a great deal but I don't know if it would be worth the extra ~$400 CAD on top of what I paid. Are we talking about a rebuild or something else?

 

[metalnwood]

Ouch, that's painful. These pedals were a great deal but I don't know if it would be worth the extra ~$400 CAD on top of what I paid. Are we talking about a rebuild or something else?

Usually a rebuild, best to wait and hear from him as I can't find the information I was going off from memory.

 

[RobertR1]

Should update. With a help of a friend walking me through the process I was able to bleed my set and it's perfect again with no leaks. No more free play or leaks etc.

 

[Met_fan]

Picked up a set used. There's some kind of metal-on-metal rubbing or binding going on with the brake pedal, and it's not smooth at all. I can feel the vibration through the pedal. Quite loud actually: https://streamable.com/qxwr9q

Seems like it's coming from the cylinder assembly (not the pedal or levers). The seller offered to take the pedals back if I wasn't happy, and said his other set is doing the same thing but not as bad. I'd like to fix them if possible.

Already sent a message to HPP about it, but anyone here have ideas?

I also have the HPP 3P-PRX-SE pedals in use since nearly two years. They make the same noise but work without a problem and I also don't feel a vibration in the pedal while pushing it.
Are they normally noiseless? Never bothered about it, but now I am curious if there might be something wrong with them.

 

[LyD-]

I also have the HPP 3P-PRX-SE pedals in use since nearly two years. They make the same noise but work without a problem and I also don't feel a vibration in the pedal while pushing it.
Are they normally noiseless? Never bothered about it, but now I am curious if there might be something wrong with them.

Interesting. Does your pedal feel smooth without the bumpers on? I am hoping the pistons just need to be lubricated or something.

 

[Kek700]

You really should bleed them with 3 in 1 oil or something equivalent.
I used mobile 0w30

 

[LyD-]

You really should bleed them with 3 in 1 oil or something equivalent.
I used mobile 0w30

Yeah I think it needs new oil. Look at this!

 

[LyD-]

You really should bleed them with 3 in 1 oil or something equivalent.
I used mobile 0w30

Should I use 0w20?

https://www.canadiantire.ca/en/pdp/quaker-state-full-synthetic-0w-20-motor-oil-946-ml-0289066p.html

Or would this 3 in 1 be better? And do you know if this bottle will be enough? https://www.canadiantire.ca/en/pdp/3-in-one-multi-purpose-oil-118-ml-0387806p.html