rear brake problem

[Petyus]

Hi guys,
Recently I visited a mechanic for brake fluid change. It went good at the front brakes but when the mechanic just wanted to bleed the rear, no air or brake fluid were coming from the bleeding slot, in spite the rear reservoir was full... Only the whissing noise were coming from the ABS module when operating the rear brake pedal, so it was clear from the sound that the brake fluid reach the ABS module but not the rear brake.
Diagnose was faulty ABS module so I went for a repair, but today the repair shop called that the ABS module is perfect, no any problem with it.
So I am completely stunned now, any idea how to proceed with the troubleshooting?
Yes, we bleed the ABS with the computer also.
The rear brake seems to be working, only it feels very weak.

 

[scottmastrocinque]

Ugh...

It is impossible to give you any logical advice if you do not state what you are trying to work on. I presume it is a Stelvio, but what year and what model?

Also, there is no "whissing" sound on Moto Guzzi ABS systems. Only BMW servo-assisted ABS brakes, used only for a couple of years around 2004, make a sound like that.

Also, you do not need to utilize a computer to bleed the brakes on a Stelvio NTX. I don't understand why you wrote that. Your mechanic appears to not know what he is doing or talking about.

What you have written makes no sense. Please clarify.

Lastly, if you are unable to get fluid to flow out of your rear brake bleed screw, you have debris caught in the very tiny master cylinder orifices which is preventing brake fluid from flowing into the master cylinder. You need to remove the reservoir and master cylinder, disassemble, clean it completely, and then reinstall it and do a complete bleed.

 

[Petyus]

Ugh...

It is impossible to give you any logical advice if you do not state what you are trying to work on. I presume it is a Stelvio, but what year and what model?

Also, there is no "whissing" sound on Moto Guzzi ABS systems. Only BMW servo-assisted ABS brakes, used only for a couple of years around 2004, make a sound like that.

Also, you do not need to utilize a computer to bleed the brakes on a Stelvio NTX. I don't understand why you wrote that. Your mechanic appears to not know what he is doing or talking about.

What you have written makes no sense. Please clarify.

Lastly, if you are unable to get fluid to flow out of your rear brake bleed screw, you have debris caught in the very tiny master cylinder orifices which is preventing brake fluid from flowing into the master cylinder. You need to remove the reservoir and master cylinder, disassemble, clean it completely, and then reinstall it and do a complete bleed.

Thank you for the answer. It is a Stelvio NTX 2015.
Sorry mistyped, hissing the correct word. This sound would indicate the fluid is coming from the brake cylinder to the ABS module.
The computer was used to bleed the air from the ABS module if any, but it did not help
Also they tried to pressurize the rear brake line and loosen the appropriate brake tube at the ABS control module and they considered the brake fluid is blocked somewhere in the ABS module.
But it seems they were wrong.
I also suspect a way of clogging either in the brake pipe or in the cylinder itself.
thank you again.

 

[john zibell]

Thank you for the answer. It is a Stelvio NTX 2015.
Sorry mistyped, hissing the correct word. This sound would indicate the fluid is coming from the brake cylinder to the ABS module.
The computer was used to bleed the air from the ABS module if any, but it did not help
Also they tried to pressurize the rear brake line and loosen the appropriate brake tube at the ABS control module and they considered the brake fluid is blocked somewhere in the ABS module.
But it seems they were wrong.
I also suspect a way of clogging either in the brake pipe or in the cylinder itself.
thank you again.

Or the bleed nipple at the caliper is blocked. I use a piece of paper towel to extract any remaining fluid in the nipple after bleeding. I've seen brake fluid congeal and block the opening.

 

[scottmastrocinque]

Thank you for the answer. It is a Stelvio NTX 2015.
Sorry mistyped, hissing the correct word. This sound would indicate the fluid is coming from the brake cylinder to the ABS module.
The computer was used to bleed the air from the ABS module if any, but it did not help
Also they tried to pressurize the rear brake line and loosen the appropriate brake tube at the ABS control module and they considered the brake fluid is blocked somewhere in the ABS module.
But it seems they were wrong.
I also suspect a way of clogging either in the brake pipe or in the cylinder itself.
thank you again.

The holes that are cut on the inside of the master cylinder are nearly microscopic in diameter. The slightest dirt or contamination can block those holes, preventing fluid from flowing.

I seriously doubt that your ABS module is the source of any problems. The brake system on the Stelvio is designed to bleed without any specialized work needed to be performed on the ABS system. It's the strongest trait of the Moto Guzzi system versus the BMW system.

 

[Petyus]

Or the bleed nipple at the caliper is blocked. I use a piece of paper towel to extract any remaining fluid in the nipple after bleeding. I've seen brake fluid congeal and block the opening.

thank you, I will also check it.

 

[Petyus]

The holes that are cut on the inside of the master cylinder are nearly microscopic in diameter. The slightest dirt or contamination can block those holes, preventing fluid from flowing.

I seriously doubt that your ABS module is the source of any problems. The brake system on the Stelvio is designed to bleed without any specialized work needed to be performed on the ABS system. It's the strongest trait of the Moto Guzzi system versus the BMW system.

thank you, any special cleaning agent I should use, or just a standard part cleaner spray?

 

[scottmastrocinque]

When I remove a master cylinder and brake line to clean, I use spray brake cleaner on the master cylinder and spray electronics cleaner on the brake line itself but that is me.

I also use compressed air to blow everything out and dry before reassembly.

 

[Petyus]

When I remove a master cylinder and brake line to clean, I use spray brake cleaner on the master cylinder and spray electronics cleaner on the brake line itself but that is me.

I also use compressed air to blow everything out and dry before reassembly.

great, thank you, I will give it a try. Today I will get back the ABS module....

 

[Petyus]

checked rear master cylinder, it seems it defected, it cannot pump the brake fluid also after cleaning. I was not able to find rebuild kit, so I have to buy a new cylinder. Original OEM cylinder is not on stock, but 2 weeks from order. So I think I buy a replacement, it is cheaper also on stock. I think if I go for 13 mm (same diam. piston as the oem) PS 13 that would be ok, if the mounting, connections and other dimensions are the same. Let me know your opinion.

 

[john zibell]

checked rear master cylinder, it seems it defected, it cannot pump the brake fluid also after cleaning. I was not able to find rebuild kit, so I have to buy a new cylinder. Original OEM cylinder is not on stock, but 2 weeks from order. So I think I buy a replacement, it is cheaper also on stock. I think if I go for 13 mm (same diam. piston as the oem) PS 13 that would be ok, if the mounting, connections and other dimensions are the same. Let me know your opinion.

Original components are from Brembo. If you can locate a Brembo dealer near you they should be able to provide a direct replacement.

 

[scottmastrocinque]

I would just get the OEM part personally.

I’m shocked that you couldn’t get a rebuild kit in Europe. I know they are available.

 

[Petyus]

I searched the web for rebuild kit, I found kit for 11 mm piston cylinder but not for the 13 mm. If you have an idea where can I find rebuild kit, please tell.
this is the OEM part : mgcycle.com/index.php?main_page=product_info&products_id=5080
and this is the replacement I would buy instead : ebay.com/itm/333153930023
this is the 11 mm kit : addictionmotorsport.co.uk/brembo-replacement-parts/brembo-11mm-rear-brake-master-cylinder-repair-kit-ducati-aprilia-ktm-110436241 , the parts are the same but the piston is 13 mm instead of 11 mm.

 

[scottmastrocinque]

If you GOOGLE “Brembo brake rebuild 110436241” literally many sites pop up. This is the cheapest for me below.

I have no idea where in Europe you are.

 

[john zibell]

Scott, he says he needs a 13mm kit, not 11mm.

 

[scottmastrocinque]

Sometimes, trying to figure out what some of these people are asking, is fricking impossible…

 

[scottmastrocinque]

It should not matter that this says KTM. That is unimportant. I’m 95% positive this is what you are looking for.

As the OP had his master cylinder apart, he should instantly recognize these parts.

This says Front and Rear.

I suggest taking a minute and emailing Gotham Cycle. I’m sure they can answer a question.

I’ve used them several times before.

 

[Petyus]

thank you , but this is for the FRONT no matter what it says... The parts in the rear cylinder are different, they are the parts what is in the 11 mm kit but the piston and the seals are bigger in diameter. I mailed to OPP, they might able to help with the rebuild kit.

 

[scottmastrocinque]

If this is indeed the case then I would change over to the master cylinder that I could buy a rebuild kit for it at the same time.

Perhaps Moto Guzzi specified a size that Brembo does not provide a kit. I doubt it but it’s possible.

The best thing is to ask the people who sell this stuff. I’m sure they have a catalog or access to online lists. They will know for sure.

 

[Petyus]

yes, this is the way : "Brembo does not list a rebuild kit for this master. You can click on the schematic in the link you provided and they do not offer a rebuild kit.
We have had some people purchase various kits and be able to use some of the items in the kit to rebuild a master but we are not aware of the specifics. "

thank you all.