Master cylinder replacement - can I use a 2020 on a 2015?

[Amm5890]

Hey guys,

I recently bought a new master cylinder (long story)


I have a 2015 GTI but the one ordered is off a 2020+. If I look on Vw’s part website and get the part number for the 2020 master cylinder (5QM-614-019-H) it says it will not fit my car (they claim it should be 5Q1-614-019-AD-REP). BUT if I look for master cylinders on rock auto website the part numbers for the 2015 and the 2020 are exactly the same. Judging off pictures they look exact as well.

Other than being a $200 price difference - is there anyway someone could confirm that the 2020+ MC would work fine on a 2015?

 

[ITGUY]

Negative Ghost rider

 

[ITGUY]

I would say this one is safe since it shows the compatible OEM part numbers Rockauto

 

[Amm5890]

I would say this one is safe since it shows the compatible OEM part numbers Rockauto
View attachment 297030

Yeah def not gonna buy the one that is on rock auto. I have the OEM 2020 MC already. I just find it strange that the one suggested for the 2015 works on the 2020, but the 2020 part number doesn’t work on the 2015 according to parts.vw.com

 

[ITGUY]

You won't buy a part on RockAuto but you'll trust what they say about what fits what??? lol

 

[Amm5890]

You won't buy a part on RockAuto but you'll trust what they say about what fits what??? lol

The rock auto example was for reference purposes only. It was to demonstrate that the part numbers, for their master cylinders, are the same on rock auto for the 2015, and 2020. However the part numbers are different on Volkswagens actual parts website.

Also, the point of the thread is that it’s weird that the suggested part number for the 2015 MC (5Q1-614-019-AD-REP) ALSO works on the 2020 GTI BUT the suggested part number for the 2020 GTI (5QM-614-019-H) doesn’t work on the 2015.

So, In theory, if VWs website is wrong, the $38 dollar 2020 MC should work with my 2015. thus saving me $150 right?

 

[DerHase]

In general aftermarket master cylinders can be a real crapshoot in my experience (17yrs as a tech). $200 is cheaper than hitting someone or something. Master cylinder failure can also leak into the brake booster and swell the diaphragm. Make sure you check for that as well.

Using Rockauto for references is questionable at best when it comes to VWs.

The things you need to confirm that may not be immediately obvious in a picture:
- Master cyl bore (different depending on PP or not IIRC)
- brake line connection threads
- mates to the booster

 

[Amm5890]

In general aftermarket master cylinders can be a real crapshoot in my experience (17yrs as a tech). $200 is cheaper than hitting someone or something. Master cylinder failure can also leak into the brake booster and swell the diaphragm. Make sure you check for that as well.

Using Rockauto for references is questionable at best when it comes to VWs.

The things you need to confirm that may not be immediately obvious in a picture:
- Master cyl bore (different depending on PP or not IIRC)
- brake line connection threads
- mates to the booster

Good deal! So I ended up just bleeding the abs and that seemed to help with the pedal tremendously. Like I said in OP it’s a long story. The reason why I thought my MC was toast was because I heard a squeak anytime I pressed the pedal hard. Turned out my ECS MC brace was a little bit loose and was gently scraping the MC and making a horrendous noise lol.

Did you ever look into the vacuum pump adaptations? Perhaps to reduce the booster assist? Love the website btw

 

[DerHase]

Good deal! So I ended up just bleeding the abs and that seemed to help with the pedal tremendously. Like I said in OP it’s a long story. The reason why I thought my MC was toast was because I heard a squeak anytime I pressed the pedal hard. Turned out my ECS MC brace was a little bit loose and was gently scraping the MC and making a horrendous noise lol.

Did you ever look into the vacuum pump adaptations? Perhaps to reduce the booster assist? Love the website btw

I'm 99% sure many of the adaptations are bullshit.

https://docs.google.com/document/d/1ituwUxAf7676mMw06GSneVTrfapKjTXSKKoxa933cPY/edit

Brake boost and Hydraulic brake booster in particular.

I actually need to update HBB at some point, because I recently found that on many MK7s if you go into the 03 - Advanced measure values you can find that HBB is disabled:

I think it may have something to do with the cars equipped with Forward Assist and/or ACC and those systems only. the above scan is from a car that does not have an Address 13 ACC sensor at all. My 2019 does show it as available though (as outlined in that document).

I need to go through a bunch of VCDS scans to determine what option(s) do/don't correlate with that being enabled or not. But the fact it's not on every MK7 indicates to me it doesn't do anything like what people "say" it does.

Which supports the fact that I wasn't able to get any kind of consistent changes when logging the CAN bus highest wheel pressures vs brake servo pressures directly.