Hi,

 

I have a stuck piston in one rear wheel cylinder, so will be replacing it.  I have a question about the sub-types of cylinder.

 

There are different sizes, my car has no brake balance controller so needs the "A" subtext part, 15.87 mm piston.  VW dealer confirmed this with my reg number.

6

1H0 611 053 A

wheel brake cylinder

15,87 FAG

https://volkswagen.7zap.com/en/rdw/polo+derby+vento-ind/po/1991-120/6/609-37000/

 

 

However various online suppliers have subtle differences for 1H0 611 053A:

 

i) Aluminium or cast iron body (the aluminium is stated as new implementation by FEBI)

 https://partsfinder.bilsteingroup.com/en_US/article/febi/06098

 

ii) Depending on where you look, the wheel cylinders have one or two mounting screw holes (to screw them to the backplate).  This is weird as in the VW 7zap diagrams, it says Qty 2 for wheel cylinders (one for each side of the car), but also Qty 2 for bolts, i.e. one bolt per cylinder.  My current setup on the car has two bolts per cylinder; there's two holes in the backplate.

 

Does anyone have any experience of different material cylinders or bolt patterns?  My gut feeling is to stick with 2 bolts per cylinder as that's what I have at the moment, if one bolt wasn't used then potentially water could splash through the hole in the backplate and trickle down any minute gap between the back of the cylinder and backplate.  Also Aluminium is softer and there's more chance of damaging a thread when undoing bleed nipples or the brake line fitting.

 

I'm also keen to avoid corrosion of dissimilar metals if the piston is a different metal to the cylinder, however I don't know what the pistons themselves are made of.

 

Any advice or experience appreciated.

 

Thanks,

 

Bread

 

I’ve had both the cast and aluminium wheel cylinders on my MK2 in the time I’ve had it.I’ve also had both types seize up, so it’s difficult to say which are best.

 

Currently I’m running on cast cylinders with the two mounting screws.

 

Ultimately It’s the bore size that is important and I think the single hole mounting variety were first introduced in the later Polo(9N?).

 

If you want to put on what was factory installed then it will be cast cylinders with two screw holes, the alu single screw type are commonly listed as an alternative for the MK2.

 

If you are changing them then also be aware you don’t seem to get new mounting screws, only the cylinder and bleed screw.

 

I think the cast ones always have steel pistons.As for the alu ones , I’m not so sure what pistons are in those.

Edited 28 July, 20215 yr by mk2tastic

Thanks for your post, very informative.  I think I'll stay cast iron if my parts place can get them.

 

Point duly noted about the mounting screws, those crusty b*stards will be getting a thorough wire brushing, needle scratching, and a squirt of penetrating oil the night before, and I should probably get some spares incase one does round off..

Wheel cylinders replaced both sides, cast iron from TRW, my local motor factor was cheaper than ECP, £15 each vs ~£27. 

 

For anyone that comes across this thread, I replaced the mounting hex cap screws with some M6 stainless ones from Toolstation - a 50 pack (only size available) was a few quid.  They had to be hacksawed to 9mm thread length but I used the old ones as a pattern and used a nut on the screw while cutting to "re-tap" the cut section by unwinding it when finished.  I'd highly recommend to anyone that they replace the screws (from whatever supplier) as a matter of course as one of my old ones partially rounded upon removal despite wire brushing and penetrating oil.  It would not have survived a "next time",  stainless should be a bonus in the future if I do another brake job.