Master Cylinder Seal

[aeo]

Is there a seal between the master cylinder and the servo? Asking for a leaking friend as seen in the photo.

Do I need to replace multiple parts here? And my brakes are soft. Even by 1983 110 standards…

 

[Z.G]

The seal is in the master itself, not really a seal between the master & servo. You just need to replace the master https://www.roversnorth.com/parts/pli706_brake_master_cylinder_defender_110_1983_1991

 

[erover82]

Your master cylinder's seal has gone. You can rebuild it if the bore isn't rusted. There are no gaskets between the master and booster.

 

[aeo]

The seal is in the master itself, not really a seal between the master & servo. You just need to replace the master https://www.roversnorth.com/parts/pli706_brake_master_cylinder_defender_110_1983_1991

Bet you know what’s coming next…

 

[Z.G]

Bet you know what’s coming next…

I figured I'd cut some of the email chain out by just giving you the part number here

 

[aeo]

I figured I'd cut some of the email chain out by just giving you the part number here

We need a buy it now option for NAS-ROW

 

[aeo]

I have the new part and I've watched some videos. Is this really as simple as siphon out the brake fluid, remove nuts, swap part, bolt back on, refill brake fluid and done?

Any warnings? Tips? Tricks? Don't do this...

Thanks,
Alex

 

[Frobisher]

Simple is a relative thing, but having just done this, yes it’s about that straightforward.

A few tips I recommend, depending on the videos you’ve watched.

1. Bleed the master on the bench. Choose your style, but I use a syringe to push fluid back up from the bottom.
2. Install master and connect your lines loosely.
3. Apply half pedal pressure and let fluid out through the lines. Tighten lines and release pedal to draw fluid back up and into the reservoir.
4. Repeat a few times to make sure any air has bubbled back up to reservoir. Tighten and cleanup.

A lot of guys here have a lot more experience than I. They may have some better suggestions or corrections, but it worked for me.

 

[aeo]

Simple is a relative thing, but having just done this, yes it’s about that straightforward.

A few tips I recommend, depending on the videos you’ve watched.

1. Bleed the master on the bench. Choose your style, but I use a syringe to push fluid back up from the bottom.
2. Install master and connect your lines loosely.
3. Apply half pedal pressure and let fluid out through the lines. Tighten lines and release pedal to draw fluid back up and into the reservoir.
4. Repeat a few times to make sure any air has bubbled back up to reservoir. Tighten and cleanup.

A lot of guys here have a lot more experience than I. They may have some better suggestions or corrections, but it worked for me.

Thank you.

This should be fun. I am sure the 110 will do everyting it can to thwart any and all progress...

 

[Frobisher]

Working on these trucks is never dull. They are many other things but never lacking in surprises.

 

[erover82]

Your master cylinder's seal has gone. You can rebuild it if the bore isn't rusted. There are no gaskets between the master and booster.

I was wrong. On 91+ there's an O-ring (SJO100080) between the master and booster to prevent water ingress. It does not prevent brake fluid egress though.

 

[evilfij]

This is your opportunity to replace the rubber brake lines, rear wheel cylinders, maybe front calipers and anything old or suspect. Especially the rubber brake lines. Anything original and rubber needs to go.

 

[aeo]

Is it Dot 3 or Dot 4 brake fluid? The master cylinder says Dot 3 but I seem to remember reading it is Dot 4.

 

[erover82]

No reason not to use Dot 4 or 5.1 since it’s backwards compatible.