Octopus block sensor thread

[Radtap]

Was chasing what I thought was a massive air bubble in brake system, nah brand new MTC junction block sensor failed and started squirting fluid into the boot. Just want to seal a bolt in there and call it good. Just need to know thread size for the sensor

 

[kyote]

M10x1.0 IIRC
You'll want to use a bonded sealing washer of some sort.
And it's not the sensor that goes bad, it's the seal inside the octopus.
PM user crazychopstick, he has done this and may be able to sell you a seal and or plug.

 

[Radtap]

I’ve got copper washers and thread sealant, I saw there was a special plug available thru iPD but I don’t really wanna wait on shipping. Got a bunch of work to do in the car so gotta get the brakes fixed. Thank you!

 

[Radtap]

It’s actually m12x1.0, the other ports are m10.

 

[dbarton]

Perhaps this info will help. Please report back on your solution.
https://www.240turbo.com/volvo240bigbrakes.html#plasticsender
Dave

 

[planetman]

Plugging the hole may stop the leak, but does not fix the root problem which is that brake fluid is getting past 1 if not both of the seals for the sliding piston inside the distribution block.

What most people don't realize is the seals for the warning switch are dust seals and are not designed to contain brake fluid under pressure and brake fluid should never be inside that port.

Worst case scenario is that both seals for the sliding piston are leaking which means brake pressure from both brake circuits are co-mingling.

And I don't think you'll ever get a good brake pedal when that happens.

 

[Radtap]

Oh so my junction has a bigger problem? I rebuilt the distribution block in my 84 and just replaced the seals and it hasn’t had issues for 6+ months now but this MTC block barely lasted before going. Also was able to find m12x1.0 pipe plugs through mcmaster. I might take the block out today and take it apart to check the seals

 

[planetman]

Also check the bore as it maybe the root of the problem.

The world's best seal won't seal on an damaged or oversized bore.

I used to sell a kit with a new original Volvo distribution block that was used on the later 240s when Volvo went to a low fluid level switch that was built into the brake fluid reservoir.

The kit consisted of the later distribution block that doesn't have a warning switch and a low fluid level switch that is built into a brake reservoir cap that can be used in place of the stock brake fluid reservoir cap.

Unfortunately, Volvo no longer sells the later junction block.

I have suggested that a failed original octopus can be re-purposed if 2 plugs are installed in the bore, 1 of each end, for the sliding piston. You can then add and wire the cap with a low fluid level switch.

 

[Radtap]

Got the McMaster pipe plugs in today, didn’t realize when ordering but they have a pretty decent lip for a crush washer or oring to seal up against and sit good in that little groove. McMaster Carr # for the plug is 9151K245 m12x1.0 hex head pipe plug. It looks nearly identical to the original sensor even with a cavity except it’s stainless steel instead. Sealing great with no more leaks but still going to look into my junction block since it has bigger issues but incase anyone wants to delete that sensor for peace of mind.