Servo failure

 It seems my servo is holding on the brakes.

Overheating so much I rolled into park foche Laon with only a hand brake.
After a bit of cooling it was fine for the rest of the day.
Sticking on again at the farmhouse and unlocked when I turned off the engine.
I removed the vacuum hose and blocked it with a tyre valve.

Similar to previous post.. do I need a servo.
Well, with current braking power, yes I do. Quite a struggle to stop.
I have a girling 7/8" master cylinder. Do the none servo cars use a bigger bore?

I'll try the air valve fix first from the archive.
But also, is there a repair kit for the lockheed type 6, 4257 729 29?

Considering I always thought the brakes were a bit hard - so assumed the servo was dud anyway - now it is dud a proper emergency stop would probably break the seats by pushing so hard. So - in my case -  need to fix it.
Of course there may be more wrong than just the servo.

My master cylinder is 7/8" - series I & II had 11/16". So I think to run without servo one ought to use a different master.

This weekend I'll clean and polish the air valve and give it a test run vacuum on.
And a fluid bleed.

I've looked under the air valve and the air valve piston seal is well worn.
So for now I've ordered enough to service what can be accessed easily from northwestclassic.

The proper full service/seal change will be done in the winter.

my servo part number is 4257-729, apparently superseded by 4257-792.

see here for servo operation http://www.mgb-stuff.org.uk/servo.htm

see here for servo rebuild https://landcrabforum.co.uk/thread/393/lockheed-servo-rebuild

on the last run the brakes stuck on again, so I missed a day trip to the National.
Weather is a bit    so pulled it all apart.

The brakes release when the engine is stopped but I'm changing all the seals in both master and servo.
The servo seals looked OK but the master cylinder seals looked life expired.
Also, despite recent bleeding of a pint of fluid, the fluid in the master still looked contaminated.

Will see soon enough. (I had some yellow that needs using up. No-one will notice)

Got it all together after the master cylinder and servo rebuild -a while ago.
Drove out of the garage and the symptoms were the same. - Brakes stayed on and would release with engine off or very low idle.

After some more looking at the drawings and how it works - In desperation (the only thing still- old) rotated the rubber hose that joins the front portion to the airvalve. It then seemed to work well enough to go to Capel car show.

I replaced the rubber hose with new and now it is working as expected - for two good runs at least.

maybe that was it.

My current theory on the hose is that it had hardened to the profile of the air valve and pipe.
So wasn't blocked but leaking. So not enough power to push the air valve back down. (Could be wrong theory)
Rotating it assisted the seal.
The pipe was easy to remove. The new one was a bit of a struggle to fit. So is well and trult sealed.

It's still OK.  
But I realise now the brake effectiveness is a bit sh t. Even with the servo.

Looking at EBC front and rear next. or Princess 4 pots.

10 volt regulator

 I've had the new regulator in the box since 2016.

The old regulator was working OK. but after some issues trying to measure the voltage I decided the time had come to install.

For curiosity I attached the scope to see the differences.
The old bimetallic system works by switching 12V on and off resulting in an average of 10V.
Fuel gauge shows 4 gallons.

The new one works by magic and outputs 9.9V constantly
Fuel gauge shows 3.5 gallons.

When it stops raining it will be interesting to see the indicated temperature and then measure the water temp by another means.

Prepare for the Laon 2023

Laon 2023 was a good event 

I even made the local paper.

- marked by the Sunbeam servo failing to release the brakes and cooking the fluid. undoing the vacuum fixed that issue but the pressure needed to operate the brakes was more than expected.

Had a good time in Laon but after the day driving around the city the Alternator light started to flash and the voltmeter change between 12v and 14v in sequence.
The next day was a drive to Honfleur but wasnt long before the warning light came on and the voltage started to go down. I stopped to investigate properly when it got to 11v and it had difficulty starting.

Thinking Alternator I checked the voltage at the exciter pin (small wire). Nothing.
So hot wired from 12V battery bus direct. And off we went again.
This wire needed to be disconnected every long stop.

10 minutes later the engine cut out and we rolled to a stop. Engine would start on the key but stop when released.

Under dash found burnt white wires on the run contact of the ignition switch. Mostly white wires melted together. (probably others but thats for tomorrow).
Removed these wires from ignition switch and slaved in a new cable to the fuse box.

Then we were able to carry on to Honfluer.

I did try the Alternator exciter wire direct to the switched 12v - but then the engine wouldnt stop  
Add a warning bulb in circuit and it would stop.
Funny things alternators

Added a fuse box inside the regulator box for the 12v Live circuit (Lights, Horn relays, hazards etc).
Another for the  Switched 12V. I need to extend a few wires now.

The fuse blown indicators don't work on LED sidelights but do work on incandescent dip/main.
Will check later if works with LED indicators (due to dashboard warning lamp providing the circuit)

 

The solenoid switch failed just before Laon. Probably been bad a long time.

It was probably dirty contacts inside. Anyway a new one fixed it.

I fed a new wire to the starter motor a few years ago - probably was the solenoid even then.