Servo full of brake fluid

[pirate-pete]

Have noticed over last few weeks I've had no servo assistance from the brakes in the mornings at the first junction off our street. By the time I get to the next junction everything is back to normal again and stays this way until the next morning. Shutting off the engine and then trying the brakes gives me a couple of brake applications before the vacuum has gone and when you start the engine with your foot on pedal you can feel it go down like usual.

Was expecting this to be a small leak in the vacuum line from servo to engine and was going to wait for warmer weather to sort. Today I took off the instrument panel as wanted to fix the intermittent clock with new capacitors. Noticed the brake fluid level almost empty and well below the minimum. No sign of any leaks around the wheels or pipes that I could see - just a crusty bit of residue under the master cylinder on the servo that looks like it has been there for years. When searching for threads about the vacuum leak I noticed some reports of master cylinders failing and leaking into the servo with no outward sign of the leak so I unbolted the master cylinder from the servo and yes, fluid started leaking out of that join.

Master cylinder is now off and will be replaced as it is leaking past the seals into the servo. Now I can see into the servo it is nearly half full of fluid so do I need to replace it or can I just clean this one out?

Second question is to remove the servo I am going to have to remove the dash. The screws at the top are rusted solid and the the heads are too small for my impact driver. I tried heating them with a small gas blowtorch but they are too close to the windscreen rubbers for my liking. What's the easiest way to deal with these screws - am thinking of either belting with a small cold chisel or drilling them. I started drilling but looks like I need some sharper bits. Any advice from anyone who has been there and done this appreciated.

[AdrianC]

It's a bit of a pig to replace, isn't it? If so, then it seems daft to risk a potentially duff one - swap it. IIRC, there's a good upgrade with one from an older BMW 3-series, just a straight-ish swap in.

Ah, here y'go.
http://www.thesamba.com/vw/forum/viewtopic.php?t=401822
E30 3-series.

BMW servo on the left, original on the right.

[pirate-pete]

Thanks Adrian - will consider it but would have thought second hand bmw one would be no more reliable than 2nd hand vw one just a bit more powerful.

That thread has a handy idea for replacing the servo without removing the dash too athough I would like my dash out just for the other jobs that need doing under there. (Blower fan packed in and would like to lube the wiper arms)

[California Dreamin]

will consider it but would have thought second hand bmw one would be no more reliable than 2nd hand vw one just a bit more powerful

Exactly...bigger servo...more assistance.....the fact is servo's are pretty reliable things on the whole but extended contact to brake fluid will have softened and weakened the diaphram. Whatever second hand servo you buy I would look for one that have only recently been removed (the master cylinder acts to keep out the elements and keep it preserved).

I'm guessing you just want a straight swap, however, the BMW replacement is tempting if you are going to the time and expense to change it.

Martin

[igotadizzy]

I would clean the old servo out, after repairing the master cylinder and test it and see how you get on. As it sounds like the servo is still working ,just suffering from reduced capasity

[pirate-pete]

That's my current plan. Should be getting a nice 500ml oil syringe in the post tomorrow as well as a new master cylinder. If I can get the dash screws out easily on Saturday then I'll remove the servo for a good check but if not I'll suck all the fluid out with the syringe. I'm sure there is more fluid in the servo than what I've topped up in the last three years. It is not quite up to the level of the opening yet but I'll see how much I can drain out.

It's a diesel van I've got so no chance of sucking any fluid down into the intake manifold but I saw a few reports from google of petrol vans stalling on braking or smoking due to sucking in fluid from the servo after similar master cylinder failure.

[California Dreamin]

In my experience the brake fluid will have seriously sofened the diapram in the servo....you may well be able to re-use it but it's a risk I wouldn't recommend that you take.
One of the traders on here will sell you a good used servo for £25 - £35 it just isn't worth re-using.

Your van should have it's brake fluid changed every two years regargless of mileage. Brake fluid is 'Hygroscopic' which means it attracts and absorbs water, much like those moisture traps you buy in the winter to protect againsts damp. It is a fact that just 3% moisture contamination in brake fluid will lower it's boiling point by 100 degrees C potentially leading to 'vapour lock' (the boiling of the brake fluid) and total brake loss as a consequence.

Martin

[AdrianC]

and total brake loss as a consequence.

Not _total_ brake loss, if you've got your wits about you - the pedal will pump up - but it certainly gets a little "entertaining" as you come down a steep Iberian mountain and find that the pedal just hit the floor...

Laundry bill aside, not changing brake fluid also leads to all the other brake bits corroding from the inside out.

[pirate-pete]

In my experience the brake fluid will have seriously sofened the diapram in the servo....you may well be able to re-use it but it's a risk I wouldn't recommend that you take.

Martin

Thanks Martin,
Here to hear of others experience so I've now learnt that the diaphragm will have softened and I will be replacing it as soon as I get the dash panel off. Trouble is until the days get longer I don't have much time to spend on it and at the moment it is sitting on road undriveable even though not my daily driver. If I can't get the dash off at the weekend then I'll suck the fluid out and fit the new master cylinder and drive it as is until I can get the dash off.

Already usually change brake fluid every two or three years on my vehicles for reasons Adrian mentioned. Brake fluid was completely changed after I got the van when I replaced disks, pads and ran clean fluid through so due a replacement this year anyway. Didn't think about the clutch though at the time so will bleed that until clean.

[pirate-pete]

Just an update.

Managed to get dash off last week so now have a replacement servo installed. Took the whole pedal assembly out so I could get to the back of the bracket to unbolt the screws. Stripped down and cleaned and lubricated all the linkages and happy to find no play in the main pedal pivot shaft. Measured the servo pushrod adjustment and found new one 5mm out (old one was fine) so adjusted that.

Old master cylinder had only one port for the brake light switch when the replacement had two ports so rather than buy a second switch I saw Brickwerks sell a M10 threaded bung so ordered that to block the spare port.

Replacing the pedal assembly was a bit more difficult than removing it. I spent a while trying to get the clutch pushrod lined up with its master cylinder but in the end decided to remove the cylinder. I did say I was going to bleed it didn't I. Anyway that all fitted together fine.

Problem when I went to open the clutch bleed screw at the slave - it is not there. Appears to have sheared years ago. Not a problem I thought - can order a new slave cylinder. My van diesel so bolts came undone fairly easily after moving starter to get a bit more access. Then went to undo the pipe union and found it rounded and siezed. Grrrrr. I didn't want to risk reversing onto ramps without a clutch and I don't like axle stands on our road as the camber makes them a bit unstable when high so left it to think about what horrors lie next and whether I will need to end up replacing all of the underbody clutch pipes if the flexi unions are seized into a lump of rust?

Anyhow this morning managed to jack it up and use axle stands at low height just enough for me to squeeze under the engine and gearbox and managed to undo the union from the metal pipe to the cylinder where it meets the flexy. Brickwerks will be getting another order as they supply this metal pipe ready made so hopefully that will be job done.

Managed to get a few other jobs done while dash out. Freed up heater motor and it is spinning so well I'll take my chances on refitting rather than replacing with a pattern part. Motor must have taken out the slow speed resistor when it seized so have replaced that too. All the flaps in the heater box now have a nice neoprene seal on them rather than the crumbling 30 year old remnants. A new radio aerial to replace the seized one and to cut down on noise I've stuck some flash banding onto the inside of the front panel.