F10 530d Manual: Replaced leaking clutch slave-cylinder.

At the end of 2018 when I replaced the clutch on the F10 I threw on a new slave-cylinder while I was there, but I used a cheap spurious part, not OEM. It has been leaking for a while but I’ve started to lose my pedal and the topping up is becoming frequent, so time has come to replace it again. This time I went for an OEM Febi slave-cyl.

The spurious part from 2018 cost just £18 and is made from cast aluminium. You can see it’s poorly made compared to the OEM part, which is made of high-quality plastic. The Febi part was £57 still in 2024, but you can clearly see the improvement in build-quality. For such a critical part as the slave-cylinder it’s worth just paying the extra and avoid having to redo a messy, fiddly job!

*GUIDE: Replacing / Clutch Slave-cylinder on F10/F11*

*GUIDE: Bleeding Clutch on F10/F11*

As you can see, the cast-alloy slave-cylinder does not have the same look of build quality that the OEM plastic one does. It lasted 5 years and only about 25k miles, but was still good value for the price!

*GUIDE: Clutch Slave-cylinder replacement and bleeding guide for E30 / E28 / early E34 and E34*

BMW E30 Heater Matrix Hoses Configuration - Right and Wrong way round + how to bleed matrix / remove air-lock

My E30 had little or no hot air from the blower inside the cabin. I have heard it is common for the two hoses running to the heater matrix to be fitted back to front, so the flow of coolant through the core is reversed. This causes air locks and severely reduces the amount of coolant flowing through the heater matrix, thus no hot air. 

The reason these hoses so often get fitted incorrectly is due to their location and the way they look when fitted. It appears obvious that the upper hose (back of cyl.-head to heater) goes to the upper stub on the heater-matrix and the lower hose (side of block to heater) goes to the lower stub on the matrix. The hoses look happier this way round, but the matrix and heater-valve are designed in such a way that flow is interrupted and causes the air-lock. 

The correct way round is actually with the upper hose connected to the lower stub and the lower hose to the upper stub, which does of course appear to be back to front, but is essential for correct flow of coolant round the whole engine, not just the heater-core. The correct and incorrect hose configurations are shown in the pictures below.

RIGHT:

WRONG:

How to Bleed system and remove air-lock from Heater-Matrix:

** This is not the normal air-bleeding process when refilling an empty system with coolant, this process is to bleed a system with the air-lock at the back of the head and / or the heater-matrix full of air. **

1. Ensure heater-matrix hoses are fitted the correct way round, if not swap them over. [You should notice if there is an air-lock that no coolant comes out of the hoses when removed from the matrix and the stubs appear dry].

2. Fully tighten the lower [inlet] hose.

3. Leave the upper hose disconnected from the matrix. 

4. Remove the radiator bottle cap. Assuming the coolant level is up to the halfway / max. mark, there should be some gulps of air and the coolant level should drop slightly in the rad. bottle.

5. Cut the bottom off a 2-litre drinks bottle and fill it with water, holding your hand over the lid.

6. Dump the water from the drinks bottle into the radiator bottle, allowing the weight of water to push the remaining air though the system. Water should start to come out of the upper heater-matrix hose from the head. Block this hose with a finger.

7. Continue to top up the radiator bottle with water until water begins to flow out of the upper stub on the heater matrix and quickly refit the upper hose, which can now be fully tightened.

8. Drain the radiator bottle back down the halfway /max. / fill line.

** You should be good to go, but can now bleed / top-up the system using the usual bleeding procedure if necessary. **

F10: Clutch Bleeding Guide... the whole nightmare! [Manual transmission / gearbox 520d, 530d, F10, F11, G07, E90, E92 3er etc.]

You will need:

• Short / stubby ... wrench.
• One-way valve type bleeding-kit.
• DOT4 regular brake/clutch fluid.

Clutch-bleeding on the F10, F11, G07, E90, E92, G20 and a lot of other contemporary BMWs can be a right pain, but if you are replacing the master-cylinder / slave-cylinder, the pipework or removing your CDV, then it is necessary. If you clamp the clutch-hose by the slave-cylinder and don't allow a lot of air back into the system, then bleeding should be pretty straight forward, but if a fair bit of air does get back into the system or you are removing the master-cylinder then it can't be helped and a full bleed is needed. The trouble with a full bleed is that these systems are notorious for air locks, primarily in the master-cylinder, which can be tricky to dislodge and get fluid into.
The main drawback with a regular bleeding process, where the bleed-nipple is opened as the clutch is pumped, is that the bleed-screw is located half way up the transmission tunnel and very difficult to access with a wrench. This makes it difficult to quickly shut the bleed-valve, which is kind of essential for this process and air can get back in. If you are able to access the bleed-screw without difficulty or have some special tool designed for the job then regular clutch bleeding should work a charm with air locks and, though it may take a while, you will be on your way.
A pressure-bleeder may give the time needed to tighten the fiddly bleed-screw, but does not work to get rid of air locks and seems to bypass the master-cylinder completely, so I would avoid using one of these kits at all if there is a lot of air in the system. Some trapped air at the top of the system seems to want to exit through the reservoir anyway, so it's better not to cap it with a pressure-bleeder as it just does not seem to want to go with the flow. If you clamped the hose and only the slave-cylinder needs bleeding then a pressure-bleeder should do that in no time.
I found that a one-way valve bleed kit was the way forward. It prevents the return of air/fluid while the bleed-screw is left open and gives time to shut it when the process is complete. It leaves the reservoir open to be manually topped up, which shows precisely how much fluid is entering the system. This was the key, for me, to finally shifting the stuck air from the master-cylinder.

I have detailed the various techniques and problems below:

Location of Brake + Clutch Reservoir:

The brake/clutch reservoir is not very apparent in the engine-bay. It is located under the black panel in front of the windscreen on the driver's side of the car. Looking from the front, left-side for RHD cars and right-side for LHD. The opposite panel covers the climate-control entry-ducts.
The panel is held in place by 4 plastic clips, which can be removed by prising up the centre of the clip and then prising the base of the clip out with a panel-popper / trim-tool or a couple of flat-screwdrivers.
The fill-neck for the reservoir is right under the bonnet-hinge and pouring DOT4 in without spilling it can be tricky, so a funnel is a good idea when topping-up. I would recommend putting a towel around the reservoir also, as brake-fluid is not a nice thing to get everywhere and it is easy to over-fill. Special care should be taken when replacing the cap - the large plug that hangs under the cap will surely displace some fluid over the top of the reservoir as the cap is dropped in.

Bleed Nipple + Regular Bleeding:

Unlike BMWs of old, the bleed-nipple on the slave-cylinder is way up in the trans-tunnel and difficult to access with a regular spanner. Getting the spanner onto the bleed-screw is not a problem, but if the spanner has any length to it then no more than a few degrees of turning is possible and the valve cannot open enough. A short spanner, the one I used was about 4.5 inches long, has just about enough room to get the bleed-valve open a half-turn or more, but it is still a fiddly process, particularly with the car on low ramps and quickly shutting the valve can be tricky. This can allow air to get sucked back in before the valve is closed fully, as below.

Air Getting Sucked Back / One-Way Valve:

With only a few seconds to shut the bleed-nipple before air gets back in, I found the best solution to be a one-way valve bleed system. These are basic, widely available kits and just have a valve with a ball-bearing in the end, which sucks back and blocks the tube so no to air or fluid re-enters the bleed-nipple after each clutch stroke. At the least it makes the return of air and fluid very slow and that gives the vital time needed to shut the bleed-screw.
I used the Vizilbleed branded kit, left in the pic, and it worked brilliantly, with a soft rubber hose to fit over the nipple and a plastic collar that slides over it to make a tight seal. It also has a built-in bottle to catch fluid and, though the tube could do with being a bit longer, the kit is a bargain at £7 from Halfords. The kit on the right in the picture is even more basic, just a tube with a one-way valve at the end, but I am sure it works just as well. This Halfords branded kit was dearer at £10, but kits like these can be bought from eBay and Amazon for less.
The clutch takes a lot of pumping to get out air stuck in the master-cylinder next to the pedal and the fluid level in the reservoir needs topping-up constantly to ensure it properly fills. The section of reservoir dedicated to the clutch fills from quite high up in the bottle, so when topping up make sure you fill into the neck of the reservoir.
The one-way valve will prevent air getting back in, so the bleed-nipple can be left open and I found the best technique was to pump the clutch-pedal about 20 times, then top-up the reservoir. The level in the reservoir after the first 20 pumps should drop significantly and continue to draw more fluid after it is first filled, so make sure it is topped right up before pumping again. This should not take more than 2 or 3 goes and I found the amount of fluid that bled out of the slave-cylinder was less than I had poured in, meaning after a couple of failed bleed attempts I had finally got that stuck air out of the system.

Pressure Bleed Kit + Air Locks:

If you have clamped the clutch-hose and don't have a lot of air in the system or any air locks, then a pressure-bleed kit should work as normal. These kits, such as the Gunson Eezi-Bleed, work by pumping fluid in using air-pressure from one of the tyres. Problem is, if you do have air locks, particularly air in the master-cylinder by the pedal, then a pressure-bleed will not work to get rid of them. I found that the kit would just pump neat fluid directly through the system, giving the impression of an air-free system, but still leaving the master-cylinder full of air and no clutch-pedal. Even pumping the clutch while pressure-bleeding did not seem to clear the trapped air, I think because it wants to exit the system from the open reservoir and has been pushing against the incoming fluid pressure.
A 'reverse' pressure-bleed kit that builds up a vacuum and sucks the fluid through bleed-nipple as it is topped-up from the reservoir might be effective in getting rid of air locks, as the reservoir remains open and the fluid/air will be pulled down from the master-cylinder, rather than pumped straight past it, but I did not have chance to test one.

Back Filling + Clutch Delay-Valve (CDV):

I have seen many articles discussing back-filling of the BMW clutches to be the easiest way to clear all air from the system. This works by injecting/pumping fluid in through the bleed-nipple using a syringe or suitable pump and ejecting the air out the top of the reservoir. While this may work great for older models, modern BMWs have a slow-return valve fitted before the slave-cylinder [pictured]. This is known as the 'CDV' or Clutch Delay Valve and works by slowing the return of fluid to the master-cylinder when the clutch is engaged. This makes it impossible to dump the clutch too hard, as it ensures a nice soft engage every time. Flow from the master-cylinder to the slave-cylinder is unaffected, so the clutch releases as quickly as you like, it is just when fluid returns that it is slowed down. This is all wonderful technology, but throws its hand in when trying to back-fill the clutch to bleed it as you are pushing against the CDV.

E60: PAS-Pump + Exhaust Vibration-Damper.

With everything else apparently working, the 530d was still of the road due to the niggling problem of an un-bleedable PAS-system and rattling exhaust.

• Bleed PAS-system with cap off reservoir and engine off, by turning the wheel lock to lock about 30 times and adding fluid until no more bubbles were coming out.
• Remove front-bumper and drive back onto ramps.
• Locate exhaust onto connecting-rods of vibration-damper.
• Modify connecting-rods to fit new exhaust position.
• Refit exhaust and reinforcement-plate.
• Refit engine centre-undertray.
• Drive off ramps, refit bumper and test drive!

PAS-Pump Bleed:

This is the hardest to bleed PAS-system I have ever come across, though the pipes / pump have been off the car for 3 weeks and could have allowed the system to drain and fill with air more than before. The pump was whining on tickover and making an almighty groan when turned in either direction. The fluid in the reservoir was also frothy white. To fully bleed it required the engine and reservoir cap to be off and the wheel turned full lock left to right about 30 times. To do this I raised the front of the car on axle-stands so the wheels were still touching, but with hardly any weight on them. The first turns lock to lock gulped the remaining fluid right into the system and so much air was coming out I kept re-checking the pipes for a leak. Eventually, the reservoir had swallowed the last of my bottle of fluid and is just about sitting up to the minimum mark, but still bubbles were popping up as the wheel was turned. The lock to lock business continued with me and my dad taking turns for quite some time until there were finally hardly any tiny bubbles rising to the surface. This whole thing was a job in itself, but the pump is very quiet now and the steering assistance is back.

Exhaust Vibration-Damper:
During the first tests there was an almighty rattle from the exhaust from tickover up to about 2k rpm. I assumed this to be because I had left off the exhaust 'vibration-dampers' that brace the bottom of the cat to the gearbox and stop it shaking. I discarded replacing it at first as, if you don't remember exactly the way it all fits together and start bolting your gearbox and exhaust back on willy nilly, then it's impossible to figure out. The long bracket with 3 holes fits around the edge of the gearbox bell-housing, held in by one of the large E14 and two of the smaller E10 Torx-bolts that hold the box to the engine. The connecting-rods then run from the foremost stud on the cat to the N/S stud on the bracket; and from the rearmost stud on the cat to the O/S stud on the bracket, as shown in the picture from TIS. Only trouble was, neither of the rods went anywhere near the brackets. I'm not sure if the entire engine and gearbox is in a slightly different position from before, or it's just the exhaust out of line, or both, but the eyelets on the left-right rod were about 5mm too long for the studs; and the front-rear ones were almost an inch too short. After 2 frustrating hours spent removing mounts and trying to relocate the gearbox / bracket to meet the exhaust I gave up and decided to modify the connecting-rods to fit the new gap lengths. The only remaining way to adjust exhaust position would be to loosen the two nuts holding the cat to the back of the turbo, only to do this requires the rocker-cover / injectors to come back off and I'm not doing that, for now at least.
The modified connecting-rods are below and, due to lack of time, are rather crudely done. I bent the left-right rod down about 3/4" at a steep angle to take 5mm length out of it and help bring it down to the bracket at a flush angle and works rather well. The front-rear was a bit less neatly done and makes use of a piece of 1mm sheet-steel, cut roughly to an inch square and bolted to the rod. It's not the best workaround in the world, but it gets the job done.
After all that, the 'vibration-damper' did not get rid of the rattle! Instead, I traced the annoying noise to the front rubber-mount a bit further down the pipe. The exhaust was banging right into the side of the metal bracket on the gearbox-mount and a bit of fiddling with the adjustable eyelet managed to separate them and killed the rattle dead, so there you go.