[ritedhawan]

I have been using a Honda Accord 2008 2.4L AT which has clocked 120,000 KM. Recently I went to an independent workshop to get the 'Brake Master Cylinder' replaced. However, once the mechanic unscrewed the 2 bolts which allows the component to stick to Brake booster and disconnected the short cable on the left of the brake master cylinder. He was 'Unable to remove the Brake Master Cylinder'. It seemed as if the 'brake master cylinder' is stuck to the brake booster!. Initially, he tried to pull it out as usual , nothing changed. Then he tried to apply additional force, still no change. Then he got some 'rust penetrant ' and applied where the 'brake master cylinder' sticks to the Brake booster. He tried again to pull the part, no change. He applied the 'rust penetrant' again and we waited for 1 hour and then tried to pull the part. Still no change.

The mechanic and his service advisor came to the conclusion that: they cannot disconnect the part and forcing it out may incur damage not only to the part but to the connected 'Brake Booster'. We collectively decided to give up the part replacement. They re-installed what was taken off during this procedure.

Let me now elucidate in detail , what required the change of the 'Brake Master Cylinder':

Its been months now that I have been facing this peculiar issue : The brake comes into effect only when the brake pedal is pressed sufficiently. For example, for the initial press of the 'Brake pedal' , nothing happens. Lets say, that the 'brake pedal travel' is being measured on a scale of 1-10. For the initial '1-4' brake press , nothing happens. Brake comes into effect between '5-10' on the scale. I keep on topping up 'Brake fluid reservoir'. Initially, I went to the same workshop which recently attempted the part replacement (WoS, Noida). There the mechanic and SA mentioned 'Brake Master Cylinder' being the culprit. I got the same diagnosis from another workshop. I have checked some YouTube videos and they confirm the fact that its the 'Brake Master Cylinder'. Therefore, when I went to the independent workshop , I had procured the AFM Brake Master Cylinder. However, what can we do if the originally one is stuck and wont come out?

This is where I need advise from fellow T-BHPian's:

What can we do IF we are unable to replace 'Brake Master Cylinder' as it seems to be stuck to the 'Brake Booster'?

I would like to inform all, that we have already done the brake bleed and it makes marginal difference to the issue. According to the SA and mechanic , if they force the part out , it would not only damage the original 'Brake Master cylinder' --This is something that I can allow, as I already have the replacement-- But it would damage the brake booster as well. This is what I fear. That is the reason we aborted the replacement. But then I am stuck with the same issue.

My constant fear is: If they force the part out albeit damaged and then on top of that the brake booster has incurred damage as well. Then I may have to get the Brake Booster replaced as well.

Lets continue with the same line of thought and we decide to replace both. What guarantee that the original brake booster wont cause the same problem that the 'Brake Master cylinder' is causing. The problem: unable to remove it. Then I will be stuck and would have no where to go. This is where I need fellow T-BHPian's advise.

[vigsom]

Originally Posted by ritedhawan

- seemed as if the brake master cylinder is stuck to the brake booster
- tried to pull it out as usual , nothing changed; tried to apply additional force, still no change, 'rust penetrant ' and applied where the 'brake master cylinder' sticks to the Brake booster, waited for 1 hour, no change.

- I keep on topping up 'Brake fluid reservoir'

1. I presume you've inspected the brake network and confirmed that there are no leaks - ABS Unit (please run your fingers at the bottom and check for leaks), brake hoses, joints, disc brake pistons, rear brake system

2. If you're needing to top up brake fluid every now and then, and you've checked that there is no leak in the brake system, then the brake fluid is leaking past the o-ring inside the tandem master cylinder (TMC) into the brake booster.

To remove the brake booster and TMC as one unit here is what can be done:

1. Remove the strut bar connecting the two strut aprons (marked in the attached pic below)
2. See if this gives one enough room to pull the Booster and the TMC out
3. If not, you will have to recover the refrigerant and disconnect the power steering hose and the AC Compressor suction hose (marked in red) to create that opening
4. Disconnect the brake pedal connection to the booster and the 4 bolts mounting the booster assembly to the engine firewall (body of the car)
5. Remove the booster assembly and then try to remove the TMC

It is likely that the booster has accumulated some brake fluid. If yes, that will need to be cleaned out only using a suitable solvent (service technicians would know best). If there is no other leak in the brake system and it is confirmed that the TMC is the only one that is leaking, your system will start working well after TMC replacement. If you find the booster damaged/corroded inside, please have it changed too. Getting a good booster - TMC from the used parts market will also do.



Attaching two pics for reference - this is from another car though

Booster front end with TMC removed


Booster assembly removed - note the mounting bolt holes on the engine firewall

[ritedhawan]

First of all, Thanks for the reply.

1. I presume you've inspected the brake network and confirmed that there are no leaks - ABS Unit (please run your fingers at the bottom and check for leaks), brake hoses, joints, disc brake pistons, rear brake system

I will ask the mechanic on the next visit to check the network again.

2. If you're needing to top up brake fluid every now and then, and you've checked that there is no leak in the brake system, then the brake fluid is leaking past the o-ring inside the tandem master cylinder (TMC) into the brake booster.

I have to top up brake fluid every 700 to 1000 km. The amount added is not more than 10 ml. I presume brake fluid is leaking into Brake Booster. There is a hose inlet on top right of the brake booster. The mechanic unplugged that hose. Seems vacuum line or something. When he unplugged the hose, he inserted a thin metal line or something in the inlet on top right of brake booster, not in the hose. When he pulled that thin line, he identified brake fluid on it.

To remove the brake booster and TMC as one unit here is what can be done:

1. Remove the strut bar connecting the two strut aprons (marked in the attached pic below)
2. See if this gives one enough room to pull the Booster and the TMC out
3. If not, you will have to recover the refrigerant and disconnect the power steering hose and the AC Compressor suction hose (marked in red) to create that opening
4. Disconnect the brake pedal connection to the booster and the 4 bolts mounting the booster assembly to the engine firewall (body of the car)
5. Remove the booster assembly and then try to remove the TMC

The first point was followed while attempting Brake master cylinder replacement. But it wouldn't provide enough room to take brake booster+master cylinder out. So the rest of the points will have to be followed to take the complete thing out.

It is likely that the booster has accumulated some brake fluid. If yes, that will need to be cleaned out only using a suitable solvent (service technicians would know best). If there is no other leak in the brake system and it is confirmed that the TMC is the only one that is leaking, your system will start working well after TMC replacement. If you find the booster damaged/corroded inside, please have it changed too. Getting a good booster - TMC from the used parts market will also do.

I am of the same opinion that booster has accumulated some fluid. I have already ordered OEM Brake Booster from boodmo. Hoping they will fulfill this order.

My constant fear is: Even if it came to the point that we have to pull out both booster and master cylinder and we have followed your required steps to gain enough space. If the booster gets stuck to the firewall after unscrewing those 4 screws, just like master cylinder is stuck to booster. Then I will be in a slough of despondency. Because then I am stuck! with replacement parts in my hand and yet unable to plonk them in the car!


Additionally, would like to add that I took the car in the same condition to Manali 10 days ago, and in the space of 4 days travelled: Noida-Chandigarh-Manali-Keylong-Manali-Chandigarh-Noida in the space of 4 days and after covering 1200+ KM had to add as always at least 10 ml of brake fluid once.

I have to take the same car to Manali in the first week of November.

[vigsom]

Originally Posted by ritedhawan

If the booster gets stuck to the firewall after unscrewing those 4 screws, just like master cylinder is stuck to booster. Then I will be in a slough of despondency

This won't happen. The booster mounted onto the firewall is a very simple joint and will never get jammed. Just for you to be reassured, you could ask the technician to loosen each nut holding the booster to the firewall by a quarter turn and tighten the nut back. That will give you the reassurance that the booster nuts and bolts are openable. In the case of the TMC, the leaking brake fluid has caused the issue of the TMC getting stuck. I don't see any other reason for this.

[Kosfactor]

In some vehicles the Brake master cylinder and booster comes as a single replacement part - considering the age of this vehicle please replace both.

[dhanushs]

If you search online, you will get to know if the booster and MC is a single unit. If not, you should not incur damage separating both. In any case, remove the Booster + MC completely, then try separating the MC.

[BusCar]

As mentioned by Kosfactor, the Brake master cylinder and Brake booster is normally a single assembly part in vehicles. Please replace the complete assembly. This should resolve the issue of oil leakage and improve brake pedal feel.
There should be not issue in replacement of this assembly on the firewall. The nut and bolts used for connecting Brake booster+MC assembly to firewall can be loosened to check this.

[priyankarb]

In my view, driving the car with known issue in the braking system is not worth the risk, especially since you intend to make another trip to Manali soon.

The independent garage you considered PROBABLY does not have sufficient expertise in attending to an Accord’s braking system – possibly due to lesser practical experience, so would you kindly consider taking the car to a Honda authorized service center if that is in proximity. I am sure the guys there will be knowledgeable enough and can fix.

Drive safe!

[car-dent]

Do not drive the vehicle before getting it repaired. We had a similar problem with our Mercedes B180, wherein the brakes were making some woosh noise on brake pedal depression. That continued for a few days and then suddenly the brake pedal got completely depressed and didnt come up. Any brake fluid we put just disappeared into the booster. Thankfully it was parked at home at that time. The car couldn't even be towed or moved as in mercs its not possible to put them into neutral from park unless you press the brake pedal( at least i and a mechanic which specialises in german cars couldn't do so.) and the brake pedal wasn't working.
The master cylinder wasn't in stock with mercedes and was backordered from Germany which took about a month to arrive. Till that time the car was parked.
It would have been really problematic had it happened while driving or at any other place.

[ritedhawan]

Day before yesterday, took some time to get the car to the repair shop in order to get the pending replacement job done. The OEM brake booster, brake master cylinder, and OEM Dot-3 brake fluid had arrived and been lying dust at my home. The job of detaching the old brake master cylinder from brake booster and getting brake booster out from the engine bay in itself required two to three hours. There wasn't enough space to get the brake booster out, the mechanic had to get the AC line out which lead to the release of any existing AC gas in the system, the strut bar had to be removed, we didn't remove the power steering hose as stated by fellow Bhpian 'vigsom'. However his advise was really helpful in terms of getting the job done.

Once the old parts were out, getting the new brake booster installed was time consuming. The replacement job started at 1145 and by 4 PM we had the old parts out and the new brake booster installed. Then the new brake master cylinder was installed and filled with OEM brake fluid. The peripheral parts taken out to get the space required for the brake booster were re-installed, AC gas refilled, then started the final phase of brake bleeding and test drove the vehicle to check everything was in order.

I have driven the vehicle for 100 KM's since the job was done and the braking is working fine.