Monday, December 1, 2008
After two days of frustration trying to bleed the hydraulic clutch on my 73 MGB I stumbled upon the quickest, easiest way to bleed a hydraulic clutch system. Not only will this work on your MGB but it should work just the same on just about any vehicle with hydraulic clutch. I spent at least an hour searching the web looking for different ideas on how to bleed the clutch. I didn't have anyone else to help me and after two different attempts in two consecutive days with blood, sweat, brake fluid, and a lot of swear words I finally got it done. If you're working alone or even if you do have someone helping you if you want to get it done fast and easy this is what you need to do, and it works beautifully. Fill the master cylinder with whatever brake fluid you're using and put a hose on the end of the bleed screw on the slave cylinder that is long enough so that you can secure it somewhere with the end being at the same height as the master cylinder or higher. Get or make a small funnel to put on the end of this hose and before you even loosen the bleed screw pour brake/clutch fluid into the hose until it is topped off, using a clear hose is best so you can see the fluid level. Open the bleed screw and pump the clutch pedal. It doesn't matter how fast you pump it just pump it enough so that you have to top up the master cylinder once more. Now close the bleed screw and pump the clutch some more, maybe for 30 seconds or something and the faster the better, then refill the master cylinder again. Get a hand operated vacuum pump. Any kind will work as long as it comes with all the accessories for bleeding. I've seen them at auto zone for twenty bucks. Put a hose on the pump and put the other end of it onto one of the fittings on an airtight jar which should come with your pump. Put another hose on the other fitting on the jar, clear hoses are best because you can see what's going on. On the end of the second hose you will need to put a suction cup type fitting on (my pump came with one) or something else that will cover the clutch master cylinder filler hole with an airtight seal. It's kind of a stretch but anyone 5'9" should be able to do this. Standing behind the drivers side door, as close to the master cylinder as you can get, hold/secure whatever fitting you found to cover the master cylinder over the filler hole. Use the pump to create a vacuum, it doesn't have to be very strong, anywhere between 5 and 10 inHg (inches of mercury, any vacuum pump will have a gauge on it). When you reach this point you might be able to remove your hand from whatever fitting you put over the master cylinder hole depending on what you use, I wasn't able to but luckily I'm 6'2". Whether you have to keep your hand over the master cylinder or not you need to get one foot on the clutch pedal, or I suppose you could use a stick or something. With your foot or stick over the clutch pedal VERY GENTLY press down on it. You barely have to touch it at all. You will hear, feel, and see the air bubbles coming out of your lines and into the vacuum chamber on your pump. You need to keep doing this until no more air bubbles come and you start to get clear, bubble free fluid in the vacuum hose. If you take your foot off the clutch or you need to take a break or whatever, it doesn't matter, you've still made some progress by getting some air out and this process can be repeated as many times as you want. If you get a lot of air you might want to remove the vacuum and top up the cylinder but really, I don't think it matters. Once all the air is out you will be good to go. After I did this my clutch felt better than it ever has in the year that I've owned my B. The pedal is nice and firm, almost comparable to the feel of the brake pedal! It only took me about 10 or 15 minutes to do this once I figured it out and I'm sure the next time will be even faster. I hope this helps anyone and everyone that has an MG, or for that matter, any manual transmission car! One other thing I will mention is that when I was searching the net for info/ideas I found some video of a guy saying that air can get trapped in the slave cylinder and to use the push rod to move the piston in as far as you can. DO NOT do this! The slave cylinders are pretty poorly constructed and if you push the piston in too hard or even at the slightest little bit of an angle you will cause damage! Even if you don't notice it right away. The seal on the piston is plastic. I learned this lesson the hard way. After pushing in the piston just once to clear the air and then bleeding the line as described above I went under the car to pick up my tools and noticed a drip coming from the rubber boot on the slave cylinder and I just put it in 5 months ago, it was a brand new Lockheed!!! I pushed the boot up a little to take a look inside and brake fluid came pouring out!!! I had to get a rebuild kit from a local MG guy. Also, I discovered after the rebuild that if you bleed the line this way, it doesn't matter if you've got air in the slave cylinder, the vacuum will take it right out. Anyways, hope this helps. It's the fastest way to bleed your clutch and it gets every single air bubble.