Readers’ Tips—

July 1, 2010 | By John Hunter

Bleeding a Clutch With a Push Pump

Removing the transmission and installing a new clutch in my old Nissan pickup, while lying in the driveway, proved to be quite a strenuous job for this amateur mechanic.

Then, after also adding a new slave cylinder, I was faced with the task of bleeding the hydraulic clutch. However, after hours of faithfully following the manual’s instructions on how to manually bleed it by myself, and even with the later help of a friend, I was unable to get any pressure to the clutch.

Pressure bleeding or using a vacuum pump seemed like viable solutions, but I lacked both of the tools and didn’t have the money to either buy or try to fabricate them.

Then I remembered the push pump I had just purchased, along with quart bottles of transmission oil,so that I could add new oil to my transmission.

As the readers no doubt know, this pump threads onto the oil bottle, and enables one to push the oil up into the transmission against gravity. The pump I had bought cost about $6, and was made by Valvoline.

I cleaned the pump before using it and threaded it onto a cleaned quart oil bottle that I had filled with brake fluid.

I attached the pump to the slave cylinder nipple via the clear plastic hose that came with it. (Note: I had to use a smaller plastic hose as an adapter between the pump’s hose and the slave cylinder nipple.) I then pumped brake fluid in reverse toward the master cylinder and got pressure to the clutch pedal right away.

Using information I found on the Internet, I then jiggled the clutch pedal back and forth, pressing in about a half-inch to an inch or so for a while. This is supposed to help the air to bubble out of the clutch master cylinder, and I think it helped with that. I then stayed under the truck and pumped the slave cylinder back and forth for a while. (This helped more air bubbles to bubble up through the master cylinder.) After doing this, I got a firm clutch pedal and was able to operate the clutch with no problem.

While using the pump, you should make sure the master cylinder doesn’t run dry of fluid (it shouldn’t, really, as you’re pumping fluid toward it.), and that the fluid doesn’t overflow over everything (just push fluid into it to the upper fluid level line). It’s also a good idea to draw out the first fluid that enters the master cylinder, and discard it as it is likely to be dirty. I also wouldn’t pump the push pump too hard, just use slow, regular strokes so the master cylinder seals are not disturbed. Another thing to keep in mind: It might be a good idea to use tape on all of the hose connections.

It worked for me, and I felt a bit proud of myself that I had bled the truck’s clutch on my own, using something I already had on hand.

After I was done, I found that the push pump fitted the threads of a 2-liter pop bottle perfectly.

Using a pop bottle could be an alternative to using an oil bottle, but I would test it first to see if it will stand up to the hydraulic pressure.

John Hunter Seattle, Washington