Tech Tip: Priming a New Master Cylinder

Tech Tip: Priming a New Master Cylinder

Priming in less time.

There are many types of tools used to prime a master cylinder — ranging from a pressure bleeder to a syringe to photo courtesy of cardoneinject fluid into the port of the master cylinder.  
Here is another one to add to your tool box.  You can use a blowgun to prime the bores of the cylinder.  Place the tip of the blowgun at 90º to the port of the cylinder and blow.  The master cylinder should be clamped with the bores in a horizontal and level position and the reservoirs filled to one half full.  It is best to start with the port next to the mounting flange.  The low pressure created in the port will draw the fluid from the reservoir into the cylinder bore.  
You will know when the bore is primed when you see vapor coming from the port.  This is all thanks to Bernoulli’s Principal.  It makes airplanes fly and carburetors deliver fuel. The velocity of the air passing the port is high and the pressure in the port and cylinder bore is low.  The high pressure in the reservoir forces the fluid into the cylinder bore and out the port.  This is the same principal that makes a carburetor work.  The high pressure in the float bowl forces the fuel out of the low pressure created in the venturi.

You May Also Like

Tools in the Eye of the Beholder

We’re here to help you see all the tools, so you can invest wisely.

"The best investment is in the tools of one’s own trade.” – Benjamin Franklin. Needless to say, I agree. We all spend our careers investing in the tools we need to do the job, but, sometimes, based on the situation, the tools we choose differ and occasionally come from unexpected sources.

Brake Lathe Basics

Resurfacing drums and rotors is a machining process with its own specific guidelines.

Refrigerant Oil Has to Be Right

Oil type is just as important as oil capacity.

Three bottles of refrigerant oil
Top 5 Tools: Steve Coffell, Auto World, Hazelwood, MO

Steve Coffell, a technician at Auto World in Hazelwood, MO, says his Top 5 Favorite Tools are: Related Articles – New Small Stud Extractor Now Available from Mayhew Tools – Matco Debuts 5-Piece Purple Screwdriver Set – Mayhew Debuts New Fluorescent Handled Screwdrivers   OTC Genisys Touch – Quick scan, bidirectional control Snap-on VANTAGE Pro

Wheel Bearing Adjustment Tools & Equipment

A wheel bearing that’s out of adjustment can reduce bearing life and can affect more than just the bearing. It’s important to adjust the wheel bearing endplay to the proper specifications. If the bearing set is adjusted too loose or too tight, it can cause the bearing to fail prematurely. There are a few types of assemblies, so using correct procedures and tools will ensure a comeback-free wheel bearing installation.

Other Posts

Multimeter Accuracy: How Important Is It?

Multimeter accuracy is critical for EV diagnostics.

More Than A Scan Tool

Scan tools serve as indispensable diagnostic hubs, offering access to a wealth of resources, from OEM technical bulletins to community-documented repairs.

scan tool
Battling Stress and Burnout

Here are some quick tips for managing stress and avoiding burnout in the fast-paced automotive repair industry.

Nadine Battah
EV Acronyms and Terminology

Electric vehicles (EVs) are here to stay and there’s a lot to learn.