Questions and Answers
Chrome Breather Cap
Q. Hi! Thanks in advance for taking time to answer my question. I would like to know what the difference between a regular oil cap and a breather cap. Obviously, the breather allows filtered air into the crankcase, but what are the effects of this? I own two Taurus SHO's a 1992 MTX and a 1994 ATX, both of these have a stock oil cap with no obvious way for air to enter the crankcase.
What effect would adding a breather cap have on my cars? I ask because while I was recently looking for a new cap to replace a damaged cap, I came across a "Chromed Oil-Filler Breather Cap" marketed specifically towards the Taurus SHO. It looks very nice, but I would like to know more.
Thanks for your input!!!
A. As you already know, the breather cap allows filtered air to enter the engine. Ford and Chrysler used these for years and GM did use them to a smaller extent.
To understand the reason for the breather cap, you have to understand a bit about the Positive Crankcase Ventilation (PCV) system. The crankcase has a hose leading to it from the intake manifold. This put's negative pressure inside the crankcase and draws engine fumes and blowby into the intake to be reburned. The system requires that clean, filtered air enter the crankcase, usually through the valve cover, to provide the proper ventilation. Today's cars have a hose leading from inside the air filter to the crankcase to provide that clean air.
But in the old days it was easier to just combine the breather and oil fill cap into one unit. This way clean air entered one valve cover, circulated through the engine and out the other valve cover into the intake. It also had the advantage that it could be cleaned and not have to be replaced as a regular breather filter does. It was also much bigger and would last longer.
Your cars do not use a breather cap and you shouldn't replace your oil fill cap with one since it will effect the emission controls of the engine. If you want to add a touch of chrome under the hood, just get a chrome filler cap from any of the larger parts stores.
Additional Information provided courtesy of ALLDATA
