Some Thoughts on Filter Bypass Valves.....

[TheLoneRanger]

In reading a lot of posts here, I see reference to "full bypass" in relation to oil filter bypass valves. This seems to imply that once the valve opens, all the oil passes through the valve. Well, in my humble opinion there is no such thing as full bypass. The valve simply opens partially and bypasses "excess" flow volume that can't go through the filter media. Most of the flow is still going through the media. I guess what I'm trying to say, is that the valve "balances" the flow both through the valve and media, according to the engine rpm, oil viscosity, temperature, etc. Maybe the valve should be called a "balance" valve instead of "bypass" valve???

If this is true, then the bypass valve must be operating much more than we think, even in a newly installed filter. Maybe every time the engine is revved suddenly, the bypass valve opens to balance out the oil flow..... Sort of like an oil pump relief valve, which is constantly operating to provide a steady pressure and flow.

When and how often the bypass valve opens, seems to be one of the last unanswered questions in this forum. Maybe Bob and Joe are getting close to finding it, with their differential pressure testing....

[ March 28, 2003, 10:54 AM: Message edited by: TheLoneRanger ]

 

[Mike_dup1]

Most all GM engines have a bypass valve built into the engine also. What more important, filtering all the oil 100% of the time and taking a rish the filter fails or something impeds the flow of oil and you lose the engine.

I would agree, that for the filter or the engine bypass to go into full bypass mode, something would have to shut down the oil flow considerably to next to nothing. One of the reasons for the bypas has to do with sub-zero weather. A filter can be a big resistance under extreme cold weather conditions.

 

[cryptokid]

i believe you are correct. the bypass valve lets by excess oil,,, but only enough excess to keep the pressure differential in check.

this means if you install an oversize filter you may never go into ybpass.

 

[dickwells]

I guess one question I have is: What is the difference in action between a coil spring loaded valve and the newer stamped poppet type valve. It figures that the coil spring loaded one would open in a gradient but possible the poppet type is either open or closed. Like those spring "crickets" we used to annoy people with as kids.

 

[darrenc]

The difference between the valves is cost and quality. The spring valve costs more to manufacture and assemble, it also works better.

Think of the bypass as a pressure relief valve.

 

[digitaldrifter91]

funnie if u get a big filter and never go in bypass how do u know ur engine is getting enough oil. i think coil spring will be better in that a pop up valve is faulty, what if dirt gets stuck between there? then it will be in slight bypass..but same may go for the spring, but the spring has resistance and will "in theroy (my theroy)" hold a seal.

just my cheap .0005 cents =)

 

[cheetahdriver]

the other thing about a filter in bypass is that it will heat the oil substantially as it passes through the bypass valve. i have had hydraulic systems burn up because the system jammed in a position where the oil had no place to go but through the bypass (gear pump) and nobody noticed until they smelled the smell of smoldering DTE26. LoneRanger is right from the standpoint that the bypass will just open enough to keep the pressure inside the filter at the specified level.

i would also question how well the stamped type valve works. my fear is also that this type valve will either be open or closed. i could even envision a senario where the oil pressure is slightly higher than the valve setting. the valve pops open, relieving the pressure. the valve pops closed, pressure builds. repeat. repeat. repeat about once a second. how long will that piece of cheap steel last popping back and forth?

finally, my solution has been to use an oversized filter. have been doing this since 79 and still find it to be the best (and cheapest) solution.