Importance of By-Pass Valve Location

[nick778]

Been reading a lot here on an oil filter's flow, filtering ability, ADV, and contruction of the by-pass but little is usally mentioned concerning the location of the by-pass valve. It is my understanding that a by-pass located like in the Motorcraft filters prevents backwash of dirt from the filter into the oil when the filter goes into by-pass mode. So, a couple of questions.
How important is the location in selecting an oil filter? Which brands other than Motorcraft usually have the by-pass in the better location or does it vary largely by application?
Lastly, how does one tell by looking into the filter if the by-pass is at the closed end or the threaded end (I presume this is the preferred location?)? When I look into my filters, I see a spring at the base of the closed end; is this the preferred location that prevents backwash?

 

[Eiron]

I'm not sure location is all that important. Where does the OEM filter have its bypass? Knowing where they have it may help you feel comfortable deciding on an aftermarket filter. On my Saabs, the bypasses have been on the "wrong" (closed) end of the filter for decades. Obviously, they've had a long time to specify a change if they felt it was necessary. Quadrun1 posted a dissection of one of these filters, & it shows just how well it works.

 

[Brian Barnhart]

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How important is the location in selecting an oil filter?

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I suspect optimum bypass valve location depends somewhat on filter application as well as personal preference. Most filters seem to have them at the “closed” end, that is, the end opposite input and output holes. I suspect putting the bypass in the closed end tends to be less costly. Closed end bypass valves also tend to be somewhat more compact, making more space available for filter media.

quote:

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Which brands other than Motorcraft usually have the by-pass in the better location or does it vary largely by application?

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I’m not sure everyone agrees on which is the better location. All things being equal (which they never are), I prefer the bypass on the threaded end. From my observations, the location of the bypass valve depends somewhat on application and filter price. In the case of the Jeep filters I’ve looked at, the more expensive filters tend to have the bypass valve at the threaded (inlet/outlet) end, and the less costly filters tend to have the bypass valve on the closed end. Filters with closed end bypass valves pass oil that is “bypassing” the filter over the “dirty” side of the filter element, whereas filters that bypass at the threaded (inlet/outlet) end don’t require the bypassing oil to pass over the “dirty” filter element.

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Lastly, how does one tell by looking into the filter if the by-pass is at the closed end or the threaded end (I presume this is the preferred location?)? When I look into my filters, I see a spring at the base of the closed end; is this the preferred location that prevents backwash?

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Look inside the center (outlet) hole. Generally, if the filter has a threaded end bypass valve, you will see the inside of a coil spring approximately ¾ inch long (deep) near the outlet opening. The opposite end of the filter element (as seen through the outlet hole) will have no valve and will typically just be a flat or slightly curved metal end. From your description, I’d say the filter you are looking at has a closed end bypass valve.

Examples of filters with threaded end bypass valves are Motorcraft FL-1A, and FL-400S, Mobil M1-204, K&N HP-2004, and NAPA Gold 1085. Examples of closed end filters are Purolator L14670 and PL14670, Fram PH16, TG16, and XG16, STP S16, Bosch 3402 and NAPA Silver 21085. Note: All of these filters, with the exception of the Motorcrafts, are specified for the Jeep 4.0L

Some engines contain built in oil filter bypass valves, and the filters for those engines need no bypass valve. Examples of these are AC PF47, and PF52.

Brian

[ May 29, 2003, 02:20 PM: Message edited by: Brian Barnhart ]

 

[quadrun1]

Ford makes a big deal out of having the bypass valve near the threaded end...

If you look at the FL-400S, the bypass is at the threaded end. But if you look at the Purolator equivalent (L20195), the bypass is at the "wrong" (closed) end. Strange thing is, Purolator makes the FL-400S for Ford!

Now with SAAB, they used German-made MANN oil filters for decades. The bypass valve was always at the "wrong" end. Then when SAAB was acquired by GM, they switched to a UK-made ACDelco oil filter (equivalent to PF53). Its bypass valve is also at the "wrong" end.

But about 1 or 2 years ago, an interesting thing happened with the PF53... production was shifted to the U.S., and the bypass valve was moved to the "preferred" threaded end. This is the PF53 available at most retail outlets.

However, SAAB dealers continue to sell the UK-made PF53, with the bypass valve at the "wrong" end. New 9-5s come from the factory with this filter.

Another interesting thing that I've observed is that if your filter's thread size is not 3/4-16, the valve is most likely at the "wrong" end. (Mitsubishi, Honda, many others...)

Based on the posts here, and my own experiences, I'm reaching the conclusion that as long as it's not a FRAM (or an STP or Bosch Premium with that funky, inadequate-looking bypass), almost any old oil filter is probably just fine. I don't see big differences in the used oil analysis.

And anyone with excessive valve clatter after a cold-start can probably remedy that simply by switching back to the manufacturer's OE filter.

Jason

 

[nick778]

Do you mean the newer Bosch/Mobil 1/STP bypass valve or the older ones with the spring at the closed end. For example, I have an OEM Nissan filter with a spring in it at the closed end and a Bosch 3300 equivalent with a spring at the closed end that looks almost the same. It is, however, about a 6 month old Bosch filter. I have not seen a Bosch yet with a different design at least in the 3300 and 3323 Bosch filters. Maybe I should stock on on the older ones before they are no longer available.

 

[Eiron]

quote:

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Originally posted by quadrun1:
... But about 1 or 2 years ago, an interesting thing happened with the PF53... production was shifted to the U.S., and the bypass valve was moved to the "preferred" threaded end. This is the PF53 available at most retail outlets.

However, SAAB dealers continue to sell the UK-made PF53, with the bypass valve at the "wrong" end. New 9-5s come from the factory with this filter. ...

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Jason,
Good call on the US-made ACDs. Since I still have a huge stock of UK-made ones, I haven't been forced to explore US construction of these filters. (I think the PF13s I use are also showing up as US made now, but I'll probably just switch to the UK-made Napa Silvers or the Purolator Pure Ones when my stock is gone.) Have you used any of the US-made PF53s, & did you notice any engine noise differences?

 

[quadrun1]

No, I currently have a SAAB OE filter on there and will try the Ultraguard Gold UPF53 filter next.

The UPF53 is identical in construction to the US-made PF53, but the filter media is different. Seems that both are made by Champion Labs.

I also got a hold of some oversized UPFL400A (taller version of UPF53), might try that first.

Jason