Five sided w123 300D oil filter!!! Why???
 

After changing the oil on my '79 300D, I observed the
old Hengst oil filter had undergone a transformation of shape!!

Normally the filter is cylindrical in shape.

This one's top half, the screen mesh half, had five flat sides.

Apparently the filter had undergone some type of extreme
vacuum like force which pulled in the sides to almost flat
sides. Five sides. (pentahedron?)


Any ideas on how this happened?
approx. 3500 miles on the filter.


Thanks!!:eek:

implosion or kryptonite?
 

Well, I was not aware of that, but I replaced it with a Mann filter.

I have one other Hengst on the shelf.


I am curious also.

X Files???

Just posted that one
 

Greetings UNK,

I just posted that same topic not more than a few days ago about the very same filter and I had the same results with it when I changed it out. I had one Mann on hand and used it as my replacement but I also have to more of the collapable types as well and had an order in for two more that arrived the other day. Hope there isn't a defect in the filter design otherwise several of us that buy four to six at a time are out some cash. I intend to pull the filter cover in the next couple of days and see what the Mann looks like after about 500 miles. Someone had mentioned the check valve in the stem perhaps sticking, but I can hold a lot of credability to that just yet as I'd think oil would be a sufficient lubrication to deter the check valve from sticking. Will try to keep you posted.

Charles

unkl300d and can-do,

After reading this and kind of having a hard time understanding how the problem could be associated with the filter brand, I got the manual out and studied the flow paths into and out of the filter and filter housing.

The only thing that can cause the deformation you describe is a pressure differential across the thin perforated metal "can" on the outside of the very fine filtering segment (upper 2/3 or more) of the filter where the outside pressure is substantially higher than the inside pressure. Since the can is perforated, there can be no static pressure differential across this can. So the only way to get a significant differential pressure is with a low flow resistance on the part of the flow path on the inside of the can. Flow in this path is controlled by a solid sheet metal disc at the bottom of the fine filter volume, separating it from the bulk filter volume below it, the seals on the center tube, dubbed the return flow tube in the manual figure, the small orifice admitting flow to the center return flow tube channel, and a check valve inside the tube about 25% of the way up from the very bottom of the tube.

There is a similar inner can shown in the manual figure, along the inside diameter of the filter. Maybe one of you guys can look to see if this is also deformed.

The check valve allows flow down the center return flow tube, where the flow is returned to the oil sump and apparently not in the other direction. While it may be possible for this check valve to be defective, I doubt it can just fall out, and if it is stuck open, the flow in the normal direction will not be increased enough to cause the pressure difference necessary to deform the filter's outer can (and possibly inner can). This is because the flow path with the valve hung up in the open position is nearly identical to the flow path with the valve operating normally and the flow losses will be about the same for this path as they are controlled not by the check valve but by the little orifice in the side of the flow return tube. Additionally, the check valve cannot determine the brand of filter, so if Hengst filters are doing this and Mann ones are not, the check valve cannot be the issue.

The other two flow path controls are very likely the source of the problem. The upper filter section is intended to provide a flow rate that is lower than the bottom portion, as it is essentially a bypass filter built into the same housing as the main filter. So, the discharge side of the main filter, a relatively low flow resistance path, is isolated from the relatively high resistance path of the bypass filter discharge. This high resistance path is what limits flow so the bypass filter structure can be inexpensive and light so it does not crush - otherwise it would have to be made of substantially more robust materials, including the filter element inside the can (usually a low resistance path, especially when new, but with next to no structural integrity to withstand high differential pressure) or a separate item altogether.

So, there is a rubber grommet like seal on the top and bottom of the bypass section that seals against the center return flow tube, preventing dirty oil from going around the whole filter at the top, and keeping the very finely filtered oil that passed through the top section on its intended path to the little orifice on the center return flow tube and down through the check valve to the sump. If this lower grommet seal is either not there or sized wrong, or coming off at installation for some reason, the bypass filter flow will join the main flow down a low resistance path. A new Hengst bypass filter element, nice and clean with lots of surface area, will try to pass lots of oil flow. That flow will create a differential pressure that likely could deform the outer, and possibly inner, cans.

If the bottom sheetmetal separator between the bypass and main filter segments is damaged, or missing, the bypass filter discharge will also access the low flow resistance path and cause the same effect, except the inner can will likely not be damaged.

So, I think one of the bent filters should be visually examined and possibly cut in half to see what the problem is. If more than one of these is like this, there is a manufacturing problem that Hengst should be willing to fix for free. Otherwise we should all avoid these filters. I doubt the condition damaged anyone's engine, but it is not what the Mercedes-Benz engineers designed, so it is not something that should be tolerated.

If the grommet is coming off when you put the filter housing cap, with the return flow tube attached, on with the filter in the housing, maybe this part needs to be lubricated with engine oil as part of the procedure. This should be apparent by feel, comparing a Mann installation to a Hengst one, the Mann assembly should be less effort. I usually lube the o-rings at the bottom and top, but do not go out of my way to slather the return tube with oil at assembly. I have never seen this deformed can situation either.

I hope this helps, and good luck. I will avoid Hengst filters for the time being. Jim

3 cornered hat- five sided filter-3 legged chair
 

I will attempt to take pictures and then dissect.

I've never posted pics here before , so it may take a week.

Thanks Jim and Can Do.

I think I'll check my new Mann filter as well after a month.

Denis

GEE , JIM, I was going to go for " your car has five cylinders so obviously it would get sucked into a pentagon "..... :) Greg

Greg,

Hmmmm, I hadn't thought about why it is five sided (pentagon?). Adding that to the problem to be solved makes the five cylinder theory sound pretty good, I mean, none of us can ponder these issues endlessly and five sides with five cylinders - does anyone really think that is merely coincidental? (LOL)

Lets see if the inner cans are five sided, and if so, that should be proof enough, right?

Sometimes you just have to take things at face value. Jim

I have a friend that knows that 'contrails' behind jet planes are composed of chemicals the government is spraying on us...Given his other theories I am more inclined to believe that the chemicals are landing on him, but that may also explain these filters compressing into themselves imitating black holes....and it is black in there when they do this if it is diesel oil they are swimming in...Are any of our Chemist forum members involved in mixing these chemicals the government is spraying on us ? I know, Iknow,,you could tell us but then you would have to kill us..... :) Greg

I've just (in the last 2 weeks) changed out two Hengst filters--no problems of deformation.

Changing filters, you're supposed to blow compressed air through the center tube, to make sure it isn't plugged. I suspect most people don't do this. The first time I did, it took me a half hour to clean the tube out.

Jim's analysis could well be right (too complicated for me), but the first thing I'd do is make sure the center tube is clear.

Nice one Greg
 

Your buddy's theory sounds about as plausible as the "Russian Crude Oil" based diesel is causing the idle surging problem.

BTW, although I did have the mysterious idle surging symptom this winter, it has gone away. Maybe the Russian Crude left the market.

JCD

dweller and unkl300d,

I am sure the little spring loaded check valve in the return flow tube is important to proper functioning of the filter. For example, if the valve fails to open the whole top two thirds of the filter becomes inert, as no oil can flow through it. All the oil has to pass through the bottom, less restrictive part, which means the oil does not get cleaned as intended. That will eventually lead to accelerated wear of the engine's bearings and other critical parts.

However, if the check valve is plugged there is no mechanism to generate a force to collapse the upper can. Remember, it is perforated to allow oil to pass into the filtering media, so if there is no flow, the pressure on both sides of the can will be equal and there is no reason for it to deform. Also, the restriction of the orifice in the side of the return flow tube would normally make the pressure drop across the filter element very low, exposing the grommet seal to nearly the maximum oil pressure most of the time. So it is unlikely the plugged line will cause the grommet to fail either, but I guess it is possible. This would still not explain the Mann filter being immune to the issue.

I did not try to be confusing in my explanation, but apparently was. Please excuse me if I got too long winded and hard to follow.

By the way, I have never tracked the manufacturer of oil filters I have changed over the last two decades, and have never seen this problem myself. Without any data that adds another brand, I think it is likely an issue with a batch of these things from this vendor. I will stop here as I do not want to monopolize the forum on this topic. Good luck and I am waiting for those photos! Jim

Didn't deform on the interior of filter
 

Greetings Jim,

I wished I had saved the filter, but it's part of our future oil reserves in the making now. I did look on the interior of the filter before discarding it and the interior metal was not deformed in the least. Whatever the pressure was that was applied, it was most likely a vacuum from the interior of the filter assembly. Looking at the oil flow diagraphm in the manual, I still find it hard to believe that the pressure or vacuum could be that great to collapse a filter like that unless oil suction pressure became so great and the bypass valve didn't open forcing oil to be pulled from the top filter only and sheer volume of oil created the collapse. Hey, I'm open to ideas as I still have four Hengst filters to use up. I think I'll pull the lid off the filter assembly when I get a day I'm not at work and blow the center tube clean with air to see if that has an impact on operation.

Charles

Just my opinion, but, to me, it sounds a lot like Hengst got a bad batch of filters made. Maybe one of the workers got mad and did substandard work.

IMHO it'd be best to see if this is happening with other filters...

Going to try once more to make the point. There has to be a mechanism to develop the force necessary to crush the outer can on the bypass section of the oil filter.

This force can not be generated by static conditions as under static conditions (no flow) the pressure on the outside and inside of the can are equal. This is because the can has holes in it (90 of them on a MANN filter as I just counted them on one I have on my desk waiting for the 240D to come back from Troy, NY for a service) which cannot sustain a static differential pressure (the pressure will equalize through the holes). Since all the flow through the upper portion of the filter goes in the little hole in the return flow tube at the center of the oil filter housing cover, and down to the check valve, a blocked check valve will generate a static flow condition and no chance for deforming the outer can on the bypass filter section.

Consequently, the force must be generated by some other conditions. At very low flow rates the situation is much like a static pressure situation. As the flow through the 90 holes is increased by lowering the pressure on the downstream side, the resistance to this flow increases (like drag on your car - at 5 mph it is hard to measure the air resistance but at 80 mph most of your engine's output is devoted to overcoming air resistance to the car's movement). This increasing resistance can sustain a differential pressure across the perforated surface of the can.

Under normal flow conditions the flow rate in the upper, bypass section of the filter is kept low by the size of the hole all the flow must travel through in the side of the return flow tube, and the resistance of the check valve mechanism. At the normal conditions there is very little resistance at the 90 holes in the outer can, as they have about 90 times the flow area of the single hole in the return flow tube.

So, to make conditions that will develop the necessary forces, there needs to be substantially higher flow through the upper, bypass portion of the filter and its outer can. A plugged return flow tube check valve will not generate this condition unless the pressure across the rubber grommet seal at the bottom of the bypass filter section (about one third of the way in the filter looking from the bottom) that results is enough to pop the grommet off. I doubt this can happen, but it is a possiblility. The grommet seal failure would allow the bypass filter flow to access the low resistance flow path of the main filter element.

So, a scenario where high flow in the upper section of the filter is needed, and any one that happens is good enough for me. I think the inner can is much less likely to deform than the outer can, just by the fact that it is much smaller in diameter (less surface area). Suggesting it might have been deformed could have been a red herring and added to the confusion.

I hope this helps, Jim

GEE, JIM, you remember the story of the poor cobler and his wife where Gnomes came into the shop at night and made the shoes for him ? That was going to be MY next theory.... Gnomes hammer these things into pentagons as part of a satanic ritual.... :) Only on nights immediately following being sprayed by 'Contrails' of course..... Greg

Out of curiosity, I just pulled the oil filter cap on both cars, to check the Hengst filters. Neither deformed--one has about 1K miles on it; the other about 2.5K. Just a data point--don't know if it means much.

BTW, it's amazing how clean the filters are, using Delvac1.

I have to agree on the Delvac 1 comment. I just changed the oil in my E300D TurboDiesel and was equally impressed. I did not have to wire brush my hands after the job either. And the new stuff actually stayed clear looking for about 50 miles, and it still doesn't look like the usual Diesel mud after 200 miles. Neat stuff. Just an observation, Jim

Exhibit A
 

Here you have the filter in question.

Hengst.
Note the post-modern lines indicating cosmopolitan tension in a war time era. Subtle hints of anxiety with fine delineations....

five sided object sublimates a hint toward the Pentagon and
classical phallus symbol.

schizo filter
 

Once again the artist has compelled the viewer to
ponder the shearing forces of social tension and unrest.
Note the schizo-morhic object with repeated
Pentagonal (war) symbol contrasted by Round
(bubble head) symbol.

Interior is uneventfulas we find all grommets intact, core intact
and unobstructed center. Symbolism is strong for Harmony- Potential.

Demon
 

Finally we view the lone artifact found amidst this visual cacophony.

The beer drinking German-Elf. Historically the imp behind all
world chaos and disruption.
Note the bubbles inside the glass and the foam droplets outside the glass.
Very symbolic.

--Hengst

Looks like mine did but more subtle lines
 

Greetings,

The filter looks somewhat like mine did but perhaps mine was six sided as the bend lines were more subtle and evenly sucked in. The top didn't seem to be deformed like yours but all sides had their mark of vast pressure or suction, that one is still up for debate from what I read. Had a day off today but ended up doing a road trip to pick up a new to me Blazer, so not much else besides baling the grass got done after I got home. Can someone please do the anti-rain dance for us here in Missouri. Two days of drying out and the grass or hay I should say is still wet to cut. Got more rain on the way the next several days, anyone need it?

Charles

unkl300d and can-do,

Well, the filter sure is bent. And the design of the outer can is different than the one on my MANN filter. Actually the Hengst one is much more perforated. The holes look to be small semi circles kind of punched into the metal. Looks like it is less restrictive to flow than the 90 holes of the MANN filter.

I guess I will have to find another way for the bypass filter flow to make it to the main filter discharge line.

Were the grommets tight on the center tube when you took it out? Which end was up? The canned end or the other end? The reason the can deformed is still that the flow through the bypass section was much higher than it is supposed to be, which makes it possible to develop a pressure differential across the can even though it has holes (lots of them!) in it. It seems there may be other means to allow the unintended flow.

How are the MANN or other replacement filters doing? Maybe you can save the grommets and see how they fit over the center tube of the oil cap when you change filters. There has to be an explanation for what happened and it bugs me that this one is so elusive.

Jim

filter x file
 

Jim, the filter was installed correctly.
Handle side up.
The washers were fine on both sides. No obstruction inside.
I don't recall any difficulty in removal. I can only
assume that it went in without incident 3500 miles ago.

Yes, it is intriguing.

unkl300d,

This is a puzzle. There are three of those grommet/washer things. One at each end and one in the middle. I believe the one at the bottom is larger than the other two (one at the top and one just below the point on the filter where the can ends). So all three were fine?

Could just be a tolerance stack up where the inner grommet does not seal on the actual diameter of the shaft. Well, if it happens to more people, it may be worth some additional thinking, but it sounds like you guys have this behind you now. Sure is an interesting phenomenon. Good luck, Jim

Just for information, here are a couple of scanned images from the manual's description of the filter and housing oil flow path. One is close up of the filter and housing cross section showing the flow path, the other is the whole page it came from with some text I hope is legible. I will make two posts to try to get the attachments in, but have no idea what it will look like. Jim

Maybe if I rotate it you can read it. Jim

Here is the other one, rotated as other than twisting your neck a little they are legible this way. Jim

bad memory
 

The filter is gone now.

I recall cutting it in half as the pictures show, and pulling some of the fiber out of the bottom portion in order to reveal
the center shaft better.

For some reason I do not recall pulling off or finding a center
grommet.

I do recall trying to pry off the top grommet but don't recall
whether I did accomplish this or not. I mention this because I vaguely recall
seeing or moving something black aside at some point..

So, if for some odd reason, the middle grommet had not
been installed in that assembly, apparently this would
cause such outcomes?

maybe that is what happened?

darn I wish I could remember better.
Before cutting it, I did look down the center and it was clear
with no obstruction.


By the way, thanks Jim for the diagrams.

That helped me revisualize.

Denis

unkl300d'

No grommet at the mid position would cause the bypass flow to join the main flow down the standpipe (21 in the figure) instead of through the orifice (5) in the return flow tube (22). That would increase flow through the top section as I suggested in the earlier posts, which can cause the can to see a differential pressure (the can becomes the throttling feature for flow). I guess I will visually examine these things better from now on, just to make sure they are going to work correctly. Jim