PeachParts Mercedes-Benz Forum - Will I still Get Filtered Oil If I Block Off My Oil Cooler Lines or Ports?

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Will I still Get Filtered Oil If I Block Off My Oil Cooler Lines or Ports?

There was a question a Month or so ago if for some reason you had to completely block off the Oil going through the Oil Cooler Circuit; if when the Oil Cooler Thermostat opened; Oil that was supposed to go through the now blocked off Oil Cooler Ciurcit would have no place to go but through the Oil Filter Bypass Valve (and that would give you unfiltered Oil).

The answer is yes you will get filtered Oil.

The answer is on page 5 of the Manual section 18-005.

LOL, have you considered putting your researched answer on the end of THAT THREAD ?

Quote:

Originally Posted by leathermang (Post 2702918)

LOL, have you considered putting your researched answer on the end of THAT THREAD ?

My turn to be Lazy.

Actually I do not remember enough about the other thread to search for it in a reasonable time.
Also to day I am trying to get my Car back together after removing the IP and the Oil Filter Housing.
(on both the Gaskets leaked Oil where they attached to the block.)

This thread is at least as interesting as the "here are pics of my new 300D I just bought Threads.

I'm still unsure whether that will always be the case

My copy of the FSM has been badly scanned - so it is hard to see - but have a look at this diagram which is on page 11

http://www.peachparts.com/shopforum/...1&d=1303234961
I understand that in the world of the ideal OM617 the oil filter housing is meant to behave as described in the FSM but I was thinking that in the real world it may (just MAY) behave differently.

The oil enters at arrow "a" as shown above - it goes through a "star valve" that's number 16 (you can hardly see that from the crappy scan though).

The star valve acts as a non return valve so the oil filter housing doesn't empty via this route when the oil pump (=> engine) is stopped.

The control valve (12) and the thermostat (11) would normally open to allow flow via "A" round the oil cooler and back to "B" at a temperature of about 95 degrees Celsius and higher.

If "A" is blocked then the oil should in principle flow upwards through the little gap next to the spring for parts 11 and 12 and into the coarse filter part of the of the filter element and back into the engine. If there is enough pressure the oil should also reach the fine filter part of the filter element above. I understand from the FSM that this gap is smaller than the normal route to the filter - the normal route is restricted as the flow is encouraged to flow via the cooler. I'm not sure about how big this gap is though as I haven't been able to get hold of the special tool to remove the thermostat housing to check.

I've been worried that if people just block off the flow at "A" the pressure relief valve could be fooled into thinking that there is a blockage in the filter as the flow is already restricted going into the filter (as described in the FSM and above). On an older car with less than ideal conditions in may (just MAY) cause the pressure relief valve to open and so you then get unfiltered oil flowing back into the engine.

That is why I think it is probably safest to either remove the thermostat if you block off "A" or alternatively just connect the two unions "A" and "B" together with a bit of pipe.

If you join the two unions "A" and "B" you can be assured that the filter housing is working as well as it should be albeit with a really crappy "oil cooler" (<= just a bit of pipe that runs down the side of the filter housing).

I too am skeptical that all the downsides are realized...MB does not do anything halfway or without a reason... I did not read Army's post , sometimes things are designed where only when something else messes up... gets blocked lets say for this example... that the engine might not be toasted as a result of the backup design element...

The thing about getting it to the other thread END is so people who find that thread will see your excellent answer.... sorta the purpose of some of these threads... LOL

Quote:

Originally Posted by Army (Post 2702970)

I used the 617.952 manual.
The whole outer portion of the Oil Filter is exposed to the same amount of Oil Pressure.

With the exception that there is a spring loaded Valve at the bottom tube that extends from the Oil Filter Cap; when that spring tension is over come the Fine part of the Oil Filter also has Oil flowing though it but at a low flow rate due to a single less than 1/16" hole at the top of that tube that restricts the flow.

I am guessing that at Idle speeds no Oil is going through the fine bypass section of the Oil filter but have no way to tell if that is true or not.
The Bypass Valve reacts to a difference in pressure between the inside and the outside of the Filter.

Unlike a simple Pressure Relief Valve in normal use the Bypass Valve has Oil Pressure on both sides of the Valve; Oil pressure on the dirty Oil side and the clean Oil side.

The manual has the Bypass Valve opening at 3.5 bar (about 50psi) of differential pressure.

Yet when I put a test Gauge on my Engine and was getting 97 psi after first starting my Oil Filter Bypass Valve was not opening and given me dirty Oil during idle; because it had nearly the same Oil Pressure on both sides of the Valve.

So If you Oil Filter is OK I do not see any reason that a blocked Oil Cooler Outlet port would cause the Oil Filter Bypass Valve to open.

Quote:

Originally Posted by leathermang (Post 2702988)

...I did not read Army's post...

So you're not playing ball because you feel this information is in the wrong place?

Quote:

Originally Posted by Diesel911 (Post 2702992)

I used the 617.952 manual.
The whole outer portion of the Oil Filter is exposed to the same amount of Oil Pressure.

...

The Bypass Valve reacts to a difference in pressure between the inside and the outside of the Filter.

Unlike a simple Pressure Relief Valve in normal use the Bypass Valve has Oil Pressure on both sides of the Valve; Oil pressure on the dirty Oil side and the clean Oil side.

The manual has the Bypass Valve opening at 3.5 bar (about 50psi) of differential pressure.

Yet when I put a test Gauge on my Engine and was getting 97 psi after first starting my Oil Filter Bypass Valve was not opening and given me dirty Oil during idle; because it had nearly the same Oil Pressure on both sides of the Valve.

So If you Oil Filter is OK I do not see any reason that a blocked Oil Cooler Outlet port would cause the Oil Filter Bypass Valve to open.

I don't quite go along with the first statement that you made about the outer part of the filter being exposed to the same amount of pressure.

This is an oil filter not a bled hydraulic system. Without the presence of air I would guess that to be true - but I think the oil filter set up will be more variable. I haven't been able to check this though - but I have big plans! (I've always got big plans I'm still sourcing equipment to measure glow plug output voltages...)

As for the second statement that I've highlighted I agree so long as the filter is OK you are unlikely to have any trouble - BUT how can you measure the condition of the filter when it is in the housing? Service intervals are set to so many thousand miles / kilometers after which it is assumed that the filter is old and so it gets changed. Would you have to change the filter more frequently because the flow through the filter is not as good as it should be? I think perhaps anyone who just blocks off the oil cooler unions ought to think about that!

I am some what perplexed by this. We have 2 very knowledgeable members with opposing views.
I have heard from many MB trained mechanics that one should never block the cooler lines.
I first heard this for a 280 motor. Something makes me think it even gets a mention in that stuff I sent you Army. I thought that the oil thermostat actually restricted the flow bypassing the cooler once it heated. A bit like the coolant thermostat. Not having ever needed to pull one to bits, I cant say for sure.
Maybe its a rule that applies to some of the MB motors & not others. As a rule, I would be against removal of the oil cooler anyway. I guess that we dont need to consider it if the cooler is kept in the system.

Quote:

Originally Posted by layback40 (Post 2703440)

Thanks for the input layback40 - from the information in the FSM (thanks) it does say that the thermostat diverts the oil from the usual route to the filter towards the oil cooler.

I'm probably not being clear enough about my opinion:-

(and it is only an opinion!)

I'm saying that under ideal circumstances blocking the oil cooler unions off probably won't do any noticeable damage - but - if things are less than ideal (say dirty oil / leaking O rings in the filter housing / dirt / bad luck etc etc) then people who simply block off the unions could (and I stress COULD) possibly be in a position where the system no longer functions as it should:-

Filters may not be useable for as long as prescribed by the FSM; in the worse case scenario the filter doesn't filter anymore because the relief valve operates because it thinks the filter is clogged due to reduced flow induced by the thermostat.

Deep breath! Here's the punch line!

If you wish to remove the oil cooler I'm advocating the addition of a pipe that runs from the bottom union to the top one so that the filter housing assembly operates as it should.

PS I don't think that I have even a quarter of the experience of diesel911 - but it is flattering to suggest that I'm on the same playing field. I'm still a newbie!

I've only ever owned one Mercedes.

Quote:

Originally Posted by Army (Post 2703457)

... in the worse case scenario the filter doesn't filter anymore because the relief valve operates because it thinks the filter is clogged due to reduced flow induced by the thermostat.

The bypass valve responds to pressure differential through the filter, not to reduced flow rate to the dirty side of the filter. It should not "think" anything unless the full-flow filter element is obstructed. (The relief valve serves an entirely different function, which is to control the upper oil pressure limit.)

Quote:

Originally Posted by tangofox007 (Post 2703506)

The bypass valve responds to pressure differential through the filter, not to reduced flow rate to the dirty side of the filter. It should not "think" anything unless the full-flow filter element is obstructed. (The relief valve serves an entirely different function, which is to control the upper oil pressure limit.)

Uh oh I feel a slap on the wrists coming on - I've done it again - the bybass valve is the one I'm talking about... (relief valve is on the pump - not even in the filter housing)

I understand what you say about the filter element being obstructed - and I agree - but - the obstruction could also come from the operation of the thermostat control valve couldn't it?

In the picture I posted the bypass valve is number 9 (this opens with a differential pressure of 3.5 bar)

The control valve is number 12 this one works in combination with the thermostat.

This is frustrating - I'm getting the impression I'm not communicating effectively!

Let me try another way of explaining.

The control valve (12) controls the way in which oil will flow into the filter.

When the oil is cold the oil flows through the control valve and above into the filter from below.

When the oil gets warm enough that the thermostat opens the control valve the flow of oil can go two ways:-

Way one - as before straight up

Way two - round the oil cooler and back into the oil filter housing

Eventually when the control valve is completely open the the flow of oil via "Way one" is restricted to a small amount that has been calculated by Mercedes to be enough oil for the engine if the oil cooler line is temporarily blocked by cold viscous oil.

So in principle all should be OK in an ideal world. No arguments from me here!

However, we don't live in an ideal world so I'm suggesting that if you wish to permanently remove the oil cooler - hence always having a blockage there! - then perhaps it is worthwhile considering that you are putting your system purposely in an emergency design situation (albeit a situation designed by Mercedes). Wouldn't it be better to either

1) Remove the control valve - so the flow of oil is always going to be as good as it could be?

2) Put in a pipe on the outside of the filter housing so that there is no "blockage"?

Interesting! I've never looked closely at the oil circuit and just took a look at FSM 18-005 Oil circuit, oil pressure, pressure relief valve and oil filter. Pretty sophiscated oil filter!

From the diagram and description, it does appear that if the oil cooler is blocked or bypassed (note the oil cooler is essentially blocked by the thermostat with a cold engine), the engine will still get filtered oil via the main flow filter component (24a), which is separated by a seal to the bypass filter component (24).

Up until now, I didn't know there are 2 separate filter components in the filter element. I'm gonna have to cut one open to have a closer look and see how it is constructed.

Quote:

Originally Posted by Army (Post 2703511)

I understand what you say about the filter element being obstructed - and I agree - but - the obstruction could also come from the operation of the thermostat control valve couldn't it?

I don't think so. That's not going to cause a differential across the filter element. But, bottom line, I am not at all convinced that blocking the oil cooler plumbing is an acceptable strategy.