Oil cooler plumbing on alloy block m117/116

[rwd4evr]

Has anyone installed an oil cooler on a alloy m117/116? On the iron block there's 2 fittings next to each other right here. Green is pressure I'm fairly certain since the alloy 3.8 I have had a pressure sensor in it. The green and large yellow appear to be on the same circuit though I haven't opened it up yet. Maybe the one up above on the front and the one down on the side? I wonder if the oil is restricted enough that the pump bypass just is used less when the oil cooler is hooked up, so could it just be plumbed to return to the pan? On the 4.5 it makes no oil pressure difference when the plumbing is plugged or to a cooler, which leads me to believe that it's not pumping the full oil flow through the cooler. I have never investigated the oil flow progression on a dissasembled engine so I'm really not sure.

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[Frank Reiner]

On the alloy block pictures the green arrows do point to the "oil out" port (for the 107 configuration)(126 "oil out" is via the base of the filter). That flow goes to the cooler and then returns to either the filter base (107), or the filter can (126).
Filter bases and/or cans may or may not be drilled/tapped for the fittings.

Even if the cooler is blocked or removed, pressure is not affected because the cooler bypass valve will open.

[Tony H]

The iron block engines have a "oil cooler bypass valve" that bypasses the oil cooler when the oil is cold. If the car does not have an oil cooler the port is plugged. So you would need the oil cooler bypass valve to make the oil circuit to the cooler. From what I have seen (at least in the iron block engines) only the sedans had an oil cooler, not 107's. Not sure what alloy block cars had oil coolers.

[rwd4evr]

Originally Posted by Frank Reiner

On the alloy block pictures the green arrows do point to the "oil out" port (for the 107 configuration)(126 "oil out" is via the base of the filter). That flow goes to the cooler and then returns to either the filter base (107), or the filter can (126).
Filter bases and/or cans may or may not be drilled/tapped for the fittings.

Even if the cooler is blocked or removed, pressure is not affected because the cooler bypass valve will open.

Ok that's Interesting. So some of the alloy block cars do have oil coolers? Checked the 500sl and it doesn't. I have a couple 380sl I haven't looked at and I do have 2 560sl parts cars I didn't check. So what part of the circuit does the cooled oil return to? Is it feeding back into the pressure side or back to the sump?

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[rwd4evr]

Originally Posted by Tony H

The iron block engines have a "oil cooler bypass valve" that bypasses the oil cooler when the oil is cold. If the car does not have an oil cooler the port is plugged. So you would need the oil cooler bypass valve to make the oil circuit to the cooler. From what I have seen (at least in the iron block engines) only the sedans had an oil cooler, not 107's. Not sure what alloy block cars had oil coolers.

That is also interesting. I can't say I can fully remember having felt my oil cooler for heat but it's definitely been full of oil. The engine in the car(78 450sl motor) was definitely a non oil cooler car and I swapped in the fittings and lines with damper from a early d jet 450sl. You are saying it's not flowing oil because of a plugged port internally?

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[rwd4evr]

Ahh ha! Finally looked at one motor still more assembled than the one I'm working on. I see the cooler fitting on the filter housing. Nice. So my question now is, do I need to do anything besides put fittings in and plumb the cooler? Is there a block off/thermostat plug like it was mentioned before? I went drifting last weekend and totally forgot to check oil cooler temperature again on my 4.5

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[Tony H]

I have a diagram and page that describes the oil circuit. I think the oil pressure is what determines if oil is routed to the cooler. I will post the diagram tomorrow. For what ever reason I don't think 107's got the oil cooler and the valve is plugged.

[rwd4evr]

That would be greatly appreciated. Now I think about it I think I have a m116/117 book but I do believe it's iron block only.

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[Tony H]

The one I have is iron block also. Cannot imaging the oil circuit was changed. You should be able to determine from this diagram. Biggest clue would be the "oil cooler bypass valve" plug in the timing cover.

[rwd4evr]

What I read here is that all the engines are equipped with the main pressure bypass to pan (oil pressure relief valve, 15), and all engines are equipped with the oil cooler bypass (bypass valve, 16). These are both covered by the closing plugs in the timing cover. The engines with no oil cooler have a closing plug where this green fitting is, sending all the oil through the 1.5 bar oil cooler relief valve into the filter housing . My 4.5 had it and I replaced it with the oil cooler fittings. If there was an internal plug then there would be no flow when the external line was plugged. It is possible there is no #16 bypass valve in the non oil cooler engine I suppose and the oil will just take the path of least resistance. I'll have to pop that closing plug out and look. is there a page "oil circuit without air to oil cooler" in there? I'd like to see that. This is an early engine in the pics I believe or possibly a sedan of some kind. My oil cooler lines on djet r107 engines are both on the block, but this diagram is almost identical to the port locations on the alloy 5.6. thank you very much this is exactly what I was looking for. I've found that the plugs in the alloy block oil galleys are the same thread as some banjo bolts I have(m14 I think, trans cooler lines maybe?), But smaller than the iron block fittings. I'm going to check out the hydraulic line place nearby, BENZ hydraulic () to see if they can match up a fitting or if not get lines made to run banjo to the original damper and cooler to banjo return. The banjo bolt could be a restriction but it would still flow oil through the cooler and just bypass anything over 1.5 bar to the cold route into the filter.

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[Frank Reiner]

The opportunity for a bit of confusion is substantial.

-- The main oil pressure relief valve in the iron block engines is in the block (item #15 above).
-- The main oil pressure relief valve in the aluminum block engines is in the oil pump.
-- There is no main oil pressure relief in the block of the aluminum engines.
-- Both iron and aluminum block engines do have a cooler bypass valve in the block (item #16 above).
-- USA aluminum block 107 engines were not equipped with oil coolers. (A sufficient number of both 126 and 107 cars came to the US as gray-market cars that a few of them may have had coolers.)
-- The plugged oil return (cooled oil) port, circled in yellow, in the picture above enters the filter element on the outside (normal flow).
-- The oil circuit for the 107 does not incorporate a thermostat.
-- The oil circuit for the 126 does incorporate a thermostat.

[rwd4evr]

Ok, so is the the low pressure(1.5 bar) oil cooler bypass is present in my US r107 560sl block? Is the thermostatic valve you mention a different one? What the service manual is telling me is that it's routing oil directly through the block to the filter and not the cooler until the oil is hot enough to flow easily through the cooler passages.

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[Frank Reiner]

Originally Posted by Frank Reiner

-- The oil circuit for the 107 does not incorporate a thermostat.

There is no thermostatic valve in engines installed in 107s. Cooler bypass is accomplished by the cooler bypass valve, which is a pressure sensing valve only; no temperature sensing.

[rwd4evr]

Great. That's fine with me. Thanks again Frank of knowledge!! Just out of curiosity is that a part that can be installed in any m117 or is there actually a difference in say an 117.967 and .968 block? What do you think about a banjo connection for the oil cooler? Too restrictive? Any thoughts on elimination of the damper body? I don't know if it's used on the alloy block cars anyway.

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[Frank Reiner]

The oil thermostat used in 126s, when installed, is in the filter base/can assembly, not in the block.