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1976 280SL, 1979 450SL
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Discussion Starter #1
Hey everybody, I'm working on my 1979 450SL (automatic), and upon doing a massive search on the web regarding draining and flushing the cooling system (radiator, block, etc), I have yet to find the actual location of the drain plugs on the block. I have searched this website, Google, and a bunch of other forums, but to no avail.

I have the picture from the service manual (link below; second picture on the second page), but I can't find what on earth the picture is of. I do see some bolts and such that might be it, but they look nothing like in the picture, and I don't want to accidentally unscrew the wrong thing and have other problems to worry about, haha.

Can somebody shed some light on the topic, as I have realized that many 107 owners are confused about the location of the drain plugs on the actual block. Thanks beforehand fellas!

http://www.startekinfo.com/StarTek/outside/11883/PROGRAM/Engine/107/M117_45/20-010.pdf
 

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1976 280SL, 1979 450SL
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26 Posts
Discussion Starter #3
I have taken off my thermostat, taken off all hoses and cleaned them and put them back on, and ran a hose through multiple intakes for the coolant until the water ran clear, but a lot of threads and websites say that you don't want to just do that and/or a flush and then put in the coolant/water mixture because a bunch of flush compound and water will be left in the engine block, so that's why I want to drain that extra water from the engine block. I would use compressed air to just blow any water out of the engine, but I no longer have my air compressor.

Does the UK spec 450SL not come with the drain plugs on the engine or no 1979 450SL comes with the drain plugs on the engine for the coolant? It would be weird if none of them come with it as the instructions and picture in the previous link I posted were from a service manual of a 79 450SL from startek's actual website.
 

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US spec MB560SL 1986, Audi A4 and A6, Ford Taunus 1964 17M and 2.0 1975
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1,419 Posts
I also put garden hose into upper radiator hose and let the tab water run through the system until the outcoming water was clear.

My -86 radiator has a drain plug at the bottom.
 

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'85 380SL (155Kmiles), '82 240D stick, '80 300SD, '77 240D, '89 BMW 535i, 3 VW Diesels, 2 Triumphs
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I can't answer your question wrt the older block, but I did find them eventually on the 380 (M116) block once I used a good magnifier.
 

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107
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So I'm assuming at this point that nobody knows where the actual drain plugs are on the engine block...? :D
Berkeley, here are pics of the coolant draining plugs (bolts). They are very, very tight on the engine case, (yet tightening torque is 45-50 Nm) just forwards of engine mounting brackets and the head of bolts are perpendicular to the ground. Replace the washers (sealing ring X 2 PN:A6369970244) once you remove them. The radiator drain is very ackward to remove, but doable.
As other members here pointed out, there is really no need to remove them if you keep a garden hose on the coolant expansion tank, run the engine and empty via the bottom hose of the radiator a couple of times or until water comes really clear.

Draining bolt on bottom radiator left side



Coolant draining bolt left side: (just forward of the engine mounting bracket)



Coolant draining bolt right side: (just forward of the engine mounting bracket)



Hope it helps.
 

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Outstanding Contributor , Bob's Your Uncle!
-----'83 280 SL----- 5 speed....The PIG
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Berkeley, here are pics of the coolant draining plugs (bolts). They are very, very tight on the engine case, (yet tightening torque is 45-50 Nm) just forwards of engine mounting brackets and the head of bolts are perpendicular to the ground. Replace the washers (sealing ring X 2 PN:A6369970244) once you remove them. The radiator drain is very ackward to remove, but doable.
As other members here pointed out, there is really no need to remove them if you keep a garden hose on the coolant expansion tank, run the engine and empty via the bottom hose of the radiator a couple of times or until water comes really clear.

Draining bolt on bottom radiator left side



Coolant draining bolt left side: (just forward of the engine mounting bracket)



Coolant draining bolt right side: (just forward of the engine mounting bracket)



Hope it helps.
Good job Elrick.
 

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1986 560SL with M120 V12 Engine, 1988 560SL Stock
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10,234 Posts
The plugs on the block go straight up. Do not confuse them with the bolts on the side of the block that hold the main bearing caps in place. On the later cars they are Allen heads.
 

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1976 450 slc
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422 Posts
the 117 985 iron block 4.5 which the OP has (like me ) are only 4 bolt mains- no side bolts
got some pics I'll dig up later
 

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mercedes 280sL 1975 4 door sedan
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draining and flushing the system

Hey everybody, I'm working on my 1979 450SL (automatic), and upon doing a massive search on the web regarding draining and flushing the cooling system (radiator, block, etc), I have yet to find the actual location of the drain plugs on the block. I have searched this website, Google, and a bunch of other forums, but to no avail.

I have the picture from the service manual (link below; second picture on the second page), but I can't find what on earth the picture is of. I do see some bolts and such that might be it, but they look nothing like in the picture, and I don't want to accidentally unscrew the wrong thing and have other problems to worry about, haha.

Can somebody shed some light on the topic, as I have realized that many 107 owners are confused about the location of the drain plugs on the actual block. Thanks beforehand fellas!

http://www.startekinfo.com/StarTek/outside/11883/PROGRAM/Engine/107/M117_45/20-010.pdf
I don't have that info right now but can get it I think. If you learn to do it yourself your better off. I stopped a few years ago to have some new tires installed before coming accross the border and home, the garage was not that small and advise it worked on foriegn cars. I went to lunch and when I came back they were concerned said the were going to thrw in an oil change an flush the rad for me. thank god they couldn't fiqure out how to open the hood. they had a hose nearby and I was running on Geliante. God knows what they would have thought when they saw green jelly. I really hate people who try to asume that they can sneak in extra service and expect you to pay for it.

Take a pictue of what you can see and maybe someone will reconized whats what under there. How long have you had veh?
 

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1965 230sl (euro spec,48k), 1979 450sl (200k)
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392 Posts
I am resuscitating this old thread because I am trying to find the plugs myself. 79 450sl. I know this is sort of a shot in the dark, but are the plugs anywhere in these pics?? I studied the other pics here and they don't look like mine. Oh and all that black stuff coating everything is what I call protective undercoating.....It was much worse before I fixed the leaking power steering pump.
 

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1973 450 SL
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I am trying to find the plugs myself. 79 450sl.
The Lurker makes a statement about M117.985 regarding 4 bolt mains that I don't understand reference coolant drain plugs (4 bolt mains sounds like crank journal talk).

Below are pictures of the drain plugs (left then right) on an M117.982. They are forward of where you are looking in your pictures. The one on the right is easiest to find reference the forward end of the starter motor. If you locate that, look in about the same fore-aft position on the left side.

Hope this helps
 

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1965 230sl (euro spec,48k), 1979 450sl (200k)
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Thank you so much cushjbc! With the help of these pictures I found on my 117.985 the same plug just in front of the starter motor (passenger side) and the other one was on the driver side, up above and slightly behind the oil pan. When I took them out, I would have sworn I was looking at the top of a broken bolt, it was even shiny. I picked at it though and sure enough, it was just crud which eventually crumbled. I have detergent in mine right now and am driving with that for a couple days but I'll try to take pics of the exact locations when I get back under there. Both require a 19mm socket, just like the radiator plug.
 

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1965 230sl (euro spec,48k), 1979 450sl (200k)
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392 Posts
Okay as promised here are a few pics to help find the coolant drain plugs, this applies only to the 117.985 engine and others are different. As mentioned before, the plug on the passenger side is to the front and left of the starter motor, and is pretty easy to find, the pics already here provide a good idea of the location. The driver side plug is a bit trickier to find. Look upward at the oil pan, and it is near the back edge, toward the vehicle center, and up above the pan. The oil drain plug is in the pictures as sort of a visual reference. In these pics I have already removed the plug and it is draining. They are both 19mm bolts and the tops face directly down, flush with the ground, so the shaft of the bolt would be perpendicular with the ground.

As mentioned I had very little trouble getting them off, I used a 19mm socket on an extension wobble after letting them sit overnight with PB blaster on them. As you can see they are pretty stout plugs and it is pretty easy to get a socket on them. What I found behind them was a complete blockage, but I used a rubber mallet to drive a small screwdriver into that and chip it away.
 

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