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1979 450SL
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165 Posts
Discussion Starter #1
I’ve got a water leak. Thing is I’ve no idea what I’m doing. The leak is from a joint (obviously) on a metal item right next to the oil filter. Any advice would be appreciated.

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4D79DD4B-430C-4187-B232-67EBDC2D3220.jpeg
 

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1989 560SL
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135 Posts
Hard to tell from the photo but my guess would be coolant trickling from the bleed hole on the bottom of the water pump.


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Registered
1979 450SL
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165 Posts
Discussion Starter #3
The leak is on the joint where it’s dark, just underneath the bolt head. It’s not a bleed hole.
Thanks for the reply.
 

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Premium Member
1983 380 SL
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3,013 Posts
Can't tell from the picture try a different camera angle from a little further away. Try to include the water pump in the picture establishing the relative position of the leak as it relates to the water pump.

Wild guess based on the fact that the leak is in the front of the engine... water pump... but more data is required in order to make a positive determination. For all we know it could be a hose.
 

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Premium Member
1986 560SL with M120 V12 Engine, 1988 560SL Stock
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10,411 Posts
I would say the bolt head, but it also looks like some may be coming out the casket for the timing cover. I would CAREFULLY take the bolt out and put some sealer on it. Threads shank and under head.
 

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1979 450SL
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165 Posts
Discussion Starter #8
Tried the bolt, it’s pretty tight and I’m wary of shearing the head. Won’t water come gushing out if I’m successful loosening the bolt?
On closer inspection I can see a green (antifreeze?) stain running along the seam.
 

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Premium Member
1983 380 SL
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3,013 Posts
Tried the bolt, it’s pretty tight and I’m wary of shearing the head. Won’t water come gushing out if I’m successful loosening the bolt?
On closer inspection I can see a green (antifreeze?) stain running along the seam.
Unless I'm mistaken there are no water passages down there. Oil yes, but not water, so removing that bolt should not cause water to gush out.

The front cover bolts to the block and provides the water pump with a sealed mounting area well above where your picture shows. There are "O" rings that seal the water channel between the front cover and the block and then there is the water pump gasket that seals the water pump to the front cover.

If the "O" rings that seal the water passages in the front cover to the block are leaking then you should see evidence of water in the oil. If it's the water pump gasket that seals the water pump to the front cover that's leaking then you may see water drip from just about anyplace around the water pump.

I suggest you ignore what appears to be leaking from that bolt head because there simply isn't any water there (unless the "O" rings are leaking that seal the water passages from the front cover to the block...in which case you would definitely see water in the oil.

In the picture below the lower red arrow pointing up is pointing to the area where you are seeing the wet. The two upper arrows are pointing to where the "O" rings seal the water passages from the front cover to the block. There are two smaller ones above and to the left in the picture but out of sight. If you're getting water leaking from that bolt in your picture (lower left) it can only come from the seal of the "O" rings to the block, or from the water pump itself. Check your oil for water (milky oil) if you find water in the oil then you know it's the seal between the front cover and the block. If there's no evidence of water in the oil then the leak is forward of the front cover... probably the water pump gasket or the water pump itself, but before you go crazy replacing parts... check all the hoses. A hose leak can spray water in a thin almost invisible stream, anywhere at all.

MercFrontOfBlock copy.jpg
 

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1979 450SL
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165 Posts
Discussion Starter #11
Thanks for the very detailed reply.
The water is definitely weeping from the place I described, I dried the area, left it over night and this morning a small amount of clear water is on the floor and around the seam. I opened the oil filler plug, looked at the dipstick and both were good, not milky.
Thanks again.
 

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Premium Member
1983 380 SL
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3,013 Posts
Thanks for the very detailed reply.
The water is definitely weeping from the place I described, I dried the area, left it over night and this morning a small amount of clear water is on the floor and around the seam. I opened the oil filler plug, looked at the dipstick and both were good, not milky.
Thanks again.
Then the water is coming from outside the front cover . There just isn't a supply of water behind that bolt.
 

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1979 450SL
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165 Posts
Discussion Starter #14
So I started to replace the water pump, removed the fan, shroud, top hose and 3 of the 4 water pump bolts. Started release the power steering pump bolts but cannot get to the bottom left and top right ones to push the assembly to the center of the engine. Am I missing something here.
Thanks in advance.
 

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1979 450SL
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165 Posts
Discussion Starter #18
In addition, I need to remove the power steering pump pulley ( to access the 3 bolts). I’ve removed the main nut, got a 3 jaw puller in position, liberally sprayed with WD40 but the pulley is not moving. I’m wary of breaking something so am I missing something?
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Premium Member
1983 380 SL
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3,013 Posts
In addition, I need to remove the power steering pump pulley ( to access the 3 bolts). I’ve removed the main nut, got a 3 jaw puller in position, liberally sprayed with WD40 but the pulley is not moving. I’m wary of breaking something so am I missing something? View attachment 2640080
I believe that may be the wrong style puller. If I remember correctly... on mine the puller tool slid behind the lip on the center hub. Your's may be different.
 
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