Engine ground strap. What gauge, length, and connect where to where?

[jf308]

Upon inspection, my 230 SL does not have a proper engine ground strap.

I can order the braided copper cable thru Napa, but need to know what gauge and proper length.

Then, where should this connect.  Photo always appreciated if someone has one.

Thanks. John

[ctaylor738]

Hmm.  For $13.50 list, you can get a genuine Mercedes ground strap from your local dealer or the Classic Center.  PN 116 540 05 31.

It's connected on the right side VIEWED FROM THE FRONT OF THE CAR (correction added).  On the engine, under one of the bolts that holds the transmission to the engine,  On the firewall, there is a threaded hole almost directly above that takes a 10mm (I think) bolt and washer.

[tel76]

It fits on the LHS of the bulkhead/firewall, looking forward.

[114015]

Hmm.  For $13.50 list, you can get a genuine Mercedes ground strap from your local dealer or the Classic Center.  PN 116 540 05 31.
It's connected on the right side.

Left hand side as Eric commented.

Here you can see where the groud strap is located on the bell housing.
2nd pic shows the attachment hole for the M8 screw on the bulkhead crossmember.


 
Achim

[ctaylor738]

My bad. Obviously left side.  Guess I was thinking viewed from the front.

[GGR]

Ground strap is important. Some years ago, I rebuilt an engine with removable cylinder sleeves. They were all pitted on the outside, where they face the water jacket. Pitting was so bad that there were holes of one to two mm in them (not going through inside the cylinder though). The machine shop I showed them to told me this was due to electrolysis by lack of engine ground strap. There is no way to check that on a Pagoda, so keeping the ground strap in place is a safe move.

[jf308]

Thanks ALL.   Very much appreciate the information and PHOTOS.  VERY, VERY HELPFUL as I learn about my 64 230 SL.

John

[jf308]

Bought one at NAPA.  Braided.  Needed about 9 inches, but went with 12 to give a bit of flex in the cable for installation.

[gorgoo]

Hello,
A pic of the strap itself maybe?
It' 240mm long, from eye to eye. And 8mm diameter.


And as I feel pedantic, a comment for CGR: I'm sorry but your machine shop is run by stupid people: if your engine is not properly grounded it will simply not start! You need "space" (actually conductivity) for 75 to 100A when under starter, so need a big strap between battery + an starter... and same size between starter and ground! By the way it's a classic mistake when a starter is slow to clean and grease the battery "+" plug and forget the "-" and the groud straps terminals, they're equally important.
Now electrolytic corrosion does exist, specially on older vehicles with iron block, aluminium head and copper heat exchangers (ever seen that somewhere?). These materials have different electrolytic potential, so basically, whith a concductor that may be hot water, they make a small battery which produces a low tension by bringing ions from one material to the other.
First thing to avoid this is to use proper antifreeze, and renew it regularly as its rust retardant properties are "eaten" by these oxydes. Then you should consider grounding your copper radiator if it's not already done.

Didier.

[Raymond]

Of course every electrical system should be properly grounded but the method isn't magic or too critical.  My car started just fine when I first re-installed the engine without the ground strap.  The engine is also grounded through the sub-frame and transmission.   Likewise I believe the radiator is grounded through the bolts to the body as is the heater core.  I did install the strap when I finally found it.  It's the best way to ensure a good ground and is kind of a belt and suspenders security.   I have since moved the battery to the trunk and have it grounded there.