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Discussion Starter #1
Okay, I found a 1986 560 SL, The car runs, no smoke, but runs very rough. It then will start to overheat. Everything else seeems to pretty good. no rust, pretty straight body, not bad paint. The car has 117,000 miles. I may be able to get it for a good price, but don't want to buy a boat anchor either.

What would be a starting point for the rough idle? Vacuum leak? Tune-up? Warped Head? I am pretty handy under the hood, so work isn't the problem, I just don't want to get into a complete overhaul.

Lou
 

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1986 560SL with M120 V12 Engine, 1988 560SL Stock
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Okay, I found a 1986 560 SL, The car runs, no smoke, but runs very rough. It then will start to overheat. Everything else seeems to pretty good. no rust, pretty straight body, not bad paint. The car has 117,000 miles. I may be able to get it for a good price, but don't want to buy a boat anchor either.

What would be a starting point for the rough idle? Vacuum leak? Tune-up? Warped Head? I am pretty handy under the hood, so work isn't the problem, I just don't want to get into a complete overhaul.

Lou
Start with a bottle of Techron because it is the easiest thing to do. Then look for obvious vacuum leaks. Then go to ignition, preferably having it put on a scope, so that you don't start changing parts ruthlessly. Then compression check. Then fuel injection.
 

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I am going to look at it in more depth this week. I am going to ask more questoins that may help lead me in a better direction. I will try to find out how/when it started. Was the overheating before or after the Rough Idle? I think it may be a clue to see which came first.
 

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2008 E320 Bluetec, 1988 560SL totalled unto death). 1997 Dodge Ram 1500, 1983 300CD
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watch the overheating

The head and block us all aluminum as you know. A seriously overheated engine has the potential of deforming the alloy under the boltheads in particular. Being aluminum, that deformation is permanent and uncontrollable leaks of coolant and/or oil may develop.

I learned that lesson working on a Mazda rotary engine.
 

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I checked for leaks, there were none around the heads, also looked at the dipstick, not coolant in the oil. So I am looking at that as a good sign. Didn't get there today, maybe during the week to check it out some more.
 

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Don't do anything until a compression test has been done to see if a head gasket blew or a head cracked when it was overheated.

Dan
 
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