76 450SL Vacuum Line replacement advise needed - Mercedes-Benz Forum

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post #1 of 6 (permalink) Old 11-02-2013, 09:17 AM Thread Starter
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Vehicle: 1976 MBZ 450SL
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76 450SL Vacuum Line replacement advise needed

All, my very nice 76 year model 450SL has the design flaw of the all in one exhaust manifold/catalitic converter assembly that resides UNDER THE HOOD. Fortunately for all other 450SL owners Mercedes only did that for 1975 and 1976. This design causes excessive heat under the hood so anything plastic or rubber suffers greatly. Things like wire insultation and vacuum hoses/plastic tubing are in jeapardy. With that said many of the very abundant plastic tubing vacuum lines are presently crumbled. They are so bad that there is a long gap between each end of the rubber tube connectors where the plastic vacuum tubing would be since these tubes have all but disintagrated. The short rubber connectors for the plastic vacuum tubes are also in poor condition. A schematic will be needed to properly route these missing lines. My question is this, do I want to use an aftermarket high heat silicon vacuum line/and connectors instead of the original equipment rubber connector on each end of a plastic tube like what came with the car? I am not a fan of modifying the OE status of cars. I am torn because I dont want to continually fight the vacuum lines so I am considering aftermarket here. I would value any thoughts on this from the forum participants. I would also value any tips on what I can do to make this challenging job easier. Where do I get the factory stuff if I should choose to go that way? Is there a kit for all those tubes/elbows/connectors etc? Does anyone have a parts list for related vacuum parts etc that should be considered for replacement while doing this job?
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post #2 of 6 (permalink) Old 11-02-2013, 12:06 PM
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I would definitely use the highest temperature rated hose I could find.

This was an especially problematic issue for these model years, and a good reason to avoid them at all costs.

All of the little fuel injection lines will go the same way as the vacuum lines, so if you're on a line replacement binge, might as well do those, too.

As for the cats, you could remove them and put straight "test" pipes in…not sure what ramifications that might have as far as the EPA or your local or state inspections, if you have them.

I live in Florida and have seen lots of these model year SLs. The engine compartments are simply toast as a result of the outrageous under hood temperatures.

I discovered this some years back when I was considering the purchase of a W107. When I found out about the model years with the under hood cats, I immediately eliminated those years from my search…

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post #3 of 6 (permalink) Old 11-02-2013, 01:12 PM Thread Starter
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Vehicle: 1976 MBZ 450SL
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thank you for the reply

Thank you for replying Dan!! The car was owned by an old man who donated it to his church. I bought it from the church for very little money even though it has excellent paint,tops perfect interior. A VERY CLEAN CAR great running car--- 104k. They sold it cheaply because it had a dead short that was draining the battery, even the brand new battery they put in it. Pushing this very heavy car to get it out of the way soured them on it!!! I found the short which was caused by a main powersource wire under the hood had sustained crumbled insulation from the under hood heat. I fixed it and whala....but those other heated items such as vacuum lines etc are going to be a chore.I Live in San Diego so California Emissions....so there is no chance of removing smog stuff...
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post #4 of 6 (permalink) Old 11-07-2013, 06:49 AM
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Maybe you would like to install a heat -wrap insulation kit on the exhaust system under the hood.Should lower the underhood temperatures substantially .
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post #5 of 6 (permalink) Old 11-07-2013, 06:58 AM
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Can you replace the exhaust with a post '77 type?

I would do that if I needed to keep the cats

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post #6 of 6 (permalink) Old 11-07-2013, 07:43 AM
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this 75/76 was common in old days , same as a 450sel , cat under hood was a bad idea , but did not notice heat damage to those cars on vacuum lines . i think you could replace cats with exhaust manifolds from other v8 , and put cats under car where they belong and be legal ?????
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