450SEL question - Mercedes-Benz Forum

 
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post #1 of 7 (permalink) Old 08-28-2004, 09:43 PM Thread Starter
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450SEL question

Hi guys.

I know this is a question for the vintage section, but some of the guys that know tonnes don't go there sometimes or sometimes it take a while to get an answer there - so I am posting here.

I am trying to sell my 1978 450SEL.

A guy viewed it today and he loved it - but the sale did not go through because of a problem which I consider it minor.

The guy idled it for a very long time.

After over 40 minutes of inspecting it and insisting it remain at idle, the overflow hose of the radiator tank started to send coolant and steam out of it. This has never happened before, then again I don't idle it for ridiculous periods - under normal driving conditions, all is sound. Inspite of this, the engine temperature remained constant and stable. The auxiliary fan did not come on.

I can contest that this engine is solid as a brick house, c'mon it's a M117 8-cylinder engine with 93,000 original miles on it.

Am I looking at a larger problem or is it a weak tank lid-valve (rad cap) letting coolant out through the overflow hose considering it's a pressurized system?

Thanks, guys

Tory



1990 560SEL - W126
-929 nautical blue metallic & 262 navy blue leather
-58,000 KM (36,200 Miles)
-Euro spec Japanese import (KAT edition)
-Complete service history since new
-5,546cc SOHC 16v V8
-10.0:1 compression
-285 hp@5200 rpm, 324 lb/ft@3750 rpm
-2.65 limited slip diff
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post #2 of 7 (permalink) Old 08-29-2004, 01:38 PM
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RE: 450SEL question

I agree that with only 93,000 miles your M117 is not at fault; my M117 has over 200,000 original miles and stays very cool. I also agree there’s a possible “weak link� in your cooling system. Why didn’t the aux. fan come on? That could be a source of overheating. There could be air in the system, a bad t-stat or water pump or a clogged rad.

When was the last time you had the cooling system flushed and refilled? If done recently was it done correctly?
[?]
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post #3 of 7 (permalink) Old 08-29-2004, 03:57 PM Thread Starter
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RE: 450SEL question

Hey and thanks for the reply!

The thing is, it's not overheating. It's running at the perfect operating temperature according to the temperature gauge on the instrument cluster and the engine "feels" and "sounds" right to me if that makes any sense. I had an Audi once and it overheated and you could simply tell that it was - I'm sure it's not overheating. For some reason it's forcing coolant and some steam out of the long rubber overflow tube coming out of the top of the coolant resevoir (pictured below from my 300SD, same system though) - is my cap assumption right or are you thinking not? Too much fluid in the system? I will try a flush I suppose.

Thanks a lot!!

Tory
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1990 560SEL - W126
-929 nautical blue metallic & 262 navy blue leather
-58,000 KM (36,200 Miles)
-Euro spec Japanese import (KAT edition)
-Complete service history since new
-5,546cc SOHC 16v V8
-10.0:1 compression
-285 hp@5200 rpm, 324 lb/ft@3750 rpm
-2.65 limited slip diff
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post #4 of 7 (permalink) Old 08-29-2004, 04:07 PM
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RE: 450SEL question

As you also noted one does not normally leave one’s car idling for extended periods of time – it may have been an “unfair� test. If it’s been a while I’d get it flushed and it should not happen again. Buyers would be more inclined to buy. [;)]
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post #5 of 7 (permalink) Old 08-29-2004, 07:05 PM Thread Starter
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RE: 450SEL question

Thanks for the information and the suggestions! I am going to try a new radiator cap and if that doesn't work, I'll try a flush. It should be fine!

Thanks again and I'll let you know,

Tory



1990 560SEL - W126
-929 nautical blue metallic & 262 navy blue leather
-58,000 KM (36,200 Miles)
-Euro spec Japanese import (KAT edition)
-Complete service history since new
-5,546cc SOHC 16v V8
-10.0:1 compression
-285 hp@5200 rpm, 324 lb/ft@3750 rpm
-2.65 limited slip diff
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post #6 of 7 (permalink) Old 07-11-2009, 12:18 PM
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Steam and liquid should show after 40 minute idle

My Mercedes is a 1979 450SEL also but I have never checked the overflow hose when hot. However I've owned a few cars (this is my first Mercedes) including a 1966 Corvette and must say that I have always seen fluid and steam come from the overflow hose when hot. Just condensation alone will account for some moisture and dripping water. Hate to be negative, but I would not sell to this guy. He will bug you continuiously about other stuff.
Do yourself a favor, find a reasonable buyer.

Meanwhile, if it fits within you budget, a radiator flush and pressure check are still a good idea. Even if just for your own peace of mind.

I have a minor heat problem with my 450 on hot days here in Southern Calif.
Ideling gets rough and restarting before cool down causes the engine to turn off under load. On one trip, I could not get above about 40mph even though the engine was not excessively heated. Don't have a clue on that. The auxillary fan never comes on either.

Hope this is OK within this thread, it seems related. Perhaps I should take my own advice on radiator and pressure check. But I would really like to find out why the auxillary fan never comes on. So if anyone has suggestions please reply.
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post #7 of 7 (permalink) Old 07-11-2009, 02:22 PM
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Quote:
Originally Posted by Timmyray View Post
My Mercedes is a 1979 450SEL also but I have never checked the overflow hose when hot. However I've owned a few cars (this is my first Mercedes) including a 1966 Corvette and must say that I have always seen fluid and steam come from the overflow hose when hot. Just condensation alone will account for some moisture and dripping water. Hate to be negative, but I would not sell to this guy. He will bug you continuiously about other stuff.
Do yourself a favor, find a reasonable buyer.

Meanwhile, if it fits within you budget, a radiator flush and pressure check are still a good idea. Even if just for your own peace of mind.
Thank you for your truly invaluable advice, but since this thread is nearly FIVE YEARS OLD, I'm sure the problem has by now been handled one way or the other.

Felicita e un bicchiere di vino con un panino.
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