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  #1  
Old 07-21-2005, 03:05 PM
83mercedes's Avatar
Ign'ance be blis
 
Join Date: Mar 2005
Location: Gainesville, FL
Posts: 306
Unhappy Worrisome engine symptoms 617.952

I'm beginning to worry about the condition of my engine (car is '83 300cdt) due to the continued existence of some worrisome conditions. I plan on taking it to a good local MB shop (run by Steve Brotherton, a member) and having a compression test done and then sending away for an oil analysis at my next change, but I wanted to get some opinions here to diversify my spectrum of assessments (and maybe give me some false hope ). Pre-emptive apology for length.
1.
Since I got the car from my dad, it has shaken pretty badly. Various repairs I've done have lessened this slightly or at least changed the quality of it, but it still moves up and down pretty ridiculously at idle when hot especially. Have done the following to remedy this: motor + tran mounts, engine shocks, engine shock mounts, rack damp. bolt upgd, and also the following which were not addressing this problem but would help: valve adjust, injectors (new), always good filters, fuel additive, IP timing set. Car is modified with K+N cone filter and magnaflow exhaust if this matters.
2.
Recently as some of my posts have gone over the temp is running around 95C in summer. Validated by IR thermo readings. Block temp is 95ish. Can't say yet if this will change in cold weather. Cooling system is all new, so now fault there.
3.
I have an intermittent metallic knock inside my engine, doesn't seem to be dependent on engine temperature, but occurs only at idle or just above in rpms. Loud enough to be noticeable in driver's seat with window open, adjacent car, or closed if AC and music is off. Don't see how this could be an "injector knock" since injectors are only 4 months old.

Oil pressure good, no noticeable coolant or oil consumption, power seems good, no excessive or discoloured exhaust, no strange noises other than metallic knock. Please advise if you can.

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"I would rather be ashes than dust!
I would rather that my spark should burn out in a brillaint blaze
than it should be stifled by dryrot.
I would rather be a superb meteor,
every atom of me in magnificent glow,
than a sleepy and permanent planet.
The proper function of man is to live, not to exist.
I shall not waste my days in trying to prolong them.
I shall use my time."

-Jack London 1876-1916

1983 300CDT (running WVO since 12/05)
1981 300SD (parts car)
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  #2  
Old 07-21-2005, 03:19 PM
boneheaddoctor's Avatar
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Join Date: May 2004
Location: Hells half acre (Great Falls, Virginia)
Posts: 16,007
How many miles are on this....and have you had a compression test done yet....
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1971 280SE W108
1979 300SD W116
1983 300D W123
1975 Ironhead Sportster chopper
1987 GMC 3/4 ton 4X4 Diesel
1989 Honda Civic (Heavily modified)
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"He who fights with monsters might take care lest he thereby become a monster. And if you gaze for long into an abyss, the abyss gazes also into you." - Friedrich Nietzsche
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  #3  
Old 07-21-2005, 03:22 PM
83mercedes's Avatar
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Unfortunately, the odometer is broken, but was working when my dad had the car....I'd say probably not more than 160-175k.

I have not had a compression test done yet, but I certainly plan to before the summer is out. I just wanted to scope out what some people thought to see if I should abandon all hope of avoiding a rebuild or what.
__________________
"I would rather be ashes than dust!
I would rather that my spark should burn out in a brillaint blaze
than it should be stifled by dryrot.
I would rather be a superb meteor,
every atom of me in magnificent glow,
than a sleepy and permanent planet.
The proper function of man is to live, not to exist.
I shall not waste my days in trying to prolong them.
I shall use my time."

-Jack London 1876-1916

1983 300CDT (running WVO since 12/05)
1981 300SD (parts car)
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  #4  
Old 07-21-2005, 03:50 PM
boneheaddoctor's Avatar
Senior Benz fanatic
 
Join Date: May 2004
Location: Hells half acre (Great Falls, Virginia)
Posts: 16,007
Quote:
Originally Posted by 83mercedes
Unfortunately, the odometer is broken, but was working when my dad had the car....I'd say probably not more than 160-175k.

I have not had a compression test done yet, but I certainly plan to before the summer is out. I just wanted to scope out what some people thought to see if I should abandon all hope of avoiding a rebuild or what.
Have a compression and leakdown test done....those miles are not high at all....you may need nothing more than a valve job. I am assuming they have been adjusted recently per your original post.

Have you done an Italian tuneup yet?
__________________
Proud owner of ....
1971 280SE W108
1979 300SD W116
1983 300D W123
1975 Ironhead Sportster chopper
1987 GMC 3/4 ton 4X4 Diesel
1989 Honda Civic (Heavily modified)
---------------------
Section 609 MVAC Certified
---------------------
"He who fights with monsters might take care lest he thereby become a monster. And if you gaze for long into an abyss, the abyss gazes also into you." - Friedrich Nietzsche
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  #5  
Old 07-21-2005, 04:10 PM
83mercedes's Avatar
Ign'ance be blis
 
Join Date: Mar 2005
Location: Gainesville, FL
Posts: 306
Yes, the shaking decreases marginally after Ital. tuneup, like other remedies I tried, but is always there, a perceptible bounce felt when sitting in the car. Does not fix metallic knocking, however. Temperatures may or may not be significant, I don't think it's a head problem because no coolant loss.

Did a valve job about 3-4 months ago, so that's good.
__________________
"I would rather be ashes than dust!
I would rather that my spark should burn out in a brillaint blaze
than it should be stifled by dryrot.
I would rather be a superb meteor,
every atom of me in magnificent glow,
than a sleepy and permanent planet.
The proper function of man is to live, not to exist.
I shall not waste my days in trying to prolong them.
I shall use my time."

-Jack London 1876-1916

1983 300CDT (running WVO since 12/05)
1981 300SD (parts car)
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  #6  
Old 07-21-2005, 04:18 PM
boneheaddoctor's Avatar
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Location: Hells half acre (Great Falls, Virginia)
Posts: 16,007
Quote:
Originally Posted by 83mercedes
Yes, the shaking decreases marginally after Ital. tuneup, like other remedies I tried, but is always there, a perceptible bounce felt when sitting in the car. Does not fix metallic knocking, however. Temperatures may or may not be significant, I don't think it's a head problem because no coolant loss.

Did a valve job about 3-4 months ago, so that's good.
You sure its a knock and not nailing?
__________________
Proud owner of ....
1971 280SE W108
1979 300SD W116
1983 300D W123
1975 Ironhead Sportster chopper
1987 GMC 3/4 ton 4X4 Diesel
1989 Honda Civic (Heavily modified)
---------------------
Section 609 MVAC Certified
---------------------
"He who fights with monsters might take care lest he thereby become a monster. And if you gaze for long into an abyss, the abyss gazes also into you." - Friedrich Nietzsche
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  #7  
Old 07-21-2005, 04:53 PM
LarryBible
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Posts: n/a
I don't read anything that you wrote that leads me to believe that there is anything seriously wrong.

There's really good news here and that is that you are in Gainesville. Just take it to Steve and let him check it out. Most folks don't have one of the very best indie shops in the US in their backyard.

Good luck,
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  #8  
Old 07-21-2005, 05:03 PM
83mercedes's Avatar
Ign'ance be blis
 
Join Date: Mar 2005
Location: Gainesville, FL
Posts: 306
Quote:
Originally Posted by LarryBible
There's really good news here and that is that you are in Gainesville. Just take it to Steve and let him check it out. Most folks don't have one of the very best indie shops in the US in their backyard.

Good luck,

All right, will do.
__________________
"I would rather be ashes than dust!
I would rather that my spark should burn out in a brillaint blaze
than it should be stifled by dryrot.
I would rather be a superb meteor,
every atom of me in magnificent glow,
than a sleepy and permanent planet.
The proper function of man is to live, not to exist.
I shall not waste my days in trying to prolong them.
I shall use my time."

-Jack London 1876-1916

1983 300CDT (running WVO since 12/05)
1981 300SD (parts car)
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  #9  
Old 07-21-2005, 05:05 PM
83mercedes's Avatar
Ign'ance be blis
 
Join Date: Mar 2005
Location: Gainesville, FL
Posts: 306
Quote:
Originally Posted by boneheaddoctor
You sure its a knock and not nailing?
I don't see how it could be injector-related with such new injectors...

if when you say nailing you are just talking about the quality of the noise, then I guess you could also describe it as that...

I'm loath to suspect the fuel system.
__________________
"I would rather be ashes than dust!
I would rather that my spark should burn out in a brillaint blaze
than it should be stifled by dryrot.
I would rather be a superb meteor,
every atom of me in magnificent glow,
than a sleepy and permanent planet.
The proper function of man is to live, not to exist.
I shall not waste my days in trying to prolong them.
I shall use my time."

-Jack London 1876-1916

1983 300CDT (running WVO since 12/05)
1981 300SD (parts car)
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  #10  
Old 07-21-2005, 06:22 PM
Old Deis
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Never doubt the ability of off shore injector rebuilders/ manufacturors to foul up new or rebuilt injectors. They work hard at it.
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  #11  
Old 07-21-2005, 06:51 PM
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I don't know how true this is but I heard new injectors might make more noise than the old ones. What is your idle speed?
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  #12  
Old 07-21-2005, 07:20 PM
t walgamuth's Avatar
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Join Date: Apr 2005
Location: Lafayette Indiana
Posts: 38,613
intermittant

metallic sound could be early signs of vacuum pump failure. of course this can be an expensive problem if the parts jam the cam chain. are your vacuum systems working up to snuff?
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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.
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  #13  
Old 07-21-2005, 07:56 PM
83mercedes's Avatar
Ign'ance be blis
 
Join Date: Mar 2005
Location: Gainesville, FL
Posts: 306
idle speed is normal (I think around 600rpms), and I'm pretty sure this is not injector-related

hopefully injectors are good, they are bosch rebuilds.

I get great vacuum readings when I hook up a gauge to the main black line, so I think my vacuum pump is okay for now; but you've got me worried saying it could screw my engine over......I suppose it could be coming from my vacuum pump, can't really locate it.

Should I do a precautionary rebuild or get a junkyard replacement?
__________________
"I would rather be ashes than dust!
I would rather that my spark should burn out in a brillaint blaze
than it should be stifled by dryrot.
I would rather be a superb meteor,
every atom of me in magnificent glow,
than a sleepy and permanent planet.
The proper function of man is to live, not to exist.
I shall not waste my days in trying to prolong them.
I shall use my time."

-Jack London 1876-1916

1983 300CDT (running WVO since 12/05)
1981 300SD (parts car)
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  #14  
Old 07-21-2005, 08:39 PM
t walgamuth's Avatar
dieselarchitect
 
Join Date: Apr 2005
Location: Lafayette Indiana
Posts: 38,613
if you do it

i would recommend rebuilding. the one from the junkyard may be worse than yours. i think the kit is about $100. the pump may work fine and still have a siezed bearing and be on the verge of failure. mine was like that. it would make a nasty noise but if i took it to the garage it would be fine. finally i gave up.... then one day on the way back from kansas city, my vacuum pump failed. not knowing that it was possible for an expensive repair i pressed on and a few hours later it broke... and broke my cam chain, and my cam and one cam tower. minimum repair was about $1500... i opped to rebuild the motor for about $4500. it was really nice when done. but...... and this was about 14 years ago, everything i expect is about 50% more.
__________________
[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.
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  #15  
Old 07-21-2005, 10:09 PM
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Join Date: Aug 2003
Location: Bryan Texas
Posts: 49
I have an "81 SD. It had a definite metallic knock. I cracked the injector lines one by one ,at the injectors, untill the noise went away. There is an extensive thread titled "knockin "81 300SD". Which chronicals my travails. But the main point being I was able to isolate the noise to one cylinder. It just so happened that it was no.1 cylinder on mine. Hope this helps. Lee

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