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  #1  
Old 09-06-2004, 10:20 AM
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560SEL motor problems. Need help troubleshooting

Hey everyone... I have an issue that now befuddleing me. My car is an '88 560SEL and has less than 70K miles. On my way home with with it it started burning oil (Car was in NY, home is Denver, oil burning started in St. Louis) Anyway, figuring it was either valve stem seals or valve guides, I decided the best thing to do was replace the valve stem seals, and while they're off to check the valve guides. Well, I finally had some time to tear into the motor this weekend and this is what I found:

I don't have my chamber number chart in front of me so please bare with me.

The spark plug from 2nd chamber from the front on the passengers side was coated in oil and appeared scorched.

When the engine was secured and air was applied through a spark plug adapter (100psi) I could hear air coming from the area of the spark plug hole. Sometimes I wouldn't get any hissing, but if I jiggled the air hose I would. I could not repeat the air leak on other chambers.

Here are a couple of pics I hope show what I'm talking about:

The spark plugs



Chamber with good seal on the air hose fitting:


Chamber with bad/hissing sound from the air hose fitting:



As you can tell, from the "bad" chamber it appears I'm getting seapage. I'm not seeing this on any other part of the motor...


Any Ideas?



Scott

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  #2  
Old 09-06-2004, 12:29 PM
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Location: Evansville, Indiana
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By burning oil, do you mean you had to start adding oil or that you started getting blue smoke?

If the plug hole is leaking, it needs a Helicoil or Timesert inlet, the threads are bad (from overtightening the spark plugs or not using ant-sieze on them).

A plug suddenly getting oily like that could mean a valve guide loose in the head, or it could mean a bad plug wire so it never fires, leaving oily gasoline resdiue on it, or a plugged fuel injector so that no fuel ever reached that cylinder. Any of these would give you a dead miss on that cylinder, too.

Peter
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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!
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  #3  
Old 09-06-2004, 12:34 PM
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Burning oil: At first having to add 1 quart every 200 miles. After 600 miles like this, having to hadd 1 quart at 100 miles. This is when I was able to park the car for repairs. No oil leaks

The valve guide didn't seem loose. I was able to get ahold of it and it didn't move at all.

My concern is what would cause the scorching on the porceline of the spark plug? The discoloration on the lable and the porceline is not oil.
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  #4  
Old 09-06-2004, 12:51 PM
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The only way you could check the valve guide is to remove the rocker and spring.

A quart in 100 miles? You must have left a blue cloud behind you that could be seen from a space!

Sounds more like a hole in a piston to me, you have to have HUGE blowby to use that much oil!

Are you trying to keep the oil at the top line on the dipstick?

Peter
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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!
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  #5  
Old 09-06-2004, 01:30 PM
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dead cylinder? scorched plug?

a spark plug that is loose in its hole will overheat. It depends on intimate contact to transfer the heat to the cylinder head and then to the cooling water. If it overheats enough, it will cause pre-ignition which WILL destroy the piston-melting a hole in the top of it. If the cylinder holds good compression, the piston is not damaged. The gross oil consumption can be caused by a valve guide that is loose and working in the head--or damaged piston rings, scuffed cylinder, etc.

Good luck. It does not sound like fun
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  #6  
Old 09-06-2004, 02:46 PM
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Doing a valve stem steal replacement involves removing the rockers and springs, which is how I got to the valve guides to determine they were not loose. Now I don't know if they would pass a go-nogo because I'm doing the valve stem seal replacement in-situo with the heads still on the block thus valves still in.

When I first noticed the oil burning my oil level light came on (700 miles into a 1800 mile trip) From that point, I added oil to keep it topped off and would continue to add until just before it got to the top of the dipstick mark, I would check the level at rest areas between fill-ups, usually requiring another quart.

Blue cloud was visible at startup but after a minute or so would go away. Just before I parked the car for repairs, the car's exhause was nasty for about a mile or so, but again, would dissipate and look normal after that, although still consuming oil. I was driving the car as little as possible once I got home becuase of the oil consumption, but... With this ammount of oil consumption I too would expect a blue cloud that would have every environMENTAList after me, but thats not what I had.

When I injected compressed air into the cylinder initially and when I have a good seal at the spark plug hole, the hissing sound from the cylinder sounds the same as the other cylinders. To determine this, I hand-cranked the engine to ignition-TDC, locked down the driveshaft, then injected 70psi raising it to 100psi. The only time I heard anything really wrong was when I wiggled the spark plug fitting and would get the hissing sound and feel air at my fingertips near where the sparkplug would sit. I plan to use some soapy water or blow smoke that way to find the origin of the leak since my fingers aren't as calibreated as my eyes (with indicator) to find leaks. I know the problem isn NOT my fitting/hose since I took it to other cylinders and did NOT get any hissing from them using the same jiggle etc.

I highly doubt there is a hole in the piston becuase on a compression test, before I started tearing everything apart, this cylinder had 135psi, consistant with the reading on other chambers.

I've also suspected piston rings, however, wouldn't the ambiant "hiss" from this cylinder sound different from the others if 1 of the 3 rings were FUBAR'ed?

Is it possible I have a blown head gasket causing that much oil consumtion?





The evidence I have for troubleshooting this problem is really inconsitant with my initial diagnosis as well as interim diagnosis, and I'm about to be clueless and just to be thurough I'm thinking about pulling the head. If I do this, I'm going to pull both and do the whole top end while I'm there. I want to fix this and have this car running as quickly as possible, but I also want to fix it right. I'm not a mechanic, but I am a mechanical engineer whose tinkered on other motors in the past, so while not an expert, I do pay attention to things that are abnormal. If anyone has any other ideas, or responces that contradict my rational for troubleshooting (I'm not perfect, its just how things appear to me) please let me know. Also, I'm sure there's details I've noticed that haven't waived a red flag that they should have, so if you have an idea, and I haven't mentioned a corresponding symptom, please ask. I will remember and probably mis-filed it as something unimportant.


I greatly appreciate the help so far! Thanks all for responding!



Scott
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  #7  
Old 09-06-2004, 03:32 PM
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I misspoke, I did not inject air at fire-TDC, I injected air and exhaut/intake-TDC
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  #8  
Old 09-06-2004, 05:25 PM
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Another edit... the scorching on the spark plug is only on the label, not the porciline. It seems to be a thin layer of glaized oil, and it scratches clean with a fingernail.
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  #9  
Old 09-07-2004, 08:37 AM
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Another possibility, along the lines of Peter's suggestion, is that the intake valve on that cylinder is not opening, causing a vacuum on the intake stroke and sucking oil into the cylinder.
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Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe
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  #10  
Old 09-07-2004, 09:09 AM
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Quote:
Originally Posted by ctaylor738
Another possibility, along the lines of Peter's suggestion, is that the intake valve on that cylinder is not opening, causing a vacuum on the intake stroke and sucking oil into the cylinder.

Would the valve stick intermittently or would it be "glued" shut? When I was removing the rocker arms et. al. they moved pretty freely when I was compressing the spring by hand. How would you recommend I test for this?

I appreciate the help!




Scott
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  #11  
Old 09-07-2004, 09:56 AM
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If the cam lobe, rocker, and ball stud are OK, then this is not the problem. I don't see how it could stick shut.

BTW. I bought a 380SL with a rocker worn so severely that the valve was not opening at all. The "ball" part of the ball stud had popped out and was laying on the top of the head.

Picture attached.
Attached Thumbnails
560SEL motor problems.  Need help troubleshooting-380sl-sept-18-rocker-stud.jpg  

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Chuck Taylor
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe
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