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  #1  
Old 02-08-2003, 03:01 PM
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Join Date: Jan 2003
Location: St. George, UT
Posts: 11
W126 Seized Camshaft

I have been lurking on this board for awhile now learning about the 1984 380SE (132K miles) I acquired a month ago, but now I have a real problem and need advice.

Last week, while waiting at a stoplight, the engine quit with no unusual noises. When attempting a restart, the starter would engage but not turn the engine over. Car towed home. I assumed the worst and removed the valve covers expecting the dreaded broken chain guide scenario. Guide rails dark brown but intact and no evidence of chain skipping, so OK there. Then I looked at the camshafts and noticed the one on the passenger side had discolored bearing towers. The front three were blackened and dry compared to the rear two which were a normal brown color. Upon further inspection, the oil supply pipe looked like it had "slipped" forward about 1/2" as it had shiny areas just forward of the plastic fittings (which were partially melted on the forward black towers). Cam lobes adjascent to the blackened towers showed evidence of galling. I took off the oil supply pipe and it had slipped enough so that it's hole no longer matched the hole in the plastic fitting, so the oil supply was effectively cut off to the cam lobes. I tried to turn the camshaft with a wrench on the sprocket bolt, it wouldn't budge.

So there's the problem, I now know that I will need to get a new camshaft, bearing towers, oil pipe and rocker arms. Typical $10 part failure causing $100's damage. I intend on doing the work myself (along with new chain and plastic guides) so here are the questions:
1. The MB CD says to remove rocker arms before removing the camshaft. Is this necessary? I cannot turn the camshaft to unload some of them. Can I just unbolt the bearing towers and remove the assy. with rockers in place? Or, is it possible to remove the arms w/o rotating the camshaft?

2. What precautions should I take when removing the bearing tower bolts so as not to strip the threads in the block?

3. Are there any pitfalls that I should be aware of in attempting to do this myself other than the obvious valve timing, etc.

I got the car for a ridiculously low price and I figured I can spend up to $2000 before I am "upside down" on it. Everything else is in great shape on the car, not even door dings. I would like to keep it for awhile and would hate to shoot the horse just because of a broken leg.

P.S. I plan to epoxy the new oil supply pipe in place to keep this from happening again!
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  #2  
Old 02-08-2003, 10:38 PM
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Join Date: Apr 2000
Location: Falls Church, VA
Posts: 5,316
You will need to remove the rockers before you install the new cam and towers, and then you will need to compress the valves to reinstall them (or new ones). You might as well buy a compressor now and take out what rockers are accessible.

You will still have some pressure on the bolts when you remove the cam and towers, but I doubt that you will strip anything. You really don't have much choice.

Good luck!
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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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  #3  
Old 02-10-2003, 01:24 PM
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Join Date: Jan 2003
Location: St. George, UT
Posts: 11
Are there any methods for "breaking loose" the seized camshaft so it can turn? I was thinking of applying PB Blaster to the bearings and letting it soak in for awhile, then applying a large wrench to one of the lobes (with chain and sprocket off) and rapping the wrench with a BFH. Or do these parts just "weld" together making efforts of freeing them futile?
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  #4  
Old 02-10-2003, 02:43 PM
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Join Date: Apr 2000
Location: Falls Church, VA
Posts: 5,316
The manual shows a large bar wrench that fits over a cam lobe, but it is used to hold the cam while tightening the sprocket bolt.

You could also try a pair of large vice-grips on the front of the cam and tapping/bashing them with a hammer.

But I really don't think you'll hurt anything if you undo the towers.
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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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  #5  
Old 02-10-2003, 09:58 PM
rmakela
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w126 camshaft

I have a 85 380se last year I replaced the right hand camshaft ,oiler tubes and rockers . I grounded out an open end wrench and heated it up to give it a slight bend in order to fit over the back end of the rocker were it sits on the lifter ball carefully I lifted up the rocker off the ball and sliding the rocker back watching not to catch my fingers if it slipped also have some towels around the area to catch the thrust piece that is between rocker and the valve spring because it pops out and it could land anywhere if you are not watching when the rocker slides off the valve spring. If you could find the proper tool buy it ,I however was unable to locate one through SNAP ON or MAC. Also the outer cam tower bolts were something else to break lose .I ended up using a 1/2'' drive with an Allen head and a impact wrench dialed down to rattel them lose make sure you blow out the bolt holes and take care starting the bolts back in very easy to cross thread .good luck with job .
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