Replacing burned Camshaft - PeachParts Mercedes-Benz Forum

Please Help · #1 03-05-2003, 07:51 PM

Dear all,

I recently burned the left cam-shaft on my 1989 w126 (oil starvation due to clogged oil tube). I cannot seem to get the flywheel side tower bearing to come loose. According to the book they are supposed to be 50 NM but I have used more force than that trying to remove them. I do not want to damage anything on the engine, and am unsure as to the amount of force that I chould be using.

I would appreciate any advice.

myarmar · #2 03-05-2003, 09:42 PM

Read this:
camshaft bearing torque HELP!

euro 287 · #3 03-05-2003, 10:14 PM

here is a good tip for all you DIYers. If you have a allen that gets stuck and you are scared you are gonna round it do the following. Clean it real good with a pic and carb cleaner. Take some valve lapping compound and put some on the end of the allen, then break er loose., Good luck

kip Foss · #4 03-05-2003, 11:23 PM

I work with heavy machinery next salt water so I deal with stuck nuts and bolts all the time. Get a steel rod about 3/4 in. dia. or slightly bigger. Cut it to about 6to8 in. long. Make sure the end cut is square. Get a 2 lb. shop hammer. Place the steel bar square on top of the allen bolt and hit it as hard as you can 2 times. Insert the allen wrench with a cheater pipe on it or use an allen socket with a break over bar (14 to 18 in.) and loosen it. Don't try to hit the top of a bent allen wrench. It won't work and it will hurt your hand.

Rapping the bolt with a hard, sharp blow sends a kind of shock wave down the bolt that fractures any kind of corrosion (not likely with a bolt that is bathed in oil) or lock tight. Don't use a socket extension as a drift. The male square end is usually not cut square, it has a slightly rounded end, and this will tend to dimple in the hole. This will make it hard to get the allen wrench in. If you do this it is nearly impossible to file/grind open the hole. Don't use a brass drift either. What you want is the steel on steel shock effect. Brass is soft and will tend to absorb the blow. Don't bother with wd40 or the likes. If, over the years of running, hot engine oil has not penetrated into the threads a shot of wd40 doesn't stand a chance.

Be sure that you have the exact size allen wrench and that it is not rounded on the corners. Once the wrench spins in the bolt you are basically a done duck. Then you either take it to a old time mechanic who will see your situation and subsiquently screw your eyes out or, if you know how (in which case we would not be having this discussion), get out your welding machine and weld a grade 10 cap screw to the top of the allen bolt and use an impact to back the bolt out.

Remember too, you can put a lot more torque on that bolt that the tighening force recommended by MB. Allen bolts are usually about grade 10 and are really tough.

Good luck.

Please Help · #5 03-06-2003, 06:14 AM

I'll try the suggestions listed. If I can be of any use, please let me know....

1989 560 SEL

diesel1mercedes · #6 03-06-2003, 12:33 PM

use a large torx bit and power it out hit it with a hammer and you will be able to get it out

afmcorp · #7 03-06-2003, 03:28 PM

hello please help

yep just had that problem a couple of weeks ago. i'm the guy in that first thread.

this was my first experience with a benz so i was somewhat nervous about messing the threads in the block up. and i've been working on cars and trucks since the 60's.

after i tried several approaches i went home to think about it and when i came back i got my largest set of sockets out and got a 3 foot pipe cheater bar and said to my self: BRUTE FORCE AND IGNORANCE WILL SUCCED WHEN CLEVERNESS FAILS. took a breath and snap the socket head broke loose.

here is that first thread camshaft bearing torque HELP!

there was no slowly backing out. it was snap and i could amost use my fingers the rest of the way. And there was no tell tale signs of aluminum block on the threads of the bolt. i did see some drops of condensation but mostly just a well zinc coated bolt.

on installation i did use a never seize compound. go to napa auto and get the bottle used for aluminum. while you are there pick up some assembly grease for cams. it's in a squirt bottle and use it very liberally on all the surface of the lobes and journals. also i hope you got new rocker arms this is an absolute must for new cams. also don't forget to raise the rpm up to say 1500 - 2000 rpms for 20 or so minutes to properly break the new cam in. otherwise you may damage the lobes/rockers all over again. i also put all new oil tube plastic on both sides.

i'm curious which rocker/lobe went on yours was it the front half or back half. my was the back half 3rd cylinder from the front on pass side. i considered enlarging the hole in the tube for the back 2 cylinders cause i'm am thinking that the oil path may feed from the front to the rear.

well good luck
tks
craig

Rato73 · #8 03-06-2003, 10:55 PM

I had a camshaft (rhs) seize last month and am just putting the new parts back in. The front two bearings seized on mine due to the shifting of the oil supply pipe so that the holes in it didn't line up with the plastic tees anymore. It's my understanding that the oil feeds from back to front as the rearmost camshaft bearing has a groove around it's circumference to allow oil from the block through the bearing and into the oil supply pipe. The other bearings are smooth.

I still don't know what caused the oil supply pipe to shift position. I plan to lock it somehow so that this won't happen again. IMHO, the cam oiler design could have been better executed by MB and owners should replace the pipes and tees annually seeing how their failure causes $$$$ damage.

afmcorp · #9 03-07-2003, 01:45 AM

hi rato73

i think the cam bear towers get their oil from the head which feeds the valve compensators ( lifters or facsimile thereof). if you look inside the journals there is an oil path from the bottom then up to the oil tube. also it appears to me that the rear of the cam could be open to atmosphere (hole) and with the holes in the oil tube venting to atmosphere as well that would or should be the end of the oil pressure system. i think the oil tubes are there more for the rockers than the bearings. although i wouldn't rule out they are design to assist in lubing the cam bearing journals.

the funny part is the cd manual (pg5-211) also implies that oil travel is thru the center of the cam. the cam is cast iron and i don't know how they would shake the core out and make the center clean enough to supply oil.

now i'm not certain about all this i'm just trying to figure out how the tube on mine plugged up just 1 little hole and none of the others. also when i miked the journals to compare to the new cam i was surprised to see the tolerance was still holding .0025 to .0045 inch. that tells me that my oil system on the journals was working just fine so i'm stumped as to why only 1 rocker bit the dust. oh well guess i should count myself lucky and as long as they run i shouldn't question why.

good luck on your project.
tks
craig

Please Help · #10 03-07-2003, 06:31 PM

Quote:

Originally posted by Rato73
I had a camshaft (rhs) seize last month and am just putting the new parts back in. The front two bearings seized on mine due to the shifting of the oil supply pipe so that the holes in it didn't line up with the plastic tees anymore. It's my understanding that the oil feeds from back to front as the rearmost camshaft bearing has a groove around it's circumference to allow oil from the block through the bearing and into the oil supply pipe. The other bearings are smooth.

I still don't know what caused the oil supply pipe to shift position. I plan to lock it somehow so that this won't happen again. IMHO, the cam oiler design could have been better executed by MB and owners should replace the pipes and tees annually seeing how their failure causes $$$$ damage.

Rato,

The oil pipe on the 560 engine lockes into place with the end elbow nipples (they are keyed) and the middle three lock into the cam towers. It really does not seem possible that the oil pipe could shift unless something is very amiss with your configuration. I'm not very familiar with your car, but take a close look at that.

Rato73 · #11 03-08-2003, 12:25 PM

Maybe this is peculiar to the 380 engine, but the front four bearing towers have no openings on the bottom to the block for oil supply. The rear bearing tower does. The oil then runs through the groove in the rear bearing and up into the pipe which feeds the front bearings via the plastic tees plugged into the tops of the bearing towers. If one of the tees or drip holes gets plugged, this could oil starve the associated bearing/lobe/rocker.

As far as my oil tube shifting, it may have had some help from one of the ham-fisted mechanics that the previous owner hired to fix a hesitation problem. The tees and end caps were still attached to their respective bearing towers, but the tube had been moved foward about 1/2" within the tees recently as evidenced by a shiny area on the pipe in front of each tee. This misaligned the holes and bingo, fried bearings.

By the way, I just installed the new camshaft and bearing towers
and the camshaft seems to be hard to turn by hand with the rockers not yet installed. Is this normal? How tight should it be?
What could cause this tightness?

Please Help · #12 03-08-2003, 12:34 PM

By the way, I just installed the new camshaft and bearing towers
and the camshaft seems to be hard to turn by hand with the rockers not yet installed. Is this normal? How tight should it be?
What could cause this tightness? [/B][/QUOTE]

In my book, it say:
"
Caution!
The camshaft should turn easily by hand.
"

Be careful, owuld hate to see you mess up your cam, bearings, et al.