Pagoda SL Group
W113 Pagoda SL Group => Drive train, fuel, suspension, steering & brakes => Topic started by: Charles 230SL on April 08, 2015, 01:20:27
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hello, would anyone happen to have a picture of an early m127 #3 bearing cap with the thrust bearing inserts? Are there thrust bearing inserts on the top half of the early main bearings?
thanks, Charles
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Charles, the early M127 engines and many of the other early engines had the separate thrust inserts on the bearing cap only (front and rear). It was actually bearing cap #2 not number three. The later bearing sets with the built-in thrust flanges, were much better and provided twice as much thrust surface since the thrust flange was on the upper bearing half as well as the lower bearing half. Some of the early Factory Shop Manuals describe how to use the later improved bearings on the early engines. A light modification is required. The thrust inserts are hard to find or NLA these days. Go with the later bearing type if possible.
During crankshaft grinding, the thrust surface of the crankshaft should also be checked and ground so the .004" clearance spec. for the #2 main journal width is achieved. In order for this to happen, oversize thrust inserts are required. These over-sizes are even harder to find. In contrast the improved later bearing sets all ready come with over-size (wider) thrust flanges so that the crank main journal width (at #2) can be ground to fit.
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The bearing journal is wider on an undersized part but we usually don't grind the crank journal wider unless it's been damaged. It this case, we make the bearing flange narrower and only remove material on the front end surface of the bearing. This will allow the crank journal to ride on a true runing surface. Crank shafts have a tendancy to push forward as they spin in the engine which is why we leave the rear contact surface as is.
You only get to grind a crank journal wider one time. Make sure it's for the right reasons.
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Actually the oversize bearings have a progressively wider thrust width for each over-size. So you get more than one chance. Yes, "lapping" the thrust flange of the bearing down is another option as Dan mentions. I like to send the crankshaft into the machine shop with the thrust bearing. It comes back perfectly smooth and fitted to the crankshaft.
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The tech at Bud's says I've got .089 run in/out on the crank but it's still within the .090 tolerance. I've never laid eyes on the (.090) spec in the BBB and I'm not even sure where this tolerance is published.
Ths motor runs strong, uses no oil, and keeps the oil pres gauge pegged at all times-regardless of rpm; I certainly don't want to tear it down. So,,I guess you guys know where I'm going with this..I'd like to be able to drop the lower pan, the bearing cap, and insert a wider thrust bearing. Before I attempt, i'd like to get an idea of how that cap and bearing looks. thanks, charles
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Hello Charles,
I would assume that your engine has the built in thrust surfaces on the main bearing. In this case you cannot install a wider center thrust bearing. Since your bearings are most likely standard, then the center thrust is the standard width. Only the oversize bearings have a wider center thrust. You cannot go to a wider center thrust without going to the first oversize on the bearings themselves. Are you having any problems because of excessive end play of the crankshaft? I believe that the end play value for the crankshaft is found in the Technical Data Booklet 1963 (p114). "Crankshaft bearing clearances" (axial flanged b) 0.1 to 0.175 mm or .004 to .007". Footnote *in case of repairs 0.30 mm (012") is still acceptable. Please have your sources review this information since this is my interpretation of the text.
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Hi Joe, since this is an early 230 chassis 003548 with the original engine (#127981-10-003227), I'm betting on it still having separate thrust inserts.
I've had no problems with the excessive end-play except that when/if the clutch is pressed while cranking, the starter gear grinds as though it’s no longer meshing correctly with the ring gear. The starter is new and the ring gear looks fine, so the only thing I can attribute this to is that the flywheel is being pushed too far forward (.089) by the clutch, causing the starter gear to 'overshoot' the ring gear enough to start skipping/grinding teeth. Sound feasible?
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You may want to remove the oil sub-pan, remove the oil pump, remove the main bearing cap and thrust bearing for inspection. If you do have the separate thrust shims, you can replace or shim them. I thought all the 230SL engines had the one-piece thrust bearings? Sounds like the back side of your ring gear may be worn? Is the .089 play inches or mm?
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The end play is .089 inches; crank/flywheel is pushed forward .089 inches when the clutch is pressed. As long as I don't cluch while starting, all's well. Ironically, neither front nor rear oil seals leak a drop. nonetheless, l'm just not comfortable with the excessive end-play and will (for my winter project) drop the lower pan, oil pump and #2 cap.
Still hoping someone on the forum will have some pictures of that cap and thrust bearing.
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Do you want pictures of the early style or latter style or both?
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The early style.. thanks!
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hello, I decided to update this topic regarding the excessive crankshaft end-play on my M127 (127981-10-003227)
I was about to change the oil and while I had the car up on the ramps, I went ahead and dropped the sub-pan and took a look at the #2 main thrust bearing. Surprisingly, there were no thrust bearing shims/inserts nor a thrust flange whatsoever. There was only a bearing shell with nothing but the edge of the bearing providing a thrust surface against the crankshaft. Appears a PO or machine shop overhauled the engine and used wrong #2 main bearing halves (see photos).
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Quite amazing! I never ran into this blunder before.
Remove the main bearing cap to see what size main bearings are in place. You can then try to fit the correct bearing in place if the crankshaft is good.
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Joe, will the bearing have the (over) size stamped on the back?
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The engine looks good from underneath - cylinder walls appear newly bored (or honed) and pistons look new. I just can't believe someone would go through the trouble and expense to overhaul this engine and yet use the wrong #2 bearing!
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Here are the pics of the early and late versions of the thrust bearing. I don't think that the 230SL engine ever had the earlier insert version?
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Most often, the bearings will have a size and/or part number on the back side.
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Hard to see from the photos, but it almost looks like the flange type thrust bearing is in place? Just way too much end play. Remove the main cap to verify.
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No flange. The edge of the bearing is all that's been providing a thrust surface. The photo (below) is one I took before removing the baffle plate - it may give a better perspective.
I'll remove the main cap this afternoon and attempt to determine the size of the bearing. Not sure what my options will be at that point...IF I can source a correct sized #2 bearing, I would think my only option (without overhauling the engine) is to replace only the lower half of #2 bearing.
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Joe, sorry for being so presumptuous. I was wrong - there is indeed a flange on the bearing. The markings on the back of the bearing are: STD 72-2058.
The crank journal looks fine but the flange on the back side of the bearing is certainly worn beyond limits. Sorry for the poor photos - my wife's iphone wasn't available at the time.
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I need to confirm my M127 crankshaft has standard main journals and has never been machined, but I can't accurately mike a journal while the crankshft is still in place. Since the part number on the back side of the #2 bearing is "Std" 72-2058, is it reasonable to assume the main journals are standard (60mm)? is there a way to cross reference the bearing part number to the journal diameter?
thanks in advance, Charles
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Hello Charles,
The bearing is showing signs of serious wear. Notice the large worn copper areas on the bearing surface itself. Most likely the crankshaft is worn also. Installing a new bearing half at this point is a very temporary patch.
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I was going to suggest that the locating bearing was installed in the wrong place but I see that you found this on your own. I saw this on a 190SL engine a while back. You would think that with only three bearings, one would figure out that it goes in the center but no......they had it in number one position. :o The crank gear did a nice job on it too. :(
And if that isn't bad enough, I had one a few years back where they had the thrust bearing located in the right position but the two outer bearings were installed upside down cutting off oil flow to the two bearings and the crank journals as well. ??? The engine had good oil pressure but it rattled like a pea in a tin cup. :D
So, yes, it seems as though screw ups like this a far more common than you would tend to imagine. ::)
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thanks Joe, yes this would be a temp fix. I just don’t want the downtime on the car right now – I work real slow, and pulling the engine now would confine it to the hangar all summer.
can you recommend a source for a set of standard bearings or know anyone with a spare set they'd like to sell? thanks, charles