OM603 Conrod ble discolouration
OM603 Conrod ble discolouration
I am rebuilding my OM603.931 engine (naturally aspirated G300 Diesel).
When I opened it up I noticed that some of the conrods had a blueish colour to them. In the manual it says not to reuse conrods that have discoloured. I sourced some conrods from an OM603.912 engine and some of the conrods are also blue. Is this common in the non-turbo engines?
Anyone seen this? Can I reuse the conrods or not?
Some comments would be appreciated.
Hi All
I am rebuilding my OM603.931 engine (naturally aspirated G300 Diesel).
When I opened it up I noticed that some of the conrods had a blueish colour to them. In the manual it says not to reuse conrods that have discoloured. I sourced some conrods from an OM603.912 engine and some of the conrods are also blue. Is this common in the non-turbo engines?
Anyone seen this? Can I reuse the conrods or not?
Some comments would be appreciated.
no problem reusing them. the MB manual states limits for play.
this blueing is related to fabrication of some of the con rods, it is not related to overheating issues.
usually when a engine overheats at the point of having discolored parts is very evident on the cap´s.
con rods and crankshaft are made from high quality mild steel, and after they are machined, the heat treatment is done only in zones where strength is most needed, the rest stay mild steal in order to withstand bending and shaking and stretching. that is from where the blue is coming from.
regards
FD,
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i seen same on my 605, and many other engines.
no problem reusing them. the MB manual states limits for play.
this blueing is related to fabrication of some of the con rods, it is not related to overheating issues.
usually when a engine overheats at the point of having discolored parts is very evident on the cap´s.
con rods and crankshaft are made from high quality mild steel, and after they are machined, the heat treatment is done only in zones where strength is most needed, the rest stay mild steal in order to withstand bending and shaking and stretching. that is from where the blue is coming from.
regards
FD,
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(07-02-2014, 12:35 PM)barrote i seen same on my 605, and many other engines.
no problem reusing them. the MB manual states limits for play.
this blueing is related to fabrication of some of the con rods, it is not related to overheating issues.
usually when a engine overheats at the point of having discolored parts is very evident on the cap´s.
con rods and crankshaft are made from high quality mild steel, and after they are machined, the heat treatment is done only in zones where strength is most needed, the rest stay mild steal in order to withstand bending and shaking and stretching. that is from where the blue is coming from.
regards
Thanks. On the om603.931 the main and big end bearings were badly scuffed and I even had the crank polished to remove the worn/melted bearing material. Still std size though. I don't have a history for the donor rods so I cannot say.
I noticed that the sump has been repaired on the G which might mean the bearings ran dry at some point which might explain the bearing damage. Also the oil pump has been changed to a Febi part from the sedan and not the G i.e. pick-up is high off the pan.
(07-02-2014, 12:35 PM)barrote i seen same on my 605, and many other engines.
no problem reusing them. the MB manual states limits for play.
this blueing is related to fabrication of some of the con rods, it is not related to overheating issues.
usually when a engine overheats at the point of having discolored parts is very evident on the cap´s.
con rods and crankshaft are made from high quality mild steel, and after they are machined, the heat treatment is done only in zones where strength is most needed, the rest stay mild steal in order to withstand bending and shaking and stretching. that is from where the blue is coming from.
regards
Thanks. On the om603.931 the main and big end bearings were badly scuffed and I even had the crank polished to remove the worn/melted bearing material. Still std size though. I don't have a history for the donor rods so I cannot say.
I noticed that the sump has been repaired on the G which might mean the bearings ran dry at some point which might explain the bearing damage. Also the oil pump has been changed to a Febi part from the sedan and not the G i.e. pick-up is high off the pan.
if the engine runs dry of oil and is allowed to work at a point where the caps melt or fuse with the cemented surfaces , we are talking of serious heat, like this u may have a loss of the heat treatment, and serious damage installed, witch is not visible.
The other thing is that when that happens the bearing surfaces are not cylindrical anymore , usually they assume an elliptical form, that why u have .25 , .50, .75. 1.0 , bearings, the repair shop determines how much they have to cut.
the same happens with the roundness of the con rod, u got to determine if they are round, there is minimum for that , if they are it is unlike that they will turn elliptical right away. there is no repair that i know for con rods in a such a small engine.
anyway last month i fixed one 605 engine with serious compression issues, and i decide against all odd just to install new rings and made a small hand job on the cylinders. well the cylinders were just on limit or roundness, and i decided not to repair it completely, now i know that it will quit sooner than it should. lets see how long it holds. ended up being 500€ cheaper.
good luck.
FD,
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if u found that is better not to take the chance, fixing a crankshaft is worth the trouble, since is something u wont do in another life time.
if the engine runs dry of oil and is allowed to work at a point where the caps melt or fuse with the cemented surfaces , we are talking of serious heat, like this u may have a loss of the heat treatment, and serious damage installed, witch is not visible.
The other thing is that when that happens the bearing surfaces are not cylindrical anymore , usually they assume an elliptical form, that why u have .25 , .50, .75. 1.0 , bearings, the repair shop determines how much they have to cut.
the same happens with the roundness of the con rod, u got to determine if they are round, there is minimum for that , if they are it is unlike that they will turn elliptical right away. there is no repair that i know for con rods in a such a small engine.
anyway last month i fixed one 605 engine with serious compression issues, and i decide against all odd just to install new rings and made a small hand job on the cylinders. well the cylinders were just on limit or roundness, and i decided not to repair it completely, now i know that it will quit sooner than it should. lets see how long it holds. ended up being 500€ cheaper.
good luck.
FD,
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(07-02-2014, 03:06 PM)barrote if u found that is better not to take the chance, fixing a crankshaft is worth the trouble, since is something u wont do in another life time.
if the engine runs dry of oil and is allowed to work at a point where the caps melt or fuse with the cemented surfaces , we are talking of serious heat, like this u may have a loss of the heat treatment, and serious damage installed, witch is not visible.
The other thing is that when that happens the bearing surfaces are not cylindrical anymore , usually they assume an elliptical form, that why u have .25 , .50, .75. 1.0 , bearings, the repair shop determines how much they have to cut.
the same happens with the roundness of the con rod, u got to determine if they are round, there is minimum for that , if they are it is unlike that they will turn elliptical right away. there is no repair that i know for con rods in a such a small engine.
anyway last month i fixed one 605 engine with serious compression issues, and i decide against all odd just to install new rings and made a small hand job on the cylinders. well the cylinders were just on limit or roundness, and i decided not to repair it completely, now i know that it will quit sooner than it should. lets see how long it holds. ended up being 500€ cheaper.
good luck.
Thanks once again. Just to be sure, the crank was not cut to repair it, only polished. I was able to use STD size bearings etc.
I guess I will choose the least blue 'rods from the set of 12 and check them for roundness, straightness etc. and use those.
The engine had good compression and didn't use oil before I took it apart. The only reason I did take it apart was an oil leak on the head gasket. I thought since it had done 300k km I might as well check the bearings etc. as it was open. Then discovered the blue conrods and the manual's recommendations. I was just surprised to see blue conrods from another engine so thought I would ask.
(07-02-2014, 03:06 PM)barrote if u found that is better not to take the chance, fixing a crankshaft is worth the trouble, since is something u wont do in another life time.
if the engine runs dry of oil and is allowed to work at a point where the caps melt or fuse with the cemented surfaces , we are talking of serious heat, like this u may have a loss of the heat treatment, and serious damage installed, witch is not visible.
The other thing is that when that happens the bearing surfaces are not cylindrical anymore , usually they assume an elliptical form, that why u have .25 , .50, .75. 1.0 , bearings, the repair shop determines how much they have to cut.
the same happens with the roundness of the con rod, u got to determine if they are round, there is minimum for that , if they are it is unlike that they will turn elliptical right away. there is no repair that i know for con rods in a such a small engine.
anyway last month i fixed one 605 engine with serious compression issues, and i decide against all odd just to install new rings and made a small hand job on the cylinders. well the cylinders were just on limit or roundness, and i decided not to repair it completely, now i know that it will quit sooner than it should. lets see how long it holds. ended up being 500€ cheaper.
good luck.
Thanks once again. Just to be sure, the crank was not cut to repair it, only polished. I was able to use STD size bearings etc.
I guess I will choose the least blue 'rods from the set of 12 and check them for roundness, straightness etc. and use those.
The engine had good compression and didn't use oil before I took it apart. The only reason I did take it apart was an oil leak on the head gasket. I thought since it had done 300k km I might as well check the bearings etc. as it was open. Then discovered the blue conrods and the manual's recommendations. I was just surprised to see blue conrods from another engine so thought I would ask.
as i told u rods with light blue colouring are from fabrication, there is nothing wrong with them, the discolouring from heating is not light blue, if u see it u will understand the diff
Can´t post pic´s sorry
http://www.atsb.gov.au/publications/inve...00620.aspx : here u can see overheating , same happens in engine bearings.
http://en.wikipedia.org/wiki/Bluing_%28steel%29 here u can see blue resulting from heat treatment
regards
FD,
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yep, what u have to measure is Crankshaft bearing roundness, if its elliptical beon specs u got to cut it (its elliptical with 300K). same for con rod, but don't worry too much 40 years ago the finishing wasn´t that good and engines like 616 are still around.
as i told u rods with light blue colouring are from fabrication, there is nothing wrong with them, the discolouring from heating is not light blue, if u see it u will understand the diff
Can´t post pic´s sorry
http://www.atsb.gov.au/publications/inve...00620.aspx : here u can see overheating , same happens in engine bearings.
http://en.wikipedia.org/wiki/Bluing_%28steel%29 here u can see blue resulting from heat treatment
regards
FD,
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