Can anyone tell me if this is normal?

[PeteMelb]

Hi All, First a bit of background to assist: This motor was purchased from a chap that strips and parts out wrecked trucks, the motor was apparently rebuilt 400,000klm before it was wrecked, at first the story was the truck twisted the frame but later he found out it was rolled so the motor may have been running on its side or upside down who knows. Anyway when it was fitted into another vehicle and started it had one hell of a knock that sounded like a gudgeon knock. but the individual that sold it to this man has pretty much wiped his hands of it so he's now come to me for help, I started it and its got a knock alright that I'm now looking into.

I have just unbuttoned the bottom end of this ISX motor and the crank journals and bearings look in excellent condition, except for the blue discolouration on the crank (photos below) something I've not seen before and wondering if its from manufacturing or if its been cooked, I would assume if it was cooked then the colouration would not be as even as these seem and the journals would be stuffed but the mains and big end bearings I dropped so far have No wear AT ALL on them and that makes me suspicious if its supposed to have done 400,000 I'd expect some wear but they look brand new, the journals themselves look blue in the photos but they are not they look perfect to the naked eye no colouring at all. the conrods have no discolouration and so far look fine so I don't think they were cooked.

Bottom line is, If the discolouration is normal then we can proceed with just locating the knock and fix that issue, but if you guys think its been cooked then I may have to break the bad news to him that its gotta come out again, I'd appreciate any advise I can get on this crank.

               

[Starlight]

The blue colour your seeing is from Cummins heat treating the crank at the factory. It looks very good to me and is nothing to be concerned with. If you would be installing new bearing then i would polish the journals a bit.

[Nilao]

try to cut one cylinder at a time. You may have a injector issue causing a fuel knock or it could be a wrist pin issue....you should be able to isolate it by taking the strain off the cylinder by cutting it out. I'm not certain where the noise if coming from but you shouldn't also rule out a compressor knock or the gears in the front housing being the source of the knock either...

[PeteMelb]

(09-01-2018 )Starlight Wrote:  The blue colour your seeing is from Cummins heat treating the crank at the factory. It looks very good to me and is nothing to be concerned with. If you would be installing new bearing then i would polish the journals a bit.

Thank you very much for your reply I thought it was to even to be over heating but it never hurts to check and I know there are some extremely knowledgeable people here who's opinions and recommendations I would trust over any stealership.

Regards Peter

[PeteMelb]

(09-01-2018 )Nilao Wrote:  try to cut one cylinder at a time. You may have a injector issue causing a fuel knock or it could be a wrist pin issue....you should be able to isolate it by taking the strain off the cylinder by cutting it out. I'm not certain where the noise if coming from but you shouldn't also rule out a compressor knock or the gears in the front housing being the source of the knock either...

Thank you very much for your reply.

I read your reply last night and thought about it more today and I recalled the owner of the motor saying the guy he purchased it from said he had changed the injectors for some reason to get it to run, so you may be onto something, Im going to pull the injectors tomorrow and have them tested before I go any further with the bottom end, apparently he also swapped out the compressor and as far as the purchaser knows he just pulled the old one and stuck the new one on so I'm also going to check the timing of that.

As I said in the above post you guys and this site are the best help I've ever found thanks again.

Regards
Peter

[Chamberpains]

A lot of the cm870 and cm871 air compressors knock\rattle while building air both new and old compressor's. The timing can be lined up perfect and all. Then stop once the governor kicks out. Its sounds like a definite engine knock. Its normal on an ISX. They just knock when building air. Are you sure your not chasing a perfectly normal air compressor noise?

[PeteMelb]

(09-02-2018 )Chamberpains Wrote:  A lot of the cm870 and cm871 air compressors knock\rattle while building air both new and old compressor's. The timing can be lined up perfect and all. Then stop once the governor kicks out. Its sounds like a definite engine knock. Its normal on an ISX. They just knock when building air. Are you sure your not chasing a perfectly normal air compressor noise?

Hi Chamberpains, thank you for your reply, I wish it was that simple, I have dealt with a few of these motors and know the compressor knock well, but this is not that unfortunately, it's way to solid a knock I spotted a run of soot from the manifold join today on the newly painted motor so Im really leaning towards an injector at this point, as soon as I can get back to it I'll post what I find when I find it.