Replacing crankshaft main bearings.

[Koreenium]

I have 2014 Skoda Rapid with 1.2L TSI ( CBZA ). 86hp, 4 ctlinders. 260 000 km ( ~160 000 miles ). Aluminium engine block. I had to take the engine out because there was glitter in oil. I discovered that all 4 cylinder walls and pistons have significant scuffing on one side but everything else looks good. I can get the cylinders fixed but problem is that my service manual specifically says that "Measuring the main bearing clearance is not possible with normal workshop equipment." and "Crankshaft must not be removed as merely releasing bearing covers will result in bearing seat deformation." This means I can't have the crankshaft removed which means I can't hone cylinders. So why on earth are there oversized and replacement crankhaft main bearings and oversized pistons for sale???

 

Surely someone knows how to remove and replace crankshaft main bearings on this engine? Any ideas where I could get some information because I'm not buying a junkyard engine.

[J.R.]

The first thing to say is that the crankshaft thrust bearings are probably worn if you have scuffing on one side of the bores, they used to be located either side of the centre main bearing but things may have changed in recent decades.

 

You can check the bearing clearances with Plastiguage but usually a visual inspection will tell you everything you need to know, whether they can be reused, replaced with standard size shells or a regrind and oversized shells.

 

I would ignore the warning, if you need to remove the crank then you have to remove it.

[Koreenium]

6 minutes ago, J.R. said:

The first thing to say is that the crankshaft thrust bearings are probably worn if you have scuffing on one side of the bores, they used to be located either side of the centre main bearing but things may have changed in recent decades.

Wear is on the thrust side of the cylinder/ piston. I don't believe that is caused by worn crankshaft thrust bearings?

Cylinder walls have lost almost all of the cross hatching so I'd think that is just from normal wear.

 

 

12 minutes ago, J.R. said:

You can check the bearing clearances with Plastiguage but usually a visual inspection will tell you everything you need to know, whether they can be reused, replaced with standard size shells or a regrind and oversized shells.

I do have some and I can use it but the problem I'm having is that there is no information what the clearance should be, no torque specs, no torquing procedure, no nothing.

I was told that because this engine block is so light weight you need to have a correct torquing procedure or you can run into problems. And as I said there is no information for this engine.

 

I don't want to pull it apart and then throw it into the trash because I can't put it back together. I could do some trial and error testing but I'm not very fond of that idea.

[J.R.]

Yes you are correct regarding the thrust face wear, I was not thinking properly, 20 years ago I was building and rebuilding engines all the time.

 

The big end bearings look perfect so you do not need to disturb the crankshaft, the main bearings have a much easier life.

 

I would just throw a set of rings at it, you could still hone the bores with the crank in situ you just need to make some preparations, I would not hesitate to remove the crank and ignore all the warnings, its eye opening to watch the manufacturers race teams during a 24 hour race paying zero attention to all the guff they insist the dealership workshops have to abide by.

[Koreenium]

Big end bearings look good because they are new. I was diagnosing issue before and I had the bottom opened up. Only one out of four big end bearings had some wear, I think it was 4th one which happens to be the furthest from oil pump, others looked like new despite being original with 260 000 km.

 

I am planning to just deglaze cylinders and put new set of pistons and rings in it. I am going to make sure I cover up crankshaft as well as I can to prevent dirt gettings into wrong places. Crankshaft itself turns very smoothly without any resistance. No visible abnormalities, which can mean absolutely nothing as I have already learned from my other engine. But slight glitter is everywhere so I'm afraid it may cause issues later down the road. I guess I have to change oil several times in short amount of time after puting it back together.

 

 

I was told that I would be fine to remove the crankshaft as long as I can find torque specs and proper torquing procedure but so far I have nothing. I am going through other manuals to see if any similar engines has proper information so I can atleast use that as a basis for my engine.

I have another car that I'm also rebuilding the engine for but that car is from 90's and it has very thick original service manual that gives you everything you need to rebuild engine properly.

 

Racing teams still have a very specific procedures they follow in order for their engines to last even dozen laps. As a beginner I atleast need some guidance so this little 86hp engine doesn't blow up after 100km.

[Koreenium]

I did some research and I found a very similar engine. 1.4 TSI CAXA / CAXC that does not share many if any components at all with my CBZA / CBZB engine but it does share many torque specs. For example both conrod big ends are supposed to be torqued at 30Nm + 90 degrees. They have nearly idenctical piston ring caps etc. Both engines also have 2 bolt main / crankshaft bearing caps. They are similar in size and shape. Similar production years etc. Surely this isn't 100% correct way but it seems that this might be the best option I have.

[silver388]

You might have already seen this from the factory manual.

 

[Koreenium]

Just now, silver388 said:

You might have already seen this from the factory manual.

 

 

Yes, that's literally what I mentioned in the first post.

 

But why would manufacturers sell new STD, oversized crankshaft bearings or oversized pistons etc if this was the case? Clearly it can be done but obviously for a dealership it's more cost effective to just replace everything and bill the client than to waste their own money and time for potentially sub-par work.