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Complete engine repair/rebuild - pic heavy
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17-05-2012 11:50pm#1Another few pics to bore you all:P
A step by step(roughly) on a complete engine overhaul/rebuild.
This engine, a z14xep from a 2008 Opel astra, was suffering from very high oil consumption and was also loosing power at higher speeds(anything above 120km/h was a struggle). A leakdown test on all cylinders, showed 70% pressure loss on number 2 and 3 and a little under 50% on 1 and 4, after adding some oil to the each cylinder, the pressure loss dropped to just over 20% on all, so worn/damaged piston rings where proved by the above results to be the main problem.
However, it turned out, after an admission by the owner, the car had only been serviced properly twice in its 4 year and 115,000km life and had been let run low on oil numerous times...so it was decided that a complete inspection and overhaul(as well as a new appreciation for vehicle maintenance) was to be done.
So........
Engine out and most ancillaries removed:
Rocker cover removed, surprisingly, it doesn't look to bad around the cams:
Crank and water pump pullies off:
Engine flipped over to begin removing the sump bolts:
And the sump removed, things looking a but worse in here:
With the sump off the chain cover come off next:
And the chain, tensioner, guides and cams removed:
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Next up the head is removed:
With the head removed, evidence of excess oil burning in the combustion chambers become obvious. Note the heavy build up on the piston crowns, cylinder 2 and 3 especially:
Engine upside down again, this time to remove the big end bearing caps to release the pistons and con rods:
Number 1 con rod and piston assembly removed:
With number 2 removed, the cause of the problem becomes visable, the oil scraper ring is completely seized into the ringland, and bad build up on the secondary compression ring and around the sides of the pistons:
Old rings removed:
All the heavy deposits cleaned from the piston, if left as they were, the amount of build up on the piston crowns would have lead to poor combustion, 'hot spots' amongst other issues:
And all 4 cleaned and ready for new rings:
The cylinder head is also getting a full clean and recondition to replace valve seals and re-seat the valves due, again, to heavy build up:
As on the piston crown, the valves showed a thick build up from the oil being burned, both on the combustion side of the valve, and, on the exhaust valves, the port side:
I won't go in to much more detail on the head rebuild as its all pretty much the same as what's in the repair after timing belt failure thread. http://www.boards.ie/vbulletin/showthread.php?p=77563130
Piston rings arriving tomorrow so ring gapping and fitting and cylinder/block preparation to come......if your really bored:P0 -
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Nice one, love seeing pictures like this
One question for you, when engine is suffering from burning oil issue would replacing the rings and valve stem seals solve the problem or would it require much more extensive work to block and head?
It depends on the extent of any damage or wear but generally, ring and stem seal will cover the cause of the vast majority of oil burning issues.0 -
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.......Part 2,
A final pic of the cylinder head with all valves cleaned,lapped and back in place:
Next step is prepping the block/cylinders with a hone. Honing firstly breaks any glaze that may have built up on the cylinder walls which can lead to the rings not sealing perfectly, secondly it adds cross hatching to the bore which is essentially sanding the cylinder walls(DON'T try it with sand paper though:eek:) which gives the rings a fresh surface to seal against. The hatchings are visible but are so fine that you can't actually feel them, the bore still feels smooth to the touch.
For this a specific cylinder honing tool is required along with a honing oil to lubricate the tool(paraffin does the same job) :
And all 4 done, after honing the block needs a good wash:
Next, the new rings need to be correctly gapped, this is done by fitting the rings into the cylinders and measuring the gap in the ring.
Fit the rings in and use the top of the piston to push the ring evenly into the cylinder:
Measuring the gap, you may think that having a gap in the rings is bad for sealing, but the rings expand when they get hot so need a specified gap to allow for this. Too small a gap and the rings can distort or even break and too large and you will loose compression. In the absence of a bore gauge, you can also use this method to check for any ovality or distortion in the cylinder by measuring the ring gap at different depths in the cylinder:
With this done for each ring on each piston, the rings can then be fitted to the pistons:
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Next the pistons are fitted back onto the block, to do this properly with risking any damage you need a piston ring compressor, this holds the rings tight into the pistons so they can be lowered into the cylinders:
A gentle tap with a rubber mallet or similar to get the pistons in:
As a final check after fitting, check that the piston to cylinder gap is all within spec:
And all shiny pistons back in and a new head gasket on:
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Back on with the cylinder head, torqued/angled to spec:
At this stage, on this engine, specific locking tools are fitted to keep the cams and crank locked in position before refitting the chain.
Cam locking plate:
Crank locking pin, from the outside and inside:
A new timing chain cover gasket goes on before the chain too:
With the chain and cover etc back on, another engine specific tool in used to position the cam sensor pick up correctly:
Finally, new sump gasket, sump, and rocker cover go back on to close up the engine at last:
And finally, ready to lift back to the place from whence it came:)
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Nice thread, not something you see so often these days on modern engines.
Did my first engine rebuild last year, 3.5 Rover V8 in my 101, sooooo satisfying when it started first turn of the key and the oil light went out immediately
Its very therapeutic work IMO, I have dozens of folders full of pics of various engine rebuilds over the last few years, mostly non standard performance Japanese stuff though.0 -
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Excellent write-up, you certainly know your stuff. I always listened to your advice for others before but after this I`d be more willing to accept what you about to say without questioning your knowledge at the slightest! Not many mechanics willing and able to do this kind of work in Ireland!Nissan doctor wrote: »Its very therapeutic work IMO, I have dozens of folders full of pics of various engine rebuilds over the last few years, mostly non standard performance Japanese stuff though.
Now only if you`d had a folder labelled Mitsubishi Lancer 1.8 GSR... 0 -
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Excellent write-up, you certainly know your stuff. I always listened to your advice for others before but after this I`d be more willing to accept what you about to say without questioning your knowledge at the slightest! Not many mechanics willing and able to do this kind of work in Ireland!
Now only if you`d had a folder labelled Mitsubishi Lancer 1.8 GSR...
I do....;)0
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