The Rebuild - Has Begun.

[Anthony10370]

Ok so after getting the engine pulled and on a stand I started disassembling and cleaning it. The reason I am rebuilding is because Cyl #6 had about 6:1 compression with some coolant in the cylinder - so it was probably lower than that due to the volume of the coolant. This lead me to believe the head gasket was blown. All the other cylinders have perfect 8.5:1 based on 14.7 PSIA. The car has 131,828 miles on what I believe to be the original ODO.

Engine on stand:




Here is getting the first head off. I found these nice extended 3/8 drive allen keys which helped with taking the cam off. I forgot to drain the block from the core plugs so I introduced some more coolant and other junk into the cylinder when I removed the head.




Got the fuel injection, water bridge, and oil "seperator" off the top.



Oooo that's some nasty junk. And I'm thinking I need a new starter ring gear.






sludgy oil pan (on the outside):




And after some "brake clean":



Can you tell the difference???:




This is wallnut shell blasting the cylinders using an abrasive blast gun and about 95 psi (60 running psi):



So it turns out that the compression leak was (what I believe to be) mainly from the sparkplug hole. Someone musn't have torqued the sparkplug properly and it backed out 3 or 4 threads and the threads in the head got carboned up stopping the sparkplug from seating all the way and sealing. This also explains why I could hear the "tssst" of the compression leaking so clearly when I was cranking.

But this theory still doesn't explain the coolant in the cylinder.

[Anthony10370]

So I have a question about the block. I was looking at the cylinder bores and cylinder #5 has some linear scratches in it just deep enough to catch your fingernail on. Does this void the block and give a potential for catastrophic melt-down or is it possibly still serviceable after a proper particulate removal? This is the only cylinder with these all the others are perfect.

Thanks,
Anthony.

[gbgastowers]

I'm no expert but I think the cylinder wall looks great and should be no problem. Gunar

[Pete R]

I put my motor back together and they were worse than that. Reworking the block was not in my budget when I did it. I would have a machine shop measure the cylinders to make sure they are round and not tapered.. but it looks pretty good. btw nice clean up job on the pan. I had a machine shop clean all my stuff in their auto parts washer and I don't know if it came out that good.

[Landseer]

Do you plan to disassemble and clean?

[Anthony10370]

Do you plan to disassemble and clean?

Yes I want to disassemble, clean the cylinders and pistons, and plastigauge the bearings.

[Pete R]

Originally Posted by Anthony10370

Yes I want to disassemble, clean the cylinders and pistons, and plastigauge the bearings.

Is it a 4.5? because I don't think new bearings are advailable. I seem to remember 928 int mentioning that to me when I rebuilt mine

[Anthony10370]

OK so I got the pistons out. I'm really happy with the way this motor looks inside.

I also just ordered a butt-load of gaskets from pelican and getting ready for the reassembly. Hoping to have the engine reinstalled and running by the end of the month.

I feel like this has been asked before somewhere but what is the best way to go about rebuilding the fuel lines? I ordered the high pressure hose from pelican, are the fittings reusable? Or is there somewhere I can buy new fittings?

Thanks,
Anthony.

[Anthony10370]

Oh yeah, it is a 4.5 US, and no I couldnt find main bearings either.

[Herr-Kuhn]

Anthony,

Those scratches are pretty deep. If it was mine I would have the block plated in Nikasil and then diamond honed and install a new set of rings compatible with Nikasil. The engine will run okay without the re-plate, but you are best to get it all 100% up to snuff and round once again for the best results. You should have the bores measured to see how out of round they are now.

If you want to go the Nikasil route, let me know as I'm a dealer for Millennium up in Wisconsin. The other option is to overbore, but then you are looking for pistons and the like.

[JK McDonald]

Hey Anthony, Many feel that the key in determining if a cylinder scratch will generate a potential sealing problem is if you can feel it as you pass your fingernail over it. Even if the proper corrective light hone and a set of new rings gets your project back up on it’s feet initially, in the long run you will regret not resolving this cylinder issue. This can be especially true if you intend to own and enjoy her for a long time.

Although the machine work needed to restore a Nikasil cylinder is usually the best route, once the damaged cylinder is factory fresh, sometimes finding a practical stopping point in deciding how much should be done to the remainder of the block can be difficult. Often a reasonable compromise (and least expensive option in the long run) is to locate a used block in good condition or even a complete newer engine. This can be especially true if parts availability for your 4.5 liter original motor is a factor. When cared for, there are many 928 engines that push 200K miles and still have lots of service left in them.

Good Luck, Michael

[Anthony10370]

I have considered the re-plating of the bore but that cylinder was producing perfect compression before the tear down. Dont know yet I still have to measure the bores so I guess that will be the deciding factor. Unfortunately I do have a pressing time limit for this rebuild.

Also I rebuilt the fuel lines and installed them in the car, the old ones were just scary and I'm lucky they didn't leak when I drove the car home. I replaced the hoses with 180 PSI Working Pressure fuel injection hose so they should last a long time.

Here's some pics.

Before:



After:




I also just got a bunch of parts from pelican although I'm still waiting for more from a different company like the center gaskets, intake gaskets, and the 1-4 head gasket. It like opening presents lol.

[Roy928tt]

Hey Gunar

There is a ring gear that is worn out !

A whole lot worse than your one and was still working.

Cheers Roy

[Mrmerlin]

pull off both heads and do both head gaskets,
if one was leaking the other wont be far behind

[Anthony10370]

Way ahead of you there




Yeah I have already taken out everything except the crank. I'm doing ALL the seals not just leaky ones and I want everything pristine before reassembly.

Speaking of ring gears, where would I find one? This one is toast.

[gbgastowers]

Originally Posted by Roy928tt

Hey Gunar

There is a ring gear that is worn out !

A whole lot worse than your one and was still working.

Cheers Roy

I put some copper colored anti seize on mine during reassembly. Worked great when I was trying to start and I accidentally used it to remove the crank bolt when I left a socket and breaker bar on accidentally. I will reinspect it again as I am in the process of pulling the engine for new rings at the moment. Gunar

[bwmac]

Very nice job cleaning your engine up. Looking good.

Brad
928 Owners Club

[Anthony10370]

OK. so I havn't posted anything on my engine rebuild in a while. It sat for a while but I have recently been able to take the engine to work at Midas, and work on it when I'm clocked out.

So here's what I've accomplished:

-I took the cylinders out and cleaned them up along with the rings and the rod bearings.
-Drilled out, tapped, and thread inserted the #6 spark plug hole. I used a drill press and an expanding thread insert kit so it actually went very smoothly.
-I cleaned the block with more brake clean and cleaned the gasket surfaces with a fine rotary buffing disc thingy.
-Then reinstalled the pistons using moly/graphite assembly grease on the wrist pins and the bearings.

[924CarreraGTP]

Holy Jesus, please take a pressure washer to that engine bay before you reinstall the block! lol I would have left the intake on, stripped the wiring and pressure washed the whole engine before dissassembly. It was full of coolant anyway. That way you don't introduce dirt into your closed system.
Take my word for it, don't do this with the transmission. Many people have problems with clogged valve bodies because they renew the filters and introduce all kinds of sand and crap into the pan. Mercedes cleans the pans with degreaser, and then removes them and cleans them with lint free rags. When I did my trans filter, I cleaned the pan with a whole can of brake cleaner. I held the pan upside down to make damn sure there was no grit left anywhere. So far shy of a slip once in while my 928 shifts good.
When I bought my 928 the sound deadener foam had fallen out all down into the engine. I took a vacuum and built a small attachment that sucked out all the debris.
Sorry, I'm a clean freak but my cars are clean upside and down.

[trucker677]

wicked job on the engine, it is looking good, have you had any issues taking it apart, I am thinking of rebuilding mine, I came into a little bit of extra money.