View Full Version : D6 9U pistons have holes in them

08-15-2009, 05:07 PM
So i torn the head off the old d6 today to replace the head gasket and found the number 3 piston has three holes in it about the diameter of a pencil eraser and 3/16 deep, 4 other pistons have similar pitts. I was told it is from anitfreeze coming from the pre cup for the injector... can this be run still or should i do an inframe rebuild? Thanks JJ

08-15-2009, 06:12 PM
wouldn't worry too much about it, those pistons are pretty thick at the top.
I rebuilt one that was pretty bad years ago(pitted) and got plenty of life out of it, with a new set of rings. You might want to have it pressure checked after putting in new o rings and seat gaskets on the chambers.Check the chambers too when you have them apart, they can pinhole through and cause you more headaches down the road.:( If you end up putting rings in it, i'd pull the liners and replace the o-rings as they dry rot with age. The main bearings and connecting rod bearings seldom wear enough to warrant replacing.

08-15-2009, 06:13 PM
I never noticed that the antifreeze caused piston damage, but it sure will clean the carbon off everything. If you see almost bare iron on the surface of the head, I would bet that that PC chamber is leaking.

Of course it would be better to rebuild it, what do the sleeves look like? If also well worn, you would have another reason to do it besides the piston pits.

Most of the time high hour engines especially with PC chamber leaks will have erosion of the neck area of the exhaust valves. You would not want to scrimp on those and have one drop the head later.

It's a slippery slope, fixing up an old engine. Next thing you know, you've done a complete overhaul when all you wanted to do was stop the PC chambers from leaking:D

08-15-2009, 06:50 PM
I believe what you are seeing is a crater caused by the exit of hot gasses from the Pre-combustion Chamber orifice. This can be caused by wrong injection timing resulting from worn liter screws/ pump plunger ends, pump drive tang/slot, restricted air cleaner, wrong rack setting for any possible high altitude operation.
Cat later on addressed this problem by fitting heat plugs into the piston crowns to stop this erosion occuring.
For a hobby machine I probably would close my eyes and continue on.
Eddie B.

King of Obsolete
08-15-2009, 07:57 PM
if it is just a hobby machine just put the head back on using lots of avation gasket goo and you should be good.

on one of my cats known as THE HOOD, he had pitts in the pistons from being under water for 3 years.


THE HOOD ran good the other night plowing dirt after fixing a water break. not bad for a winter freighting cat, LOL

Published Author

08-15-2009, 09:12 PM
5 out of the 6 sleeves are pitted pretty bad also. Another thing is the Pc chambers are set at different depths. I talked to someone about this he said they all need to be set and the same depth and that the pc chambers are a bear to get out without destroying them.

08-16-2009, 04:45 AM
Might not hurt to take the nozzles to a place that can check them for breaking pressure etc.Also I never heard of chamber depth causing a problem and when an engine had glow plugs they had different thickness washers to position the glow plug right but not the chambers that doesn,t have glow plugs.Sounds as was mentioned worn cylinders or rings or broken rings.Also worn valve guides cause oil to get by them too.Also as was mentioned taking the ex. maniold off you probably will see which cylinders are getting oil by the rings or wherever.

08-16-2009, 09:04 AM
Normally with broken rings you'll see vertical scratches.

If the liners are pitted you might as well get the overhaul done now. Don't be suprised to find the crank worn out of round. Mine had 0.010" wear when I went to do my inframe. If course it's no longer an inframe project.

Assuming we are talking about a D318 here is a link for pistons, liners, rings for $150 a hole. http://www.truckengineparts.com/caterpillar-d315-d318-piston-kit-fp-8h2000-wp-fp-diesel-brand.aspx?MMP=1015373850

08-16-2009, 06:10 PM
How hard was the inframe rebuild? My machine is no where near a shop building, I going to have to do it where she sits.:)

08-17-2009, 07:40 PM
It wouldn't have been too bad doing an inframe, but you should pull your side covers and inspect the crank and the bearings. Before digging in. Mine crank just had too much wear to not grind it down.

08-18-2009, 04:26 PM
When you pull the engine out is it easier to pull the whole nose off the machine?

08-18-2009, 05:37 PM
So ACT gave me the run down on the parts, looks to be $2266 worth of stuff. Is this about right for price?