Cat 12 Motor Grader questions

Welcome farmerboy I'm sure the ones in the know will show up with the details.Not a grader guy,but D318 was used from 49 to 59 in the D6 tractor.I still farm with those D6's have never had a head crack or gasket failure.Have learned to pull pre combustion chambers,if they don't show a lot of pitting put a new copper washer (seal)in .Just did this to one a few months ago.It was pushing water though the water pump seal.I don't learn very fast rebuilt the water pump twice before I looked for other problems.If you need new precups have had good results from the ones from Regal(look in the parts supply sticky at the top of discussion page),much cheaper than Cat.Mcmaster Carr has the copper washers,the last Cat ones I got were steel with copper paint and didn't crush and seal like copper will. The special tool to remove the precup will be the most expensive part unless the precups need to be replaced.Much less work than pulling the head,and more times than not this will fix it.Good luck on making her go.
Ray

Farmboy,
The 8T5478 frame serial # is a 1950. Motor serial # 8T 593 is 1947 and the 4F8430 on block is a part number. catskinner

Thanks for the info guys. I got her out today to do a lil more checking. There is air bubbles in the rad when idling and i can see some leakage by the head gaskets. I am gonna do a hail mary and poor some stop leak in to try and get it where i can put a few more hours on it till a good crop comes. How hard is it to pull the pc chamber to check em?

Not hard to remove,just need a special tool.I always borrowed one, but I think about 40 buck 20 years ago.Just remove the injector and put tool in and unscrew.Tool looks like a bolt but has splines.
Ray

hey guys, the stop leak was a waste, still bubling in radiator. I went ahead and pulled injectors, tried to pressure cooling system cap and overflow would not hold and I couldn't see anything in the precups. However, after that I hit the starter and it is blowing water out of #2 and #5. I am goin to try and get a tool and pull those precups. Is the part number to the tool the 5F8353. And what is the part numbers for the precups and the little copper seals. Is that the only parts I will need or is there more seals or orings that I might need. Thanks for the help.

The no. you have for the tool is what is in my book.There are several different chamber assembles as Cat calls them.Non glow plug models new no. are early 1s1967 or late 2s1273 the copper ring or gaskets new no. is 5b3265. I have had better luck with a real copper washer from mcmaster carr as Cats are steel with copper paint.There are three o rings used on each the old no.'s are 2h3088,4f5607,and 8f4994. Almost forgot Cat has other no.s for the gasket as they are of different thickness to put the put the glow plug in the right place to keep it out of the way of fuel lines.If you have glow plugs these are the wrong chambers. I have had people with much more experience than I say they have never seen a 318 engine with a cracked head.I had a temperature gauge that would not read above 205 degrees it turned out.Working in conditions that plugged the radiator every hour or so,started pushing a lot of coolant.Finally figured the gauge couldn't be right but the damage was done. Pulled the head still no cracks but was some warping so had it surfaced and a new gasket and put it back but it still pushed water.That's when the person doing the head work gave me real copper washers which fixed the problem.Good luck getting it sorted out.
Ray

How do I know if I need early or later model. I can't find a number on head. Where exactly do i look for head number. I checked with regal co for pre cup $12. For washer $.39. That sounds awful cheap. Cat wants $61 and $4. Thanks for the reply.

Your 8T593 engine uses the early replacement which I show to be:
1-2S1273 chamber (1-pc style)
1-7B6868 seal ring
1-5H7225 inj. valve retainer nut

OR

1-1S1967 chamber (later 1-pc style)(beginning 1952)
1-2H3088 seal ring
1-5H7225 inj. valve retainer nut

The one piece chambers require a different inj. valve retainer nut which is shorter than the old original nut.

Well my parts finally got here. I was able to pull precups with no problem. However the new ones looked totally different. I thought it might be better design, but they are about 3/16" smaller in diameter. So I cleaned up the old chambers good with buffing wheel, I see some pitting but nothing major, poured some gas inside and no leaks. I decided just to place new washer and give her a whirl, but as I was spinning her over with starter still have bubbles in radiator. Should I try changing chambers or is head gasket coming to mind. Old Chambers have 1H-7653-13 on the top after the buffing wheel went over em. I only tried #2 and 5 because they where the only one shooting water after pressure to radiator. Any help would be appreciated. Is it possible the previous owner put a different head on this thing?