Starting a new thread as advised. Purchased a Cat 931 without doing due diligence and now I have a bucket of questions that need help sorting out. I have been unable to find a serial number on the machine bevel gear housing will be my last try in the morning. The machine had a jasper engine installed and threw a rod after 20 hours of ownership. Been a long time I was snoogered, but I got taken on this one. Motor medic and saw dust will stop a knock until it burns off it seems. I will post pictures of the Jasper engine but it is a 3204 of unknown arrangement. I have procured a 3204 long block with a serial number of 45v22532 arrangement 7N5139. Replacement block is at the machine shop and I have the out of frame internals for it with 3 ring pistons.
Is that ventilated block the Jasper job? Pretty standard jasper stuff. They are very famous for turning good parts into scrap.
All photos are of Japer engine
What made the conrod let go, was it broken big end bolts, or did the little end open up? The opening seems to indicate broken big end bolts. They really need to be replaced at every rebuild, IMO, I've seen too many 3200 engines with ventilated blocks. Those pistons don't look correct for the DI engine, I don't believe they should have the heat plugs - but if they're aftermarket, the aftermarket manufacturer may have been producing an older Cat design piston. That block is repairable, a good cast iron repairer should be able to recover it, as long as there's no major internal damage to the casting. The crankshaft will need to be checked out for alignment and whether it can still be reground. There's a great deal of interchangeability all through the 3204 engine range, the major differences is when the engine went from PC to DI. The Arrangement number is your best guide, my 931B has the original engine with a S/N of 45V29120, and the Arrangement number is the same on my tractor - 7N5139.
Never saw heat plugs on a DI engine
That looks like a PC engine with the glow plug wire harness inside the valve cover and the pre-cups
What's the tractor Serial Number.? Edit: I just saw that you said you couldn't find it. Not to worry, take a look at the table in the attachment and pick out the options (e.g. type of transmission and does it have standard or LGP undercarriage) that your machine has. At least we ought to be able to narrow it down. It's looking very likely that the 7N-5139 long block you've bought could be very close to or even identical to the original engine arrangement that was installed in the tractor when it was built.
56Wrench is correct, that's a PC cylinder head, I wasn't looking closely enough at the head photos, I was concentrating on the block damage photo. That's why the pistons have the heat plugs. Not sure what the engine S/No break was, for the change from PC to DI, but it was around 1978 or 1979 IIRC, my 931B tractor is 1980 production, and it's DI.
If it's a straight 931 I'm pretty sure it would be a PC engine. A pic. of the machine would verify it's a straight 931. Very noticeable difference around the operators station. I think sometime in early 931B production is when they went to the DI engine. I have an 86 931B but also a Cat bulletin on improvements to the 931B. The 931B may have been when they went to the DI engine. The bulletin lists the 931 at 62 HP and the 931B and improved 931B at 65HP. A brochure from 11 82 lists a DI engine. There is a thread from earlier this year where someone rebuilt a 3204 and made some modifications but I think it was for a D4H. Can't remember exactly though.
See below pictures. It is a straight 931. No LGP. I believe the arrangement will work. If you notice in the photos the previous owned bypassed the fuel pump in the accessory drive and ran an inline electric pump straight to the filter. My question regarding conversion is, Will the fuel flow be enough for a DI engine. I do not see where any different internals are listed for a PC injection pump Vs DI. Also will the timing require advance or retarded? Another issue is the glow plug set up. Without the PC cups that the glow ran to, how would i go about the prestart warming sequence? I am sure more issue will present themselves as work progresses. The engine i am building as a replacement requires a ,020 cylinder bore and a .1 rod bearing turn. I have already gotten the new internals on hand. Is there anything I should go over regarding the transmission while i have it out? How about the injection pump, should i rebuild it? Oil pump gears and bearing appear to be in good shape, should i refit new gears anyway? Torque converter need any attention? Shifted fine when he engine was running. Anything else you all may suggest would be greatly appreciated. I have turned plenty of wrenches in my time but I am not familiar with the CAT 3204 engine and do not want to miss something and have to pull the drive train again...... Once was more than enough. Thanks in advance.
Conrod let go at the crank bolts. Have yet to pull the crank and pistons to get a better look.
Nige, Thanks a million sir. Thats exactly what i needed. I should have read it completely before my last post. You are a great resource sir!
The DI engines had an ether injection system for cold weather but you could just give a tiny spray in the air intake. I took my ether injector off because it needed a new temperature sensor that goes in by the thermostat housing. It wouldn't allow the system to work when the coolant was warm. There was a loose wire that arced one time and I think shot a tiny bit of ether. I don't use my machine much in the winter so just took it off. My machine will start without ether down to about -10C maybe even colder but I usually give it a tiny shot to save the starter. Plugging in would be best but I don't have power at my property.
So based on it being a straight 931 rather than a B there are only 2 choices of S/N prefix because both the 8N & 10N prefixes are LGP machines. 78U & 81U were both built in Japan. Production of 81U started in 1973 and of 78U in 1976. If your machine is/was a lower S/N than 81U930 or 78U3913 the original engine would have been a 3204 PC of 4N0169 Arrangement Number. If it was 81U931 or 78U3914 or higher, it would originally have been built with a 3204 DI engine of Arrangement Number 7N3800. The arrangements above are broadly similar to what would have been installed in a straight (non-B) D3 tractor of the same era. 7N-5139 appears to be a DI engine arrangement only used in D3B tractors with a 3F-1R type transmission as opposed to the 3F-3R. I'll do a bit of digging and see just how different it is to a 7N-6938 that would have been installed in a machine with a 3F-3R transmission. EDIT: And............ I'm back. The only difference between those two engines above is the flywheel. 7N-5139 Arrgt has a flywheel Part # 4N-0184. 7N-6938 Arrgt has a flywheel Part # 7N-6937.
Nige, does it list different HP ratings between the PC and DI engines in the straight 931 machines? I'm sure I read somewhere that there was an improved DI engine in later 931B/D3B machines. Also curious what is different that a 931C got a jump from 65 HP up to 75 HP?
Nige, I believe all the 931's were built in Japan. TnTrouble, I see no reason to bypass the standard 931 fuel pump, the system works just fine if the lines and tank are in good condition. But the tank and lines can end up with internal corrosion (and external corrosion will cause pinholes and create more trouble) - and both these conditions will create fuel flow problems. Also, tanks often have a buildup of debris inside them, such as fluff from rags, foreign materials accidentally dropped in the tank - and dirt and water (from condensation). So a fuel tank cleanout and new fuel lines are always a good start when rebuilding - particularly if the lines display any form of corrosion. You don't have to buy Cat fuel lines as a part, you simply manufacture new ones with some new steel tubing, and a small cheap tube bender. Re the transmission, seals and o-rings go hard and cause leaks and shifting problems, so replacing as many as you can get at without a complete transmission disassembly would be a good move. Check the transmission oil pump for wear levels (clearances), and the pump screen for debris and trash and look for metal. The oil pump gears should not need replacement if they fall within wear specifications. As a general rule, .003" to .005" clearance is good, .006" to .008" clearance is getting into the region where you probably should replace the components that are required to produce and hold oil pressure. There is a bushing that supports the transmission valves control shaft where it goes into the transmission. Replace that bushing and the seal on it, as wear here allows dirt entry. Check the shaft condition, to ensure the seal seating area, and bushing support area, are not severely worn. The injection pump should not need attention, these old style injection pumps have a very long life as long as the filters have been working properly. I don't have the injection timing degrees readily to hand for the PC engine, but the DI engine injection timing runs at 21° BTC. There will most likely be a difference in timing between the two engines, the service manual advises the injection timing under "Engine Specifications".
You are correct. I was more trying to kick off the identification process of exactly what machine the OP has.
I think confusion reigns between sources that quote Gross Power and those that quote FWHP......... From the earliest model to to C there is only 5 BHP of difference.
The main ID for the 931 are the two aluminium tags - one for the tractor, which is normally located on the upper outer vertical face of the RHS loader tower support (just above the "CAT" decal on TnTroubles tractor) - and the other on the upper left rear of the engine block, just below the head gasket line. Both these tags appear to be gone from TnTroubles tractor. Some Cats have the numbers stamped in the metal under the tag - but the tags on my 931B are still in place, so I can't check that angle on my tractor. I have seen some Cats with the engine S/No stamped into the metal of the lower front left of the engine block, just above the oil pan join line - but I haven't checked my block for that, and my block is currently still at the engine reconditioners. The other angle TnTrouble could try, is to find a casting on the tractor with the NUMERALKOD in it, and acquire a date from that casting. The 2-post ROPS indicates an early 931. The 931 was first manufactured in 1973. "The Caterpillar numerical code contains the date of manufacture. This date is translated to a format of day, month, and the last two digits of the year, and then coded into a six-digit sequence with no spaces in between digits. When the day or month is less than ten, a zero is inserted before the number to maintain the six-digit sequence. Use the following legend to decode the date: N U M E R A L K O D 0 1 2 3 4 5 6 7 8 9 Example: December 18, 1985, is translated to 181285 which is coded UOUMOA September 7, 1985, is translated to 070985 which is coded NKNDOA"
I have that same chart. The next listing is a 931C Series II at 70 flywheel HP. My mistake the 75 HP is the gross HP rating but the 931C Series II brochure lists the flywheel HP at 69. Another interesting note is the 935B is 75 FWP, the 935C is 78FHP and the 935C Series II is 80 FHP. I'm curious if the IP is just turned up or there's different pistons or a combination of things to go from 62 HP up to 80HP?
A simple way to see if the transmission in decent order is to look at the screen (3F 1R)or the filter (3F 3R) to see if there are black particles in it. When my engine was done they checked the screen and said it was really clean indicating it was in good shape. It's great they checked and I'm very glad it didn't need to be taken apart. The engine was expensive enough!
The level of engine accessories can affect engine HP output, and the figures are always a bit "rubbery", anyway. Cat and Allis-Chalmers used to have verbal and sales brochures wars, over engine HP claims, as A-C used to strip all the accessories off their engines before they tested them for output, and thereby claim more power output, than what the engine actually produced in the tractor. Cat HP variations are usually related to injection pump tweaking and different injector designs. The Cat Rack Setting chart or Fuel Setting chart is your best indicator of HP and injection pump settings. Here's one for sale on eBay - CAT Caterpillar Truck GAS Marine Diesel Engine Rack Setting Chart Service Manual | eBay Find many great new & used options and get the best deals for CAT Caterpillar Truck GAS Marine Diesel Engine Rack Setting Chart Service Manual at the best online prices at eBay! Free shipping for many products! www.ebay.com
I was kind of wondering what changes were done to get up to an 80 FHP rating on the 935C Series II? I'd think comparing Cat's own brochures would be apples to apples.
IIRC that is only for D300/D330 series engines.
Started to build the 3204 di. Have the block back bored .020. Crank turned .020 ay the rod lobes, standard at mains. Resurfaced the top plane to the limit without having to modify pistons. Checked the rod pin bearings and they are to spec. Also checked out the rod bolts but opted to change them and the main bolts. Also went with the 3 ring piston from Mcbee. I have some more photos for review, if you all see something amiss let me know. Based on what Nige said regarding the differential of arrangement and seeing as how i have a 3f/1r transmission I think the flywheel I have will work out. Should be the same for either arrangement option. Thanks for all the input. so far
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Looking good there, TnTrouble. Does it say on any of the McBee parts boxes, where the components are made? On a few forums, end-users are not happy with McBee components and have been getting variable results from them. Some seem to think a lot of the McBee components are from China. I'm getting ready to re-assemble the 3204 in my 931B as well. My block was bored .020" oversize, but the crankshaft was in excellent shape, it stayed at standard bearing sizes for both big ends and mains, and it just needed polishing. I went with IPD 3-ring pistons, IPD out of frame gasket kit, IPD camshaft bearings, and a full set of new IPD conrod bolts/nuts. I don't trust those old conrod bolts, even though mine specced as re-useable. I did go with a set of genuine Cat little end bushings. I was surprised to find these were still made in Japan. All the IPD components were made in the U.S.A., that makes me feel better than installing Chinese components with their often dubious QC. I'm re-using my oil pump rotors, they look just fine and are still well within specifications for wear. The price of new oil pump rotors kind of stuck in my throat, I think US$700 for aftermarket and US$1200 from Cat, is the worst reaming out I've encountered in many years. I'm in the process of fabricating a new heavy duty engine stand, that little engine is heavy! - and I don't trust the weight ratings on Chinese engine stands.
I will have to shoot some pics of the stand I made. I used a frame from a dunnage cart set on two 6 wheel equipment rigging skates. The Mcbee parts I have received are mixed bag. Pistons and rings say USA, Pins and snap rings say China. Rod bolts and main bolts came from Off Road of Alcoa Tn. I will be digging into the oil pump gears tomorrow. The face of the outer ring appears grooved and therefore I am hesitant to reuse it. The head has all new springs and exhaust guides, the intake guides speced out. All the Valves were relapped. I hope to get the head set and lifters and push rods installed in the morning.
Hopefully no issues with the Mcbee pistons.
For my cylinder head, I went with machined guides to take K-Line bronze inserts (the original heads have no guide inserts), all new valves from IPD (no indication of origin), and new valve springs from SB International (U.S.A. made). The 8 new valves cost me a total of AU$208 (US$138), and the springs were AU$93 (US$62). At that money for the new valves, I didn't consider it worth grinding the old ones, even though it appears they could have been re-used. The important spec on the oil pump is the rotor lobe clearance. Cat allow up to .011" clearance as the re-useable dimension, my rotor lobes measure up at .008" clearance. Look for bad scoring on the tops of the lobes, mine only show minor scratches. I replaced the outer bushing that supports the outer lobe. Don't forget to check and clean the suction pipe and screen for the oil pump, nasty metal contaminants can hide in there, and be resistant to washing.
Good evening, anyone have a head for the pre combustion engine or the whole thing? I need to replace the head on a old D3 and it used the same engine with pre combustion.
I'd check with rebuild shops and dismantled machines on Machinery Trader.
Bit of a heads up chap the injector pump gears are not marked so before you get to keen on unbolting things remember this as you might need to do some thinking.
I have a pre-combustion head sitting on the self. I would not use it without getting it checked out and new guides. What part of KY you in?