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Monday, April 30, 2012

Diesel Engine Inframe Rebuild Part 1


       Hello again and welcome to an overview of an engine inframe service. This is not meant to be a repair guide, just an outline of what’s involved in the job.
       For a complete guide on rebuilding the DT466, click on the book sales tab above this post.
       One of the biggest complaints customers have about an inframe rebuild is the high cost involved, especially the labor quote. This work requires more hand work, fitting, and cleaning than any other type of job, by far. It is work that can’t really be handed off to a lower paid apprentice or helper because an experienced tech will be looking for problems and inspecting parts for flaws as all the work is done. The engine in this example is an International 466E, a very robust medium duty engine. Although it is one of the simplest engines in terms of numbers of parts and assembly, the job still requires about 30 hours of work, not including removing cab parts to get the doghouse off or test driving.
Before we get started we need to review heavy duty engine construction. The 466 is a wet liner engine, as are most modern diesel truck powerplants. The liners provide a cylinder wall that is replaceable for rebuilding, and when installed its outer surface is in contact with the engine coolant. The head gasket seals the top of the cylinder, and O-rings seal the bottom from the crankcase. The typical inframe kit includes bearing shells for the rods and mains, liners, pistons, and rings, and all gaskets needed. The result is basically a new engine except for the oil pump, cam and bearings, injectors, and head(s). Everything can be done without machine work (usually), and with a minimum of special tools. An engine can be rebuilt multiple times for a very long service life, and many inframe kits are still being sold for engines 40 or 50 years old.
The object of this rebuild came into the shop leaking massive amounts of coolant into the crankcase and had an audible knock in one cylinder. Removal of the oil pan revealed coolant leaking down the outside of the liner for cylinder #3. Often the cooling system must be slightly pressurized to reveal a leak, but this one leaked so bad that just pouring water in the radiator was enough to find it. It is important to pinpoint the leak exactly, as there are several was coolant can get into the crankcase, including from the front cover seals, pinholes in a liner, or a damaged block.

466E in a 4300 chassis


The first order of business is usually to drain the oil and water. If the truck had been running lately, oil will continue dripping off the block for days, so I usually leave the pan on with a container under the drain, while I take the top of the engine apart. Working under an engine dripping both coolant and oil is one of my least favorite things, so I let it drain as long as possible before the oil pan is removed.
Some preliminary work had to be done to gain access to the engine itself. Most modern chassis have the engine pushed back as far as possible, and in the 4300 International, about the rear 1/3 of the engine is back of the firewall. In order to remove the doghouse over the rear of the engine, the passenger seat was taken out and the threshold plates holding the outer edges of the floor mat were removed so the floormat could be rolled back. The doghouse edge is under the floormat, and removing it with the mat in place will tear the mat at the corners of the opening. The automatic shift selector and the parking brake handle were also taken loose but left connected to their cables. Under the hood, the air cleaner assembly was taken off and then the windshield wiper and linkage assembly and the panel at the bottom of the windshield removed. The modular component assemblies on this model make it one of the easiest brands to work on, once you have a little experience with it. 
Now that we have access to the engine, components attached to the head can be taken off and the head removed. The valve cover and intake manifold are integrated in one casting as is the thermostat housing and A/C compressor mount in front of the valve cover. I usually leave the turbo attached to the exhaust manifold and remove/install as a unit. This is heavier than dealing with each component separately, but dealing with turbo mounting nuts can eat up a lot of time. As long as the gasket doesn’t leak and none of the studs are broken, I leave it alone. If you do choose to renew the gasket, it is much easier with the manifold off the engine. Unusual on this job was that the head of one exhaust manifold bolt was broke off, and its mate broke when I tried to remove it. It is unusual to find this problem on the 466; normally the bolts come right out. Luckily, they broke off right under the head and were extracted by welding a nut to them and twisting them out. Always remove the injectors before pulling the head; if an injector tip is bumped while swinging the head out or putting it on the bench, the injector will likely be ruined. You need to check the injector bores and cups for damage or leaking, anyway. 
When removing the head, I try to back the headbolts out a turn or so at a time until they turn freely, especially the long ones holding the rocker shaft in place. This may be more cautious than necessary, but it doesn’t really cost anything in terms of time. When the rocker shaft is removed, I make a point to carefully inspect the ends of the valves and the rocker arms for damage. Quite often one or two will be damaged and need replacement. I think when the valve adjustment is not done for a while, the arm hammers the end of the valve, mushrooming its end and the contact pad of the arm. The turned over edge of the valve stem needs to be removed with a die grinder so it will pass through the valve keeper when the valve is removed. Use a little valve grinding compound to lap the new valve to the seat. 
Once the head is off, it is inspected closely for cracks in the combustion chamber. This is seldom a problem in this engine, but they can crack from the injector hole to a valve seat. If all is well, I turn the head with the exhaust ports up and fill the ports with Stoddard solvent and let it sit a few minutes. Any leaking valve will let solvent out the bottom of the head. If the exhaust valves pass the test, do the same with the intakes. 

The head is off, the pistons
and liners removed.
Note the large gap in the
coolant seal of liner #3


























        Removing pistons and rods is straightforward, just unbolt them and push them out with the handle of a hammer. Unfortunately, in order to remove the oil pump pickup, the vibration dampener must be removed, there is never much room to get a puller in, and they often pull off pretty hard. This one actually needed to be warmed a little with a torch to get a pull started. You can bend up a 10mm box wrench and loosen the bolts from behind the crossmember without pulling the dampener, but that isn’t too easy, either. 
Caution should be used when pushing the pistons out. The liners in this engine are not as tight to the block as some other makes; occasionally the liner will push out when a piston hits the wear ridge. It’s no fun to take a coolant shower when you are under an engine. I have very seldom needed to use a liner puller on this engine; just drive the liner up about ½” with a big punch, then pry them up from the top with a big bar. The engine in this case had a large gap in the coolant seal in cylinder #3. The lack of coolant around that cylinder overheated that piston, which expanded and was very severely scored. The slap from this damaged piston would account for the knock we heard when we pulled the truck into the shop. 
With some parts cleanup, that usually concludes the first day of work. Check soon for part 2 of this survey, where we clean everything up and start assembly.


All parts for 466 inframe removed for inspection and reassembly.

2 comments:

Loïc Séguin said...

Great blog Bruce.

Unknown said...

Hi, you make mind blowing ideas and a spectacular article here.


Rebuild engines