LD28 Timing Belt Replacement

[TorreyWP]

*This may belong in the maintenance section at some point, I plan to edit this further for others who have experienced the symptoms of a broken or stripped timing belt or want to do this job preventativly.


As a mechanic, I like to know what I'm actually doing in the repair and fully understand the whole situation. My professional training is mostly OTJ and more formally through Mercury Marine and focused on their pod drive systems, diesel engines and advanced fuel injection systems that are now used on both their outboards and inboards. The LD28 is by most standards a "modern" overhead cam (chain driven) diesel engine that uses a belt driven Bosch Kiki style rotary injection pump to inject fuel into the combustion chamber at the right time. The belt is a critical point and the Achilles heal in my opinion. The belt, in relation to a mark on the crank, a mark on the pulley on the injection pump and valve position sets this injection timing perfectly for complete combustion.

If it breaks, your engine will shut down suddenly and wont restart.

The steps that I will try to document I discovered by using some online resources and general overhead- cam diesel engine knowledge. If the belt has broken under way, what we need to do is “phase the engine” first. That is to get the engine on number one cylinder top dead center on compression stroke. There are two factors: cam shaft position (or valve position) and the timing mark on the flywheel to be in postion. The rest is simply access, fitting the belt and rusty bolts.

Parts you need to aquire:

Your favorite penetrating oil: My personal fav lately is AeroKroil, Amazon has it, but whatever your favorite is, hose the critical points down every couple days prior to this job. Focus on the crank pulley allen head bolts, there are 6.
Timing Belt: Nissan PN 16806V0700, Dayco 95086. (I suggest keeping a spare on board if your has broken)
Accessory Belts: if necessary
Coolant: properly mixed if you plan on removing the heat exchanger for access.
Belt tensioner: these are NLA so hope you dont need one, there are used around but scarse. Inspect this part for smooth rolling with the belt removed.
Front crankshaft seal: if you have oil leaking from the front of the engine, this is most likely the cause and now is the time to address it. NAPA PN NOS18970

First; remove both the alternator belt and the water pump belts. This makes rolling the engine over by wrench a little easier and is necessary for access. This is accomplished by releasing tension on the 2 alternator bolts (on mine the adjuster bolt is 1/2'' and the bottom bolt that has a nut on one end under the engine mount are 9/16'' and the 2 (most likely, depending on the pump you have) bolts that hold the raw water pump in place. I have an updated Jabsco pump, the bolts are 9/16''.

The other thing you might want to remove is the heat exchanger to get a better look from the top at what you are doing. I think there are 3 to 4 bolts involved and 4 hose clamps. Coolant and water will go everywhere, be ready for that. This really helped me the first time I was playing around down there, plus you can inspect the status of the heat exchanger and sent it out to a radiator shop if necessary.

Next, remove the dust cover over the injection pump pulley and timing belt area. I think there are 4 screws around the outside and one 7mm bolt in the middle that is easy to miss. This thing is really to protect the belt and tensioner bearing from road spray in car/industrial applications, I never put mine back on, it made inspection of a critical belt easier and hopefully your bilge does not have anything like road spray!

Now for the crank pulley. Hopefully you have soaked those 6 allen bolts with some penetrating spray. These are usually pretty rusty, use a proper 6mm allen wrench and make sure you are all the way in the head making full engagement before trying to loosen. The pulley comes off as an assembly. This is where you would continue with disassembly if you needed a front crank seal, I'll leave that for another time.

Next, you need to put the tensioner in “free” position. Loosen the bolts (8mm?) and push it down and tighten in this position for now. If you belt has not broken, remove the old one now.

FSM Pulley mark.jpg

At this point, I would identify all the marks that you need to line up. The pictures in the manual show these positions pretty well. Identify that you need the “B” mark on your injection pump pulley, Identify the small notch indicating the mark on the crank hub. Once you are ready to turn the engine over by hand, note the line on the flywheel as it come into view by looking through the “window” in the flywheel housing near the starter (there may be a black rubber plug in it) Line up the line scribed in the flywheel with the marks on the sides of the window. I would put a dot of paint pen, chalk, silver sharpie whatever on these marks, especially the crank hub and pump pulley.

FSM timing 2.jpg

Now it is time to phase the engine, the critical step. The engine rotates counter clockwise if you were standing at the bow looking at the front of it. The nut on the crank pulley is 1 1/16'' or 27mm, I used a ¾in drive ratchet (big, with a long handle). It takes some of the work out of baring the engine over. This is slightly awkward, get comfy because you will probably miss all the timing marks the first few times. One more time: make sure the valve is in the position shown in the book, the line is in the window of the flywheel.

IP Belt Install 2.jpg

Next, working at the front of the engine; its time to fight the belt into place. I would suggest placing the belt over the crank hub, being sure to line up the belt mark with the notch on the hub. If you got the dayco belt there are white lines on the belt to identify 20 cogs of space, if your belt has no markings on it, no worries. Just be sure to follow the pictures and mark 20 cogs. Now you may need to rotate the injection pump pulley a bit to get your B mark to line up. Fight the belt into place confirming that you have gotten both marks lined up.

FSM LD28 Timing.jpg

The factory service manual is pretty good at showing all this, I believe it is still available in the library section. I would highly recommend poking around the nissan diesel forum:

nissandiesel.dyndns.org/

Sometimes their page is slow due to hosting and most of it reference egr systems, fans and other things that the cars got but we luckily don't have to deal with. It is a valuable resource to those of us running these engines still.

Part sources can be difficult, rockauto.com is great. Look under Nissan, 1983, Maxima then L 2.8 diesel for parts. Napa can be helpful as well locally.

When I am back home near my boat I will take some pictures and edit this post as necessary, Just wanted to get it up quickly to help a mate out!