Replacing front crank seal and camshaft seal 4JG2 UBS 69.
This write-up begins once the timing belt, idler and tension pulleys, as well as the water pump are all out of the way. I replaced all of these since the Bighorn had reached 200 000. The injector pump pulley and the camshaft pulley are both locked at 2 OÆclock by their M8 bolts, and the crank pulley is at TDC. The job is to remove the crank pulley and the camshaft pulley to change the seals behind them. I did not see the need to remove the radiator and a plywood board taped against it offered enough protection. There was plenty of room to work in.

Parts and Tools
Belt: Sun A446H32MM 119teeth Part no. 8-94419-856-0
Water Pump: ASAHI A4282 Part no. 8-97062-796-0
Idler Pulley: NSK 67TB0806 ENSL 803
Tensioner Pulley: NSK 67TB0805B01 ENSL 612
Crank seal: Isuzu part 8-97049145-0
Camshaft seal: Isuzu part 8-97352745-0 / SKF 550232 is a tighter fit.
Replacement O-ring for the cam seal carrier from any parts store.
A handful of 8mm dia (M8) bolts with round Allen key heads for making DIY gear pullers. Buy a few pairs from 5-8 cm long.
A pair of 6mm bolts 5cm long.
A 24mm bolt with the same thread as the Crank pulley bolt but twice as long.
A bolt with the same thread as the Cam sprocket bolt but twice as long. I happen to have had both of these among my assortment of bolts gathered off the ground at scrapyards.
Two pieces of flat steel. One about 30cm long and 10cm wide, to drill out for a combination puller tool; the other 70cm long and 8cm wide or wider. This is for making the crank pulley tool. Thickness from 5mm up.
Drill press.
Your favourite liquid gasket maker. I used Loctite 518.
Torque Specs
Water pump bolts 20Nm 15ft lbs
Tensioner pulley and idler pulley bolt 70Nm 52 ft lbs (there is a variation in the manuals that goes up to 76/56)
Upper and lower cover 10mm bolts 8Nm 6 ft lbs
Cam Gear and Injector pump gear flange bolts 19Nm 14 ft lbs
Cam Gear 19mm bolt 64 Nm 47 ft lbs (see 4JB1 manual p. 1981-1982)
Cam seal carrier 12mm bolts 19Nm 14 ft lbs
Damper pulley 12mm bolts 19Nm 14 ft lbs
Crank pulley 24mm bolt 206Nm 152 ft lbs
A. Undoing the Crankshaft pulley nut.
Make an anchoring tool to stop the crankshaft turning. Inspiration for this came from Pig and the guys at Club Isuzu. Use the 70cm long rectangular flat piece of steel. It bolts on by two or more of the 12mm damper pulley bolts. Making it will take about 20 minutes and all it takes is some marking and drilling.
To mark the holes, draw a centre line on the steel. Take the damper pulley and place it at one end of the steel so that two opposite holes sit on the centre line (outer one about 2cm from the edge) and the hole for the pointer pin is positioned at 45⁰ towards one of the corners. Mark the position of the holes, and mark out a centre hole so you can drill out a ring large enough for a 24mm socket. Two bolts were enough for me, but if your steel is wider than mine, do all four. The idea is to make the tool bear against the ground under the truck as you undo the bolt. When you come to retighten the bolt at the end of the job, you can simply flip the tool around. 70cm was just the right length for the height of the truck and the crankshaft stayed as close as possible to TDC all the time.
With the steel bearing against the ground, a good tug on an extended breaker bar will have the crank bolt free.
B. Pulling off the crank pulley in two sections.
This time take the shorter piece of steel and again using the damper pulley, mark a pair of holes so you can insert two M8 bolts through the steel into the crank pulley on either side of the shaft. I made the holes at the end of the steel so I could hold it easily. Within 10 minutes youÆll have a puller tool similar to the one pictured in the 4JB1 manual p. 2097. It will allow the two bolts to grip the pulley while a longer bolt inserted into the crankshaft is turned anti-clockwise against the steel using an open-ended 24mm wrench. I had a 24mm bolt about 12cm long that did the job. The tool gently pulls off the outer part of the crankshaft pulley. No banging needed to get that stubborn section off.
To get the inside part (the actual sprocket) off, manufacture a smaller puller with the two 6mm bolts placed 42 mm apart. I happened to have an old Toyota sliding door bracket with an 8mm nut welded onto it that became my puller. This part of the pulley came off very easily. In any case the process happened with care and nothing was damaged.
Pulling off the camshaft pulley
To loosen the 19mm centre bolt, I took some extra insurance and anchored the wheel using the long flat steel bolted into one of the wheelÆs flange bolt holes, and resting on a jackstand. The manual says just use the M8 bolt but I had a longer one that started bending and I got the heebie jeebies. Maybe the best is to use a bolt with a head just long enough to stop (not too tightly) against the wheel.
It is not necessary to unbolt the three 10mm bolts on the gear wheel that fasten it to the pulley centre. The wheel comes off the shaft with the pulley centre attached. See the 4JB1 manual section 6A1 û 66 (p. 1981) for pictures (and fitting instructions).
To make a 10-minute puller for this wheel, use the short flat steel again for two round-headed M8 bolts to catch the back of the wheel by their heads. Measure the distance between the inner edges of two of the four round holes on the wheel. Add one bolt diameter and that will give you the centre to centre distance for drilling. When the two bolts are fastened by a pair of nuts on either side of the steel, they will remain rigid at 90⁰ once the puller is fitted onto the wheel. But youÆll have to let one bolt hang slightly loose to get its head past the lip of the wheel hole. Then lock up the tool by tightening up the nut. Once again the wheel was pulled off by turning a longer bolt anti-clockwise to push outwards against the flat steel. If you have a nice long locking bolt in place the wheel will be prevented from dropping once it is off the shaft. This puller was very useful because I could pull and install the wheel a couple of times (see below).
Undo the 12mm bolts fixing the seal carrier onto the engine and pull it off by twisting and wiggling. The O-ring will probably be nice and hard. Pop out the old seal using the 2mm pilot hole and blunt self-tapping screw method. Nothing to beat it.
C. Removing Crank Seal
I am new at this business so was reluctant to use any metal prising tool against the shaft, so I put a 2mm drill bit into a chuck and hand-turned it until I made a small hole in the middle of the seal wall. It took a while but prevented me from doing anything idiotic. Screwing in a small blunt-ended self-tapper popped the seal 30 seconds later. Tap in the new seal with a block of wood. A good way to do the final seating of the seal is to reverse the crank sprocket and draw it onto the seal using an array of spacers and the crank bolt.
D. Putting Everything together
The manual says to put some liquid gasket on the seal carrier with its new O-ring. Bolt it back on (19Nm).
Clean all the caked residue off the gears. I used brake cleaner and those things the kids shove into their ears and then clog up the toilet, whatever they are called.
I had the standard problem of dealing with a groove worn half way down the shaft of the gear centre. The trick is to make sure that the new seal ends up on a clean spot. I spent a lot of time on this with much head-scratching. No engineering shop wanted to regrind the shaft. I assume this is because grinding would wreck the hardening. I tested the depth of my nice Isuzu factory seal by greasing the end of the gear centre and drawing in the wheel to see how close the grease smudge gets to the ring. I did this a few times with the seal seated as deep as possible. I came close to leaving it, but it seemed to sit too close to the groove. I decided to sacrifice that nice seal and get another one to protrude outwards by 2mm. Day two and no oil appearing. Touch wood. Torque the pulley bolt to 64Nm. Locking bolt should hold it fine.
E. Refitting the Crank Pulley
Flip your anchor tool over to the right hand side and bolt it on. Clean out the bolt hole and the bolt, put on some Loctite and fasten to 152 foot pounds or 206 Nm.
F. Fitting the belt.
There are many good write-ups on this. See Club Isuzu FAQ. The 4JB1 manual from p. 1981 is very clear.
Here is a tip that made my life a lot easier:
Before removing the old belt, do yourself the favour of marking it as carefully as possible. I drew a line on the belt corresponding to a tooth at each of the three sprockets, and I marked those teeth on the sprockets with a permanent marker, including down the front of the wheels. Transfer the marks onto the new belt and double check by counting teeth. If anything goes awry during the belt-fitting process, you can always take a deep breath, bring the crank to TDC, insert the two bolts in the cam and IP gears, and then match the marks on the belt with the marks on the sprockets. It eliminates all guesswork.