Toyota 4WD Surf Owners

Problems with swapping over a Toyota 2L 2.4L normally aspirated diesel engine in a 1989, NZ assembled LN65 Hilux 4x4 utility vehicle, with the “same” engine from a Toyota Hiace van. Note that this is relevant to a previous 2012 posting, in which the cause of ludicrously high oil pressure was sought, but seemingly never resolved...
Jagnut, February 2020


I recently had cause to replace the “early” 2L diesel engine in my August 1989 (first registered in NZ), New Zealand assembled Hilux truck. This was because the engine had seized due, as it later became apparent, to a catastrophic oil-pump failure, in which the drive splines were completely stripped off the oil pump drive rotor and damaged beyond repair on the crankshaft.
A cursory glance at almost any Toyota enthusiast website indicates that a 1989 Hilux should have the later “2L2” engine, with the pressed-steel rocker cover, rather than the earlier 2L, or “2L1” engine with offset camshaft and alloy rocker cover. My guess is that the NZ assembly plant had a load of old components to get rid of and hence these rules did not apply here in the colonies! In any case, there is no doubt that my engine was an early one and was definitely the original fitted to the truck, as per the manufacturer’s plate in Fig. 1.

Figure 1. Manufacturer’s nameplate – yes it is an “early” 2L engine, fitted new in late July 1989

Now, getting the 2L engine rebuilt was considered and quotes of between NZ$5,000 and $8,000 were obtained. Given the age and book value of the vehicle this sort of expenditure didn’t look very sensible, so the hunt was on for a second hand lump. Unfortunately there seemed to be a great many more turbocharged (2L-T) engines on the market than normally aspirated ones, until finally an early 2L engine became available (it was suggested to use a 2L-T engine without Turbo, but the compression ratio is so low that the performance of the vehicle, which is already well-short of electrifying, would be altogether risible!). After ensuring it should be compatible I duly purchased it and got it shipped down from the North to South Island of NZ. Unfortunately the engine was from a Hiace van (LJ variant), rather than a Hilux truck (LN variant), meaning that there are several differences, due to the different mounting of, and access to, the engine in the two vehicles:

1. The oil cooler/filter bracket assembly are different – primarily the Hiace van has the oil filter facing down, whereas the Hilux truck has it facing sideways
2. The oil sump pick-up is different
3. The oil pan is a different shape to accommodate the above
4. The oil pan gasket and mounting methods are different
5. The engine brackets are subtly different, such that the belt length for the power steering pump is different

It was relatively easy to deal with items 2 to 5, swapping over the relevant parts from the “old” seized engine. Unfortunately I foolishly imagined that the same could be said of item 1. I, and everyone else I spoke to later, including Toyota main agents and the Haynes manual (92736) were unaware of a hidden pitfall – at some point between engine numbers 2L-1465266 and 2L-1907947, the block and oil cooler/filter bracket castings were subtly altered…
Having swapped over all the bits and installed the “new” engine, which consisted of Hiace engine number 2L-1465266 – i.e. the “new” engine was older than the “old” engine, but had the advantage of having a rotating crankshaft – the problem gradually manifested itself:
Unfortunately the Hilux does not have an oil pressure gauge, just a switch – otherwise a great deal of time could have been saved.
Initially the “new” engine ran fine, taking the truck down to the local garage to get a new Warrant of Fitness (unbelievably required every six months for pre-2000 vehicles in NZ). However, the next day, on starting, the oil filter miraculously loosened itself and dumped 75% of the sump oil all over the drive.
No problem – replace the oil filter; do it up really tight and mark it; refill the sump; start… Runs OK into work and back a couple of times (40km/25 mile round trip). No problem, except there’s oil weeping out of the oil pressure relief spring plugs on the oil cooler assembly.
Take the pressure relief springs and pistons out, fit new washers, put some sealant on them and do them up really tight. Problem seems to be fixed on the next trip to work and back.


Next day, on cold start-up, the oil-filter O-ring gasket blows out of its metal groove and dumps 75% of the sump oil on the drive again…
Now it’s time to investigate just how the oil pressure relief system on this engine is supposed to work. Haynes doesn’t really give any useful information, so refer to Toyota workshop manual, LU – Lubrication System Chapter. Figure 2 shows how Toyota think the system works (at least whoever at Toyota wrote the manual!).

Figure 2. Toyota’s guess at how the oil pressure relief system works – it doesn’t work like this! (Courtesy Toyota)

Actually, there is no oil pressure relief valve on the oil pump itself on this engine – this has been proven by taking the oil pump to pieces – sure, there is a hex drive plug that looks as though it could have a valve in it, but actually there is nowhere for it to go inside the oil pump casting. I.e. the relief valve drawn around the oil pump in Fig. 2 does not exist.
There is a relief valve in the oil cooler assembly, just before the oil filter (oil enters the filter from the outer holes and comes out the threaded hole in the middle). However, the relief valve (let’s call this Valve 1, if it opens, dumps oil straight back to the sump. I.e. the second relief valve in Fig. 2 is in the right place, but the output dotted arrow should go back to the oil pan, not to the oil cooler.
There is also a second relief valve, which we will call Valve 2, which really does bypass the oil cooler, if it opens.
Valves 1 and 2 and their springs are identical, BUT Valve 1 has its spring compressed much further and therefore needs more pressure to open. Figure 3 shows the actual respective locations of Valves 1 and 2.
(The above was verified by pushing a wound guitar A-string through the various oil ways of the block of 2L-1907947 and the oil cooler bracket.)


Figure 3. The right hand valve is Valve 1; the left hand valve is Valve 2. As shown correctly, the plug on the extreme right is a dummy, with no valve. (Courtesy Toyota)

So, what to do?
The guess was evidently that there was way too much oil pressure, indicating that Valve 1 was not working.
However, to avoid “blind” blundering, we replaced the oil pressure switch with an electronic sender and gauge, replaced both valves, springs and gaskets with new parts, fitted a new “real Toyota” oil filter, topped up the sump and fired her up…
The oil pressure hit the end of the gauge (100PSI) at tick-over, with cold oil, and wanted to go even higher when revved. When warm, it dropped to around 40PSI at tick-over but would still go off the scale when revved…
Remove both the valves and springs, refit the plugs and gaskets and start again…
Same deal – evidently the oil return from Valve 1 to the sump MUST be blocked in some fashion. Therefore there is no option but to remove the oil cooler assembly again and investigate what’s going on…
Figure 4 shows the cause of the problem.

Figure 4. 2L-1465266 “new” earlier block on left; 2L-1907947 “old” later block on right – Note the rightmost oil hole which is in a casting recess on the right hand picture, but in a flush machined face on the left; this is the relief return path to the sump for oil exiting Valve 1 in the oil cooler assembly.

Clearly these two blocks are not identical – what seems to have happened is that the later design (on the right) has been introduced to reduce the amount of metal in the block, or to reduce the amount of surface machining, or both.
When married with the respective slightly different oil cooler assemblies, it is possible to unwittingly block the access from the outlet of Valve 1 in the cooler back to the sump.
Referring to Figure 5, it can be seen that the earlier design on the left would work with both blocks, whereas the later design on the right would only work with the later block, unless a channel is machined (as shown at top right of right hand figure) to allow access for oil from valve 1 to the relief to sump hole in the earlier block design.

This begs the questions:
1. Why did they do it?
2. Why didn’t they document it?

Essentially the received wisdom that there is an “early” engine – now referred to as “2L1” and a “late” engine – referred to as “2L2” – is incomplete. There is a “2L1a” and a “2L1b” engine, and who knows, maybe even more variants…

Figure 5. The relevant mating surfaces of the earlier oil filter/cooler assembly, as fitted to 2L-1465266, left, and the later assembly, as fitted to 2L-1907947, right. The more compressed spring of Valve 1 (top) is clear, as is the hole through which pressure-relieved oil flows. Note the groove machined in the later assembly, to mimic the early casting.

Figure 5 shows what the solution is: machine a groove in the alloy to allow oil released by Valve 1 to get to the hole in the block. The alternative would be to file a groove in the block, but alloy is a lot softer than iron!

Problem solved. The oil pressure when cold is now 80PSI, dropping considerably at tick-over when warm, but limiting at 80 when revving hard.

Apologies for the Figures not appearing - I'm new to this forum and there seems to be no obvious way to include them or post them to another location...