ENGINE FOCUS Spotlighting the M60/M62 V8
As good as the old BMW straight-six M30 engine had been, it’s fair to say that by the late 1980s it was just about finished. Not only was it lacking in power compared to rivals such as the V8 Lexus LS400 and the forthcoming 24- valve 2.5 BMW M50, but it was also heavy, expensive to make and thirsty with it. Mercedes had been making V8 units for years by this stage, and the newer, post-1987 units were not bad engines at all, albeit a bit basic (still two-valves-per-cylinder), and not overly powerful, with an output of 220hp.
Development of the M60, as it was known, started in 1986, after the E32 7 Series went into production. However, the initial studies related to it began in 1984, and it was to be a completely new engine sharing nothing with any other production BMW engine. Sizes were to be 3.0- and 4.0-litre, with power outputs well in excess of rival units and, like the existing 3.5-litre M30, the new 3.0 would produce around the same power as the 4.2-litre Mercedes-Benz V8.
The basis of the new engine was an alloy block with a 90° bore angle and, rather than using pressed-in steel liners, BMW opted for the Nikasil bore coating. This was a nickel-silicon coating that was applied at the factory, then honed to produce a very hard, wear-resistant coating intended to generate less friction than a standard steel bore. Nikasil had been used by Porsche for a few years, and it was proven to work.
A counter-weighted, five-bearing steel crankshaft (forged on the 4.0-litre, grey-cast iron on the 3.0) was used with stubby connecting rods of sintered metal, and fractured big end caps. Rather than having a con rod where the big end cap was cut off, then both mating surfaces were machined and the result line-bored, the sintered rods had the big end caps fractured off by force. This meant that the caps were guaranteed to be a perfect fit, and more accurate than the normal, machined type.
A four-valve cylinder head was fitted to each bank, employing hydraulic tappets with double valve springs and chill-cast camshafts. The latter had five bearings each, plus a bolted-on oil spray bar, and the inlet (inner) cams were driven by a single Duplex (twin-row) timing chain. The exhaust cams took their drive from the inlets, via a separate chain each.
Sturdy tensioner rails were fitted with an idler gear for the main timing chain, with a single tensioner for the main chain plus a smaller one for each of the exhaust cam short chains. The oil pump was bolted to the base of the block at the front, and driven by a short chain from the crankshaft, and an external oil filter used hydraulic hoses to connect it to the engine.
A two-piece sump consisted of a base plate and a removable front oil bowl. A nylon/plastic inlet manifold was used, together with Bosch Motronic M3.3 electronic management, coil pack ignition, camshaft sensors, an air mass meter (MAF) and knock sensors. Dual-mass flywheels were fitted to manuals and cast magnesium cam covers were used to filter out any valve train noise, while a spring-loaded roller tensioner took care of the wide, multi-rib drive belt for the water pump and alternator.
A 95°C thermostat was fitted to cars with catalytic converters, while those without got 85°C units (not sold in the UK). The result was an absolutely superb engine and easily the best unit BMW had ever made. The 3.0-litre variant was a short-stroke, big-bore motor with a 2,997cc capacity achieved thanks to an 84mm bore and 67.6mm stroke.
The new engine could really fill its lungs, thanks to four big valves per cylinder, although this did limit low-speed torque. Power output was rated at 215hp at 5,800rpm – almost identical to the outgoing 735i M30 six – and torque was a very reasonable 290Nm at a fairly high 4,500rpm. The 3.0-litre was definitely more of a revving engine than the old 3.5, which made the performance about the same between the two engines. By way of a comparison, the 735i produced 211hp at 5,700rpm, with a torque figure of 305Nm at 4,000rpm.
The 4.0 though was the superstar, with an 89mm bore and 80mm stroke giving a 3,982cc capacity and 282hp at 5,800rpm. Torque was rated at 400Nm at 4,500rpm; enough to give the 540i and 740i models some real wallop. Specific power output? A lazy 71hp per litre on a 10:1 compression ratio, and the 3.0 had the same specific output on a 10.5:1 compression ratio.
As a comparison, the old 3.5-litre gave 60hp per litre, and the M30 3.0 six slightly more, at 66hp per litre. But don’t let the figures fool you into thinking that the new V8 wasn’t that much better than the old M30, because it was light years ahead. Mated to the new five-speed automatic, or close-ratio manual, the V8 was a good 5mpg more economical, as well as being much quieter and more refined. I got a genuine 36mpg brim-to-brim from a 1992 730i Auto on a long run up to Scotland on cruise control, sitting at a GPS-confirmed 70mph (my 1989 M30 car could just about achieve 30mpg on the same trip).
But, if the 3.0 was a lovely engine, the 4.0 really was a tremendous thing which immediately rendered the 5.0-litre V12 superfluous. The V12 was a nice talking point but, at 295hp at 5,200rpm with 450Nm at 4,100rpm, it wasn’t a lot more powerful and it drank a lot more fuel (there’s a good 8-10mpg difference between the two).
The M60 was an immediate hit, revitalising the E34 and E32, beating Mercedes and crucially, the Lexus LS400. The big Toyota V8 was a superb engine but, with 250hp and 353Nm, it just didn’t have the oomph of the 740i. The 4.0 also found a home in the E31 8 Series, to become the 840i; effectively taking over from the dead-duck V12 850i, and saving the expensive Coupé from early extinction. Problems? Well, the main one was the Nikasil bore coating. What behaved perfectly on a test rig, developed bore wear problems in service, not helped by the massive sulphur content in UK and US fuels. What also didn’t help was that to get the engines to fire up instantly, BMW programmed the ECU to deliver some pretty aggressive cold-start fuelling. Too many of these would lead to ‘bore wash’ and a loss of compression. Only cranking the engine with the fuel pump fuse removed would get it going but, if the bores were worn (the coating would start flaking away at the top), it was necessary to remove the spark plugs, squirt engine oil into the bores and spin the engine on the starter to distribute the oil and reseal the rings.
That was only a short-term solution, but BMW did the honourable thing and replaced thousands of short engines, free of charge. Apart from that, the M60 was a great motor. It may have suffered with the odd oil leak down into the plug wells from a tired cam cover gasket, and/or low idle oil pressure due to the oil pump bolts loosening. But these were easily remedied with the oil drained and the front sump pan unbolted.
It never suffered from camshaft wear, crank problems and only rarely head gasket trouble. The crankcase breather valve is built into the back of the inlet manifold and needs changing periodically. If maintained correctly, though, this engine would simply run and run to 200,000 miles; if excessive cold starts were avoided, even the Nikasil units could do some monster mileages. The secret was to fire it up from cold and not shut it down until it was good and hot.
The M60 was a great engine and was used in the E34, E31, E32 and the 1994 E38 730i and 740i, but BMW was working on a replacement, the M62. Some of it was an improvement but, regrettably, a lot of it definitely wasn’t…
THE M62 3.5 AND 4.4
Production of this engine began in late 1995, to power not only revised E38 cars (735i and 740i), but also the new E39 5 Series (535i and 540i). The 840i also got the new engine, and the M62 went into production in September 1995 in readiness.
On the face of it, the M62 looks just like an M60, and you need to be sharp-eyed to spot the differences – the remote oil filter housing is the most obvious way. The extra capacity was achieved by fitting a longer-stroke, 78.9mm crank to give a capacity of 3,498cc. Power was rated at 232hp at 5,700rpm, and torque increased to 320Nm at 3,300rpm – a useful boost.
The compression ratio was reduced to 10:1 and revised Bosch M5.2 engine management was fitted. The 4.4 has a bore of 92mm and a stroke of 82.7mm, producing 4,398cc capacity. Power remained the same, at 282hp at 5,00rpm, but torque was up to 420Nm at 3,900rpm. So, it wasn’t as big an improvement over the 4.0 as the 3.5 was over the 3.0.
In pursuit of better economy, the M62 was revised to be a lower-friction, hotter-running engine, and this is where the troubles started (especially once the years started rolling by). The cam chain was reduced from a sturdy duplex type to a single row simplex and, while the new one was OK, the tensioners break up and cause havoc – listen for a grating noise at around 2,000rpm.
The previous chain idler gear was replaced by a curved guide that isn’t as good. Single valve springs replaced doubles as well, but that’s not a problem. The cooling system was also fitted with a mapped thermostat controlled by the engine ECU. This allowed the engine to run incredibly hot on low/part throttle, and temperatures of up to 116°C have been noted. Under load, the thermostat would open and reduce this slightly, but the engines did run very hot and relied on a cooling system that became pretty marginal in older age.
There’s a radiator cap that keeps a lid on things but, open the bonnet on an M62 that’s just done a motorway run, and the heat being produced will be incredible. This led parts of the cooling system starting to explode as they became old and unable to deal with the high temperatures any more. The top radiator hose, the heater hose at the back of the engine and the header tanks all became vulnerable to this sort of failure. Just think of a pressure cooker with a dodgy seal, and you’ll get the idea.
However, this can be cured by replacing the mapped thermostat with one from either a 740d unit on post 9/98 cars with push fit hoses, or an M60 stat on cars with Jubilee clip-type hoses. There’s a lower, 85°C 840Ci stat available as well, and the part number is 11531742964. This will reduce coolant temperature considerably, and give the whole unit a much easier life and really, fitting a cooler stat is essential now.
A by-product of the M62 running so hot is that the rubber gaskets and seals will eventually become cooked, brittle and leaky. Consequently, most units nowadays will now need resealing – mainly the cam cover gaskets that can leak oil down into the spark plug wells (small, under-bonnet fires have been known).
As with the M60, the kinked coolant hose that comes from the back of the engine and runs into the heater matrix, can go pop, so it’s always a smart move to replace this before trouble strikes. Nikasil was used on early M62 engines, but finally discontinued in mid-1996. In its place came Alusil, which saw the entire block being cast from an alloy with a very high silicon content. The bores were then machined and finished to expose the minute silicon particles on which the pistons could run.
Launched in September 1998 on the 5 and 7 Series – but not the 8 Series – the TU version of the M62 was the last before the engine was replaced by the N62, between 2002 and 2003. It was also used in the 4.4 BMW X5 and the L322 Range Rover, and the changes made were pretty significant.
Vanos was fitted to the inlet cams, push-clip-fit rad hoses were used with a revised cooling system and a water-cooled alternator. For this, a new front timing cover was introduced with a big hollow ‘bucket’ into which the sealed alternator fits. Fly-by-wire engine management (Bosch ME7.2) was used and, with the Vanos system, this resulted in a much healthier torque curve – the revised 3.5-litre unit was particularly good, and not far off an older 4.0.
The M62TU was used in 4.6-litre form in both the X5 4.6iS as well as the Alpina B10 V8 E39. This engine was developed by Alpina, and the design sold to BMW for use in the X5. The extra capacity came from an overbore to 93mm, and a new crankshaft with an 85mm stroke. The compression ratio was 10.5:1, and different cams were used in the revised heads, resulting in 342hp and a torque figure of 480Nm at 3,700rpm.
Unfortunately, though, the ‘TU V8’ was no more or less reliable than the previous V8, but the 4.6 is pretty well known for head gasket failure, which is an expensive fix.
The M62TU’s phasing-out run began late in 2001, when the E65 7 Series arrived, and the last was built in 2003 when the E39 5 Series was replaced by the E60. The X5 was re-engined that year with the same N62 V8.
The M62TU V8 was used to power the E53 X5 4.6iS, and was an engine developed by Alpina.
Clockwise: The M62 looks just like the M60, and you need to be sharp-eyed to spot the differences – the remote oil filter housing is the most obvious way. • This is a Vanos-equipped M62 TU engine, showing the chains and the curved guide rail. These break-up with old age. • The upper chains on the M62; you can see the tensioner plunger extending • Look closely and you can see the lighter section at the top of the bores; that’s the start of the Nikasil coating wearing away on this M60 engine.
A new M62 mapped thermostat; you can see the electrical connector that takes power to the element to open and close it.
This PCV (Positive Crankcase Ventilation) unit bolts on to the back of the M60’s inlet manifold, and is a bit of a cow to change.
One cylinder bank on a 730i E32; you’ll need to remove the coils one by one to change the plugs, and to check for oil leaks.
The basis of the M60 V8 engine was an alloy block with a 90-degree bore angle and, rather than using pressed-in steel liners, BMW opted for the Nikasil bore coating.
The basis of the M60 V8 engine was an alloy block with a 90-degree bore angle and, rather than using pressed-in steel liners, BMW opted for the Nikasil bore coating. The M60 chains never go wrong, but you can see the idler gear here instead of the M62’s U-shaped guide rail.