ENGINE
A mere 168bhp from a 2.5-litre V6 might not sound much, but the ST24 made the most of its bog-standard Duratec VE powerplant. Even a high-mileage example should feel smooth, torquey and happy to rev.
If not, you’ll need to investigate. General sluggishness is most likely to be caused by a faulty IMRC (inlet manifold runner control), which should give a surge of power under full throttle by opening the secondary inlets at 3500-to-4000rpm. It lives under a plastic cover near the exhaust manifold and tends to get hot, causing a transistor to overheat. If you’re adept at soldering it can be repaired, but most owners replace the IMRC altogether (about £150) and reposition it away from heat. Bypassing the IMRC is possible, setting the secondary inlet butterflies constantly open, but is rarely satisfactory.
You may be lucky, though, because the secondaries are also prone to getting clogged with grime, and a thorough clean-up could be a very cheap cure.
Misfires may be more of a concern. Yes, they’re probably due to knackered plugs, leads or coil pack, but a blown head gasket can be the cause. Indeed, the early Duratec V6 had a reputation for head gasket failure, and in the case of a cheap ST24 it’s generally accompanied by a phone call to the nearest scrap dealer.
Don’t expect to see coolant and oil mixing, but it’s worth checking there’s no mayonnaise on the dipstick or steam coming from the exhaust. Usually, head gaskets blow to atmosphere, resulting in a ticking noise that sounds similar to a blowing exhaust manifold – which is actually more likely to be to blame and much cheaper to fix (manifolds leak from the gaskets or due to sheered bolts).
Similar ticking sounds also come a from faulty EGR system (many EGRs have by now been blanked off) or even a loose plug lead. Nothing to worry about.
Water pump failure was prevalent on the early ST24 at around 70,000 miles or even less; the black plastic impellers on water pumps were prone to snapping, causing overheating, head warpage and/or gasket failure. Find out whether the seller has changed the pump, and consider replacing it with a robust (post-1999-type) pump with metal fins.
Many Duratec V6s burn or drip out a bit of oil, and allowing it to run low leads to catastrophic consequences. Even leaving the engine too long between oil changes can lead to camshaft wear.
So listen for nasty noises when starting from cold: tapping from the top of the engine might point to worn cams (expensive to replace) or a tired timing chain tensioner (complicated and pricey to change). A slow-sounding starter motor is normal (and cheap enough to fix) but heavy knocking from the bottom end suggests crankshaft problems and another ST24 on its way to the crusher.
That said, there are loads of second-hand Duratec V6s around, and a popular ST24 upgrade is the 200bhp ST200 unit or even the three-litre ST220 powerplant; it’s not an easy job, but it makes the most of the ST24’s sweet chassis.
Finally, remember an ST24 is now 20 years old, and if you want to use it everyday there’ll be niggles due to age and wear. Fuel pump failure, for example, is expensive if you opt for a genuine Ford part, but very feasible if you buy a nongenuine pump.