Question 1

Head Gasket Failure

Accepted Answer

The head gasket blows, allowing coolant into the combustion chambers and/or oil passages. White smoke from the exhaust, coolant loss without visible external leak, overheating under boost, milky oil on the filler cap, and bubbles in the coolant overflow tank. In severe cases, hydrolock (coolant filling a cylinder and bending a connecting rod on startup). Toyota designed the 7M head with only 10 head bolts, insufficient clamping force for the cylinder pressures generated under boost. The factory composite head gasket degrades over time and eventually fails. Thermal cycling accelerates the process. Every 7M-GTE will eventually blow a head gasket on the factory bolts, it's a matter of when, not if. Strip the head, machine it flat (check for warpage, common after overheating), install a Cometic multi-layer steel (MLS) head gasket, and secure it with ARP head studs (part number 203-4205). The ARP studs provide dramatically more clamping force than the factory bolts. While the head is off, replace the valve stem seals. Retorque the studs to ARP's specification (typically 85 ft-lb with ARP moly lube). Total cost: $1,500-2,500 including machining, gaskets, studs, and labour.

Question 2

Low Oil Pressure at Idle

Accepted Answer

Oil pressure drops below 10 psi at hot idle. The factory oil pressure warning light may flicker or illuminate at idle, particularly in traffic on hot days. The engine may develop bearing noise (deep knocking from the bottom end). The oil pump wears internally over time, reducing output at low RPM. The oil pressure relief valve spring weakens with age, allowing the valve to open too early and dump pressure back to the sump. Using incorrect oil viscosity (too thin) compounds the problem. Start with an upgraded relief valve spring, this is a $30-50 part and a 30-minute job. It's a bandaid but effective if the oil pump is only mildly worn. For a proper fix, replace the oil pump ($200-400 for the pump, plus labour to access it). An oil cooler relocation kit ($150-300) moves the oil cooler from the factory position to a more exposed location for better cooling, which helps maintain oil viscosity in hot conditions. Use 15W-40 or 10W-40 oil, do not use 5W-30 in a high-mileage 7M.

Question 3

CT-26 Turbo Failure

Accepted Answer

Loss of boost pressure, excessive oil smoke (blue/grey) on startup or deceleration, whistling or grinding noises from the turbo, and oil in the intercooler piping. The CT-26 has a limited service life. Shaft bearings wear, allowing the compressor and turbine wheels to contact their housings. Seal wear allows oil past the turbo seals into the intake (compressor side) or exhaust (turbine side). Running the turbo hard and shutting down immediately (no cool-down idle) accelerates seal and bearing failure. Rebuild or replace. A CT-26 rebuild runs $400-800 at a turbo specialist. For anyone planning to increase power beyond stock, this is the time to upgrade. Common replacements: Garrett GTX3076R for mild builds (300-450 hp), BorgWarner S362 for mid-range (400-550 hp), Garrett GTX3582R for serious builds (500-700 hp). Upgrading from the CT-26 requires a new exhaust manifold (or adapter), oil and water lines, and an ECU retune. Budget $2,000-5,000 depending on the turbo choice.

Question 4

Cooling System Inadequacy Under Boost

Accepted Answer

Coolant temperature climbs rapidly under sustained boost, particularly in traffic or on hot days. The temperature gauge sits higher than normal and doesn't recover quickly. The factory radiator was adequate for 1986 driving conditions in Japan but struggles in Australian heat, particularly with any power increase. The fan clutch wears and stops driving the fan at sufficient speed. The intercooler and piping add heat to the engine bay. Replace the radiator with an aluminium performance unit ($300-600), this is one of the highest-value modifications on a 7M-GTE car. Replace the fan clutch if it spins freely by hand when cold ($150-300), or convert to an electric fan setup with a quality controller ($300-600). Ensure the fan shroud is intact and properly sealed to the radiator, gaps allow air to bypass the radiator core.

Question 5

Fan Clutch Wear

Accepted Answer

The engine runs hotter than normal, particularly at low speeds and idle. The cooling fan doesn't seem to pull much air through the radiator. The viscous fan clutch uses silicone fluid that leaks out over time as the internal seals wear. Once the fluid level drops, the clutch can't engage fully and the fan freewheels. With the engine cold, try to spin the fan by hand. A good fan clutch should have definite resistance, you shouldn't be able to spin it easily. If it freewheels, replace it. Aisin or OEM Toyota units are preferred ($150-300). Alternatively, delete the clutch fan entirely and fit a quality electric fan with a thermostatically controlled relay ($300-600 for the conversion).

Question 6

Head Gasket Failure (Less Common)

Accepted Answer

Question 7

W58 Synchro Wear

Accepted Answer

Crunching or grinding when shifting into 2nd or 3rd gear, particularly when cold or during quick shifts. The synchros may improve slightly once the gearbox oil is warm. The W58 is a light-duty gearbox with brass synchros that wear with age and aggressive use. The W58 was designed for the naturally aspirated 7M-GE and is marginal even at stock turbo torque levels. Anyone driving a modified turbo car through a W58 is on borrowed time. A W58 rebuild with new synchros runs $800-1,500. However, if the car is making turbo power, the money is better spent swapping to an R154 ($1,500-3,000 for a complete swap including gearbox, bellhousing, tailshaft, and clutch). The R154 swap is one of the most well-documented modifications on the A70 platform.

Question 8

R154 Input Shaft Bearing Noise

Accepted Answer

A whining or howling noise that changes when the clutch pedal is depressed. The noise is present in neutral with the clutch engaged and disappears when the pedal is pressed. The input shaft bearing wears over time, particularly on cars that have been driven with heavy clutch setups or high power levels. The bearing can be replaced without a full gearbox rebuild, but the gearbox must come out of the car. Budget $500-1,000 for the bearing replacement including removal and refitting the gearbox. While it's out, inspect the synchros and replace the gearbox oil with a quality 75W-90 GL-4 fluid.

Question 9

Rear Subframe Cracking

Accepted Answer

Cracks develop in the rear subframe, typically around the differential mounting points and the subframe-to-body mounting brackets. May manifest as unusual handling, the rear end feeling "loose" or inconsistent over bumps. High-mileage, hard driving, drag launches, and increased engine power all stress the rear subframe beyond its design limits. The factory subframe was designed for 200-230 hp, not 400+. Inspect the subframe carefully, you need to get under the car on a hoist. Small cracks can be repaired by a qualified welder, but the subframe must be removed for proper access. Aftermarket reinforced subframes and subframe bracing kits are available ($500-1,500). For high-power builds, this is a preventive upgrade worth doing before cracks appear.

Question 10

Spherical Bearing Wear in Suspension Arms

Accepted Answer

Clunking over bumps, imprecise steering response, uneven tyre wear. The car may feel vague at turn-in. The A70 uses pressed spherical bearings (not rubber bushings) in the suspension arms. These are precision components that wear over time. The bearing surfaces corrode and develop play. This is often misdiagnosed by mechanics unfamiliar with the A70's suspension design, they'll suggest poly bushes as a "fix," which actually makes the problem worse. Replace the spherical bearings with correct OEM-spec replacements. This requires pressing out the old bearings and pressing in new ones. Specialty suppliers stock these, they're not common hardware store items. Cost: $50-100 per bearing, plus pressing. Some aftermarket arms come with replaceable bearings for easier future maintenance.

Question 11

Differential Bearing Wear and Noise

Accepted Answer

A click or clunk from the rear that occurs once per wheel rotation, most noticeable at low speed when coasting to a stop. Or a continuous whining/humming that varies with road speed but not engine RPM (persists in neutral while coasting). The A70 uses a Toyota 7.5-inch ring gear differential, rigidly mounted to the rear subframe with no bushings (unlike the A80 which has bushed mounts). This rigid mounting means any internal differential noise transmits directly into the cabin. Pinion bearings, carrier bearings, and the crush sleeve all wear over time. Cars that have been used for drag launches or drifting wear differential components much faster. A differential rebuild with new bearings, seals, and crush sleeve runs $1,500-3,000. Sourcing rebuild kits can be challenging, as the A70 diff doesn't share rebuild kit listings with common vehicles. Toyota OEM bearings purchased individually are the reliable route, as aftermarket "kits" often have incorrect bearing sizes. The factory ratio is 3.91:1 on turbo models and 4.30:1 on some NA models. If changing ratios, the lowest aftermarket option available is approximately 3.54:1 (Nitro Gears). For cars making serious power, differential failure is a real possibility. The factory diff is rated for stock power levels. High-torque builds (400+ hp) benefit from a diff cooler and regular fluid changes.

Question 12

LSD Wear

Accepted Answer

The car spins the inside rear wheel easily in corners or on power application, behaving like an open differential. Reduced traction on corner exit. Turbo A70s came with a viscous-type LSD from the factory. The viscous coupling loses its locking ability over time as the silicone fluid degrades. After 100,000+ km, many factory LSDs provide minimal locking effect. The viscous unit cannot be rebuilt — it must be replaced. Options include a Torsen T2 unit (available from JZA70 turbo models or aftermarket, bolt-in replacement, $800-1,500), a Kaaz clutch-type LSD ($1,500-2,500), or an OS Giken Super Lock ($2,000-3,500). The Torsen is maintenance-free and works well for street use. Clutch-type LSDs provide stronger lockup for track use but require periodic plate replacement and LSD-specific oil additive.

Question 13

Front Caliper Seizure

Accepted Answer

The car pulls to one side under braking. One front wheel is noticeably hotter than the other after driving. Uneven pad wear. In severe cases, a dragging sensation and smell of hot brakes. The A70 uses single-piston sliding calipers on the front. The caliper slide pins corrode and seize, preventing the caliper from floating properly. The piston seals harden and the piston itself corrodes in the bore. Cars that sit for extended periods are worst affected, as moisture in the brake fluid accelerates piston corrosion. Strip, clean, and rebuild the calipers. New seals, dust boots, and slide pin boots: $30-60 per caliper. If pistons are pitted, replace them ($50-100 per caliper). While apart, clean and grease the slide pins with high-temperature brake grease. Replace all rubber brake hoses at the same time — collapsed hoses act as one-way valves, trapping pressure and causing the caliper to bind even after rebuilding. Caliper rebuild cost: $100-300 per corner. A common upgrade is fitting A80 (MK4) front brakes, which are a direct bolt-on with the correct adaptor brackets. The A80 4-piston front calipers provide significantly better stopping power and heat management. Full MK4 brake conversion including rotors, calipers, lines, and brackets runs $800-1,500 using secondhand parts.

Question 14

Brake Master Cylinder Internal Bypass

Accepted Answer

The brake pedal slowly sinks to the floor under sustained pressure (sitting at a traffic light with foot on the brake). The pedal may feel normal on initial application but gradually loses firmness. The internal seals in the master cylinder wear and allow fluid to bypass internally. This is a common age-related failure on any car of this vintage. The seal degradation is accelerated by old, moisture-contaminated brake fluid. Replace the master cylinder ($200-400 for a new or remanufactured unit, 1-2 hours to fit). Flush the entire brake system with fresh DOT4 fluid after replacement. This is not a rebuildable item on the A70 — replacement is the correct fix.

Question 15

Targa Roof Seal Deterioration

Accepted Answer

Water leaks into the cabin when it rains or when washing the car. Staining on the headliner, musty smell, and damp carpets. In severe cases, water collects in the footwells and causes corrosion of the floor pan and electrical connectors. The rubber seals around the targa roof panel perish with age and UV exposure. The seal channels can also accumulate debris that prevents proper sealing. On cars that have sat for extended periods, the targa bolts can seize, making removal difficult and damaging the seal channel. Replace the targa seals. Genuine Toyota seals are still available (check with a Toyota dealer, they're surprisingly reasonable). Clean and lubricate the seal channels. If the targa bolts are seized, use penetrating oil over several days before attempting removal, forcing them will strip the threads in the body. New seal kits: $200-400 installed.

Question 16

Targa Bolt Seizure

Accepted Answer

The bolts that secure the targa roof panel to the body seize in place. Attempting to force them strips the threads or breaks the bolt heads. Dissimilar metals (steel bolts in aluminium threads) combined with moisture create galvanic corrosion. Cars that sat for years without the targa being removed are worst affected. Soak bolts in penetrating oil (Wurth Rost-Off or similar) for days, not hours. Apply gentle heat with a heat gun if accessible. If the bolt head strips, you'll need to drill it out and helicoil the thread. Preventive measure: remove the targa panel twice a year, clean the bolts, and apply anti-seize compound on reassembly.

Question 17

Pop-Up Headlight Motor Failure

Accepted Answer

One or both headlights fail to raise or lower, raise slowly, or raise unevenly. Clicking or grinding noise from the headlight motor area. The electric motors and their nylon gearboxes wear over time. The gearbox teeth strip, or the motor itself fails electrically. Water ingress through worn seals accelerates failure. The motor and gearbox assembly can be replaced as a unit. Toyota OEM parts are still listed but expensive ($200-400 per side). Aftermarket replacements are available and generally adequate. The motors can also be rebuilt by replacing the gearbox gears with aftermarket metal replacements ($50-100 DIY). Some owners convert to fixed headlights, but this changes the car's appearance significantly.

Question 18

ABS Module Failure

Accepted Answer

The ABS warning light illuminates permanently. The ABS system may activate inappropriately (pulsing brake pedal during normal braking) or not function at all. The ABS module on the A70 uses early electronic technology that degrades with age. Internal solder joints crack, capacitors fail, and the pump motor wears. The module is also sensitive to voltage spikes and poor grounds. ABS module repair specialists can sometimes reboard the module ($300-600). Replacement modules are rare and expensive. Many owners disconnect the ABS system entirely and run without it, this restores normal braking but without anti-lock functionality. For cars that have had a manual transmission swap from an automatic, ABS integration issues are common because the speed sensor signals and wiring differ between auto and manual variants.

Question 19

Power Steering Pump Whine

Accepted Answer

A persistent whining noise from the power steering pump, most noticeable at idle with the steering wheel centred (no load on the system). Internal pump seals wear, allowing air to be drawn into the hydraulic fluid. The fluid becomes aerated, causing cavitation noise. Low fluid level from leaking hoses or rack seals worsens the issue. Check and top up the power steering fluid first. Inspect all hoses and the steering rack for leaks. If the whine persists with correct fluid level and no leaks, the pump needs rebuilding or replacing ($300-500). Use genuine Toyota power steering fluid or a quality ATF, the wrong fluid accelerates seal wear.

Question 20

Engine Wiring Harness Degradation

Accepted Answer

Intermittent electrical faults, random misfires, fluctuating idle, gauge malfunctions, check engine lights with inconsistent fault codes. After 30+ years, the factory wiring harness insulation becomes brittle, particularly in the engine bay where it's exposed to heat. Connectors corrode internally. On modified cars, spliced wiring from previous owners adds further failure points. For a stock car, carefully inspect the harness, repair damaged sections, and clean all connectors with contact cleaner. Apply dielectric grease to connectors after cleaning. For modified cars with extensive wiring issues, a complete aftermarket engine harness from a specialist (e.g., Wiring Specialties) is the definitive solution ($500-1,500 for the harness, plus installation).

Question 21

Injector Failure/Inadequacy

Accepted Answer

Rough idle, misfiring under load, lean conditions (visible on wideband O2 gauge), and poor fuel economy. On stock cars, the original injectors (260 cc on 7M-GTE) clog from age and contaminated fuel. On modified cars, the stock injectors are undersized for the increased airflow and can't deliver enough fuel at high RPM/boost. For stock engines, professional injector cleaning and flow testing is the first step ($15-20 per injector). If the injectors are beyond cleaning, replace with new OEM-spec units. For modified engines, common upgrades: 440 cc injectors for mild builds (up to ~350 hp), 550 cc RC Engineering injectors for moderate builds (350-500 hp), and 1,000 cc injectors for big-power builds. Any injector change requires a retune.

Supra (A70)

Supra (A70) known problems