GarageBoy 
Is it safe to pressure wash an engine? Yes, but only on a cool engine, only with low pressure and a wide fan nozzle, and only if you have protected or disconnected the electrical parts first. High pressure forces water past connectors and gaskets that were never designed to hold it back, so the risk … Read more
What causes a puddle under the car? Usually the air conditioning. Moisture in the cabin air freezes on the cold evaporator core behind your dashboard, and when you park, that ice thaws and drains out a small tube near the passenger side. That clear, odorless puddle is normal and needs no repair. The second most … Read more
How to find an oil leak with UV dye comes down to four things: add the dye to the engine oil, circulate it until every molecule of oil is tagged, scan the engine in the dark, and read the glow. The first three take about 20 minutes of work and the last one takes five. … Read more
A faint fuel smell in the first few seconds of a cold start is common, because a cold engine runs a richer air-fuel mixture while the oxygen sensor and catalytic converter warm up. A smell that hangs around past warm-up, or reaches you inside the cabin, points at a real leak, an evaporative system fault, … Read more
What causes black smoke from the exhaust? It almost always means your engine is running rich: burning more fuel than the incoming air can fully combust, so the leftover fuel leaves the tailpipe as black soot. A thin puff on a cold start is normal enrichment. A plume that follows you down the road is … Read more
A sweet smell in a car almost always means a fluid is escaping where it should not be. The usual suspect is engine coolant, which is deliberately scented sweet so leaks are easy to notice, but gasoline, refrigerant, brake fluid and a sugary spill in the cabin can all produce the same kind of odor. … Read more
Blue smoke from the exhaust means your engine is burning oil inside the combustion chamber. Oil is getting past a seal, ring, gasket or turbo seal, igniting with the fuel, and leaving the tailpipe as a fine blue-grey plume. Yes, you can usually keep driving for a while — but only if the smoke is … Read more
If one brake pad is wearing faster than the other, something on that corner of the car is not releasing properly. The caliper is failing to retract, so that pad keeps light contact with the rotor while you drive, and it grinds away at road speed instead of braking speed. On a BMW, the usual … Read more
To pressure test a cooling system, let the engine cool completely, take the radiator cap off, fit the correct adapter onto a coolant pressure tester, and pump the system up to the pressure printed on your radiator cap, usually 13-16 PSI. Watch the gauge for at least ten minutes. A gauge that holds means the … Read more
A low brake fluid warning light usually means the fluid in the brake fluid reservoir has dropped to the level of a float switch inside the reservoir, and the switch has closed to tell you. The usual suspects, in order of how often they turn up: worn front brake pads pulling the caliper pistons back … Read more