Find the fault before anything comes apart
Engine work gets expensive fast once parts start coming off, so the first job is proving what is wrong while everything is still together. A rough idle with a misfire code on one cylinder, for example, could be a coil, a spark plug, an injector or low compression. Moving the coil to another cylinder and seeing whether the misfire follows it rules one of those in or out in a few minutes.
If the basics do not explain it, a compression test shows whether each cylinder is sealing. A leakdown test goes a step further and tells you where the air escapes, past the rings, through a valve or into the cooling system. Testing like this is billed at $120 an hour, before tax, and it stops when the cause is known. The car diagnostics page covers how we approach faults that only turn up some of the time.
Oil leaks and where they come from
Almost every engine leaks oil eventually. The useful questions are where it is coming from and how fast. The usual sources, roughly from cheap to expensive:
- Valve cover gaskets, which harden with age and seep down the back of the engine.
- Oil filter housing and oil cooler gaskets.
- The oil pan gasket, or a pan rusted through, which is common on Ottawa cars after years of salt.
- Front crankshaft and camshaft seals behind the timing cover.
- The rear main seal, which means taking the transmission out to reach it.
Oil runs downhill and spreads with the airflow, so the wet spot underneath is often well away from the leak. The engine gets cleaned, run and checked again so the repair goes where the oil really starts. Oil dripping onto a hot exhaust manifold is a fire risk. A slow seep at the oil pan can often wait, and you will be told which is which.
Timing belts and chains
Engines with a timing belt have a replacement interval in the owner’s manual, given in kilometres and in years, because rubber ages whether the car is driven or not. Many of them are interference engines. If the belt breaks, the valves and pistons collide, and that repair costs several times more than the belt would have. On a lot of engines the water pump is driven by the same belt, so replacing it at the same time saves paying for the same labour twice.
Timing chains are meant to last the life of the engine, but some designs stretch. The sign is a rattle for a few seconds on a cold start, loudest after a night at minus 25, sometimes with a code for cam and crank position not agreeing. Clean oil changed on time is the best protection a chain has, which is part of why the oil change interval matters.
Head gaskets and coolant that disappears
A head gasket seals the cylinders from the coolant and oil passages. When it fails, coolant can burn off through the exhaust as sweet smelling white steam, or combustion gas can be forced into the coolant and push it out of the overflow tank. Milky oil happens too, though less often than people expect.
Overheating is the most common cause, which is why an engine that has run hot gets checked for combustion gas in the coolant before anyone signs off a simple radiator job. If the head gasket is fine and the coolant is still going somewhere, our cooling system page covers the other usual leaks.
Ticks, knocks and rattles
Noises are easier to sort with the hood open and the engine running. A light tick that follows engine speed can be a lifter or an injector, which is normal on many direct injection engines. A tick that is loud when cold and quietens as it warms is often an exhaust manifold leak from a cracked manifold or a broken stud, common on engines that have been through a lot of salt.
A deep knock that gets louder under load is a different matter. A knock from the bottom of the engine means stop driving it, since it often means a rod bearing is failing and the next stage is a broken connecting rod.
Repair or replace the engine
When an engine is too far gone, replacing it with a used or remanufactured unit can make more sense than rebuilding. Whether it is worth it depends on the rest of the car. If the body and subframe are rusted out, a new engine in a tired car is not money well spent, and you will hear that plainly.
Booking an engine check
2 and 1/2 Mechanics is at 1345 Marchand St in Cyrville, Ottawa, Ontario, about 1 km east of the St. Laurent Centre. Drop the car by 9am and catch the O-Train at Cyrville station, four minutes away on foot, or bring it in Saturday between 8am and 3pm. Book an engine diagnosis, describe what you hear or see, and attach up to four photos, such as the drip on your driveway.
Questions
How do I know if my timing belt needs replacing?
Timing belts rarely give a warning before they break, so go by the interval in your owner's manual, which is set in both kilometres and years. If the car's history is unknown, a sticker under the hood or an old invoice may show when it was last done. On many engines a broken belt lets the valves hit the pistons, which turns a scheduled job into a major repair.
Is an oil leak serious enough to fix right away?
It depends on where it is and how fast it drips. A slow seep from a valve cover can often wait until the next service, while oil dripping onto the exhaust manifold is a fire risk and should be fixed soon. Check the dipstick weekly until it is looked at.
Why does my engine rattle for a few seconds on a cold morning?
A brief rattle at startup that fades once oil pressure builds often comes from a stretched timing chain or a worn chain tensioner. It is usually loudest after the car has sat overnight in the cold. It should be checked before the chain jumps a tooth or sets a cam timing code.
What does an engine diagnosis cost at a shop in Ottawa?
At 2 and 1/2 Mechanics engine diagnosis is billed at $120 an hour before tax. Many faults are found inside the first hour, while some leaks and noises need more time or a test drive. You get a call with the findings and the repair price before any work is done.
Is it worth replacing the engine in an older car?
Sometimes. It depends on the rest of the car, mainly rust on the body and frame, the transmission's condition, and what a replacement engine costs against what the car is worth. We lay out those numbers so you can decide.
