This design is called an interference engine. A non interference engine is an engine design that has the valves and pistons spaced far enough away from each other that there is no possible way for them to contact, regardless of the timing.
If the timing belt or timing chain is replaced but the engine is not timed correctly, it is very easy to bend a valve on an interference engine. Turn the engine over by hand a couple of times to make sure no internal components are contacting before you button everything back up. If the timing belt were to snap on an interference engine, there is a very good chance that a piston will contact a valve and bend that valve.
This is one of the reasons why it is critical to change your timing belt on time. There may be no warning at all before a timing belt snaps. At the very least, a broken timing belt will leave you stranded. Timing chains usually require no maintenance unless there is a problem with a chain tensioner. Engine oil is critical for the health of your engine. If the engine oil level is too low to deliver adequate oil pressure to the whole engine, any number of problems could occur.
Few problems caused by oil starvation are cheap to fix, but checking and maintaining your oil level is very cheap. The best way to tell if you have a bent valve is to remove the cylinder head so you can physically get your hands on the valves. Since this involves a lot of work, most people will do a compression test or leak down test instead. A compression test will tell you how much compression each cylinder is making.
It is a quick and easy litmus test to gauge the health of your engine. If you do a compression test and find the compression on one cylinder to be low, you can then move to a leak down test. A leak down test will tell you exactly where air is leaking out of your engine on the compression stroke, when the combustion chamber is supposed to be sealed. A leak down test is performed by hooking up compressed air to the spark plug hole of a vehicle and turning the crankshaft until that cylinder is on the compression stroke.
Once that is accomplished, the crankshaft gets turned until the cylinder is at the compression stroke. This is when you hear where the air is rushing out of the engine.
On the other hand, air coming from the exhaust points to a bent exhaust valve. However, air coming out of these locations could also mean that there is just carbon buildup on the valves leading to a poor seal. Further diagnostics might be needed from a qualified mechanic if you are unsure. Ask any car question in our new community!
Magnus is the owner and main author of MechanicBase. He has been working as a mechanic for over 10 years, and the majority of them specialized in advanced diagnostics and troubleshooting.
Certified Automotive Diagnostic Technician. Here is a more detailed list of the most common symptoms of a bent engine valve: Contents show. Check Engine Light. Engine Backfires.
Low Compression. Shaking Engine. Lack of Power. Excessive Oil Consumption. What are Engine Valves? How to Test Bent Engine Valves. Checking Compression On Petrol Engine Still have questions? Leave a reply. If you have a car question, submit it to our community for a faster answer.
Cancel reply. Your Comment. Leave this field empty. Related Posts. DOT 3 vs. Latest Posts. The cylinder head, along with the valves, tappets and lifters all exist in an environment with tolerances that are measured in millimetres. Any damage to the valves can knock out the positioning and smooth movement of surrounding parts. This will invariably lead to noises from the top of the engine that would not normally exist.
Some engines as they get older develop a ticking noise that can often be mistaken for damaged valves. This noise is usually caused by wear to the valve lifters and not the valves themselves.
Worn lifters usually make a ticking noise as opposed to a knocking or clicking sound when the engine is running.
When it comes to checking the condition of the inside of the engine, there are two basic tests that you can carry out. The first is an engine compression test. This is a test of how effectively the engine creates pressure in each of the cylinders. To carry out the test, a special engine pressure gauge is connected to each of the cylinders in turn and the engine is then cranked a few times and a pressure reading is taken.
The ideal pressure inside of an engine cylinder can vary from engine to engine. In general petrol engines should give a pressure reading of between 80 and PSI. A compression test is a great test to start with if you suspect bent engine valves. It can give you an idea of the condition of the valves, valve seats, and piston rings and whether the timing of the engine is set correctly.
The second type of test that you can carry out, is a test of how effectively each cylinder in the engine can hold pressure. This is performed in a similar way to a a compression test, but instead of cranking the engine, the pressure is pumped into each cylinder using a special engine leak-down tester tool. To perform an engine leak-down test , the piston must be at top dead center for the cylinder you are testing.
This ensures that the valves are closed and the cylinder is set up so that minimum leakage should occur. Any leakage that is detected can be attributed to wear or damage to the valves. The leak-down tester is connected to the cylinder via the spark plug hole and air is pumped into the cylinder usually by compressed air source until the pressure exceeds PSI this depends on the engine. If the leak-down test revealed a leak, then it may be possible to figure out the exact cause of the problem before you take apart the engine.
Once you have identified the source of the leak, the next steps involve stripping down the engine to physically check the condition of the valves, valve seals, pistons and cylinder head. The following symptoms are a sign of minor damage to the valves. The role of engine valves in the combustion process If the ECU detects a problem with the fuel combustion process it may try to over compensate by tweaking the amount of fuel delivered to the affected cylinder.
Symptom 2 — Low Cylinder Compression Especially At Idle A classic symptom of bent engine valves is low compression in the affected engine cylinder.
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