A valve cover plays a critical role in protecting the engine components, including the rocker arms, camshaft, and valves. Therefore, when you see smoke emanating from this area, it can be worrying.
But what are the causes of smoke coming from the valve cover? Smoke will come out from the valve cover if the valve cover gasket is faulty. The smoke can also be caused by piston blow-by, excessive oil, a bad or clogged PCV valve, and a blown head gasket.
So, how do you diagnose the exact cause of the smoke problem and fix it? In this discussion, I will delve into the different causes and solutions to this problem.
Table of Contents
Top 5 Causes of Smoke Coming From Valve Cover
Smoke coming out from the valve cover can be a sign of several underlying issues within the engine. These include:
1. Faulty Valve Cover Gasket
If the valve cover gasket is leaking fluids, you could see smoke from the valve cover. This happens when the oil drips onto something hot, like the exhaust manifold, causing it to burn and produce smoke.
Diagnosing and Fixing the Problem
Apart from the burning oil smell, another way to tell the gasket is leaking is low engine oil. So, to fix this issue, I suggest replacing the valve cover gasket, and here is how to do it:
Step 2
Next, unfasten the screws and nuts that secure the valve cover.
Step 3
Remove any cables, hoses, and connectors attached to the valve cover.
Step 4
Lift out the valve cover and remove the old gasket.
Step 5
Clean the valve cover, including where you will be mounting the new gasket. I recommend using a brake cleaner and clean rags.
Step 6
Apply a lubricant or sealant on the sides where the new gasket will be mounted.
Step 7
Install the new gaskets in reverse order and torque the valve cover bolts to the correct specs.
Typically, the cost of replacing the valve cover ranges from $110 to $340, including labor and parts.
2. Piston Blowby
If you notice white smoke from the exhaust after the valve cover gasket change, it could be due to excessive blow-by. Piston blowby is when the piston rings are not seated correctly.
When this happens, oil usually gets into the combustion chamber and into the crankcase. Once the oil burns, you may see smoke coming from underneath the valve cover.
Diagnosing and Fixing the Problem
To diagnose this issue, place the oil filler cap upside down on the opening. If it blows off immediately, you have a piston blowby due to excessive crankcase pressure. Also, loud sputtering noises from the engine are signs of blowby.
One of the best ways to fix piston blowby is to replace the piston rings. Here is how to do it:
Step 1
With the engine off, drain the coolant and remove the exhaust manifold.
Step 2
Disconnect the distributor and the spark plug wires. Then, unfasten the valve corners.
Step 3
Remove the pushrods, rocker arms, and pistons. Then, take out the cylinder head.
Step 4
After removing the pistons, use a piston ring tool to remove the old rings.
Step 5
Install the new rings in reverse order, starting with the oil scrapper one at the bottom.
You can expect to pay between $1,000 and $4,000 to replace the piston rings. This depends on your vehicle’s make, model, and engine type.
3. Too Much Oil
Too much oil in the engine usually creates excessive pressure on the crankshaft. When this happens, the motor oil can splash onto hot engine surfaces, causing smoke in the valve cover. The smoke coming from inside the valve cover is usually bluish-white.
Diagnosing and Fixing the Problem
You can diagnose the problem by checking the oil level using the dipstick. If it is above the high (H) or Max line, you know it is overfilled. The correct oil level is usually between the low and high mark.
If there is an overfill, the best solution is to drain the excess via the cap using an oil extractor pump. Alternatively, you can draw out the excess oil by removing the drain plug.
You will spend less than $100 to drain the oil, which is the cost of the extractor pump.
4. Bad or Clogged-up PCV Valve
The positive crankcase ventilation (PCV) valve removes gasses produced by the combustion process. Simply, it prevents blow-by at the gaskets and seals.
When this valve becomes faulty or clogged, it will cause pressure under the valve cover. As a result, oil could be pushed out through the valve cover and burn, causing smoke.
Diagnosing and Fixing the Problem
A common sign of a bad PCV valve is a hissing or whistling noise from the engine. Other signs include the check engine light illuminating and the engine misfiring at low rpm.
If the valve is clogged, clean it using PCV solvent or compressed air. But in most cases, you will have to replace it. I will discuss the replacement steps below.
Step 1
Locate the PCV valve on the valve cover at the top of the engine.
Step 2
Loosen the vacuum hose clamp and pull out the PCV valve.
Step 3
Install the new valve in the reverse sequence and start the engine.
You need to pay between $90 and $110 to replace the valve at the dealership. However, replacing the valve yourself is cheaper as the part only costs about $10 to $20.
5. Blown Head Gasket
Unlike the valve cover gasket, the head gasket creates a seal between the engine and the cylinder head. This prevents the engine coolant from leaking and contaminating the engine oil.
If the head gasket blows, coolant will mix with engine oil and burn, creating a bluish or white smoke. The smoke could appear like it’s coming from the valve cover area.
Diagnosing and Fixing the Problem
To diagnose a blown head gasket, check if the engine oil is white or milky. Other signs are engine knock, low coolant level, and engine overheating.
The best solution I recommend is to install a new head gasket set. Unfortunately, this is a complex job for most average DIY enthusiasts. So, I recommend you let a professional mechanic handle it.
That said, below is a detailed illustration of how to install a replacement head gasket:
Generally, the average cost of replacing a head gasket is between $1,000 and $3,000, including parts and labor.
Conclusion
Smoke coming out of the valve cover is a common problem that I have witnessed in different car makes and models. Therefore, knowing how to correctly diagnose the problem is crucial. The good news is that, in most cases, a visual inspection is all that is needed.
However, you must seek professional assistance for a more in-depth diagnosis. This is because if you disregard the problem, it could lead to more significant engine issues and decreased performance. And if you are not mechanically inclined, you should take your car to an experienced mechanic for repairs.
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