Head job (hey doc, what do you see in there)


There seems to be fad in installing an oil-catch system on some cars nowadays. I even see it on some diesel-powered cars. Owners usually complain that they have excessive oil coming from the breather hose going to the intake manifold. The breather hose is connected to the valve cover and to the intake manifold. I used to see these on prepped-up engines. The theory is with the engine screaming at high rpms (revolutions per minute), pressure builds up and the oil in the valve train is sloshed around too much. The breather hose is there to relieve some of that pressure but along with it is oil making its way to the intake manifold. On a stock engine, minimal oil makes it to the intake manifold. But on prepped-up engines, the oil going to the intake manifold could be excessive. So an oil catch system is placed in between the valve cover and the intake manifold. The oil-catch system collects the oil but also allows the air pass to through freely. In some designs, the oil is allowed to drip back into the engine.

Now, if you notice that you have excess oil coming from your breather hose and you have a stock engine, then it is a sign that something maybe wrong. If you check your owner’s manual, it will state that after about 5,000 or 6,000 kilometers, you may lose a little bit of oil. Anything more than that may merit some concern. Some car owners are in denial that there may be something wrong.

What are possible causes of excess oil coming from the breather hose?

One way to check is to have a compression test done on your vehicle’s engine. This test can help take out a lot of guess work. Carbon build up in the cylinder and around the valves, a worn valve guide or a worn valve seal can be the culprits. On high mileage cars, these are expected to be the causes. Even the brand of oil can be a cause of excessive oil in the breather hose or the oil may not be compatible with your engine.

If you decide to have your cylinder head refurbished, it would also be nice to have the rocker arms, camshaft and valve springs checked for cracks or deep scratches. The valve springs should be checked for squareness and tension. A good machine shop can do these things.

While the head is down, you could consider having the manifolds match-ported to the cylinder head. This means that the shape of the ports of the intake/exhaust manifold will be the same as the ports on the cylinder head. This will help the engine breath better. It would also be a good idea to check the bolts that secures the cylinder head to the engine block. Just because it doesn’t look broken doesn’t mean it’s not. A fatigued bolt doesn’t have to break in half to declare to the world that it has failed. The bolt can stretch too much when it is tightened. Yes, it will stretch, but at an acceptable amount. It is possible that once you assemble the engine and start it up, it may seem like it is okay. But when the engine starts to heat up, the bolt or stud bolt will expand and can stretch too much-meaning it is tired.

The continuous explosions in the cylinders forces the cylinder head to go up or away from the engine block. The head can lift off and it doesn’t take much clearance to lose proper sealing.  This can lead you to believe that the problem is a head gasket failure.

I am not saying not to put or use an oil catch system. All I am saying is before you install one, figure out first why your vehicle’s engine needs one. We sometimes don’t want to face reality as we want to avoid the actual cost of doing it right (which may be a costly repair).

A little reminder – if you forget to inspect the oil catch system and it gets full…that can lead to other problems.


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