How to remove and refit a cylinder head ?

Technical

May 22nd, 2019

How to remove and refit a cylinder head ?

How To Remove and Refit a Cylinder Head on a Vehicle

Every car owner is familiar with that sound. That lingering noise we all hate to hear, you hear it, and you somehow know that there’s something wrong with your car. Often, it’s problems with the cylinder head leading to car overheating and other performance problems on and off the road. There are other ways of detecting problems with the cylinder and engine like emission of odor from the engine block, due to the leaking of coolant into the engine; but in many of these cases, removing, fixing and reinstalling the cylinder head is the next course of action.  

WHAT DO YOU NEED 

The first thing to check when beginning this mechanical adventure is your toolkit - Safety first. What better way to ensure safety than by making sure that all tools are ready and available whenever you need them, so you don’t have to wing anything. So before you begin, make sure each of these is available- Spanner set, screwdriver set, pry bar, rags, torque spanner, breaker bar, socket set, and engine seals.

Step 1 – Removal

 First, lift the front part of the car on jack stands to make a nice work space. Then drain the engine coolant; this can be done by simply placing a large pan under the radiator and opening the drain valve and leaving it for some time to collect. 

 The next step involves removing all parts around the cylinder head, including the steering pump mounting, the air filter system, and the throttle body that may interfere with the removal process. 

 Using the spanner and socket set, you can then remove the intake and exhaust manifolds and subsequently the valve covers to allow access to the cylinder. This should be pretty straightforward as you only need to unbolt each around the cylinder as opposed to having to remove them completely. 

Removing a push rod Cylinder head

 For people using engines that come with push rod head, this next step that involves unscrewing the rocker-cove bolts is one of the more important steps. If your engine comes with the overhead cam head, skip this and jump to the next stage; but keep reading if you own a push rod head engine. These screws can easily be undone by holding the rocker cover to the top of the head, making it easier to lift off the cover. Place it inverted on any clean newspaper or magazine to acquire any oil drops.

 Sometimes, it is required to slowly and sequentially unfasten the support pedestals of the rocker-shaft before removing them. Carry the shaft after loosening and lay it out. Then lift out the push rods one at a time numbering them to ensure that they are easily remembered and refitted in their normal places.

Some engines come with rocker arms that are mounted separately. So to bring them out in this case, remove the bolts harboring the arms and the pivot balls and arrange them in a row, with each correspondingly numbered in their correct order.

Next, take up the push rods and stick them through numbered holes in a piece of cardboard. Keep them in a clean place before sequentially loosening and tightening the rocker shaft bolts in. It should now be relatively easier to unfasten the bolts holding down the head in reverse order of the tightening sequence for the engine. To do this, some engines may require a special adapter tool to fit the bolts. So check the manual to know which category your vehicle falls and what to do.

 You can then, with help, carefully lift off the head. Keep in mind that every engine has its own special sequence and torque setting for the head nuts or bolts. Again, gently hit the side with a soft hammer if it sticks. Arrange the head on wood blocks immediately to protect the complex machinery underneath the surface. Take out and dispose of the head gasket, after checking and making sure that the new substitute head is identical in every detail.

 Be careful to avoid letting dirt or dust particles enter into the engine while you are working on it.

Overhead-cam cylinder Head 

 Removing an engine with an overhead cam head is slightly different from a push rod so follow these steps if your vehicle falls in the category 

Overhead cam engines usually come with belts. First, you have to unbolt the cover of a timing belt and separate it somewhere. 

 Next, check if the engine has a timing belt and if it does, unscrew the bolts securing the belt cover to the front of the engine and pull the cover off. Ensure you avoid getting oil stains on the belt while doing this.

You will need to free the belt from the camshaft sprocket. This means that you have to slack the locking device of the belt tensioner, loosen it and push the wheel until the belt is loose enough to be set free. 

Take the belt off the camshaft sprocket, but make sure you try your best to avoid rotating either the camshaft or crankshaft. Then unbolt and remove the camshaft cover.

Hold the camshaft cover to the head and undo the screws, then carefully lift off the cover: Set it upside-down on clean newspaper to catch oil drips and discard the gasket. 

Again, keeping in mind that every engine has a special sequence and torque setting for the head nuts or bolts. You can then go ahead to remove the cylinder head, using a socket and bar in loosening securing bolts in the reverse order of the special tightening sequence for the engine. Some engines need a special tool to fit the bolts. A gentle sideways tap with a soft-faced hammer will often release a sticking head.

Carefully lift off the head – you may need help. Make sure to protect the machined under surface by setting the head way up on wood blocks. Remove and discard the head gasket, taking care not to let any dirt or carbon fall into the engine.

 When you have a push rod engine, removing the cylinder head is quite a breeze, but it is not so with overhead camshaft engines as they are more complicated. This is so because you first need to disconnect the timing chain or belt. You need to research further on the kind of engine your car has. The methods differ from one engine to the other, so consult a handbook if possible to verify those details.

Second Step  – The Preparation

Make sure to clean out accumulated grime and grease off from the surface of the cylinder head thoroughly before replacing it. You can make use of a scrubbing pad for this; but then, you need to follow it up by cleaning also with parts cleaner using a piece of cloth.

  Carefully consult the service manual to easily align the timing mark that is on the cam gear. This will make sure that you have the valves in the right places. Also, you should hold them in place with a locking tool. Then align the marks on the crankshaft to those on the block. You need to get a new cylinder head gasket ready just before putting on the new engine head.. Ensure that you have the correct side facing upward. Make sure that everything is lined up correctly by locating it over the pins on the block.

Check the manufacturer’s instructions to see if the new cylinder head needs to be sprayed with aluminum paint before installation and if it can, spray both sides and let it dry. Set the clean head down on the engine block and ensure that it sits properly on the dowel pins before firmly pushing it into place.

Step 3- Refitting the cylinder head

This is essentially just a reversal of the process of removal, but just as in removal, there are different and individual steps for each of the different engines.

Begin by making sure you thoroughly check that the head and block faces are completely flat. This can easily be done using a steel rule. 

Secondly, having gone through and determined that they are indeed clean, you can now put the new gasket on the block. Gently bring down the head into place; it may prove a little tricky, but try as much as possible to ensure that you do not miss the gasket. Refit the head bolts and fasten them the right way according to the mandatory torque setting. Refit every other component, except for the cover and the air cleaner. 

Push rod engine 

After making sure that the push rods are all properly engaged with their rockers. You can begin screwing up bolts, tightening nuts and arranging them in their original spaces, before placing the rocket shaft and subsequently the rockers. In each case, carefully ensure that the upper part of each push rod is securely locked in its rocker and that the lower half is correctly seated in the tappet before fastening the bolts. You can always consult the car service manual or a dealer in order to be sure of the appropriate sequence to which rocker-shaft bolts should be tightening. 

Overhead-cam engine

 To refit in overhead-cam engines, the first step before installing the cylinder head is to twist the crankshaft with a spanner on the pulley nut until number one piston is at the top-dead-center position of its compression stroke. To make sure you are on course, you can easily verify this from the top-dead-center mark on the crankshaft pulley. Keep moving the camshaft until the mark on its sprocket get to the right location for No. 1 cylinder firing. Finally, you can now lube each one of your bolts and begin fixing them in place. A torque wrench is the most efficient tool to make sure your engine head is firmly held down. The bolts must be tightened down in the correct order and to the right torque so enlist the information about the recommended specifics in your service manual. 

When everything is in place, and each bit is tightly held down, you may now begin to reattach all other engine elements in the reverse order to which you disengaged them. 

 Cross check everything from the belt for tautness, the bolts, and nuts for tightness, the cylinder head for correct installation and other components for correct arrangement before lowering your vehicle from the jack stands. 

Finally, before heading out on the open road, you can listen for any problems by running your engine and listening out for irregular noises or overheating.

So if you ever for any reason need to remove or refit the cylinder head in your Engine. You can go through these steps carefully and be sure to get your desired result. 

Whilst this is a general guide that highlights both push rod and overhead cam engines, It is always advisable to check out the peculiar instructions for your own make and model of car before embarking on any removal or refitting process.