FAQ
Having bought a car with a “slight leak from the dip stick” to find it had a full blown head gasket leak, I’ve leaned a few things.
First off you can remove the cylinder head without removing the inlet manifold first; in fact it is really difficult not to do it that way. Most stuff just unclips and even though I didn’t de pressurise the fuel system, the fact it had sat on the drive for at least a week meant that no fuel was spilled.
Well, I was concerned it wouldn’t be the head gasket; however I will let you decide.
The answer was yes by the way as you can see by the oil in this picture
So I have checked out the flatness and it looks totally flat, so just poorly installed in the first place.
However having got this far, here’s some edumacation on your cylinder head.
Engines really are quite simple in reality. The rotating crankshaft turns the oil pump and oil is pumped through the oil filter, passed the oil pressure gauge sender and through the pressure limiting valve. Too much pressure is bad also.
So oil is passed up through the little hole here
The big holes bottom right and top left of centre are oil drain holes; there are two more on the left of the head.
The oil is pumped up though this one single small hole at pressure and all the oil in the head is supplied from this via two oil galleries, one either side of the head which suppliers oil via small holes (oil jets) in each cam bearing position and the 16 hydraulic valve lifters housings.
In this picture you can see the single gallery that the oil is pumped to on the left. The gallery is drilled the whole length of the head and plugged with the hex socket plug centre left. All the left hand / exhaust oil jets are fed from this. The wire shows one of the cam bearing oil jets.
This picture show how the right hand is fed with oil for the Inlet cam. The rear of the head is cross drilled to join the two galleries; this is the plug level with the fuel injector on the right. Remember all this is supplied from that single hole on the block.
Ok, teaching everyone to suck eggs, for the engine to operate, the valves that control the flow of gasses into and out of the cylinder need to be operated in sequence and often a very high speed. The point at which these open and close is dictated by the cam shaft(s) The relationship to piston position and also between both inlet and exhaust is critical and has a great effect on performance. If there is free space between the cam lobe and valve, then those relationships to the piston and each other can vary with a loss of performance and efficiency. On older cars, these clearances used to be set with adjusting screws and feeler gauges, and had to be done either cold or hot to allow for expansion of the differing components at temperature. Hydraulic Valve Lifters took all this problem away by providing dynamic and constant adjustment of this clearance by basically putting little hydraulic pistons between the cam and the valve. These devices work like this. Inside the cap that the cam lobe acts on is a spring energised piston. The cam shaft, individual cam lobes and Hydraulic Valve Lifter cap is shown here.
The spring presses the piston out so that when it is in position in the cylinder head the piston is pressed on to the top of the valve stem and the cap of the lifter is pressed against the cam lobe removing all the clearance and also compensating for any variation in temperature. In the picture above the two left HVL’s are in this position. However, because the spring would just compress when the cam pressed the cap down (Third cam – picture above) and so the valve would not open, there needs to be a way of locking this whole assembly solid when the valve is required to open.
So in the next picture the oil jets are shown for both the cam bearings and the HVL’s. Also you can see the valve stem that the lifter acts on.
Oil travels out of the jet in the HVL housing, around the grove in the HVL cap and in through this hole.
The oil passes to the inside of the HVL and to the inside of the piston.
During the period when the cam is not opening the main cylinder valve, the HVL cap hole aligns with the oil jet and oil can flow into or also out of the HVL cap. However, once the cam starts to depress the cap, the holes are moved out of line. Because the clearances on the cap and housing are very small, this effectively then seals the oil in the HVL. This then causes a hydraulic lock between the internal piston and the HVL cap and although this is pressed outwards with a spring, the oil now means it can not compress and so makes both the cap and the piston move as one thus opening the main valves.
Once the cam rotates far enough and the HVL returns to its rest position, oil can again flow into or out of the cap.
As I am sure most of you know, these this clever little lifters can get very noisy.
So having taken my cylinder head off and removed the lifters I found that only one of then had any “spring” in it, al the others felt rock solid with no give.
So I took them apart.
Using a pair of pliers, don’t worry, unless you are silly you won’t damage the hardened piston, grip the internal piston and rotate it first, then gently pull it out.
This then gives you the piston assembly. It’s not a great picture, but you can see the “O” ring seal on the piston and also the dark shadow at the rear is old oil deposit which is what gum this little things up.
Turn the cap upside down to allow as much of the old oil to drain out and also give it a wipe on the inside to remove build up of oxidised oil. Be prepared, these hold quite a bit of oil.
Then Take the piston apart. This is the bit in particular that stick as the seal is made just purely on the toleranced fit and oil deposit jams it up so the spring can’t work.
Give them a wipe and then reassemble. You can’t really go wrong; the main danger is dropping bits on the floor. Ensure everything is clean, you can imagine what a bit of grit would do.
Put the spring on the little perch, then put the piston over the top and slide together. Then put the piston back into the cap. It is better to hold the cap with the opening downwards so that the spring doesn’t fall into the cap and gently push back together. You will feel when the “O” ring seats and now you should be able to press the piston down in the cap and feel it spring back.
Now you just have to put your engine back together!
Certainly this is a job that can be done quite readily if you are changing a cam belt or any work on the head.
When you first start the engine after doing this, expect it to be very noisy to start with until oil has circulated into the caps.
Great info + pics!
