Taking off the cylinder head of this huge 4.0L 6-cylinder engine is supposed to be pretty straightforward but we did hit a snag.
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Last Thursday was a busy car day. Spanner mate Peter was coming over to start the work on the Jeep. But first thing; The Mercedes W123 needed its bi-annual APK (The Dutch MOT). You have seen this numerous times on this thread. All my cars require APKs.
You get a notification in the mail from the Dutch RDW, the governmental agency in charge of everything related to cars, registrations, testing, APK, and so on. Depending on the age of your car, an APK is valid for 1 or 2 years. When you are over 30, it’s valid for 2 years. Without a valid APK, you are not allowed to take your car on a public road. Neither is your insurance valid.
As per usual, a straight pass! On the way home I picked up this very fancy tool from my neighbour Jack. We will need it to measure the internal diameter of one of the cylinders of the Jeep.
I need to measure with an accuracy of better than 0.003mm. Anorak fact; the model engines I make myself have a piston/cylinder clearance of only 0.002mm.
These things are very very expensive. Very glad Jack had one, and let me borrow it!
Just to recap what and why are we opening up the Jeep’s engine? In an earlier post, you can read and see the problem. The engine has what is known as a piston slap. Many Jeeps, even pretty new ones, suffer from this phenomenon.
Piston slap occurs when an engine has an excessive clearance between the piston and the cylinder wall. During the combustion process, the piston moves up and down within the cylinder, and if there is too much clearance, the piston can make contact with the cylinder wall, resulting in a knocking or tapping sound.
A less technical term would be a “wobbly” piston. Because that is what it is, actually!
My Jeep suffered from this problem when I bought it. But it went away completely when the engine warmed up. I noticed that it is still audible these days, even with the engine at normal operating temperature.
Conventional wisdom is to just leave it until it gets a lot worse. I don’t want to do that for several reasons.
When it gets worse it usually means a piece broke off the piston skirt! That almost certainly will lead to damage to the cylinder wall.
By doing this repair early I am hoping the cylinder wall is still in decent shape, so I only need to replace the one piston!
Also, I am an engineer and I just don’t like this sound! So here goes.
On Wednesday afternoon I had already driven the Jeep for about 15 minutes to warm up the engine, more importantly, the engine oil. Because it needs draining.
My special oil drain canister. Note how I have to put something underneath it, or the oil would splatter everywhere. It just shows how “high” this Jeep sits on its massive tyres. Very easy to crawl underneath it.
Taking off the cylinder head of this huge 4.0L 6-cylinder engine is supposed to be pretty straightforward.
I studied my workshop manuals, looked at some Youtube videos
The first thing is to make some room by removing the air intake filter and inlet pipe.
Next, you unclip the bracket with the three cables going across the valve cover to the throttle body.
You loosed the serpentine belt. Because both the hydraulic power steering pump and the AC compressor need to be loosed as well. A lot of this stuff is just loosened to the extent it can be moved out of the way.
The exhaust and inlet manifold need to be disconnected as well. Both share a common seal and bolts/nuts. Again, we are not removing it completely. So the injectors, wiring and fuel lines are just left on. We just need it moved a few centimetres so we have access to the cylinder head. Various other bits need to come off as well, such as the thermostat housing. Obviously, we had to drain the cooling system prior to disassembly too.
Peter busy spannering
With the valve cover removed
Undoing the rockers. This engine has an underhead camshaft. Which makes removing (and installing) the cylinder head a lot easier. No timing worries.
Very important; The rockers and the pushrods and other bits do wear. So it is important to ensure every bolt, rocker, and pushrods goes back into its original position. Hence this fancy system to track where everything came from.
We had been working for about 4 hours and were ready to undo the cylinder head bolts/nuts. Unfortunately, we hit a snag. These cylinder head bolts/nuts are of a very special size and shape. None of our metric or imperial tools would fit properly. We called around to all other spannering mates and nearby tool shops. Nobody had this particular socket. So I had to order it. Will take a couple of days. So we could not pull the head!
We decided to tackle two other small jobs on my Mini and Peter’s Jaguar.
I had noticed that the horn on my Mini wasn’t working well. It sounded pathetic.
So we removed the right-hand light unit. Just four bolts and unclip the electrical connector
That gave us access to the horn. took it out, cleaned all electrical connections and now it is fine again.
Peter’s Jaguar had an even smaller problem. His fuel cap has one of these little plastic cables attached, so it doesn’t drop on the ground. Somehow that cable had come loose. So I rummaged through some of my boxes with many different types of these fittings/clips. sure enough, I found one that fitted perfectly.
This Sunday Mrs. D and I are leaving for a short trip to the UK. Driving the Jaguar obviously. Our good friends Cees and Annelies are in the Netherlands as their B&B in France has closed for the winter.
So maybe Cees and I can take the cylinder head of this next Friday as I return from the UK. It is a two-man job, because this cylinder head weighs a tonne!
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