8V cam Pt 2: follow-up

[belfastguzzi]

The 8V thread, Part 1, is 108 posts, so this is nearly there.

Let's keep things neat and orderly and finish this on 108 too.

Actually Part 1 was 108 replies, so it was 109 posts. It's now closed at 110.

[belfastguzzi]

 

Antonio, you aren't pulling your weight. 1 post!?

[belfastguzzi]

BMW rocker shafts break :!:

[belfastguzzi]

BMW cam followers wear too

[belfastguzzi]

Post 110

 

Time to move to 8V Cam Part 3

 

 

Sideways Postscript just for fun and education

Excerpt from Practical Boat Mechanics

 

– these paragraphs were all mixed up – I have rearranged them to make more sense, but it may not all be in proper order yet –

 

The initial teardown is meant to complete troubleshooting of the failure and to enable an accurate parts order list. The goal is to positively know what caused the failure by the time you make up your parts list. Make note of the engine hours early in the process, as this will affect your strategy: A low time engine can have a quick visual inspection of the oil pump. A high time engine, on the other hand will require the oil pump to be completely disassembled.

 

Make note of conditions that will point to extensive pressure testing of engine components such as the oil cooler, and other components. 

Is the engine paint burned or darker in some areas due to overheating of the engine or some part of the engine? 

 

If the head and upper engine are discolored, watch for signs of internal overheating damage. This damage will include things like cracked heads or a damaged cylinder block.

 

How does the exterior of the engine look?

 

Are aluminum pieces corroded and iron pieces rusted? If so, the engine may have been wet often or even submerged in water. Does the oil pan or even the cylinder block have a high water mark that indicates swamping?

 

Is the exterior of the engine dented, scuffed, or are there bent or broken parts on the exterior of the engine?

If so, it has had rough handling.

 

Are there streaks of leaking oil running down the side of the engine?

This indicates an oil leak.

 

Are there streaks of white mineral residue running down the side of the engine?

This indicates a coolant leak with poorly maintained coolant containing high levels of dissolved solids.

 

Are all locating dowels present on the front and rear cover and on the top of block?

Note: locating dowels protrude upward from the cylinder block and they are what aligns the head gasket and the head to the cylinder block.

 

Are the fasteners you are removing all similar and of the type the manufacturer used when the engine was new? Or does the engine have a mixture of some factory and some aftermarket fasteners?

To tell the difference, just look at the markings on the bolt heads. These are more clues to help you learn if the engine has been previously repaired, and if the job was done well. Do not take the engine apart into separate pieces, just in case someone else must put it back together. Parts to keep whole during your teardown are the fuel injection pump, timing advance unit, and the turbocharger.

 

When the oil pan drain plug is loosened, what appears first, water or oil?

If water shows first, then there is water (or coolant) in the oil pan. As the disassembly progresses, it is vital to find the source of this water.

 

After cutting open a fuel filter, is it full of rust, algae, or even water?

These are signs of water in the fuel. Finding water in the fuel can turn what was supposed to be a quick “in-frame” overhaul into a more costly job because the injection pump and injectors will need to be replaced.

 

After cutting open the oil filter and inspecting the pleats of filter media for contamination, is aluminum present?

This is piston material.

 

Are there a lot of black soot particles?

This shows excessive piston ring blow-by, too much time between oil changes, or poor maintenance.

 

Before removing the water pump and alternator belts, did they allow slippage and are they glazed?

Are the belt pulleys badly worn? These are signs of belts slipping. If the engine overheated, it is possible it overheated because the coolant pump was not turning as fast as it should have.

 Collect and test the antifreeze for freezing protection and also do a pH test. Many drug stores sell pH tape for the testing of water-based fluids. The coolant must be slightly alkaline in pH to prevent galvanic corrosion from attacking dissimilar metals inside the engine. Inexpensive pH tape is available at most drug stores. Acidic coolant means the engine you are reconditioning may be going back into a boat where the cooling system needs cleaning and flushing. 

 

How does the valve cover gasket look? Is the gasket crushed from over-tightening of the cover bolts?

 

Over-tightening of these bolts, using excessive silicone sealer on a valve cover gasket, or using it instead of a gasket are all signs of a novice. Cat green (contact cement) or 3M weather-stripping adhesive on the valve cover side of the gasket are signs of a pro.

 

Do the engine’s gasketed surfaces show signs of someone having previously scraped an old gasket off during a previous rebuild?

If so, the engine has been rebuilt. If not, it may be that you are rebuilding the engine for the first time since it was new. Are the scraped surfaces gouged or scratched? If so, you are not the first to repair the engine.

 

Is the bottom wear surface on the rocker shaft excessively worn?

This will show the engine has a high amount of hours on it. If so, new rocker arms will need to be ordered.

Notice the valve setting before you remove the rocker arms, after checking them to see if they are loose or over-tight. This can tell you what state of tune the engine was in.

 

Loosen the valve adjustment lock nuts and back off the valve lash before removing the rocker arms. This will help you avoid bolting the rocker arms back onto the engine in a bind later. This is important because the cylinder head valves and seats will be cut during the rebuild, and the valve stems may protrude upward through the valve guides a little higher after the heads are done. Bolting the rocker arms back in with insufficient valve lash settings could cause a valve to hit a piston and bend as the crankshaft is being turned during the rebuilding process.

 

Note: Before removing the head bolts, be sure to remove the injectors, because the injectors sometimes take a little force to remove. Injectors are easier to remove while the heads are bolted securely to the engine. Injector tips also often protrude through the cylinder head and will be damaged if the head is set on a workbench, so remove the injectors to prevent injector tip damage.

 

Be sure to notice the level of head bolt tightness as the bolts are removed: Are they uniformly tight?

Any engine will have a certain number of head bolts under the valve cover, protected from the elements. These inside bolts will have no paint on their heads. There will also be a certain number of outside head bolts. However, these bolts will have painted (and possibly rusty too) heads from when the engine was painted.

As you disassemble the engine, make note if any painted bolt heads are found under the valve cover. Likewise, notice if any of the unpainted bolts were used as outside bolts. If any irregularity is found here, it will prove previous service work was done. It will also indicate that the work was unprofessional.

Head bolt threads must be lubricated during assembly, according to the manufacturer’s directions, which usually call for engine oil on the threads of the bolts and under the head of the bolt. Never-Sieze compound, also known as anti-seize compound, is a thick paste often containing minute flakes of graphite, copper, nickel, molybdenum, and grease. The compound works great, but it should not be used on bolts inside the valve cover or crankcase because the residue will contaminate any oil analysis sampling that is done on the engine.

As the head bolts are removed, smell the oil on the bolts. If the engine has been overheated, the oil will have a very strong burned smell.

 

Can you wiggle the valve stems much?

 

Can you see a mark on any of the pistons that will verify that contact was made?

Another important check for hollow tubular pushrods, like those used in older Cummins engines with PT fuel systems: Hold them up by one end and tap them gently with a hammer to make sure each rings with the same resonance. This indicates they are not filled with oil. When one has a different tone than the others, then it does have oil inside and must be replaced.

Inspect the head gasket surfaces on the head and block immediately after removing the head. Watch for discolored areas where coolant or compression may have been poorly contained.

A bent valve actuating pushrod tells you that a valve contacted a piston. When removing the pushrods, keep them in order. As the pushrods are removed, check to see if they can be rolled smoothly on a flat surface. If so, they are straight. If not, they are bent. Put a dial indicator on the stem and measure the movement. How does this amount of movement compare with the service manual specifications? If the guides are far out of specification, the engine, or at least the heads, will have a lot of running time. If not, they may not have been torqued properly, or one may have been missed during the tightening procedure. If you find one that was not tight, notice which cylinder it was near. Then, once the head is off, make note of any places the head gasket may have blown out. These places will show darkening or actual destruction of the head gasket.

 

Similarly, watch for a deep scratch or gouge under a critical area of the head gasket. Scratches will let fluids pass under gaskets, preventing them from holding pressure.

 

Watch for mismatched, wrong length, or various bolts of various strength ratings, and bolts with painted heads inside of the engine covers. This includes the flywheel housing, the timing gear cover, and the oil pan and the valve cover. Mismatched bolts are signs of poor or sloppy workmanship.

When inspecting the heads further, look for cracks between the exhaust valve (often the smaller diameter valve in each cylinder) and the injector hole. Cracks here prove overheating occurred.

 

Are there gouges on surfaces where gaskets have been scraped? Is the head straight and true according to a straightedge?

If not, it has been overheated.

 

Take the lid off of the injection pump (if it has one) and look for rust in the pump. If there is rust in the pump, the injectors and injector lines must be replaced.

 

is there any trace of red (rust) in the intake or exhaust ports of the head or the passages of the exhaust manifold?

If there is, this is a sign of water in the corresponding cylinder.

 

Looking into the exhaust ports of the head, are all of them flat black in color and tone?

This is good. It shows that the cylinders were in good shape and that each was probably doing its share of the work of keeping the crankshaft turning. On the other hand, are one or more of the exhaust ports a shiny wet-looking black color? If so, this indicates the possibility of weak cylinders, and especially cylinders that are low on compression and not completely burning the fuel

 

Do the exterior (out of the crankcase) bolts have Never-Sieze on them?

Good! This is a sign of craftsmanship. However, if interior bolts have Never-Sieze on them, this is not good, and is the sign of a novice at work. As mentioned above, Never-Sieze compound inside of the crankcase will cause faulty oil sample results. Never-Sieze compound will make an oil sample from a sound engine appear as though it is self-destructing.

 

After the cylinder head (or heads) is removed, it is time to check the tops of the pistons for evidence of contact between a valve and piston.

 

What is the condition of the main and rod bearings that are farthest from the oil pump?

If the engine runs low on oil, these will be damaged first. Are the oil pump gears scratched? They are supposed to be soft, so that hard particles will embed rather than lock the pump gears. Scratches, though, indicate contaminants in the lube oil system. This could explain damage of the crankshaft bearings even when there is no fuel in the oil.

Are the O-rings hard on the lube oil pump suction tube? Hard O-ring seals on the suction side of the lube oil pump will aerate the oil, as will faulty suction pipe gaskets and loose bolts on the pipe.

 

What is the condition of the water pump impeller? If it is missing a blade, the missing blade may be trapped in the cooling system. It also means the engine may have been running hot.

 

Is the crankshaft rear main bearing sloppy?

This indicates extreme crankshaft wear and poor maintenance.

 

 

BLE (Excerpt from Practical Boat Mechanics)