Engine Failure bad luck

What really happen when something in the engine fails?

When your engine starts to make a bad noise

Engine failure/damage can be caused by many things such as:

• Maintenance or the lack of.
• Engine used beyond limits
• Abuse
• Poor design or construction
• Just bad luck

In the picture the customer had a great running one owner truck that had about 120,000 miles with no issues. No knocking, burning oil, or really any major leaks. And, one day it just started knocking like someone turned on a switch. In his case it was probably due to bad luck. 

     The crankshaft had a fracture that grew over the 120,000 miles and finally became large enough to break the crankshaft just rear of the first rod journal. The break was at an angle and acted like a wedge between the #1 and #2 main journals. Being that the #1 journal is on the end of the block and the weakest it lost the battle. This allowed the crankshaft to expand and break off the 1st main cap. Amazingly enough the engine still ran it just had a pretty heavy knock. 

     The original cause ultimately could have been poor construction, but the fact that the engine lasted for so long without any signs of problems just files this one under "Bad Luck". 

P.S. we did get him back on the road with a rebuilt long block. 

Cross hatch in a cylinder.

In engines with a traditional cast iron, aluminum block - iron sleeve, or CGI (compacted graphite iron) block there is a required surface on the cylinders.
Cross hatching is the series of intersecting scratches on the surface of the cylinder that are used to help the piston rings seal the compression/combustion pressures in the chamber above the piston. While they are scratches they are very controlled in depth/width and angle.

Depth/Width: can range 10 to 35 micro-inches (.000010"-.000035") This needs to be deep to be able to retain oil so the piston rings have a surface of oil for sealing and lubrication. The pistons rings do not actually touch the metal of the cylinders it rides on a thin film of oil  that supplied by the cross hatching. The width is usually a function of the depth the deeper the scratch the wider it is.

Angle: The angle of the crosshatching is also controlled and will vary depending on the application. Most engines are honed with a 45-40 degree angle. This angle is required for oil propagation up the cylinder walls. Oil is thrown onto the cylinder walls from windage in the pan and mostly from the connecting rod bearing leakage of that cylinder. But, that oil is not directly supplied to the upper part of the cylinder which is on the other side of the piston. The groves allow a zig-zag route for the oil to be scrapped up the cylinder wall. Kind of like using a squeegee across a tiled surface the water just travels through the gaps in the tile and never gets totally removed. 

One of the biggest misconceptions about cross hatching is related to purchasing a used engine.  Too many times someone buys an engine block or engine assuming that the cross hatching that they see is an indication of "No wear" this is absolutely not true. Cylinders can massive amounts of ring wear and still have what looks like cross hatching. The best way to measure for cylinder wear is with a dial bore gauge and actually gauge the cylinder in at least 4 locations. Two measurements 90 degrees offset at the top and bottom. Use the largest amount for the actual bore diameter.

If you ever need help in measuring and you're in our area don't hesitate to call on us.
North Texas Speed & Machine your OEM and Performance engine rebuilder.  (972)221-8811

What if your engine is making a noise...

Engine noises can be some of the hardest things to diagnose. And, some of the reasons they are hard to pinpoint is because of vehicle and engine construction. With engines being efficiently built around it doesn't leave a lot of room to access the outside of the cylinder block, cylinder head, front end, or even the oil pan. If access to engine components is hard you are relegated to using some rules of engine noises and diagnostic tools.

1. light knocking when an engine is cold that stops once the engine get up to temperature may be piston to cylinder wall excessive clearance. 
2. light knocking toward the top of the block that stops when fuel or ignition is removed from a particular cylinder may be connecting rod bearing failure.
3. a double knock that may lessen when the engine rpm is allowed to lower from high rpm. 
4. heavy knock from lower end of block all of the time may be main bearing failure.
5. light ticking noise from top of engine may be excessive valve lash.   
6. rattling noise from front of engine may be timing chain preload.  

The diagnostic tools:

1. Scan tool. Always check for DTC's (diagnostic trouble codes) because they may help locate a particular cylinder. And, in some situations they can help identify low oil pressure. 
2. Manual oil pressure gauge. Most times these are not the easiest to install they are the best way to interpret engine oil clearance conditions. If the oil pressure is lower than specifications or is oscillating wildly you may have an main bearing, rod bearing, or oil pump concern. 
3. Engine vacuum gauge. Cheap, easy, and easy to interpret. They usually come with a "text book" diagnosis that most times can diagnose piston ring, valve sealing, and valve timing issues. 
4. Compression gauge another quick way to check engine condition. 

Not all of the tools listed above will be useful by themselves, but when used all together they help you to figure out what is needed to fix your dilema.

      Then there are times engine noises might be characteristic to a particular engine. If you suspect your noise to be characteristic the best diagnosis may be a side-by-side comparison. Find a similar vehicle with the same engine and transmission an just listen during the conditions in which your's occur.

If you ever need help diagnosing and your are in our area don't hesitate to call on us.
North Texas Speed & Machine your OEM and performance engine rebuilder. (972)221-8811