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Some automotive problems easier to solve than expected
On The Road AgainNovember 9, 2011 | 2,778 views | Post a comment
The other day, a customer brought his small truck in for a noisy lifter he wanted repaired. A lifter is actually part of the valve train. It is between the camshaft and the valve and may use a pushrod, rocker arm, and/or other hardware in order to work as well. The lifter may be mechanical or hydraulic, and sometimes they can be adjusted and sometimes not, depending on how the engine was manufactured.
A worn or weak lifter can cause a loose valve adjustment which would cause an audible “ticking” sound, which would increase and decrease with engine RPM exactly. The truck certainly sounded like it had a bad lifter, so we broke out the engine stethoscope to identify which lifter it was -- as every four-stroke engine that uses lifters has between two and four of them per cylinder -- it can sometimes be difficult to identify which one is loose or faulty.
The stethoscope could not pinpoint the sound in either the engine or the pulleys on the front of the engine. The sound seemed to bounce around and it was odd. Why couldn’t the scope pick up the noise? It had never happened like that before; the stethoscope always intensifies noises, and so this was peculiar.
I noticed that the belt tensioner was rocking back and forth which seemed strange as well, but the noise didn’t seem to follow the tensioner’s movement exactly. The best way to clear up the mystery was to remove the serpentine fan belt, and run the engine for a few seconds without it to see if the sound remained or not.
Once the belt was removed, I spotted a huge chunk missing out of it and knew immediately that the lifters were fine -- it was the belt going through the pulleys that was causing the noise. We cranked the engine without the belt installed to be certain, and, of course, it was as quiet as a church mouse. A new serpentine belt made the little truck sound like a sewing machine once again.
The customer was elated because he had gotten a good deal on the vehicle due to the suspected lifter, which can be considered a major repair on certain models. Having the noise turn out to be just a belt was good news. Removing the belt and running the engine is a great way to test for noise, if the noise persists when the belt is off, it can’t be a problem with accessory pulleys, as none of them are turning. And, of course, if it goes away when the belt is removed, the pulleys and belt become suspect.
Always be careful not to run the engine for very long without the serpentine belt in place. Oftentimes, the water pump and/or the engine cooling fan may not be turning while it is removed. That could cause the engine to overheat rather quickly. The exception would be those vehicles that utilize electric fans and timing belt driven water pumps.
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