Explaining Intermittent Problem Diagnosis

Repairing Intermittent Problems

When a vehicle has a problem that occurs unpredictably it is called in intermittent problem. An intermittent problem may not occur while operating the system or even during a test drive. This presents a diagnostic problem of a very difficult nature.

Fortunately, you have chosen a repair shop equipped with the latest repair information, technical service bulletins, and recall information. If your vehicle has a system or component with an inherent safety, emissions, or reliability problem and here is a factory fix available for it, we will be able to make you aware of it and repair the problem for you.

Regardless of the type of problem or the system at fault, certain aspects of diagnosis remain the same. You see, in order to accurately diagnose the cause of any problem the technician needs the problem to (predictably) occur twice. This is because a first observation provides the technician with some insight needed to plan a focused testing strategy. A focused testing strategy saves diagnostic time and dollars. The problem must occur a second time, while the technician has his test equipment hooked-up monitoring the system or components that may be involved. Although the technician is prepared to attempt to recreate whatever operating conditions are necessary to make the problem occur, if the problem does not surface, a focused strategy cannot be planned.

This means testing all systems with the ability to cause the symptom until a defect is found. This all-inclusive systematic method takes more time and dollars, and there is no guarantee that the correction of a defect discovered this way will resolve the problem.

This is because there is no proof of a defect discovered during this systematic testing is the real cause of the problem. Another strategy to fix in intermittent problem is to perform a repair based on an educated guess of what is causing the problem. This can be risky because, in most cases, the part cannot be returned and the labor for the installation is non-refundable. However, when the symptom cannot be observed or testing does not disclose the defect, it can be the only choice left.

Diagnosing intermittent problems can be very time consuming and requires your patience and cooperation for us to be successful fixing the problem. It may require more diagnostic time then originally estimated to recreate or find the cause of the symptom. It may be necessary to leave the vehicle for several days, or return several times, so we may observe the symptom or judge the results of diagnosis and/or repair to insure the problem is corrected.

The service writer will give you an initial estimate for diagnosis. This estimate is an educated guess of how long it may take to discover the cause of your problem. This initial estimate does not guarantee a discovery of the cause of the symptom or include the cost of repair. The repair cannot be estimated until after the diagnosis is completed. During the course of this diagnosis we will keep you informed of our progress. If additional diagnostic time is required to discover the cause of the problem, we will ask for your authorization of the cost before proceeding. After diagnosis we will ask for your authorization of the repair cost before proceeding.

Now that you are aware of some things that can come up when trying to fix an intermittent problem, it is time to talk to the service writer about the specifics of your situation.

What can make an engine overheat

Overheating is a caused by anything that leads to a loss of coolant, prevents the cooling system from getting rid of heat, or causes excess heat in the engine itself:
Coolant leaks (water pump, radiator, heater core, hoses, freeze plugs, head gasket, engine internal).
Weak radiator cap (does not hold rated pressure and allows coolant to boil over). Pressure test the cap to check it out.
Cooling system clogged (deposits built up in radiator or in engine due to maintenance neglect or use of hard water). Use a cleaner, then reverse flush the system to clean it out. A badly clogged radiator may need to be rodded out or replaced.
Thermostat stuck shut (replace).
Slipping fan belt (tighten or replace).
Inoperative electric cooling fan (check fan motor, relay and temperature switch for correct operation).
Bad fan clutch (replace if slipping, leaking or loose).
Missing fan shroud (reduces cooling efficiency of fan).

Too low or too high a concentration of antifreeze (should be 50/50 for best cooling).
Bad water pump (impeller eroded or loose – replace pump).
Collapsed radiator hose (check lower hose).
Debris in the radiator (remove bugs and dirt).
Late ignition timing (reset to specs).
Restricted exhaust system (check intake vacuum readings and inspect converter, muffler and pipes).
Radiator and/or fan undersized for application (increase cooling power by installing larger radiator and/or auxiliary cooling fan).
   



Periodically Replacing Brake Fluid

DOT 3 and DOT 4 brake fluid are glycol based and absorb moisture over time. Moisture contamination causes the fluid boiling point to drop (which could lead to fluid boil and brake fade during hard use).

Moisture contamination also contributes to internal corrosion in the calipers, wheel cylinders, and steel brake lines. The reason for replacing fluid periodically is to get rid of contaminated fluid and restore fluid heat and corrosion resistance.

Moisture seeps in through microscopic pores in rubber seals and hoses. It also enters every time someone opens the master cylinder reservoir to check the fluid. Most fluid reservoirs are transparent so level can be checked without having to open the lid.

Brake fluid is so hygroscopic (attracts water) that leaving the lid off a can of fresh brake fluid can ruin it overnight. It will absorb so much moisture from the air that it becomes too badly contaminated to use.

How often should the fluid be replaced? By the time a new car is only 12 months old, its brake fluid contains about 2% water. After 18 months, the water content is approaching 3%, which is enough to lower the boiling temperature by 25%. After several years of service, it is not unusual to find brake fluid containing seven to eight percent water. For this reason, many experts recommend replacing the fluid as a preventative maintenance service very two years or 24,000 miles. At the very least, it should be replaced when brakes are relined.


Why should ball joints and tie rod end be changed in pairs?

It is not absolutely necessary, but many professional installers insist on replacing both even if only one is bad. This is because both have more or less the same mileage and sooner or later the other one is going to fail too.

In many instances, the companion part on the opposite side is marginal, so it makes sense to replace both ball joints (uppers and/or lowers) or both tie rod ends (inner and/or outer) at the same time. It also saves the customer the inconvenience of having to bring his vehicle in a second time.

There is some evidence to suggest that suspension and steering components on the right side of a vehicle have a somewhat higher rate of failure than those on the left side. The right side takes more punishment when it comes to close encounters with curbs, potholes and other obstacles, and the typical vehicle makes more right hand turns than left hand turns.

Even though all suspension components have the same mileage, those on the right side often need to be replaced at a lower mileage than those on the left.

It is important to check tie rod ends when doing any type of suspension work.

Some components also wear faster than others. Loaded ball joints (those that bear the brunt of the vehicle’s weight) wear out faster than unloaded ball joints. Loaded ball joints are the lower ones on the vehicle where the spring rests on the lower ones on vehicles where the spring rests on the lower control arm, and the upper joints on vehicles where the spring rests atop the upper control arm. The lower ball joints on FWD cards are unloaded.

Outer tie rod ends also tend to wear out faster than inner tie rod ends because the outer ones experience more deflection and are more exposed to road splash, salt and dirt. Inner tie rod sockets on a vehicle with rack and pinion steering are protected by bellows, so the rate of replacement for the inner sockets is only a fraction of that for the outer tie rod ends.