Dear Motor Medics,
I have a 2001 Jeep Grand Cherokee with a 4.0 six-cylinder engine that failed. This is the first time I have ever had to replace an engine in a vehicle and with only 80,000 miles and a faithful maintenance history I am shocked that it failed. They told me the camshaft failed because I was not using an engine oil additive and that if I did not use one on the new engine every time that the engine warranty coverage would be void. Why have I never heard of using an additive before? I thought they were not needed for everyday use. The place that changes my oil is not where I go for bigger repairs and I have not had to see them for several years.
Thank you, Scott in Dell Rapids, SD.

Dear Scott,
Seeing a Jeep engine with low mileage fail when oil additive has not been used is not a surprise to us. The lack of ZDDP in the engine oil was likely the cause. ZDDP was removed from engine oil around the time diesel fuel had most sulfur removed. ZDDP protects high pressure areas such as the flat tappets of the Jeep cam. All oil change facilities should be offering the additive to you as a choice. A yearly check-up at a full-service shop is also a good way to get good advice. They can often advise you of recent changes. Take care, the Motor Medics.

Dear Motor Medics,
I replaced the air conditioning compressor on my Dodge Caravan before the last winter and it worked great for the short time, I used it before winter and again this spring until the first really hot day. The system stopped working and started making a grinding noise just like before. The shop that fixed it installed a new drier and a new compressor and charged me for Freon and labor. Did they miss something, or did I get a bad part?
Thank you, Jennifer in Missouri.

Dear Jennifer,
It worries me when you say the system is grinding again. By the list of replaced parts you gave it is possible that the failure could be due to the way it was repaired. Not to doubt the install but when a compressor grinds it is usually coming apart internally and leaving metal shavings in the system which will plug passages in the condenser and expansion devices. If there was metal found in the system, any parts contaminated must be replaced. Just flushing the parts is not an option because of the small passages that can’t be accessed. Partially plugged systems may work well on cooler days but will fail when high temps raise pressures. When the system is repaired this time ask about these parts and if they need to be replaced and why or why not. With the high cost a second opinion is not a bad idea either. You don’t want this to happen again.
Take care, the Motor Medics