So what are the things I do to a used vehicle when purchased. It is basically fluids, filters, and depending on mileage spark plugs and wires as well.
- Engine oil and filter service - First thing is first check the oil level, it should be in the normal fill range, if not the engine might have an excessive leak or be burning oil. Then check to see that it is in the normal range of color (light clean tan to darker brown indicating it is time for a change) if it is really black they may not have changed the oil as regularly as they should have. If it is milky then there is either a head gasket leak that is causing coolant to leak into the oil or there is a plugged PCV valve/system. If you have milky oil hope it is just a plugged PCV valve otherwise return the vehicle if they didn't tell you it had a bad head gasket or valley pan gasket (not all vehicles have a valley pan). At this point I have all the info I can gather from the oil so I just do my normal oil and filter service even if the oil is reasonably fresh. This enables me to know exactly when the oil was changed and if there were any deposits you just flushed them out.
- Transmission fluid and filter if automatic - Most people neglect their transmission especially automatics. Here I check the level to ensure there isn't a leak and then change it. If it is an automatic you should change the filter as well and clean out the pan to remove any filings that are in there. Manual transmission don't have a filter but when changing fluids always open the fill plug before opening the drain plug (this is a common theme). You do this to ensure that you can refill the thing before you empty out all the fluid. If I can't get a plug out (I have only had this happen once) I am willing to make it someone else's problem as a fluid change isn't that expensive on a manual transmission or differentials. Once they crack it open it will be easy the next time you want to do it and you won't have to pay someone else to do it this time. Fresh fluid and filter will greatly extend the life of an automatic transmission.
- Coolant - Here I check the level and also check to see if there is any oil in it. Once done I drain it and fill it back up with a 50/50 mix of distilled water and antifreeze. If you have oil in your coolant then you might have a blown head gasket or bad valley pan gasket. Use distilled water it doesn't have all the minerals that tap water has in it that can cause corrosion and lime scale build up and will extend the life of your cooling system.
- Transfer case fluid - check the level to ensure that it doesn't leak and then drain and refill. Again here always open the fill plug before opening the drain plug since you don't want to drain it and then not be able to refill it.
- Differential fluid - Again here check the level before draining and refilling to ensure that there isn't a leak. When changing it always remove the fill plug before removing the cover or drain plug to ensure you can actually refill it. Once the cover is off clean up the interior of the differential using paper towels to wipe out any material and remaining oil you can. You will need to scrape off any gasket material that may still be stuck to the differential or the cover. The nice thing is if they have been using different color RTV gasket material you can tell how many times it has been changed. It appears on my Jeep it has been done at least 2 times as there wasn't the factory paper gasket (this is all Jeep used) and there was some old orange RTV gasket material and newer gray RTV gasket material. Also you can check for excessive wear marks or scoring on the gears.
- Fuel filter - Who knows when this was last changed and they are cheep.
- Air filter - Even if it looks clean these are cheep and easy to do so might as well
- PCV valve - Again here it is cheep and really easy to change
- Spark plugs and wires - With 368,??? on the Jeep the $12 in plugs and $14 for wires seemed reasonable. This also gives you a great insight into what is going on inside the engine and how it is running if you want to read your spark plugs (not my site but this diagram is a common one and is correct). Also since this Jeep still has a distributor I also changed the cap and rotor as they looked to be the factory originals and I didn't want to get stuck for the $11 it cost for new ones. It is cheap insurance and you are already working in that area of the vehicle.
- Power steering fluid - This also seems to be a neglected fluid much like transmission fluid is. I always do a partial exchange when changing oil so might as well get some clean fresh fluid in there. Just use a fluid transfer pump to empty the reservoir and refill with clean fresh fluid. You probably only change out 1/3 to 1/2 of the fluid but do this a few times and you will be near all new fluid in your power steering system.
Additionally I give the vehicle a good once over checking all the belts and hoses to ensure that they aren't in need of replacing if you find one that needs replacing do it now not later, road side repairs suck and tows are expensive. Also at this point I will convert a vehicle to fully synthetic fluids for all their added benefits. Now that most things have been done and you know when they have been done you can just follow a regular maintenance schedule and hopefully have years of worry free operation.