I've been waiting for some smart people to reply, but since that hasn't happened yet, I can share a few tidbits.
It's ok to check the brake fluid level, but never add any. This is one place where customers mistakenly accuse professionals of doing poor work. During a routine service, such as an oil change, it is customary to top off washer fluid, engine coolant, and power steering fluid, but not brake fluid. If the brake fluid is low, where did it go?
There are only two possibilities for low brake fluid. It leaked out or the front brake pads are worn. If there is a leak, it must be addressed immediately before stopping power is reduced or lost. Usually leaks are accompanied by a low or slowly sinking brake pedal although some leaks won't always be noticed or obvious. Most cars today have an extra "low fluid level" switch that will turn on the red warning light on the dash. That's the time to add fluid, but suspect a leak. If it happens again, there is a leak.
When disc brake pads wear, the pistons move out of the calipers to take up the slack. That is how they stay in adjustment. Each front piston is about 3" in diameter and will move over half an inch throughout the life of the pads. The space behind them fills with brake fluid and will cause the level to drop in the master cylinder reservoir from "full" to "add", or more commonly from "max" to "min". "Min" is used now so it won't confuse people into thinking they have to add fluid. There is no problem caused to the braking system by adding fluid. As most mechanics know, however, the low fluid is a quick, fairly accurate indication the front brakes are worn and in need of inspection or replacement. When new, thicker pads are installed, the pistons must be forced back into the calipers to make room for them. All that fluid that was behind the pistons will go back up into the reservoir. If someone filled the reservoir previously, the fluid will spill out and run down the firewall. Besides making a big mess brake fluid eats paint.
After pushing the brake fluid back into the reservoir, many reputable mechanics will draw out as much of it as possible, then replace it with new fluid after all the other brake work is done. This is one of the many things do-it-yourselfers never do. Over time, brake fluid becomes dark. That is normal and is caused, in part, by being hot. It also absorbs moisture from the air. Moisture can seep in past lip seals, from leaving the reservoir cap off, and, believe it or not, through the porous rubber hoses. Moisture promotes corrosion of metal parts, and it lowers the boiling point of the fluid from well over 400 degrees to 212 degrees. When the fluid gets hot from normal braking, the water will boil and turn into vapor which can be compressed. That causes one form of brake fade and a mushy pedal.
So, ... Go ahead and check the level, but don't add any unless necessary due to other service work.
I don't mean to imply your son-in-law is a dummy, but the engine was stopped when he checked the oil level, right? I saw a fellow destroy a Volkswagen diesel engine within one mile of adding oil at a gas station. He checked it while the engine was running and pumping the oil around. He added six quarts to get it to "full" on the dipstick. It only holds five quarts! The overfull oil got whipped around by rotating engine parts that whipped air into it. That foamy oil worked its way into the engine which considered it fuel and air. The engine ran wide open until it died on the side of the street.
Don't think I'm promoting this but my Grand Caravan often gets so low on oil it won't touch the dipstick. That is only two quarts low. I will add oil, ... Eventually. I've learned it's no reason to panick. It lasted 378,000 miles, so I just wait until I get home to add some. I wouldn't have added oil as long as she was going to have it changed right away. It's good she's learning how to check the level, but no sense teaching her to panic unnecessarily.
As for the overheating, I doubt sticking his finger in there caused a problem. An air pocket behind the thermostat could prevent it from opening, but that happens after some other service necessitates its removal. Thermostats do not open in response to hot air; they must be hit with hot liquid. I would be more inclined to look for an inoperative radiator fan.
If I'm right, the engine will not overheat at highway speeds. The fan isn't needed then because of the high air flow. To verify it is operating properly, while the engine is running and still cold, unplug the coolant temperature sensor. There are two of them. The single-wire sensor is for the gauge on the dash. You want the two-wire sensor for the Engine Computer. When it is unplugged, the radiator fan will turn on and the Check Engine light will be on. If that happens, the fan circuit is working correctly. It will turn off a few seconds after the sensor is plugged back in.
If the fan is working, (even if it isn't), look for air bubbles blowing into the coolant overflow reservoir. That is a common sign of a leaking head gasket. That is usually accompanied by white smoke out the tail pipe.
Overheating due to broken impellers on the water pump are fairly common, ... On Volkswagens; not on Chrysler products. Cold air from the heater would be a clue. Unusually hot air from the heater is proof the coolant is circulating. If the thermostat is stuck closed, the radiator will feel cold when the engine overheats. The radiator hoses will be cooler than normal too, but some heat always migrates over from the engine so they could still be too hot to hold onto for very long.
Sunday, March 7th, 2010 AT 11:11 PM