Hi guys. I just stopped by to see if I could learn something, and I have a few observations. Mostly I was confused by the description of the symptoms. There seems to be at least two totally different things going on here.
First of all, when referring to "doesn't start", that can mean different things that have totally different causes and diagnostic steps. At issue is whether the starter spins, (cranks), the engine. If it does not, we have to look at the starter system or a seized engine.
The second "doesn't start" is when the starter cranks the engine normally and at normal speed, but the engine doesn't run. This is when we have to look at the things all engines need to run. That is fuel, spark, compression, and proper timing of those things.
The third observation is we have a list of symptoms that are occurring now, but we have the luxury of knowing the symptoms that occurred during the original failure. That is something we usually don't get when working with a mechanic who is working on a customer's car. Now we have to figure out which symptoms are related, and which may have been caused by improper or unrelated repair attempts.
If there was a puddle under the car, you either parked over someone else's previous puddle, or a fluid leaked from your car. For a dark fluid, engine oil and transmission fluid are the logical suspects. You found the oil level to be okay. That leaves transmission fluid. Was that checked? With the engine not running, that fluid should be quite over-full on the dip stick.
The next issue is you never fully described how the car slowed down. You said the car slowed down even though you pressed harder on the accelerator pedal. What happened to engine speed? Did it speed up too much or did it slow down? If engine speed increased while road speed went down, that is due to the transmission slipping, and that would correlate with loss of transmission fluid. If the car slowed down because engine speed slowed down, we have to look for an engine problem.
The first thing to do is shove someone underneath who is familiar with what is engine and what is transmission, and determine which one leaked fluid. The two can be hard to tell apart for anyone not familiar with cars. Be aware that cars with automatic transmissions have a fluid cooler up front, usually built into one side of the radiator, or it could be a separate cooler. The steel and rubber lines going to that cooler can develop a leak and cause engine speed to increase when the car slows down. The puddle will be close to just behind the front bumper. Repairing a leaking cooler line is a relatively minor repair. Trying to drive the car with low transmission fluid, however, will cause severe slippage in the transmission's clutch packs, and that can lead to the need for a total rebuild very quickly.
The place to start now if the engine doesn't crank is to suspect the battery is run dead. Use an inexpensive digital voltmeter to measure its voltage. If the battery is good and fully-charged, it will measure 12.6 volts. If it is good but fully-discharged, it will read close to 12.2 volts. If you find around 11 volts or less, it has a shorted cell and must be replaced. To add to the misery, by 2005, GM had added more unnecessary computer controls to complicate the starter system. In the past, a weak or discharged battery would cause slow cranking. With these computer controls, some computers will prevent the starter relay from engaging at all when battery voltage is just a little low. That injects a totally inappropriate symptom for the cause. For that reason, start by measuring the battery's voltage, and post your findings. If it is even a little low, connect a portable charger and charge the battery at a slow rate for an hour or two, then see if the starter will crank the engine.
The noise you heard can be caused by a broken connecting rod in the engine, and that can break a hole where the oil leaks out. We'll discount that for now based on your findings the oil level is okay. A loud noise from the transmission is much less common. A better suspect is the transmission's bottom pan hit something in the road that punched a hole in it. The fix for that is typically to replace the pan and refill the fluid. The damage should be obvious, and there will be fluid dripping from the hole for some time.
One more thing to consider is if a CV joint broke. The car will coast to a stop, probably with a clunking noise, but more importantly, transmission fluid will spill from where the inner CV joint slid out of the transmission. That spillage would be minor and it would not be the cause of the car slowing down. When one front half shaft becomes disengaged or broken, neither will rotate to drive the car. That's a simple matter of replacing the half shaft and replacing the one or two quarts of transmission fluid that spilled out.
Wednesday, October 7th, 2020 AT 10:20 AM
(Merged)
