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#13601 of 13621 2004 Chevrolet Impala LS 3.8L V6 - Coolant/Gas mileage Issues
Aug 06, 2009 (10:06 pm)
As in the title of the post, I have a 2004 3.8L V6 Chevy Impala LS with approximately 110,000 miles on it.
Recently, while my girlfriend and I were taking the car for a drive, the car overheated (luckily as we were pulling into a parking spot at home); I checked the coolant level in the reservoir and there was none in the reservoir. I proceeded to put coolant into the car as instructed in the owner's manual (e.g. opening the bleed valve, adding 50/50 dexcool to the radiator until full, turning the car on to cycle, adding more, etc., filling the reservoir, etc., closing the bleed valve (maybe closing the bleed valve before filing the reservoir, I can't remember, but I know I followed the instructions in the manual.)) Since then, the car hasn't had any issues with overheating and the fluid level seems to be remaining pretty constant (or there hasn't been enough of a loss in the reservoir for me to notice).
However, since I refilled the coolant, I've noticed a severe drop in fuel efficiency. For example, tonight I filled up and compared gallons to miles on my trip meter and realized that since the last fill up I was only getting about 10.5mpg when normally, even in the worst stop and go conditions, I would expect around 18-21mpg.
I'm not sure that the empty coolant system and the fuel efficiency issues are related, however, it seems likely that they are since they sprung up around the same time. I guess it could be coincidence, but again, I think that's unlikely.
I've checked the oil which doesn't seem to show any indication of coolant/oil mixing (e.g. milky white color) and appears otherwise normal.
The climate controls in the car seem to be operating normally (e.g. both the heat and air conditioning operate and seem to normally heat up and cool down, respectively) without appreciably effecting the temperature of the engine.
I haven't check the fuel or air filters as of yet, but they haven't been changed in over a year.
The car seems to run just fine, that is, there don't seem to be any issues behind the wheel like rough starting, rough or loud engine noises while driving, or anything like that; or at least, the car seems to be running alright to me.
I haven't noticed any white smoke coming from the exhaust pipe and when I was running my car after I refilled the coolant, I didn't notice any bubbling over of the coolant reservoir or any bubbles forming in the coolant reservoir. (I think these are symptoms of head gasket issues).
I haven't really checked anything else and don't have any more information about the state that the car's in at this point.
So, my questions are:
What would cause a slow (almost unobservable) coolant leak and a drop in fuel efficiency? Does it seem plausible that these issues are related?
Could these be unrelated issues that popped up at the same time by coincidence? What could be causing either of the problems if they are unrelated?
What other symptoms should I check for to report back about? Or is there any other information that would be necessary to give at least a semi-educated diagnosis of the problem?
That's all I have for now. Thanks.
#13602 of 13621 Re: 2004 Chevrolet Impala LS 3.8L V6 - Coolant/Gas mileage Issues [cliponties]
Aug 23, 2009 (7:16 pm)
Hello, I have a 2003 Chevy Impala with 112,000 miles on it that is exibiting similar issues. It overheated on me in the fast food drive through a couple of nights ago and the radiator was very low on coolant. These cars are notorious for having coolant leaks around the intake manifold and heater hose outlet from the engine. The Dex/Cool attacks the gasket material causing internal and external coolant leaks and degrades the plastic block fitting in the bypass hose to the heater core. The leaks can easily ruin an engine and while not that difficult to fix, involve a lot of labor and consequently can run into over a grand to repair at a dealer. There was a class action lawsuit against GM where you could recover a portion of the repair bill for the Dexcoolant issue, but it ended last year in October.
I am in the process of isolating where the leak is coming from. I checked the coolant with a block tester and there are no combustion gasses present. The oil looks normal, but I had it changed today because I was worried the high temperature reached when it overheated may have caused viscosity breakdown. I use Mobil 1 synthetic high milage. The engine runs fine as do heater and a/c. The oil change guy said it was leaking from the passenger side, which is where the water pump and heater hoses are.
GM must have known they were going to have problems, because most GM cars with the 3.8 liter engine have a computer program in the engine management system that disables half of the fuel injectors and turns them into reverse air pumps to cool the engine when total coolant loss occurs. Taken from a GM service bulletin: If an overheated engine condition exists and the
messages COOLANT OVER TEMPERATURE and
REDUCED ENGINE POWER are displayed, along with
the Check Engine light, an overheat protection mode
which alternates firing groups of cylinders helps prevent
engine damage. In this mode, you will notice a loss
in power and engine performance. This operating mode
allows your vehicle to be driven to a safe place in an
emergency; you may drive up to 50 miles (80 km).
Notice: After driving in the overheated engine
protection operating mode, to avoid engine damage,
allow the engine to cool before attempting any
repair. The engine oil will be severely degraded.
Repair the cause of coolant loss, change the oil and
reset the oil life system.
I am taking mine to a "GM Only" repair center this week to see if they can isolate the leak and get an estimate on the repair. I am very dissatisfied with our dealer's service department, as when the catalytic converter went out at 110,000 miles and cost us $2,200 in repairs, they were working right below the intake manifold and could have let us know that this was a potential trouble spot and recommended replacement of the intake gaskets at the same time. The convertor problem was a recall in earlier Impalas but is not covered anymore. No more GM cars for me! The poor milage condition could well be related, do you notice a fuel odor? A leaking intake gasket can play havock with the computerized fuel mixture controls.
#13603 of 13621 Re: 2004 Chevrolet Impala LS 3.8L V6 - Coolant/Gas mileage Issues [jergold]
Nov 26, 2009 (12:40 pm)
Did you ever find where the leak was coming from? I had a similar problem and the intake gaskets were replaced in Aug. 09. Everything was fine until last Sat. when the car over heated causing me to limp home in low power mode. The dealer could not find anything wrong except for being a little low on coolant. I have a feeling that my issues are not over yet. In addition, the heat will not get hot until the car is driven and then the temp is unbearable. The heater issue and over heating may or may not be related.
#13604 of 13621 Can transmission problems and water pump problems be related?
Jun 13, 2011 (9:14 am)
The water pump in my 2004 chevy impala started leaking and Tire Kingdom replaced it. they also talked me into a radiator flush. They recommened a transmission flush, which I refused. Because I had gotten one done the year before(which they did not know.) The same day car ran hot. I called them and they said that it probaby had an air bubble in it and that it would work itself out after running it for a while. If not I could bring it in. I called them the next day and told them still running hot. I informed them that I would bring it in after work the next day. On the way back from work it got hot again and the transmission started slipping on the way there. It was apx 20 miles. The tow truck got there, we checked the transmission oil, which it had some. He also noticed it was hot and he said he wasn't sure what could have happend, but might have something to do with water pump. We took it back to Tire Kinddom and they looked at it. The next day they called me and said that my transmission had no oil in it and that the dip stick had burnt transmission oil on it and that it locked up. I asked them how from when tow truck guy checked to when it got there it could burn oil and lock up. The said it wasn't odd for it to burn overnight and lock up, if the car was that hot. They said that I should have done the transmission flush because they would have checked fluid levels and noticed themselves that it was low or didn't have any. After arguing with the manager he asked me to take my car if I wasn't happy with their service.
QUESTION: DOES WATER PUMP REPLACEMENT(RADIATOR FLUSH,) HAVE ANYTHING IN COMMON WITH TRANSMISSION PROBLEMS, OR IS THIS JUST BAD LUCK????
#13606 of 13621 2005 Chevrolet Impala Overheating/Head Gasket
Aug 27, 2011 (6:17 am)
We have the above model Impala giving us fits with overheating and looks like a blown head gasket. The more we read and look, the more the problems mulitply.
Car has 106,000 miles on it -- ran fine until the other day. Should we put it out of it's misery, or pursue repairs. Anyone have similar problems that have been solved?
#13607 of 13621 Re: 2005 Chevrolet Impala Overheating/Head Gasket [smartoldman]
Aug 29, 2011 (8:44 am)
If it is just a head gasket you can fix it yourself for a couple hundred dollars and about 2 days of labor. Most of the cost is for getting the heads pressure tested for cracks and resurfaced. The rest of the cost is for gaskets, oil and coolant. You may even be able to find someone who would do the work in their garage for you. Most repair shops and dealers will charge $1500-$2000 but a shadetree mechanic may do it for $500.
#13609 of 13621 Re: 2004 Chevrolet Impala LS 3.8L V6 - Coolant/Gas mileage Issues [it247365]
Jan 13, 2012 (7:30 am)
I'm curious to know as well. I have had to replace my water pump and radiator! My water pump showed signs of leakage and was suggested that it be replaced before it went out and my 2004 Impala Ls overheated on me along with a few small but annoying problems that add up. Oh and yes my check engine light is on.....fuel tank small leak! Smh. My car has over 100,000 miles on it well cared for and I will not be retuning to purchase a Chevy again-lease but never buying again. Sorry Gm.
#13610 of 13621 Re: Can transmission problems and water pump problems be related? [americaflorida]
Jan 13, 2012 (10:44 am)
An overheating / cooling system problem could impact your transmission, especially if parts in the transmission are made from aluminum. Aluminum heats up much faster than steel. If your car runs hot or overheats, then the transmission fluid will heat up and the transmission's components will heat up. This excessive heat will damage your transmission. If your car overheats, it is a safe practice to change your transmission fluid irrespective if you had changed it recently, prior to the overheat condition. I am unsure whether key transmission components are made from aluminum in GM's products. However, this may explain the problem that you had experienced. Good luck.