1991 Grand Prix SE - 3.1 questions

Good morning guys and gals from the not so sunny city of Edmonton :)


I want to scream "Houston, we have a problem" but somehow I don't think that NASA would help me with something as paltry as fixing a car... so here I am and here comes my series of problems... oh yes, like we havent a clue that this make and model isn't plagued with problems :screwy: :lol:

So it goes kinda like this... we have owned this car for alomost 2 years now... when we purchased it it had a new engine installed and it ran wonderfully for the longest time, but as of late it has been giving us nothing but headaches...

first the alternator went... that was ok, we were expecting it, the fact that it lasted as long as it did surprised us... we replaced it but things are still funky

the battery loses charge without cause... we have checked that all the lights are off and nothing is draining it as best as we can tell... all the connectors are clean and not corroded and it is a new battery (less than 6 months old)... there is a CD player in it and a rather large sub in the trunk... could this be causing a drain even tho its not on most of the time?

then last night on the way home (my husband works in another City about 45 minutes away) the thermostat went out... fine he replaced that as well... and the car seemed to be working properly... this morning on the drive back out to work, the car over heated and the heater still wasnt working... our friend who sold us the car and is a mechanic suggested that the was an air bubble in the cooling system... could this be the case?

Any thoughts here would be fantastic as I am in total and complete love with this car and would hate to see it go the way of the wrecking yard.

Welcome to AF!!

It is very possible that you have air in the cooling system that may be causing your overheating issue. Remove the radiator cap and start the car with the heater on high. Run the car and watch for the water in the radiator to drop. Refill and repeat. This will get the air out of the system and decrease the overheating problem. As for the subs, they can drain a battery even if you only us them occassionally. Put a 1.0 farad capacitor in the line and the problem should go away. Otherwise check the drain from the battery with a digital volt meter. While checking with the meter pull the fuses one at a time. If the draw on the battery drops you have found the problem. This is a long drawn out process and will take you some time but should solve the issue.

a parasitic drain of 20 to 30 mA on a battery is normal. This load is what retains radio presets and such. Any more than 30mA is getting on the higher side. I would almost suspect that your largh amp power wire might be chafing to ground somewhere. Might just unhook the power once and see if the problems are fixed.

If you didn't bleed the air out of the cooling system after changing the t-stat, you do have air trapped in the cooling system. These cars are notorious for air pockets causing no heat/ overheating. Search the forums for the proceedure, if you can't find it, I'll see if I can and post you a link.

morning guys :) thank you all for your input... so far we are a little further along that we were, but still not quite there yet... so I wanted to give you a little update...

Replaced water pump Sunday -- it seized at some point during the week last week

Took out new thermostat -- was apparently hooped (thanks NAPA), but once it was out car was blowing heat

Blew out the lines and everything appeared to be fine last night... gauges were reading 50 C and was geting decent heat in the car

However, we are still missing something because the car overheated this morning again on the way to work and the rad was empty again... *sighs* so now we are back to the drawing board... *EDIT to add* my husband just told me in an email that the overheat began about 1/2 way to where he was headed and the temperature dropped a couple of times but then shot straight up again

Any additional thoughts would be appreciated here because we are at a loss.

....However, we are still missing something because the car overheated this morning again on the way to work and the rad was empty again...

Last time that happened to me, I had a 95 Grand Prix.

All I had to do was pull the dipstick out, and I found out were all my radiator fluid was going. I hope this doesn’t turn out to be your problem. This is a well documented prob.

Or some radiator fluid loss is caused by pin hole leaks in the hose, and they don't leak fluid unless under pressure. :2cents:

Typical symptoms of air in the system are sudden rises and drops in the temp guage, bubbling over coolant from the overflow reservoir, and loss of heat. It can be quite tedious and difficult to bleed the air from these cars, so it's possible you still have air trapped. When the sensor for the guage is no longer immersed in coolant, it will shoot all the way to hot, then as the air pocket moves, it will drop back down.

As for the subs, they can drain a battery even if you only us them occassionally. Put a 1.0 farad capacitor in the line and the problem should go away.

I know this is old, and a little off topic, but if anyone searches and finds this I would like them to have the correct information...

1) Subs have nothing to do with draining a battery. It depends on what amp is being used to power the sub. If you have a sub (or subs) and a 100w (rms) amp you could listen all day at full volume and never even tickle the alternator or battery. It would consume much less current than the car's headlights.
200w, 300, even 500w amplifiers are rarely a problem for the typical electrical system.
Why? Music is not a constant demand. It's a wave with a few high demand points and a whole lot more low demand points. Even though an amplifier MAY be capable of producing 500w -- there is no music that will draw more than 200w average through that amp, even at full power. That explains why it takes a LOT of "music power" to strain the average battery and alternator.
(for what it's worth - I have an 1100w rms soundsystem, a 110A alternator and a 7 year old walmart battery and my electrical system works perfectly)

2) If you ARE in the rare situation where it's been determined your soundsystem IS draining your battery - a power capacitor is NOT the answer. In effect, a capacitor is just a small, fast-acting battery, and just as any other storage device it has to be charged. It makes no sense what-so-ever to add another storage device (capacitor) to an electrical system whose source (the alternator) is incapable of charging the PRIMARY storage device (the battery).

Don't mean to rant, just wanted to get the correct info out there.

As far as what COULD be draining the battery...
There is a remote turn on circuit in the amp. It is generally connected to the head unit's remote turn on wire which turns the amp on when the hu is on and off when it's off. Sometimes, by mistake, the amp's remote turn on gets connected to a constant power source which can cause the amp to remain on at all times. Without playing music it doesn't draw a LOT of current, but it's enough to drain a battery if it sits for several hours.