New Car

tblake · #1 05-16-2007, 10:58 AM

Hi everyone. Im considering buying a grand prix gtp with the supercharged 3.8 motor in it. I am familiar with what problems to look for with a 3.1, but not so much with a 3.8. Can anyone give me any advice to use on a text drive before i buy one? Thanks!!!

GTP Dad · #2 05-16-2007, 02:21 PM

There may be a few items to check. First, check for supercharger rattle especially at idle. It can indicate that the coupler is bad and needs to be replaced. Another issue will be the performance of the supercharger itself, check for full boost under hard acceleration. If it fails to reach full boost you may have a problem. Transmission problems can be an issue on these cars. Check for maintenance records on the tranny as well as oil change intervals.

Finally, check the usual stuff, brakes, condition of the exterior and interior, exhaust. Find out if the car is stock or modified. A heavily modified car can cause some issues especially if it has been raced.

And don't forget the Carfax report. Spend the money to make sure you get a clear title and that it has not been wrecked.

tblake · #3 05-17-2007, 10:24 AM

yeah, great. That kind of stuff is exactly what i am looking for. You say a rattling at idle indicates a coupler is bad? I am totally not familiar with superchargers. If the coupler is bad, does that mean that the whole super charger needs replacing, is it a very labor intensive job?

GTP Dad · #4 05-18-2007, 11:56 AM

No! The coupler can be changed with just a few hand tools and a couple bottles of supercharger oil. The coupler attaches the nose drive to the rotors and the holes wear and become egg shaped. When this happens you will hear a rattle especially at idle. Kind of sounds like rocks a box. The coupler costs about $40 and two bottles of oil are around $20. About an hour of labor and you are back in business. One thing though is that you can't purchase the coupler from GM. You can get it from zzperformance.com however along with the oil.

BNaylor · #5 05-18-2007, 01:31 PM

We have tech procedures to replace the coupler and do a complete snout rebuild which includes bearings and seal with pics at our Tips & Maintenance subforum.

See links below.

M90 Coupler Replacement

M90 Snout Rebuild

richtazz · #6 05-18-2007, 03:51 PM

hey Tblake, you'd be a welcome addition to our GP forums. You're an asset to the Lumina Forums, and I'm sure you would become the same over here. What year is the GTP you're looking at? Different years have a few different issues. The other two guys answering this thread (GTP Dad and bnaylor) are very knowledgeable on the GTP (and this forum's moderators). I doubt there's much if anything that they couldn't help you with, including the best value per dollar mods if you decide to do so.

GaryFenza · #7 05-18-2007, 04:24 PM

good luck, im stuck with the 3.1 2001 V6 Grand Prix, o well, still a Grand prix!

tblake · #8 05-19-2007, 12:23 AM

hey, thanks for the compliments Rich!!!!! The one i am currently looking at is a 2000 (i know, I own a 2001 right now), a 2000 grand prix gtp. It has everything... leather, HUD, moon roof. Its just perfect. It has 75,000 miles, and the dealership is asking $8500 for it. I really like it. its maroon metallic in color, tinted windows, and a grandpa traded it in to buy a new impala. It seems quite snappy, and the transmission shifts smooth. I will have to check over the supercharger rattle though, but i think even if the coupler is bad, from the tutorials i've read, i think i will buy it anyways. What do you guys think? Decent price? Yes No? the first thing i will have to do is put brakes in it though. I think the rotors are warped. I took it for a drive on the freeway, and put it to the wood, and back down. Was smooth all the way up to 80, but with the brakes applied at that speed, the car seemd to shake quite a bit. It had been sitting at the dealership for a while, so maybe they were just rusty. Let me know what you guys think. Like i said. From working on the 3100sfi i know that motor like the back of my hand. The 3.8 is totally new to me aside from changing oil and plugs and wires and things, so any little tid-bit of information would be greatly appreciated.

tblake · #9 05-19-2007, 12:26 AM

oh yeah, and as far as mods go, I would probably keep it bone stock untill I get it paid off completly. I really cant afford much beyond a car parment and insurance on it.

richtazz · #10 05-19-2007, 05:35 AM

I would agree on you with the brakes pulsating, it may just be from sitting. When you replace the brakes, go with ceramic pads. I have them on my 99 GT and love them. No black dust, no squealing, and good stopping power. $8500 for that mileage isn't a bad deal if it's clean. I can't say from personal experience because I've never done one, but the S/C coupler has been done by a lot of people with success, and I know you have the mechanical ability to do it no problem.

jeepgclwj · #11 05-19-2007, 09:11 AM

Sounds like a pretty nice car. I paid 7 grand for my 98 with 76k on it back in early november. I would have probably spent another 1500 on a 2000 if I had found one with low enough miles in good shape.

Once you get you GTP you will be pleasently surprised at how good of a car it is. I had a few problems with mine when I bought it but after taking care of those things it runs very good.

Good luck

tblake · #12 05-19-2007, 09:42 AM

Thanks guys, you are of great help. I was hoping on going back down to look at it this morning, but i have to work at 12 noon, and being an hour away I dont think there is enough time without pushing it. The dealership will be closed when i get off, so maybe i'll have to head down maybe monday morning. Maybe in the meantime i will keep on searching the net for one i want. I really like this one though, great color and has everything. I have never driven such a nice car.

tblake · #13 05-19-2007, 09:50 AM

Rich, thats again for the great comments. Your giving me a big head, ha ha. But yeah. funny story there with the brakes. It was during rush hour. During the first test drive, i took a little trip on the interstate. When i got on, i hit the gas, got up to 80, and then ahead a little I got off. On the off ramp, it shook quite a bit when i used the brakes. So i turned around, and took the freeway back to the dealership. I got on and hit the gas quite hard again. Then the jeep about 2 car lenghts ahead of me didnt see the car in front of him was a dead stop, and slammed on his brakes. That started a chain reaction, and i gave the ABS a good test. Ha Ha. Got stopped with plenty of time, but the car went straight and didnt seem to shake much aside from the growling of the ABS. So the rust on the rotors may have just needed to be cleared off.

tblake · #14 05-22-2007, 12:50 AM

Before i buy into this supercharger thing, can anyone tell me if the coupler can be replaced with the SC still on the car, or does it need to come off? Also, if something should happen to the supercharger, am i able the put just a regular 3.8 manifold on it to save money? I've never owned a Supercharged vehicle, and never have worked on one aside from replacing the ignition cylinder in a buick. Thanks a ton for the insight!!!!!

tblake · #15 05-24-2007, 12:37 AM

Hey guys, i just put some money down on a gtp. the one i was looking at. Seems like its real nice. They only will give me 2000 for the old lumina, but i guess i got my money's worth. Gotta sort out the insurance and get the titles all sorted around, and hopefully go and get it saturday morning!!!!!

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