: 94 Northstar question



Frosty
01-21-04, 02:16 PM
Hey guys...possibly working on a deal for a 94 STS.

I have a few questions. I know the northstar motor is a good motor but how long do they generally last? I'm looking at my friend STS with 84K miles on it...I can probably get it for around $7K. I know the car has been taken care of.

Any major problems to look out for? How are the trannies?

Thanks for the input :)

Anthony Cipriano
01-21-04, 03:11 PM
The Northstar engine and 4T80E transmission are very robust. The "soft spot" for a 94 was the fact that it was factory filled with the conventional, green silicated coolant that needed to be replaced every 2-3 years/24-32K miles to keep the corrosion inhibitors up to strength. If the coolant wasn't replaced frequently and the corrosion inhibitors became depleted (which they will with the all-aluminum engine) serious internal engine problems can develop later in life due to internal corrosion. The most common of which is cylinder head gaskets as the steel core of the gasket can start to rot from the coolant jackets outward and it will fail when the corrosion reaches the fire ring around the cylinder. This is the failure mode of most all the head gaskets you see mentioned on the early model 93/94/95 Northstars. The 96 had the DexCool coolant so that is not an issue as the coolant would retain it's corrosion protection even if the coolant was not changed and the system not maintained. The good news here is that the head gaskets can be replaced and the head bolt holes in the aluminum block timeserted easily if a repair becomes necessary.

Otherwise, the engine is capable of running several hundred thousand miles if it's maintained reasonably well. The lower ends are very robust and any problems in the lower end of the Northstar are almost non-existent. You might see people around here talking about how their 150,000+ mile Northstar still runs like new. They're not kidding.

Regarding the transmission, about the most chronic issue is the occasional high mileage failure of the transmission input speed sensor. That will set a code but not render the transmission undrivable. The bad news here is that the transmission typically has to come out of the car for the input speed sensor as it is buried under the side cover of the unit. The other transmission issue is an occasional high mileage shift solenoid replacement but those are relatively easy to replace as they are accessible in the bottom pan with the trans in the car. There is a service kit for the shift solenoids to replace them and upgrade the mounting bracket.

$7000 is top dollar for a 94 STS based on eBay and the local papers around New York. If it is a perfect car and has had the coolant system maintained over the years it may be a good buy but there are certainly much less expensive 94 STS's around. Certainly it's known heritage provides some extra value but I doubt that he is going to sell it for that on the open market even with "only" 84K on it.

Keep in mind that a 94 STS is a complicated luxury car. It is not the most inexpensive car to repair and maintain at higher mileage. Father time is active on gaskets and seals and wire connectors and modules and such even though the miles are relatively low. Keep this in mind when repairs come about and it's an excellent luxury automobile and should deliver many more miles.

Frosty
01-21-04, 04:22 PM
Wow, thanks for the info man!!!

Yeah it's top dollar for the car but its in VERY good condition...moonroof, the chrome rims..etc

Only thing it doesn't have is the heated seats.

Now for an interior question, which I'll post later :)

Any more info is much appreciated

thanks again!!!

lido
01-24-04, 07:55 PM
Mr. Cipriano,
First of all thank you for being here in this forum,you help me several times on my 94 sts problems ie, hard starting(PFR) and intake cabon builup ect..You were at the GM forum last year.The coolant issue on older northstar, I was wondering if I should change to dexcool or stay with my current coolant?I replaced my water pump 3 months ago and the Impeller which is made up of steel rather than alluminium is hardly corroded its only the bearing seal that failed.My sts only have 64k miles on it and I drain and replenish the cooling system once a year with 50/50 coolant.

Frosty
01-25-04, 11:32 AM
Also, with that kind of mileage anything specific that I might want to watch out for that should be replaced?

Should I convert to Dex-cool? I know it's in a PITA but is it worth it?

Anthony Cipriano
01-26-04, 01:36 PM
Mr. Cipriano,
First of all thank you for being here in this forum,you help me several times on my 94 sts problems ie, hard starting(PFR) and intake cabon builup ect..You were at the GM forum last year.The coolant issue on older northstar, I was wondering if I should change to dexcool or stay with my current coolant?I replaced my water pump 3 months ago and the Impeller which is made up of steel rather than alluminium is hardly corroded its only the bearing seal that failed.My sts only have 64k miles on it and I drain and replenish the cooling system once a year with 50/50 coolant.
I'm glad the information provided was helpful.

There is no advantage to switching to the DexCool coolant in the older Northstar engines. Once the engine is run on the green, conventional silicated coolant the inside of the engine is plated with silicates and the long life feature of the DexCool is eliminated. With the long life feature of the DexCool gone there is no advantage in having it in the system. Both the DexCool and the green conventional coolant cool the engine the same and both adequately protect against corrosion. So, there's no reason to switch and nothing to be gained with the DexCool.

If your water pump rotor was corroded then sometime in the past the system was run without service to the point that the corrosion inhibitors in the coolant were depleted and that allowed the rotor or impeller to rust. That's the only way that could happen. As long as the greeen silicated coolant is replaced frequently as you describe there is no way anything in the cooling system will corrode.

lido
01-26-04, 08:13 PM
I Think you read me wrong I said the Impeller has no corrosion.So I will continiu to use the Green stuff so long that I use the 50/50 and take your advice not to flush it with a garden hose.I just drain as much as it will drain from removing the radiator hose so It wont have 100% water left in the system to ofset the 50/50 coolant to H2O ratio.I do this once a year regardless of the mileges.

Aurora By Olds
01-27-04, 11:58 PM
Remember to refill with distilled water.
For the price, its worth every penny.

Anthony Cipriano
01-28-04, 03:12 PM
I Think you read me wrong I said the Impeller has no corrosion.So I will continiu to use the Green stuff so long that I use the 50/50 and take your advice not to flush it with a garden hose.I just drain as much as it will drain from removing the radiator hose so It wont have 100% water left in the system to ofset the 50/50 coolant to H2O ratio.I do this once a year regardless of the mileges.
You're right. I reread your post and I realize I misread "hardly corroded" as "badly corroded". Definitely keep using the green stuff and refresh it at least every 2 years for maximum portection. The green silicated coolant provides excellent corrosion protection (as evidenced by your experience now that I understand it) but it does need to be replenished occasionally.

Frosty
02-05-04, 12:20 AM
Any other problems I should be aware of with around 80-90K miles on the motor? Timing chain/belt? Water pump,alternator etc...

Thank :)

Anthony Cipriano
02-05-04, 01:44 AM
Any other problems I should be aware of with around 80-90K miles on the motor? Timing chain/belt? Water pump,alternator etc...

Thank :)
Nothing chronic, really... The Northstar has chains driving the cams and they are good for several hundred thousand miles so that is not any sort of issue at all.