anybody familiar with the oldsmobile aurora.

[dav-02ws6-m6]

The thing is that the other day my brother bought a 98 aurora( it has the 4.0 v8 north star engine.) The thing is over heating it seems like it has air on the cooling system. Also how can you tell when you have a blown head gasket?

[Smittro]

A blown head gasket usually shows up as a heavy coolant smelling fog from the exhaust, misfires, sometimes a high idle will be seen but not always.

If you do have an air pocket there maybe a purge valve in one of the coolant lines iirc.

This was how GM combated the dreaded air pocket in many of their FWD cars.

What's the mileage ever replaced the water pump?

Over heating those engines is bad as the heads and carriers can get out of wack (warped) and then you're looking @ a new set of heads.

Those are not cheap for the little DOHC v8..

[SMWS6TA]

In addition to above look in the coolant and see if it gives an oil appearance and also check the oil dip stick too. If the oil looks like sludge or like chocolate milk you have a very bad coolant leak.

[dav-02ws6-m6]

It doesn't show any fog. I already check the oil and it looks normal, the cap for the oil is clean, it run at normal idle( 700-800 rpms). The car has 174xxx miles. It seems like the person that owned change the thermostat. Also the upper radiator hose feel like there is no water.

[SMWS6TA]

If you can post a pic of his engine bay I could point it out to you.


look for a small bolt on a metal coolant pipe. This is what Smittro is referring to. To vent the system using this small bolt/screw the car must be cool, then warmed up to operating temps that the theromstate should open. Turn car off and then open the bleeder slowly. You should hear a hiss and see some spray. When it becomes constaint close the bleeder. You may have to do this a couple of times to get the air out.


One more thing to check is the radiator cap. They fail over time and let in excess air into the system. As old as it is if it is still the OEM cap that came with the car I would go ahead and get a new one. Only are around $12-15 and it's one less issue that is a PITA to problem solve.

[Smittro]

It doesn't show any fog. I already check the oil and it looks normal, the cap for the oil is clean, it run at normal idle( 700-800 rpms). The car has 174xxx miles. It seems like the person that owned change the thermostat. Also the upper radiator hose feel like there is no water.

Air pocket or bad water pump..

Both can heat your engine up.

[Smittro]

Remeber these engines do not have a conventinal water pump setup..

The pump yes,, however they're nearly always offset to one side and set high or low off center.

An air pocket can become trapped in the water pump chamber on these and cavitate the pump.

Then coolant goes nowhere @ all till it's hot..

The trick is to blow off any air while the engine is running and starting to warm..

(BE SLOW AND DELIBERATE/CAREFULL)

This perticular Nstar, has an open jacket design in the block, each bank of cylinders is isolated by a mote of coolant..

When or IF you drop a head gasket.. It's usually over..

If it's still running without issue other wise, you have a cooling problem.

Again stemming from either, air in the system, or your pump has died, bad thermostat, or all of them combined..

Taking note of the mileage..

[SMWS6TA]

Smittro - I'm going off my niece's old POS Cavalier on how to bleed the air pocket out of the system. Was I wrong in my post in giving him those directions?

[Smittro]

Smittro - I'm going off my niece's old POS Cavalier on how to bleed the air pocket out of the system. Was I wrong in my post in giving him those directions?

Not really,, the v6's and v8's are just different.

I basicly posted my own found technique and what works better.

You're only a little off, you need the thermostat nearly open to fully open to get all the air out and it needs to be running.

Just have to use more caution. I've seen and tried the "cold" purge and it took a few times to get the air out,

and still had air caught in the system..

Where as,, when the system is in full flow (thermo open) @ idle and getting hot or is hot, you can purge the air in one try..

It's a little more messy, but it nearly always works.

Slip a pan under it and then clean up the rest after you're sure you have good flow..

Temp guage and the actual coolant temp will become more stable instead of cooling way down then shooting up,

then down again which is the tell tale sign of air in the system.

Four valve heads tend to not ping, like 2 valve heads when they get very very hot..

They warp instead..

[SMWS6TA]

I think on her POS it was because the starter was right under the purge valve. I started doing it all hot after I got tired of waiting. Took to damn long....

[dav-02ws6-m6]

Thanks for the replies. Sorry if I couldn't reply sooner.

I tried to bleed the air from the system while its running, but it seems like it is sucking the air in instead of blowing it out.

I have been doing some research it seem like I have a vacuum leak somewhere. I been considering on buying a used engine and just dropping it in.

[SMWS6TA]

have you replaced the radiator cap yet? Like I said above, if it's leaking you will continuously get air into the system.

[cammed goat]

If the manifold is plastic, that could be warped. I have heard vehicles with composite intake manifolds that overheat tend to have warped manifolds causing either a coolant leak or vacuum leak.

[Wfolsom]

Have you ever installed a northstar engine before ?

If you deciede to motor swap this car I bet it will be your last northstar you ever wanna touch again

[Smittro]

Have you ever installed a northstar engine before ?

If you deciede to motor swap this car I bet it will be your last northstar you ever wanna touch again

If you don't have the tools for working on an Nstar I would say "yes" that is true..

They are complex, and they require a good working knowledge of the Nstar line, and many times special tools..

The water pump it on the back of the engine on the Aurora 4.0 DOHC so getting to it is'nt hard.

FWD cars in general are a breed of their own.

All your running gear is under the hood and can be unpluged,

and the entire cradle can be dropped engine and all as one unit..

Which is the proper way to do it on just about EVERY, FWD GM there is.

THAT is the time, to freshen these up,, NOT after the engine is already in the car..

[Smittro]

Well unless of course you like to bleed and swear..

[Smittro]

Thanks for the replies. Sorry if I couldn't reply sooner.

I tried to bleed the air from the system while its running, but it seems like it is sucking the air in instead of blowing it out.

I have been doing some research it seem like I have a vacuum leak somewhere. I been considering on buying a used engine and just dropping it in.

Is your resivour full? Scott is right also about your rad cap..

If air is getting in you may have an air leak elsewhere.

If the bleeder is sucking in air then you're likely not getting sufficient coolant to the heads.

Air should try to escape from there and pull some coolant with it.

[dav-02ws6-m6]

Thanks guys for the advice. I went ahead and bought a thermostat, water pump, resivour cap and special tool to remove water pump. I'll try to install it tomorrow.

[Smittro]

Keep us updated, let us know of any changes or problems.

[dav-02ws6-m6]

So I was at work and then it cross my mind if I should do a compression test before I install all this stuff. Just to make sure there isn't anything else wrong with the engine.