Anyone know what year DexCool was changed in Bonnevilles?
Also thoughts on flushing system.

My car was manu in June 1995 (MI plant)..It threw code P0325.
Inspecting it to replace sensor we noticed the radiator was filled w orange fluid.
Flushing it and overflow I found lots rust.
Is it worth it to use a flush kit?
Or is it best to just flush w straight water?

My car runs smooth and very quiet.

From page 7-41 of your 1995 Pontiac Bonneville owner'* manual, it is normal green glycol-based antifreeze:



Drain it, fill it. My preference is Prestone "concentrate" mixed 50/50 with distilled water. Drive it around for a week then drain and fill it again.

Cool!

Interesting. In OBD2 world, P0325 is [knock sensor malfunction]

But you say yours is a 1995, which should have OBD1.x

But if you read it with a OBD2 scanner, it is probably a 1996 model year car.

What model year does the emissions decal (under the hood) and the door tag (on the driver door or in the driver doorjamb) say the model year is?

Between 1995 and 1996 changes the PCM and the PCM location as well.

This also tells me that this is a 1996, because from page 7-41 of a 1996 Pontiac Bonneville owner'* manual, it is supposed to be DEX-COOL:



So, you're already flushing it?

Rust or some other kind of junk that reminds you of rust but maybe isn't actually rust after all?

I wouldn't suggest it. Especially if you don't have a lot of experience working on cars. Done properly, it might be good to flush it. Done improperly, you have potential to create major issues. Also depends on what "flush kit" you're talking about. There are several ways to flush the cooling system of an engine.

I wouldn't flush with straight water. Too much garbage in it.

So, I think the next step is to identify for sure what model year Pontiac Bonneville you are talking about. One of the decals I mentioned has the answer, but the easy way to estimate would be to tell us what color the Bonneville is on the cover of your owner'* manual, red or white:




Regardless, I wouldn't worry about flushing the coolant until you get it to run reliably.

It'* a 1995.
According to door panel, and the manual cover (in photo above it'* the red car).
It also states many in Michigan.June 1995.
It does Not run w OBD1.
The 1st sensor the car had was crank sensor. I replaced that, and the harmonic balancer.
Now 2 weeks later it threw the P0325. Removed that sensor and replacing it today.
The radiator and over flow are now cleaner.

Is the PCM next to the air box?

Since it'* a 1995, maybe someone inappropriately filled yours with Dexcool. Not a great idea.

Can you post a picture of the engine (like from just standing there with the hood open) and the emissions decal?

This is with the cover off

Yep, definitely a 1995 and definitely a 3800 Series 2, but then it says it is OBD1 certified while you're able to pull OBD2 codes from it. This is a weird one.

For the coolant, I would suggest the coolant be replaced completely with green coolant (such as what I mentioned above) mixed 50/50. While doing this, you may as well replace the thermostat with a quality unit, and replace hoses with quality replacements if they are original to the car. If it has plastic coolant elbows, replace those as well. Flushing might help, and/or it might create more issues.

Thank you very much for all the great tips.