Thread: p0304 code and engine overheating!!!!!!!

Hey dudes,
I am the tech manager at Prestone and own a shop that specializes in heavy engine repair. My experience is always that the freakin bleeder has to be opened after the t-stat opens.
Here is the GM factory instructions-
Draining and Filling Cooling System



Ethylene glycol/water fill ratios have been established to ensure a minimum of 50 percent ethylene glycol in the coolant flush and drain procedure, and ensuring that all engine block drains and air bleeds were utilized. The cooling system capacity for the 3100 engine is 10.4 liters (10.9 quarts) . The cooling system capacity for the 3800 engine is 9.6 liters (10.1 quarts) . The coolant recovery reservoir capacity is 0.75 liters (0.80 quarts) to the COLD mark on the reservoir. The quantities listed in the filling procedure include the additional quantity to displace the air remaining in the coolant system after a static refill.
Using the correct fill ratio and the following procedures will ensure a minimum concentration of 50 percent ethylene glycol in the coolant system and simplify the customer fill task.
Every 5 years or240,000 km, (150,000 mi.) , whichever occurs first, the cooling system should be drained and filled using the following recommended procedures.

Caution: Refer to Radiator Cap Removal Caution in Service Precautions.

Notice: When adding coolant, it is important that you use GM Goodwrench DEX-COOL or HAVOLINE DEX-COOL coolant. If Coolant other than DEX-COOL or HAVOLINE DEX-COOL is added to the system the engine coolant will require change sooner; at 50,000 km (30,000 mi.) or 24 months.

Draining Procedure

Important: This procedure significantly increases the amount of used coolant and diluted hazardous waste.

1. Park the vehicle on a level surface.
2. Remove and clean coolant recovery reservoir.
3. Remove the radiator cap when the engine is cool:

3.1.Slowly rotating the cap counterclockwise to detent. Do not press down while rotating pressure cap.3.2.Wait until any residual pressure (indicated by a hissing sound) is relieved.3.3.After all hissing stops, continue to rotate counterclockwise until the cap is removed.Important: Recover coolant and store in a used coolant holding tank and submit the used coolant for recycling on a regular basis. This procedure significantly increases the amount of used coolant and diluted hazardous waste.

1. Raise and support the vehicle. Refer to Vehicle Lifting.
2. Place drain pan under vehicle to collect all drained coolant.
3. Open the radiator drain valve located at the bottom of the radiator tank. For procedures requiring the cooling system to be partially drained, opening the radiator drain valve should provide sufficient draining and no further actions should be necessary.
4. Open the air bleed vent on the thermostat housing.
5. For the 3100 engine, remove both engine block drains. The front engine block drain is located between the starter and the engine oil filter. The rear engine block drain is located by the engine crank sensor.

1. For the 3800 engine, remove both block drains (knock sensors).

Important: Dispose of used coolant in a proper fashion. NEVER POUR USED COOLANT DOWN THE DRAIN. Ethylene glycol antifreeze is a very toxic chemical. Disposing of it into the sewer system or ground water is both illegal and ecologically unsound.

1. Allow the coolant to drain completely.

Filling Procedure

Notice: DO NOT use cooling system seal tabs (or similar compounds) unless otherwise instructed. The use of cooling system seal tabs (or similar compounds) may restrict coolant flow through the passages of the cooling system or the engine components.

Restricted coolant flow may cause engine overheating and/or damage to the cooling system or the engine components/assembly.

1. Close the radiator drain valve. Install all the engine block drains.
2. Remove the coolant recovery reservoir and empty. Flush the reservoir with clean water, drain and reinstall.

Important:

• When refilling the engine coolant system, add GM approved new Ethylene Glycol Coolant DEX-COOL GM P/N 12346290.
• If the cooling system is being refilled ONLY (no flush), a 50 percent ethylene glycol and 50 percent clean water mixture should be used to fill the system. Fill the system until the level of the 50/50 mixture has reached the base of the radiator neck. Wait 2 minutes and recheck the level of the coolant mixture, add a 50/50 ethylene glycol/water mixture as necessary to restore the coolant mixture level to the base of the radiator neck.

1. Slowly fill the cooling system through the radiator neck using the following procedure:

3.1.If the coolant system has been flushed first add 100 percent ethylene glycol in the amount listed for the appropriate engine application.3.2.Slowly add clean water to the system until the level of the coolant mixture has reached the base of the radiator neck.3.3.Wait for two minutes and recheck the level of the coolant mixture, add clean water if necessary to restore the coolant mixture level to the base of the radiator neck.

1. Install the radiator cap making certain the arrows line up with the overflow tube.
2. Close all air bleeds. DO NOT over-torque the air bleed valve. The air bleed valve is made out of brass.
3. Add 0.75 liters (0.8 quarts) of a 50/50 mixture of ethylene glycol and clean water to the coolant recovery reservoir.

Notice: The Low Coolant warning/indicator lamp may come on after this procedure. If after operating the vehicle so that the engine heats up and cools down three times, the Low Coolant warning/indicator lamp does not go out, or fails to come on at the ignition check, and the coolant is above the full cold mark in the reservoir, refer to Low Coolant Warning/Indicator Lamp. If at any time the Temperature warning/indicator lamp comes on, immediate action is required. Turn OFF the engine and allow the vehicle to cool. Do not remove the coolant recovery reservoir cap at this time.

1. Inspect the freeze protection of the engine coolant after the engine heats up and cools down three times using a refractometer or a hydrometer to ensure proper freeze -37°C (-34°F) protection. Obtain the coolant mixture for the inspection from the base of the radiator neck, NOT from the coolant recovery reservoir.

Terms of Use

Ok guys i bleed the cooling system. cars running 190-195 but well under 210. I have been checking the coolant levels with no noticable drop in it. i have pulled the plug again its not cracked. new wires new fuel filter. i replace the #4 injector then take it to the local gm dealer where they also read p0304 they tell me it has to be the injector they inspect the plug wire and plug and coil also they say they are fine. that its the injector. so i replace yet again the injector not once but twice and i continue to receive p0304. I also get a random p0300 and have noticed the rpms usually staying around 900 rpms then it will spike to 1200 or so then drop down again. the spike in rpms is rare and have only noticed it twice. so I think im getting maybe bad injectors so i get one from different parts house thats 3rd new injector no change still throwing the same code. i have blown out the vaccum lines with compressed air. Exhaust is clear(no white smoke as from coolant. What am i missing? could it be fuel pressure reg? The car drives great tons of power only time you notice the misfire is at idle.

What should be the normal cylinder compression for this engine? My handy dandy Haynes manual says minimum should be 100 psi that cant be correct i would think it would be higer as a norm for a supercharged engine.