94 GM cooling system issues.

[94_marquis]

Hey,
I recently bought my GM. Its a 94 Grand Marquis GS(4.6L). I love the car but it has its issues. One recent issue i found was with the cooling system.
My coolant is disappearing from the reservoir everytime i drive my car. I fill it up to the cold fill line and its gone. There is no visible leak under the car of coolant. Before my mechanic flushed the system he said the stuff that was in there was a nasty brown/red color and had to be flushed about 10 times before it came out "clean".
My next issue i am noticing is when accelerating i can hear a gurgling noise under the hood. Its only under acceleration. I know from experience and common sense that this means there is air in the system, but does it signify where it is coming from generally?
I just had a fresh oil change and since the oil change i have checked the oil and i havent noticed any coolant in the oil, although I am not 100% what coolant in oil looks like. My oil looks like fresh changed oil.
Now this may just be the low temps here, but whenever i have driven the car even after driving for a half hour, the temp gauge stays in about the left 1/4 of the normal range. Like i said, it may be the cold temps here or just that this is the norm, but i figured it would at least get halfway up the normal scale. This may also have to do with my coolant being low.
Anyways, what are some checks i can do to see where this coolant is going? Like i said no visible drips are showing up(parked it over fresh snow over night).
Also, where is the radiator cap on these cars, or is it just the reservoir cap? Because i pulled up the black trim over the radiator and didnt see a cap, but i could have missed it. Because of this i dont know if the radiator is also low or if it s just the reservoir that is low.
The checks i plan on doing but cant due to the freezing cold temps here is a compression test to check for head gasket issues, get the resevoir cap checked for a leak, and i was gonna look into the radiator if i can find a cap somewhere.
Any other checks i should do? My mechanic was busy and couldnt get me in for a few weeks. He runs a 2 man shop and does great work so everyone in town goes to him for most of their car problems. I dont want to pay the local dealer to check it because they charge $90 to diagnose when i know i can get it diagnosed for free at my mechanic. Anyways, if anyone has any tips or suggestions please let me know.
Thanks.

[miamibob]

Pressure test the coolant system yourself or have it done. As for the "noise" under the hood, if it is a hissing it may be a vacuum line or possibly the EGR air pipe that most people miss. Happened on my Dad's '93 until I figured it out!! Bobby

[HiFiMerc]

The cap is on the reservoir. No cap on the radiator like the older models.

[94_marquis]

Hey. Thanks for the advice. I'll get the system itself pressure tested. And it's too bad there isn't a radiator cap. Looking into a radiator would tell me a lot more as far as how low the level is dropping and what everything looks like. Oh well.
As far as the noise, it's literally a bubbling or gurgling sound, like if you gurgled water in your mouth. It's really strange and I've never heard this noise on a car before. And it only happens under acceleration.

Sent from my XT907 using Tapatalk

[miamibob]

Check that EGR pipe for the noise. It cracks very easy and NO ONE finds the cause!

[jaywish]

Is it possible the engine was never actually full?

Perhaps you add a bit it gets sucked (correctly) into the engine/radiator and it is still thirsty.

How much coolant have you added so far?

Is the reservoir dry/very low after every run/cool cycle?

How many times have you had to add coolant?

[sly]

there should be a small hose from the top of the radiator to the top of the coolant tank on the fender. that helps the system burp as you fill it. With the engine cold, crank it and fill the tank to the cold like while it's running. Then you should be pretty close to topped up and one burp (full temp cycle) will allow the rest to be filled up. If that little line is not in there and the barbs are capped, that could be a possible issue. coolant in the oil will make it a milky brown. The older 4.6L engines are not known for intake leaks as much as the plastic ones, but it could be an issue. Pressure test will find that though. It could be sucking coolant into the intake and exhausting it as you run down the road. whitish exhaust smoke and a coolant smell to the exhaust are indicators of that as well. Also, check the valley between the heads for stains (light brown) or pools of coolant as some leaks will pool in the valley and evaporate off instead of leaking down the engine onto the ground. One more thing to check is the passenger side under the floor mat. check for coolant there and peel back the carpet at the firewall and see if there's any coolant there. That would indicate a leaking heater core or bad seal on the heater core hoses (tighten the clamp). I've also had a pinhole leak on a heater core that leaked into the car through the holes the heater core poked through as the pinhole was aimed just so and my floor was wet with coolant. new hose fixed that one.