I have a '98 Bonneville with 273,000 miles on it. Oil pressure was very eratic today.... my wife said it dropped to almost 0 for a sec at a stop light.... Normally sits around 40, maybe a bit lower... but its be varying quite a bit, seems to hit 40 or above while driving, but occasionally hits the top of the red while stopped. It would get well above 40 when I last drove the car, but my wife has been driving the car for awhile and now just over 40 seems the max. I read about faulty sensors, but when it hit lower oil pressure for 20-30 seconds, I could smell burnt oil, so I have a feeling it is actually low pressure. Any thoughts on next steps I should take?

Look for leaks. Don't run it long until you figure out what's wrong. If the engine is too caked, clean the motor down carefully and then start from there looking for a leak (doesn't have to be the culprit but can be a candidate for a burnt oil smell if it's leaking off onto the manifold(

Well .... I assume this is probably not good.

Antifreeze was low.... bottom of the car was soaked in oil and antifreeze. I started it up and it made a pretty loud hissing sound.... oil and antifreeze started leaking onto the ground about a drip or two per second. Thing is, its coming from the back side by the firewall on the passenger side... and I can't see exactly where its coming from. I had the issue with upper intake leaking around the egr valve and replaced the upper/lower intake gaskets a couple years ago... about 6 months ago, I noticed it was eating coolant... figured the intake gasket probably failed again (i had an issue getting the lowers on, so figured they might be leaking)... but this is looking more like a head gasket I assume... thats the only thing I could think of that oil and antifreeze would both be coming from... not sure about the hissing noise... sounds like air being let out of a tire.

Anyone think this might not be the head gasket?

What is the oil level in the engine? Is it up to normal? Above normal? Is there any evidence of coolant in the oil? Drain a bit of oil from the pan and check it for coolant.

From the area of the engine you describe, perhaps you are losing coolant from one of the hoses to or from the heater core. If it is mostly oil you are losing from that area, I would check the oil pressure sensor. They can fail and result in a serious oil loss and erratic gauge readings.

Check out all other possibilities before going after the head gaskets. It's not impossible, but it doesn't happen much.

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1998 3.8 Dodge Caravan 214K
2000 3.3 Dodge Caravan 175K
1949 Plymouth Special Deluxe 4-dr sedan 25K (needs some work!)

Thanks for the response! Did you mean head gasket failure doesn't happen much? The only thing that threw me was the loud hissing noise its making... Oil level was about a quart low since the last time I checked it... No evidence of antifreeze in the oil thus far, but I haven't changed it since this happened. Oil leak seems to be coming from higher than the oil pressure sensor, but I will double check to see if I can isolate exactly where it is coming from

I took the passenger side wheel off and could see the oil streaming straight out of the sensor, so good call on that!

The water was coming out right under the water pump... So I'm happily foiled by my pessimistic mind again! Be swapping that sensor and water pump tomorrow night. Only thing I'm left wondering about is the hissing sound... could that be the water pump grinding away?

Thanks for your help Bill!

Yes, it can be the sound of the water pump. I've found out that water pumps can make all sorts of noises...lol

You're welcome, Ryan. I always like to check out the cheaper things first. With any luck, a new sensor and water pump will fix you up fine. IIRC, the four big bolts on the water pump enter coolant passages, so it is a good plan to put some thread sealant on those as you are re-installing them. I use the white Permatex stuff - seems to work okay. For future reference, here is an image of some of the places on that end of the engine that can spring a coolant leak.

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1998 3.8 Dodge Caravan 214K
2000 3.3 Dodge Caravan 175K
1949 Plymouth Special Deluxe 4-dr sedan 25K (needs some work!)