I have oil in the antifreeze. Checked spark plugs to see if head gasket leak. Doesn't seem to be that. Maybe Intake Manifold gasket? How to check that?

Gasket,check coolant level,how low is.intake manifold look around from top on side.Up to $1000.00 to fix.try head gasket fix.I did works good no problems.$30.00 to $50.00.

intake gasket might cause it if the coolant froze and broke the seal between the head and intake and is leaking directly into the lifter valley

If you have white smoke coming out your exhaust, it has to be a head gasket. The symptoms of an intake manifold leak are either and external leak (leaking on the ground) or water in the crank case (mixing with the oil and making it look like chocolate milk-shake) A leaking intake gasket will not cause the antifreeze to enter the combution chambers.

To diagnose which head is leaking, you can remove the valve covers and remove all the rocker arms then put compressed air into each spark plug hole and watch the radiator for bubbles. Looking at the spark plugs may also tell you without having to do this...The spark plug in the leaking cylinder will be very white on the electrode.

Is it leaking oil or antifreeze?
If it's oil at this location ,it is most likely the seal on the sealed (not used) distributor hole plug.(an easy fix).
If it's antifreeze it will most likely be the gasket between the head and intake.A little work but not bad.You will have to pull the valve covers and the intake but the heads stay on.

If you have the V-8 Engine, just totally disregard this post.

If you have the 3.8L V-6 engine, your oil consumption problem is most likely to be caused by the PCV Valve if you cannot find any external leaks. These are also known for the upper intake plenum leaking antifreeze. The ports in the manifold that go to the throttle body are made of very thin plastic. The EGR tube, with its hot exhaust gasses, goes right between them. This causes the plastic to heat up and crack, causing an antifreeze leak that goes directly into the intake and gets burned in the combustion chambers.

DORMAN makes a replacement upper plenum kit to fix this problem. The kit includes the upper plenum with thicker coolant passage walls, an intake manifold gasket set, a smaller-diameter EGR orifice, and a new PCV Valve. This kit will probably fix BOTH of your problems.

The DORMAN part number for your car is 615-180 Shop around...prices vary considerably.

You have to remove the parts to see where the leak is. Remove the manifold carefully to preserve the evidence. You can check the manifold mating surface with a straightedge. You may find the leak is actually in the head gasket. Make him show you the warpage before letting him sell you new parts. A metal part like the head can be resurfaced at a machine shop.

The loss of antifreeze with no apparent leaks could be the sign of many things including blown head gasket, cracked tank, or leaking water pump. I would lean toward a head gasket first. Have you checked the oil for signs of antifreeze? A head gasket won't leak until the system is under pressure and running at normal temperature. You could also have a cracked head although that is pretty rare. Check the oil and plugs for signs of anti freeze. Also check the tanks on the side of the radiator they could be cracked which only leak while under pressure. Check all hose connections and if so equipped tranny cooler lines to make sure they are all attached correctly.

it water mixed with your oil,it could be condensation or some how coolant entered the oil system.

You may have a lower intake manifold gasket leak (or a head gasket leak-slightly less probable) the lower intake can leak onto the serpentine belt and fling oil (and/or antifreeze). The lower intake manifold gasket is usually the culprit here. There is much information about changing it if you are inclined to do it yourself. If not, expect around 800 to 1200 to fix at dealer/mechanic. This is usually accompanied by (but not always) oil in the antifreeze, or antifreeze in the oil...

This sounds like a blown cylinder had gasket. Although on some engines you will find core plugs below the rocker coverin the head.