Oil pressure problems

I would think you have a badly leaking engine cylinder head gasket. Have a shop test for that.

you need to check i"m not positive on that head gasket pattern but if its upside down you could have covered a oil port causing your oiling problem

The oil cooler is almost definatly the problem

The reason for this is.

Your oil pressure is normaly anywhere between 2 and 5 Bar depending on engine temp and oil type, where your water pressure is never more than 1.2 bar. Thus the oil pushes into the cooling system due to the fact that it is of higher pressure.

In the event of a head gasket leaking it will push water into the oil not the other way round causing the oil to eventually go white.

These cars are known to have problems with their oil coolers from time to time.

You don't have to take the head off to verify a coolant leak into the combustion chamber. A coolant pressure test will tell, or even a leak down test.
But...if the head needs to be removed, it is a costly job, and if you have been driving it this way for a long time, it will do permanent damage.

Head gasket has failed and your engine from what you have described will need to be replaced, the clack and no power indicates that your crank shaft bearing has slipped and your you have low oil pressure now throughout your engine.
Oil pressure is created by the crankshaft bearing and for you to have to push hard on your brake peddle to stop also indicates that your engine is low on vacuum caused by a blown head gasket.
Thank you for using fixya and sorry for the bad news that a new engine is called for to fix this issues.

if you had a head gasket starting to go and you put a chemical seal in the system(is not permenent) you stand the chance of water still being in your oil. change the oil and see what happens. they are hydraulic tappets and need good clean oil.

Fix this ASAP, Coolant in oil will ruin bearings. Have a shop check it ASAP. I would check the intake manifold gaskets first.

If you have steady thick white smoke and it smells like anti freeze it is most likely the head gasket. The head gasket can fail in different areas. If it has white smoke it failed between a coolant passage and the combustion chamber. If the oil is milky it failed between the coolant passage and an oil passage. Just because the oil isn't milky doesn't necessarily mean that the head gasket it's blown.

A head gasket leak (blown head gasket) is highly likely. ($200)

Check your oil dipstick If it contains a milky fluid, that is water mixed with the oil. A sure sign of a blown head gasket.

Other symptoms of a blown head gasket include:
1. White smoke and excess water dripping out the tailpipe.
2. Overheatinmg engine
3. With radiator cap off, steam and water will erupt, sometimes violently.

Whichever tailpipe has the smoke is the side that the blown head gasket is located.

... sorry ...

Everyone automatically assumes that oil and water mixing means a blown head gasket or cracked engine block. Of course common sense is usually not that common. Oil in coolant is a different problem than coolant in oil. The former is a low pressure leak, and could indicate only an intake manifold gasket. It could also be an early or small head gasket leak. Coolant in oil is usually a cracked block or torn head gasket, and has concomitant symptoms of white exhaust smoke and milky oil on dipstick. If you replace the head gasket and the problem persists, an intake gasket could have fixed the problem.