Had oil leaking into the coolant, changed head gasket, still same problem

Sounds like a warped head take to a mechanic have a compression test done. DO NOT USE ANY GASKET SEALER

It leaks what... coolant or exhaust gas?
If it's exhaust gases it's more likely to be the exhaust manifold gasket at fault.

If it's coolant leaking out somewhere it could be a hose/radiator/coolant tank, though coolant can also leak from the head gasket area.

A classic sign of a leaking head gasket is a creamy white/grey sludge on your oil dipstick. This is caused by coolant finding its way via a blown head gasket into the oil system

A creamy sludge on the dipstick - caused by coolant finding its way into the oil system because of a leaking head gasket.

Other indications of a leaking head gasket/head is overheating and rough running.

You can also try removing the cap from the coolant bottle and letting the engine idle. If bubbles continually appear this may be due to the exhaust gases finding their way into the cooling system via a leaking head gasket.

In most cases replacing a head gasket requires the cylinder head to be skimmed as well. This is because the alloy of the head tends to warp slightly.

A workshop would be able to diagnose a faulty head gasket within minutes. Having a head gasket replaced and the head skimmed isn't a cheap job.

Nowadays there are 'guaranteed head repair' additives available. Just follow the instructions on the can if you decide to use one. I personally haven't used such an additive.

This is common issue early sign head gaskets failure for EJ251 SOHC engine for external coolant leak. Second gen 96-99 with EJ25D is worst because when head gaskets failed, it's an internal leak that allows coolant and oil mix together in the combustion chamber to destroy engine.
You can drive it for at least 6 months or more as long as you keep top up coolant since the leak should be small at a slower rate leak. I drove mine for a while before change head gaskets. You're looking at `$1000-1200 job a dealership since you might as well change the timing belt, water pump, idlers while engine is pulled to replace head gaskets.

This is caused by a leaking head gasket. When a head gasket leaks you can get oil in the coolant or coolant in the oil of the engine or both. You will need to pull the cylinder head off, have it checked for cracks and if none are found have it machined flat again and replace the head gasket. Use only a quality head gasket set either from the Toyota dealer or a well known quality brand like Fel-Pro (available from NAPA and others). This is a job that requires some special tools and a great deal of car repair knowledge, time to do the job is about 6 hours.

CHECK FOR COOLANT LEAKS AROUND THE RADIATOR LOOK DOWN BETWEEN COOLING FANS AND RADIATOR SIDES FOR SIGNS OF ANTIFREEZE.CHECK ALL RADIATORS HOSES AND HEATER HOSES.IF ALL LOOK GOOD CHECK ENGINE OIL FOR COOLANT LEAKS.IF OIL LOOKS LIKE MILK SHAKE COOLANT LEAKING IN CRANK CASE.YOU HAVE A HEAD GASKET LEAK.YOU NEED TO CHANGE OIL + FILTER. GET THE HEAD GASKET FIX.BECAUSE LEAK IN THE CRANK CASE WILL LOCK UP THE ENGINE.IF CRANK CASE OIL LOOKS OKAY.YOU DONT HAVE THE COOLANT CORRECT MIXTURE.YOU SHOULD HAVE 50/50 ANTIFREEZE AND WATER.

water or coolant is getting in oil. could be a bad head gasket. If the coolant level continues to drop, but there are no signs of coolant leaks on the ground or from the exhaust pipe, there is a good chance that coolant is entering crankcase and mixing in with the oil. check head gasket and manifold gasket for leaks.

U have a leaking engine cylinder head gasket, very common on this van.

Head gasket, if you have a V6 or a V8, can't tell which one is at fault, so both will might as well be changed.
If the leak near the maifold is oil, the valve cover gaskets are leaking.
When head gaskets are changed, all the necessary gaskets come in the gasket kit.

If there is oil inside the coolant liquid that is the head gasket.

Check first if oil can leak into the coolant tank from the cap.

Usually when you get oil into the coolant liquid you have an head gasket problem, do a compression test, or buy the home tester below.

eBay.co.uk Guides - HOW TO TEST FOR A FAILED HEAD GASKET
Head Gasket or Combustion Leak Test Procedure (Gasoline Engines Only)
Blown Head Gasket? how to check

The blowing of air into the coolant resevour is caused by a leaking head gasket. What's happening is the cylinder is blowing air into the cooling system causing this to happen.