Question about 1999 GMC Yukon

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I have oil in my engine coolant reservoir as well as my radiator and im not sure what caused this. is this something that can be fixed?

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  • Johnny Apr 13, 2012

    i had this problem on a toy camry. it was the trans cooler in the radiator, it was busted leting oil get in the water.


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To answer your question directly; yes it can be fixed.

As far as causes, it could be a variety of things.

I would check the vehicle to see if there is an oil cooler which is either in the radiator or has lines in very close proximity to coolant lines. You may quickly find the source of your problem there.

It could be caused by other things such as a bad head gasket a cracked head, intake manifold or intake gaskets.

Odd cross contamination of fluids is something I have seen more and more in the past several years. For your problem I usually check for an oil cooler leak first, hoping to avoid the labor associated with head gaskets and cylinder heads. As far as a logical, understandable explaination goes for why a gasket or head might cause what you are experiencing, I offer the following.

My theory on your somewhat odd symptom of oil in your coolant without associated symptoms indicating a gasket failure is a result of having been puzzled myself on several occasions by what I consider the "new kind" of head gasket leaks. They seem to occur more often in cars that have aluminum heads on iron blocks and I have attributed that to the materials expanding, contracting, heating and cooling at different rates. They also seem to occur (in my experience) more often overhead camshaft motors, but I have not reasoned why that would be other than the ohc motors are more likely to also have iron blocks and aluminum heads. My best guess at a problem like you are having is head gasket or a cracked head because that is where all the flius involved are in close proximity to the others and where the conditions exist that could cause a part to fail which could result in cross contamination or leaks. The oddball single symptom is likely due to changing fluid pressures in your cooling system and engine oiling system. Starting cold, your engine coolant is not under pressure, but as soon as running you have oil pressure. If you have a leak or breach in a gasket or crack between pressurized oil passages and coolant passages you can get oil in your coolant. As the engine warms up, pressure greatly increases in the cooling system while it usually decreases slightly in the oiling system. If the pressure in the cooling system becomes greater than your oil pressure and there is a breach that allows the coolant into an oil galley you may end up with water in your oil as well. But it is possible that as the engine heats up, increasing coolant pressure, small leaks or crack close up as the metals and/or gaskets expand due to the heat keeping water from getting into the oil. If your oil cooler is ok, I suspect this is what you are experiencing.

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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 ...

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Went to add coolant to reservoir there was oil in it! checked radiator only coolant disconected reservoir from radiator until i get it fixed. think previous owner added oil here. any other ideas?

The way to tell if something is wrong check oil cap. Look for a white foam sometimes it's brown showing coolant in oil also look for white or blue smoke coming out of tailpipe. If you don't see any of these simple drain reservoir and flush it. I would also drain radiator to be on safe side. It is possible that last owner put oil in reservoir I have seen strange things like that and worse

May 06, 2016 | Cars & Trucks

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Chevy 2005 cavalier low coolant light keeps coming on and the coolant reservoit tank is empty after only 200 miles. what is causing this?

  1. Check the hoses and clamps going from the reservoir to the radiator and from the radiator to the engine. Make sure they are flexible and in good condition.
  2. Check the reservoir and radiator for leaks.
  3. Replace any parts they may be failing. If no leaks are found proceed to next step.
  4. Check engine oil. If oil has coolant in it you may have a blown head gasket or crack in the head or engine block. Another sign of a coolant leak into the cylinders is white smoke coming from the exhaust after the engine is warmed up.

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Oil in the radiator

oil in the radiator is from a failed transmission oil cooler that is in the radiator tank. You will also have water in the transmission oil as when you shut off the engine the coolant pressure may enter the oil lines through the crack in the cooler.

Sep 23, 2013 | 2003 Chevrolet Venture Passanger

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Coolant reservoir is full and radiator is empty why is it not circulating?

Hi Tiffany,

The engine coolant does not "circulate" through the reservoir in your Jeep. This system works on the fact that things expand when they are hot and contract when they are cold. When the radiator is full, the coolant expands when the engine gets hot and the overflow runs down the small hose to the reservoir. When you shut the engine off, the coolant contracts and a vacuum is created inside the radiator causing fluid to be drawn out of the reservoir and into the radiator. When you start your engine and it gets hot, the cycle begins again.

If the radiator is empty, this sytem cannot work. There will not be enough vacuum generated in the radiator to draw the fluid from the reservoir (too much empty space and not enough coolant contracting as it cools).

You need to find out WHY the radiator is low. If it is low, there is a reason for it. Either something is leaking EXTERNALLY like a hose or water pump, or something is leaking INTERNALLY like a blown head gasket or a cracked cylinder head. Proper diagnosis is recommended.

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1 Answer

I am losing coolant on my car and I see that the coolant from the reservoir is leaking from a little black rubber hose that"s connected to the firewall.

The black rubber hose may be bad and needs replaced. This hose should connect to the radiator at the radiator cap and run along the firewall to the coolant reservoir. Also the coolant reservoir might be cracked and leaking on to the rubber hose, if this is the cause just replace the coolant reservoir which may be a dealer only item, check at you local auto parts store and they will tell you if it is a dealer only item. If you have to replace the coolant reservoir, make sure the car has not been run and the coolant at the radiator is cool, cause when the engine is hot the hot coolant runs into the coolant reservoir till it cools and returns to the radiator when engine is turned off and cools.

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My heater is blowing cold air and the temp gauge is rising; do I need a new heater or is it something else? I regulary put in fuel injector cleaner every 3000 miles. When I searched for Heater Cores it...

it sounds like you are running out of coolant. refill and check for leaks. The coolant reservoir may have a leak. Your thermostat may need replacement.

Jan 14, 2011 | 2002 Pontiac Grand Am

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depends on the type of oil in the reservoir!! Typical issues that will cause this on your 4.2L I-6 engine; 1. (usually pink/reddish oil) trans fluid leaking via faulty radiator, blown head gasket from overheating (severe), or someone accidentally added oil to your radiator!!

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My engine is overheating, and when i lift the hood it appears that the coolant in my coolant reservoir is boiling/bubbling....there doesnt seem to be a leak except from the reservoir itself, the reservoir...

With the engine cool open radiator cap. If the level is low you are losing coolant. Go for a 30/40 dollars, radiator compression test. Might be a bad radiator cap seal, water pump leak cylinder head gasket.
If the coolant level is in top, then there are many other reason.

Sep 04, 2010 | 1996 Toyota Avalon

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Replace a coolant reservior on a 1999 ford taurus

If you need Illistration I Can Email it to you Im at
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CAUTION: Do not mix Standard (green) Coolant with Extended Life Coolant (orange). If mixing occurs, drain engine cooling system and refill with originally equipped coolant type. If this contamination occurs, the service change interval on Extended Life Coolant will be reduced from 6 years/150,000 miles to 3 years/30,000 miles.

  1. Drain radiator until engine coolant is out of degas bottle. Disconnect radiator overflow hose and engine coolant vent hose at degas bottle.
  2. Remove power steering oil reservoir retaining screws and position power steering oil reservoir out of the way.
  3. Remove degas bottle return hose and clamp. Remove degas bottle retainers and remove degas bottle.
  1. Position degas bottle in vehicle and install retaining screw and nut. Tighten retaining bolt and nut to 9-12 Nm (80-106 inch lbs.)
  2. Connect degas bottle hose and clamp to degas bottle.
  3. Position power steering oil reservoir onto degas bottle and install retaining screws securely.
  4. Connect radiator overflow hose and engine coolant vent hose to degas bottle.

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it seems like the radiator of your car needs attention. check for coolant level in it, when its cold. if les add some coolant and then see if the problem persists.
--than there are chances of chocking in the coolant pipes, may be they not reached to engine..  
--Check the chock,, that it is not turned on. 
--May be sum loosing nut in engine.

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