Question about 1998 GMC Sonoma

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Expansion plugs ,location on engine

Coolant leak at back of cylinder head,too much in way to see

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  • Bruce Buysman
    Bruce Buysman Apr 14, 2014

    Sounds like a freeze plug. Yes, hard to reach. You will have to bite the bullet,and start excavating.

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  • Contributor
  • 24 Answers

The heater pipes are leaking

Posted on Apr 13, 2014

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2002 Lincoln LS Check engine temp and reduce speed came across screen, car started reducing speed then died NowThe coolant keeps disappearing its not leaking anywhere. What could be the problem?


Coolant just does not disappear!!!!!!! Either you have a leak somewhere or perhaps one of your engine head gaskets is shot and leaking coolant into the oil passages. Check your oil for color. If it has the color of a brown mud that is the cause of your problem.

Re leaks check all of your heater and engine hoses and clamps. Do not overlook your radiator cap nor your expansion tank for leaks.

Feb 15, 2016 | Lincoln Cars & Trucks

2 Answers

Engin oil is mixing with water. What can this be?


If the oil is in the coolant look for a leaking expansion plug on the top of the cylinder head under the valve cover. If water is in the oil, check for faulty head gasket, cracked head or cylinder block.

Sep 04, 2015 | Cars & Trucks

3 Answers

Where is the freeze plug located on a 1999 Chevy Lumina 3.1L


On the block ( the bottom part of the motor ) below the intake manifold

Jan 27, 2015 | 1999 Chevrolet Lumina

1 Answer

Freeze plup location


Back of engine, eh? The freeze plugs (3, maybe 4 on that back side) will be on the engine block, below the cylinder head, and below where the exhaust manifold mounts up. Look in back of the exhaust manifold for the plugs. Check for indication of leaking, it should be evident. If you have an engine block heater installed in one of the freeze plug holes, that may have loosened and started leaking. If you find a plug that needs replaced, put a stout screwdriver or punch on the freezeplug, not at the center of plug but to the edge, and whack it good. That edge will go in and the other side will stick out- grab with pliers and remove. Clean the area well to remove rust and scale where freezeplug seals in the block. It will be hard, possibly, to put in a new freeze plug with everything in the way. So buy a rubber expansion plug at the parts store-easy to install, just put a wrench on it to tighten. Take your old freezeplug with you to get the right sized expansion plug.
Good luck, hope you find it.

Dec 23, 2012 | 2006 Scion tC

1 Answer

1998 for expedition 4.6 engine leaking water beteen the back of the motor and the transmission


Not very likely, check the coolant passage between the cylinder heads. (The front part of the intake, right behind the alternator) That piece which is part of the intake manifold has been a source of coolant leaks for many vehicles like yours. The alternator is pretty easy to remove... Disconnect the negative battery cable, turn the belt tensoner to remove the belt from the alternator, take out the two long 10mm bolts under the alternator and the three on top. I would check for leaks there because it was a common problem area, coolant would leak behind the alternator, fill the space under the intake manifold, and leak down right where the transmission bell housing is. There are expansion plugs, and allen plugs on the back of the cylinder heads, but they rarely leak.

Jan 24, 2012 | 1998 Ford Expedition

1 Answer

Put coolant in and strts tripping in back of engine even if car is cold


Possible leaking expansion plug in the rear water jacket or maybe a warped cylinder head or blown head gasket. Lights and mirrors will help track it down. Might get expensive to repair if it's the head or it's gasket. Hope this helps!

Jun 27, 2010 | 1994 Mercury Grand Marquis

4 Answers

Loosing coolant no visible leaks about 1/2 gallon every 100 miles


How To Find & Fix Coolant Leaks

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WHERE COOLANT LEAKS OCCUR
Coolant leaks can occur anywhere in the cooling system. Nine out of ten times, coolant leaks are easy to find because the coolant can be seen dripping, spraying, seeping or bubbling from the leaky component. Open the hood and visually inspect the engine and cooling system for any sign of liquid leaking from the engine, radiator or hoses. The color of the coolant may be green, orange or yellow depending on the type of antifreeze in the system. The most common places where coolant may be leaking are:
Water pump -- A bad shaft seal will allow coolant to dribble out of the vent hole just under the water pump pulley shaft. If the water pump is a two-piece unit with a backing plate, the gasket between the housing and back cover may be leaking. The gasket or o-ring that seals the pump to the engine front cover on cover-mounted water pumps can also leak coolant. Look for stains, discoloration or liquid coolant on the outside of the water pump or engine.

Radiator -- Radiators can develop leaks around upper or loser hose connections as a result of vibration. The seams where the core is mated to the end tanks is another place where leaks frequently develop, especially on aluminum radiators with plastic end tanks. On copper/brass radiators, leaks typically occur where the cooling tubes in the core are connected or soldered to the core headers. The core itself is also vulnerable to stone damage. Internal corrosion caused by old coolant that has never been changed can also eat through the metal in the radiator, causing it to leak.

Most cooling systems today are designed to operate at 8 to 14 psi. If the radiator can't hold pressure, your engine will overheat and lose coolant.

Hoses -- Cracks, pinholes or splits in a radiator hose or heater hose will leak coolant. A hose leak will usually send a stream of hot coolant spraying out of the hose. A corroded hose connection or a loose or damaged hose clamp may also allow coolant to leak from the end of a hose. Sometimes the leak may only occur once the hose gets hot and the pinhole or crack opens up.

Freeze plugs -- These are the casting plugs or expansion plugs in the sides of the engine block and/or cylinder head. The flat steel plugs corroded from the inside out, and may develop leaks that are hard to see because of the plug's location behind the exhaust manifold, engine mount or other engine accessories. On V6 and V8 blocks, the plugs are most easily inspected from underneath the vehicle.

Heater Core -- The heater core is located inside the heating ventilation and air conditioning (HVAC) unit under the dash. It is out of sight so you cannot see a leak directly. But if the heater core is leaking (or a hose connection to the heater core is leaking), coolant will be seeping out of the bottom of the HVAC unit and dripping on the floor inside the passenger compartment. Look for stains or wet spots on the bottom of the plastic HVAC case, or on the passenger side floor.

Intake Manifold gasket -- The gasket that seals the intake manifold to the cylinder heads may leak and allow coolant to enter the intake port, crankcase or dribble down the outside of the engine. Some engines such as General Motors 3.1L and 3.4L V6 engines as well as 4.3L, 5.0L and 5.7L V8s are notorious for leaky intake manifold gaskets. The intake manifold gaskets on these engines are plastic and often fail at 50,000 to 80,000 miles. Other troublesome applications include the intake manifold gaskets on Buick 3800 V6 and Ford 4.0L V6 engines.

INTERNAL COOLANT LEAKS
There are the worst kind of coolant leaks for two reasons. One is that they are impossible to see because they are hidden inside the engine. The other is that internal coolant leaks can be very expensive to repair.

Bad head gasket --Internal coolant leaks are most often due to a bad head gasket. The head gasket may leak coolant into a cylinder, or into the crankcase. Coolant leaks into the crankcase dilute the oil and can damage the bearings in your engine. A head gasket leaking coolant into a cylinder can foul the spark plug, and create a lot of white smoke in the exhaust. Adding sealer to the cooling system may plug the leak if it is not too bad, but eventually the head gasket will have to be replaced.

If you suspect a head gasket leak, have the cooling system pressure tested. If it fails to hold pressure, there is an internal leak. A "block tester" can also be used to diagnose a leaky head gasket. This device draws air from the cooling system into a chamber that contains a special blue colored leak detection liquid. Combustion gases will react with the liquid and cause it to change color from blue to green if the head gasket is leaking.

Head gasket failures are often the result of engine overheating (which may have occurred because of a coolant leak elsewhere in the cooling system, a bad thermostat, or an electric cooling fan not working). When the engine overheats, thermal expansion can crush and damage portions of the head gasket. This damaged areas may then start to leak combustion pressure and/or coolant.

Cracked Head or Block -- Internal coolant leaks can also occur if the cylinder head or engine block has a crack in a cooling jacket. A combustion chamber leak in the cylinder head or block will leak coolant into the cylinder. This dilutes the oil on the cylinder walls and can damage the piston and rings. If the coolant contains silicates (conventional green antifreeze), it can also foul the oxygen sensor and catalytic converter. If enough coolant leaks into the cylinder (as when the engine is sitting overnight), it may even hydro-lock the engine and prevent it from cranking when you try to start it. Internal leaks such as these can be diagnosed by pressure testing the cooling system or using a block checker.

A coolant leak into the crankcase is also bad news because it can damage the bearings. Coolant leaking into the crankcase will make the oil level on the dipstick appear to be higher than normal. The oil may also appear frothy, muddy or discolored because of the coolant contamination.

Leaky ATF oil cooler -- Internal coolant leakage can also occur in the automatic transmission fluid oil cooler inside the radiator. On most vehicles with automatic transmissions, ATF is routed through an oil cooler inside the radiator. If the tubing leaks, coolant can enter the transmission lines, contaminate the fluid and ruin the transmission. Red or brown drops of oil in the coolant would be a symptom of such a leak. Because the oil cooler is inside the radiator, the radiator must be replaced to eliminate the problem. The transmission fluid should also be changed.

continue...

Mar 12, 2010 | 1998 Oldsmobile 88

1 Answer

Loosing antifreeze


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WHERE COOLANT LEAKS OCCUR
Coolant leaks can occur anywhere in the cooling system. Nine out of ten times, coolant leaks are easy to find because the coolant can be seen dripping, spraying, seeping or bubbling from the leaky component. Open the hood and visually inspect the engine and cooling system for any sign of liquid leaking from the engine, radiator or hoses. The color of the coolant may be green, orange or yellow depending on the type of antifreeze in the system. The most common places where coolant may be leaking are:
Water pump -- A bad shaft seal will allow coolant to dribble out of the vent hole just under the water pump pulley shaft. If the water pump is a two-piece unit with a backing plate, the gasket between the housing and back cover may be leaking. The gasket or o-ring that seals the pump to the engine front cover on cover-mounted water pumps can also leak coolant. Look for stains, discoloration or liquid coolant on the outside of the water pump or engine.

Radiator -- Radiators can develop leaks around upper or loser hose connections as a result of vibration. The seams where the core is mated to the end tanks is another place where leaks frequently develop, especially on aluminum radiators with plastic end tanks. On copper/brass radiators, leaks typically occur where the cooling tubes in the core are connected or soldered to the core headers. The core itself is also vulnerable to stone damage. Internal corrosion caused by old coolant that has never been changed can also eat through the metal in the radiator, causing it to leak.

Most cooling systems today are designed to operate at 8 to 14 psi. If the radiator can't hold pressure, your engine will overheat and lose coolant.

Hoses -- Cracks, pinholes or splits in a radiator hose or heater hose will leak coolant. A hose leak will usually send a stream of hot coolant spraying out of the hose. A corroded hose connection or a loose or damaged hose clamp may also allow coolant to leak from the end of a hose. Sometimes the leak may only occur once the hose gets hot and the pinhole or crack opens up.

Freeze plugs -- These are the casting plugs or expansion plugs in the sides of the engine block and/or cylinder head. The flat steel plugs corroded from the inside out, and may develop leaks that are hard to see because of the plug's location behind the exhaust manifold, engine mount or other engine accessories. On V6 and V8 blocks, the plugs are most easily inspected from underneath the vehicle.

Heater Core -- The heater core is located inside the heating ventilation and air conditioning (HVAC) unit under the dash. It is out of sight so you cannot see a leak directly. But if the heater core is leaking (or a hose connection to the heater core is leaking), coolant will be seeping out of the bottom of the HVAC unit and dripping on the floor inside the passenger compartment. Look for stains or wet spots on the bottom of the plastic HVAC case, or on the passenger side floor.

Intake Manifold gasket -- The gasket that seals the intake manifold to the cylinder heads may leak and allow coolant to enter the intake port, crankcase or dribble down the outside of the engine. Some engines such as General Motors 3.1L and 3.4L V6 engines as well as 4.3L, 5.0L and 5.7L V8s are notorious for leaky intake manifold gaskets. The intake manifold gaskets on these engines are plastic and often fail at 50,000 to 80,000 miles. Other troublesome applications include the intake manifold gaskets on Buick 3800 V6 and Ford 4.0L V6 engines.

INTERNAL COOLANT LEAKS
There are the worst kind of coolant leaks for two reasons. One is that they are impossible to see because they are hidden inside the engine. The other is that internal coolant leaks can be very expensive to repair.

Bad head gasket --Internal coolant leaks are most often due to a bad head gasket. The head gasket may leak coolant into a cylinder, or into the crankcase. Coolant leaks into the crankcase dilute the oil and can damage the bearings in your engine. A head gasket leaking coolant into a cylinder can foul the spark plug, and create a lot of white smoke in the exhaust. Adding sealer to the cooling system may plug the leak if it is not too bad, but eventually the head gasket will have to be replaced.

If you suspect a head gasket leak, have the cooling system pressure tested. If it fails to hold pressure, there is an internal leak. A "block tester" can also be used to diagnose a leaky head gasket. This device draws air from the cooling system into a chamber that contains a special blue colored leak detection liquid. Combustion gases will react with the liquid and cause it to change color from blue to green if the head gasket is leaking.

Head gasket failures are often the result of engine overheating (which may have occurred because of a coolant leak elsewhere in the cooling system, a bad thermostat, or an electric cooling fan not working). When the engine overheats, thermal expansion can crush and damage portions of the head gasket. This damaged areas may then start to leak combustion pressure and/or coolant.

Cracked Head or Block -- Internal coolant leaks can also occur if the cylinder head or engine block has a crack in a cooling jacket. A combustion chamber leak in the cylinder head or block will leak coolant into the cylinder. This dilutes the oil on the cylinder walls and can damage the piston and rings. If the coolant contains silicates (conventional green antifreeze), it can also foul the oxygen sensor and catalytic converter. If enough coolant leaks into the cylinder (as when the engine is sitting overnight), it may even hydro-lock the engine and prevent it from cranking when you try to start it. Internal leaks such as these can be diagnosed by pressure testing the cooling system or using a block checker.

A coolant leak into the crankcase is also bad news because it can damage the bearings. Coolant leaking into the crankcase will make the oil level on the dipstick appear to be higher than normal. The oil may also appear frothy, muddy or discolored because of the coolant contamination.

Leaky ATF oil cooler -- Internal coolant leakage can also occur in the automatic transmission fluid oil cooler inside the radiator. On most vehicles with automatic transmissions, ATF is routed through an oil cooler inside the radiator. If the tubing leaks, coolant can enter the transmission lines, contaminate the fluid and ruin the transmission. Red or brown drops of oil in the coolant would be a symptom of such a leak. Because the oil cooler is inside the radiator, the radiator must be replaced to eliminate the problem. The transmission fluid should also be changed.

continue..

Mar 12, 2010 | 2007 Hummer H3X

2 Answers

Overheating


If the temperature gauge isn't moving you are either completely out of coolant or your coolant isn't circulating.

It would be worth your time to check your coolant level, then look for leaks. If you are also noticing that your heater doesn't work it would help to confirm this diagnosis.

Could be several things causing a lack of circulation: a blockage in your coolant lines somewhere, your water pump is not functioning, or you have a blown head gasket or warped cylinder head. An engine overheat can also cause the blown head gasket and/or warped cylinder head as well, so you would be best served by driving your car as little as possible until you've diagnosed the problem.

If you are out of coolant, you should check a few places for leaks. Obviously at your main coolant lines, but also along the heater core is a good place to check. If you can't find any obvious leaks, you may want to try flushing your radiator, since it's relatively simple to do and certainly can't hurt. Also change your oil: if it comes out looking opaque and like a milkshake, you're getting coolant into your cylinders, which means you've blown the head gasket or warped the cylinder head.

-R

Aug 13, 2008 | 1993 Volvo 960

1 Answer

Overheating


There's many causes of overheating (on all cars..).
The first and most obvious thing I would do after checking the coolant level in the radiator expansion tank was at the maximum level, would be to check for coolant leaks while the engine is running with a 'few revs' on a warm engine.

Hoses can split internally and also become soft and collapse internally through age. When this happens the hose becomes blocked and prevents the coolant from passing through easily. If a hose feels 'soggy'/soft and is easily squeezed flat by hand, it's suspect.

Coolant can also leak from the heater hoses, the heater unit, the bearings/seal on the water pump and of course the radiator. Nor is it always easy to see a leak let alone find it. If the in-car heater unit is leaking the carpets may be wet at times and sometimes, the windows may mist up when the car is standing - this is the coolant condensing on the interior of the glass.

Ok... you can't see any leaks while the engine is running. Is the car losing coolant when it stands? Or is it losing coolant when the engine is running? ( a split hose may only leak when it is pressurised with warm coolant) Or is it just losing coolant when it overheats?

Remove the cap from the radiator expansion tank when the engine is cold. Make sure that the water level is at maximum. Leave the expansion tank cap off. Leave the car standing overnight and next morning look at the coolant level. If it has dropped there's probably an unidentified leak somewhere. If the coolant level hasn't dropped, it points towards a problem that is caused when the engine runs.

With the expansion tank cap still off (get a flashlight to help you) start the engine and peek into the expansion tank. Watch what happens to the coolant (though do keep your face out of harm's way). As the coolant begins to circulate air bubbles will probably appear within the coolant. This is quite normal - air is 'bleeding out' of the coolant as it circulates. The air bubbles should stop after a couple of minutes.

As the coolant warms it will rise up in the expansion tank (keep your face out of the way ..). If the air bubbles continually appear or, there's a constant and continual stream of bubbles or a 'violent bubbling' then this may point to problems with a warped/cracked cylinder head or leaking head gasket (or both).

A defective cylinder head/gasket can allow exhaust gasses to be pumped into the water jacket (the coolant system) simply by the compression action of the pistons. Just like a hypodermic needle can inject air into your bloodstream. When this happens - pressurised exhaust gasses being forced into the cooling system - the cooling system itself becomes pressurised.

The coolant itself can find its way into the cylinders where it is vapourized and pumped out of the exhaust along with the exhaust gases. If you can't find any leaks - the missing coolant may be going out of the exhaust as steam (though you may not see any steam as such). A classic sign of cylinder head/gasket problems is overheating. Check your oil - if there's a yellowish/creamy mayonnaise/sludge that's another sign of head problems. The sludge is caused by coolant finding its way into the oil.

No leaks, no bubbling expansion tank - and if you're happy that there isn't a head/gasket problem, turn your attention to the radiator, thermostat and water pump.

With age, cooling fins on the radiator can corrode and crumble away, reducing its cooling ability. Whilst coolant still passes through the radiator it isn't being cooled sufficiently. Check the condition of your radiator. Radiators can also suffer from an internal blockage. With a warm engine that is switched OFF, feel the top radiator hose - it will be hot. Then feel the bottom radiator hose. If the bottom hose is cold it indicates that coolant is not finding its way down/being circulated maybe due to a radiator blockage or failed thermostat. Flushing may cure blockages.

A thermostat can fail in the 'closed' position. When this happens coolant is prevented from getting into the radiator via the top hose. The coolant in the block then overheats causing the temperature gauge to hit red. The thermostat is located (usually - it depends on make/model variations) on the cylinder head where the top radiator hose joins. They're very easy and cheap to replace.

The water pump can leak water when the bearings/seal fail. Coolant that slowly drips onto a warm engine soon evaporates making detection difficult. Way back, some water pumps had plastic impellers (perhaps they still do). The plastic vanes on the impellers used to wear away with age and use, leaving a spindle spinning uselessly in the coolant - not pumping it. Think of an airplane with a propeller. If the propeller blades wore away the 'nose cone' would just spin uselessly and no air would get moved ..

Before jumping to any conclusions and replacing parts unnecessarily, get a workshop to look at the car. A workshop will be able to test the coolant for exhaust contaminants within minutes (or pressure test the coolant system. If there's contaminants present - there's a head problem. No contaminants present - the fault lies elsewhere.

Back to the cylinder head:
It's a 2-3 day job to do the work yourself. A cylinder head must be skimmed prior to refitting. Refitting an unskimmed cylinder head back onto an engine cures nothing.

Years ago, here in the UK, there was a liquid additive called 'head weld' (and one for the radiator called 'radweld') which provided a TEMPORARY get-you-home fix. Head-weld was a liquid added to the coolant system. It contained fine particles in suspension ... these particles were carried to the crack/leak in the cylinder head and formed a 'dam' that was held in place by the water pressure until they (the particles) hardened.

Recently I noticed an advert for a product called 'steelseal' - here in the UK. The advertising blurb claims that it uses new technology without particles to form a permanent fix for cylinder heads/gaskets. It's a clear liquid that you just pour into the cooling system and then run the engine until its fixed. I've never tried it. At around 45 dollars a bottle it isn't cheap, though if it does what is claimed then it's a hell of a lot cheaper than having a cylinder head/gasket fixed. No doubt there are similar products on the shelves of car accessory and parts shops near you.







Aug 12, 2008 | 1992 Volvo 960

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