Question about 1995 Oldsmobile Eighty Eight

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Coolant leak i took the plastic plenum off and the top of the manifold is covered in antifreeze

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  • weldjonshar Feb 05, 2009

    my car losees coolant over 2-4 days. There is no "steam" coming from top of engine and no pooling collant when the car is off and sitting still. I changed the thermostat gasket where there was steam emerging and it's gone. I find the radiator coolant level drops and the reservoir empties over 2-4 days. My mechanic said there was no problem with freeze plugs, didn't see where the fluid was going. The water pump is not making noise, and the engine hot light never comes on. Can a pressure test help identify the problem? Clueless & Cool-less



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Had this same problem. The plenum has a coolant port for the EGR valve which lets in a small amount of coolant. The intake plenum is plastic and will leak coolant into the lower manifold. You will need to replace the warped leaking plenum with a new one, flush the engine, Coolant DOES NOT LUBRICATE THE MOTOR!!! CHANgE OIL & FILTER.I did this myself, lots of stuff to remove & replace. Runs like new after replacing the plenum.

Posted on Oct 16, 2008

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1.Stop leak works if you have a pinhole leak in the radiator itself. Your coolant leak is in the engine.
2. The radiator holds the coolant mixture that passes through the engine and back into the radiator. The air that flows past the coils in the radiator reduces the temperature of the coolant. When the coolant passes through the engine, the temperature of the coolant increases. When you lose coolant directly from the engine, you reduce the cooling system efficiency and on a hot summer day, take more of a risk of overheating the engine and causing the pistons to sieze. If this happens, you need a new engine.
3. Anytime you can put less than $1000 to $1500 in repairs into a car in a year, that's a pretty good deal. You can spend well over $350 each month to make a car payment.

Posted on Jun 12, 2008


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Car knocks when I start it

If it has the 3800 engine, usually the issue with this engine is at some time, the upper intake manifold (plenum) developed an internal coolant leak, from the plastic housing just under the throttle body, from the EGR tube that flows in to upper plenum. This causes the coolant to seep into the lower intake manifold ports and into the engine cylinder, on top of the piston, and when the engine turns over, sometimes this coolant causes this concern. If at any time you started your engine, and it stopped turning (cranking) over for a split second and then cranked over to start, this could cause the connecting rod to bend slightly causing the internal engine knock. Was your coolant/antifreeze ever low?? Is your engine oil have a milky color?

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When is the last time you had the radiator flushed. Check for leaks on the top of the engine, if you see antifreeze you will have to replace the upper and lower plenum gaskets. I even replaced the plenum to get a steel guard for the EGR valve. This is a known GM defect that affects ALL 3.8 liter engines. also, do you see antifreeze anywhere on the engine or ground? Another known problem are the plastic coolant elbows on the front of the motor (where the pulleys are). They leak and look like an intake manifold leak. I would also replace the thermostat. Check the overflow and see if you are losing antifreeze on a regular basis.

Dec 20, 2012 | 2000 Pontiac Bonneville

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The 3.8 liter for this year has a plastic intake manifold. These manifolds are known to fail around the EGR port. When this happens coolant will leak into the intake right behind the throttle body. Dorman makes a replacement upper plenum that has been reinforced in this problem as along with a new gasket and an updated EGR tube. This will more than likely solve your issue. If you see a little coolant behind the throttle body this repair needs to be done ASAP. If this area completely ruptures it will hydroloc the engine. This means that coolant will fill one or more of the cylinders and the engine will not turn over/start.

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The passage in the upper plenum that the egr tube passes through has ruptured. This is a very common problem with the plastic plenums. The aftermarket plenums have been reinforced in this area and come with smaller egr tubes to help prevent this from happening again. Replace the upper plenum, soak up all the coolant under the plenum, pull the plugs and rotate the engine by hand at first to push out the coolant in the cylinders, and change the oil. After that you should be good as new. Let me know if you have any questions and I'll do my best to answer them. Thank you for using!

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I have a 2005 pontiac gxp that has been using oil and antifreeze but I checked the antifreeze and there are no signs of oil and also the oil dipstick has no antifreeze on it either.....I used about 3...

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.

Feb 02, 2011 | 2005 Pontiac Bonneville

1 Answer

Can a bad intake plenum leak antifreeze into the engine on a 2002 century 3.1?The computer code was misfire #1 cylinder. Complete tune-up done, same problem, new#1 injector, same problem. Now the coolant...

I see a lot of lower intake gasket leaks on these but usually you get an external leak or you'll find coolant mixed with the oil, not a misfire. Upper plenum is dry on the 3.1 and just bolts onto the top of the lower intake. We usually apply pressure to the cooling system overnight with the spark plug removed from the misfiring cylinder. If there is coolant in the cylinder come morning then you only have to figure out where it is coming from. If the plenum is removed during the test you might be able to see where the coolant is or isn't coming from with a borescope by looking down the intake runner.

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Apr 11, 2010 | 1998 Pontiac Bonneville

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Coolant leak at intake 1994 Buick LeSabre 3.8 ltr

There are several areas of possible leakage. One is the hose and plastic outlet from the intake manifold on the passenger side of the engine. The hose runs low, underneath the alternator. The plastic outlet cracks, the hose gets old, the clamps on the hose can also be loose. The replacement outlet from the dealer is steel, not plastic.
Another possibility for leakage is on the driver's side of the intake manifold. Underneath the air inlet is a metal cover on the end of the intake manifold. This covers the coolant passages at the end of the intake. Mine was oozing don't have to pull the intake to replace this.
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1 Answer

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I'm assuming you are talking about the 3800 v6 engine?
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And NO green coolant in a 97 Dexcool only!

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