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 OK , you "late model" gurus, help me out.

 

  I have a '95 Park Avenue with 130,000 miles.  It has started, recently, losing coolant.  Nothing obvious externally.Does not appear to be going into the oil. The inside of the filler cap is clean and dry. which leads me to fear the intake manifold, again. It was changed at about 105,000 miles, three years ago, or so.  SO, how does one CONFIRM the manifold is leaking, or not leaking. I just hate replacing something and learning the problem is still there.  Open for ideas.

 

  Thanks

 

  Ben

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How fast? I had a pinhole in heater core for years before it became a major problem. Do you hear any gurgling? Is the temp guage erratic at all?

I had an intake leak on a '97 3100, but initially the water would leak slow enough that it would evaporate before it would obviously show on the dipstick. The bummer of it was that the gasket surface was terribly corroded by the time I figured out what was going on. I wasn't sure I'd ever get a gasket to seal there again.

Best advice I've got is to pressure test the system, listen for leaks (14 psi isn't very loud), and hose things down with Mr. Bubble. Kinda hard to do on the core, though...

Edited by SpecialEducation (see edit history)
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I had 2 coolant loss problems with my 93 LeSabre.The car only has 65000 miles.The first was the gasket between the throttle body and the intake plenum.It was such a small leak that i could smell the coolant long before i actually saw it dripping.It was turning to steam on the exhaust crossover.The second was the elbow out of the manifold connecting to the bypass hose near the water pump.Mine was plastic and cracked.Worth checking both before doing maifold gaskets again.

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Here is a probably good fix for your problem.

 

Look here.  https://www.youtube.com/watch?v=IFiICANvre4

 

and here  http://forums.edmunds.com/discussion/14412/pontiac/park-avenue/1995-2004-3800-intake-manifold-coolant-leak-cheap-fix

 

and here  https://www.youtube.com/watch?v=SInd0jUogrM

 

Also look in the area of the EGR valve and the intake manifold.

Edited by Larry Schramm (see edit history)
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Yep, that makes me think, does that radiator have plastic ends?  A small crack there can be hard to detect, too...

Yep, that makes me think, does that radiator have plastic ends?  A small crack there can be hard to detect, too...

Every response above is valid and should be visually checked for any sign of leakage. The radiator with the plastic ends are the home of the self sealing leak and spotting a crack in the plastic today would be a gift.

Even at 20 years old and 130,000 miles the 3800 motor is still darn near bullet proof and the Park was one well built car, if you didn't use the GM coolant when you had the gasket replaced it should still be good. That GM coolant is a great coolant until it's not and must be changed when it should be, because when it gets old it gets corrosive. The Northstar engines have a really pricy gasket replace cost and if they aren't to bad, a system flush and a real good engine leak seal treatment will usually work. It's a $50 risk and it works, or it doesn't. If it doesn't work the first time a second time is tossing good money after bad.

How do you know if you have a leaking intake gasket, at the gasket coolant can only leak into, or out of the motor. You have noticeable coolant loss, no obvious outward leak, or obvious coolant in the oil and if it is the gasket, there is only one other place it can go; that's into the combustion chamber. It takes quite a leak to be tea kittling steam out the tail pipe, a lot less to clean the pistons and plugs. Guessing you got new spark plugs when your gasket was replaced 25,000 miles ago, you might be able to find one or more clean plugs depending on how much coolant you are loosing. Only one really clean plug would point more towards a head gasket and not likely on a 3800 that hasn't been overheated.

For the noticeable coolant leak that doesn't film the windshield, smell sweat in the cab, or puddle on the ground, I would look to the 20 year old radiator after you check your plugs.

Plastic and aluminum expand and contract at different rates and eventually these radiators will leak at the seal between the two parts. This is an insidious little leak as when it first starts it will also self seal and when it first starts it usually only occurs when everything is warm and the car is parked for a period of time pointing into a wind that causes rapid cooling. The finger crimps that hold the plastic tank tight to the seal get fatigued after so many expansions and they're not quite as tight as they used to be. Once started this leak only gets worse. In the part of the country where I am it can take a couple of years to get bad enough to find as you first notice the coolant loss in the winter, then the weather improves and if next winter isn't as cold as this winter it might not get large enough to find for a couple of years. Not that it has stopped leaking, but it's harder than heck to find a 10 drop a week, warm weather leak.

As crazy as the weather has been this winter, this normally frozen north problem could be happening as far south as Florida and taping a couple pieces of paper towel below the radiator end caps will tell you if you have this type of leak.

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Seems like that when the cars were newer and the leaks started, there was a GM TSB on this subject.  Not many parts to replace, especially as things progressed.  I remember a smaller, thermostat gasket-shaped sponge-rubber-type gasket and two speed nuts with sealer/"anti-loosening" compound in them.  If it was bad enough, the manifold would need to be replaced.  As time went on, new TSBs were issued, with the final one being to just replace the speed nuts holding things together.  In many cases, our techs just put some blue Loctite (or similar) on them and reused them.

 

Seems like there were only a few years of this problem?  Related to the material the manifold was made from (metal or plastic)?  Dorman has replacement manifolds.

 

Ethylene glycol coolants are corrosive due to their basic nature.  It's the additive package that keeps the ph level where it needs to be.  Where DexCool does cause corrosion is, by observation, when the coolant level gets low and stays that way.  We had a string of S-10s that used the plastic/metal radiator cap.  The TSBs blamed the caps for loosing their pressure-holding capabilities, letting too much coolant out, and not pulling it back from the reservoir, especially after the corrosion accumulated in the filler neck.  So the "fix" was two doses of 2-part DuPont radiator flush/cleaner, a new cap, and fresh DexCool mixed to specs.

 

I know that many still like "metal" radiators, but the aluminum core/plastic tank GM radiators have proven to be very troublefree.  I liked this new design as it made the tanks replaceable, even with the special crimping tool, but few issues resulted which needed a tank replacement, in normal use.  ACDelco even had some "upgrade" replacement radiators of this construction in the earlier 2000s.  I got one for my '77 Camaro and it cooled much better than any copper radiator I had in it (even the Modine 3-cores).  On the spring day when I finally replaced the clogged Modine, it took 45 minutes for the thermostat to open with the engine idling.  Just my experiences and what we saw in the service department.

 

The reason for these composite radiators, other than improved efficiency, is that they don't use lead to hold them together.  Ethylene glycol doesn't like lead, which (again) is what the additive package is for.  Plus probably the pecan shell pellets.

 

You might be able to find the GM TSBs online somewhere.

 

NTX5467

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Since I deal mainly with the '88-91 3800 engines,  all I know there were problems with cracks and leaks on the later series of engine with the plastic intake plenum. 

  This was apparently bad enough that you could by an aftermarket plastic intake that was designed to solve the problem

I have a neighbor with a 1999 Regal and he has replaced the plastic intake because of a crack. 

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