Coolant Leak / Head Gasket

[RGibbs]

OK, long post here but I need some answers so I can decide what to do.

I have a 94 SLS with 160k. I have been chasing a coolant leak for about three years. It has never been really bad until recently. So here is the story.

I noticed a leak about 3 years ago and took it in to my mechanic. He saw that it was a hole in the radiator and replaced it. About 3 months later the radiator is leaking again, they replaced it for free. About 4 months later the water pump started leaking, and it was replaced. A few months later and a hose starts leaking and it was replaced. Then another radiator and more hoses.

Basically, the problem would over time manifest itself as a major leak and the part would be replaced. But, through it all, I was constanly adding a 50/50 mixture of antifreeze as my "check coolant level" warning on the dic would come up about every other month. So even though parts were failing and being replaced, it was always slowly leaking somewhere, although I never saw a puddle under the car until a major piece failed. I occassionally saw steam from under the hood on the driver's side. and smelled antifreeze burning off almost constantly.

Which brings us to current. The water temps stays between 220 and 230 as it has always been since I have owned the car. The leak is still there but now I am getting "check coolant level" a lot more frequently. I carry in my trunk three gallons of antifreeze and 3 gallons of water (to supplement the case of oil I have in there for the dreaded N* oil leak) Back to the shop I go, a busted hose is repaired and a new thermostat is put in and I am ready to roll. The car operates at about 201 to 207 all the way home Perfect! The next day the car shoots to 255, and before I can park it, it is back down to 214. Two days later the water pump is spitting so bad that I am topping off my coolant every 50 miles or so. Back to the shop to get the water pump replaced. I don't smell antifreeze or at least not yet, and the steam seems to be gone, but I got the "check coolant level" this morning after 96 miles since the water pump was replaced, and put in a half gallon of coolant.

After that "fix" I am told that the problem is terminal. It is explained to me this morning that the rear head gasket is bad and the anitifreeze is now leaking into the combustion chamber and being sent out the tailpipe. This problem is causing my car to start rough (which it never did before, but in the 2 days since the water pump has been fixed it has done it each morning). Further, the fix is basically a new engine because the current one can't really be fixed with any certainty. It is further explained that the design of the N* is the culprit here and that because the rear head is pretty much up against the firewall, it never gets the cool air the front head gets. This, over time, causes the rear head to overheat thus stretching the head bolts. I must admit my car has at least 3 times in the pat year given me the "stop engine now" warning due to overheating, and in each case I have been able to immediately stop. Additionally since I monitor my tempature alot more over the past year I have watched my car climb to 250+ temps, and watch it the temp go right back down just as quick. Although this was explained as the water pump sucking air through the leak that caused that to happen, and then when it starts sucking coolant the temp goes down.

Finally, it was explained that some how the engine is causing all the problems with the cooling components due to back pressure. In short, the leak can never be fixed for certain, the leak will get worse especially with summer and hotter temps coming and I would be better off to buy another car, given the age and mileage of the car.

I trust the guy who told me this, but I wanted to run it by you all first.

Your thoughts....

[STS 310]

Sure sounds as if you have had your fill of cooling problems. I havent heard the explanation of "the rear head is too close to the firewall". I would like to hear BBOB'S response to that. Seems like that is something that would have been thought about well before production of the N*.

It does sound as if the headgasket may have failed, especially with the eratic temperature readings. Then again lets hear what some of the other fine members have to add.

[danbuc]

I think that car originaly came with Dexcool from the factory. When it started leaking, did you flush it first, or just keep dumping in new coolant. Was the coolant the green stuff? If it was, that might be your problem. Dexcool does not mix verywell with regular green coolant. It can be flushed and replaced with it, but I think you still have to use the coolant suppliment tablets to help prevent corrosion. It sounds to me like the coolant was slowly eating away at the engine, causing leaks to occure. At this point, you are probably better off buying a new car. From the way you described it, it sounds like your mechanic thinks the heads are now warped. In the future, if you have a car with Dexcool, make sure you top it off with Dexcool, or drain it first before filling it with the green stuff. This will prevent major problems like the ones you had. Good Luck.

[BeelzeBob]

Originally Posted by RGibbs

It is further explained that the design of the N* is the culprit here and that because the rear head is pretty much up against the firewall, it never gets the cool air the front head gets. This, over time, causes the rear head to overheat thus stretching the head bolts.

...

You might trust him for all the work he is doing but don't trust his "explaination" of the rear head "not getting cool air".....LOL...or that the head gasket cannot be repaired (if that is the problem and the source of the leak)

Utter nonsense. The engine is liquid cooled, not air cooled. It it was a Harley I might consider that logic for a moment but since it isn't I won't. The coolant circulates equally thru the entire engine...block, left head, right head. "Cooling air" around the engine itself has nothing to do with it. The engine would survive fine wrapped in fiberglass insulation as the heat rejection and thermal stability of the engine is determined by the internal coolant flow. There is no appreciable cooling of the block and heads by the air circulating around it in the engine compartment so there is absolutely no substance to the explaination given.

It sounds like you may have a head gasket problem....but....

Before throwing in the towel there are several things to do:

Go to the search feature on the forum tool bar and type in "head gasket" and read the myriad of posts on the subject. There is a tremendous amount of info on this in the archives including a pictorial of timeserting the head bolt holes to effect a repair if the head bolts strip any threads during the repair. LOTS of info there for you to peruse. The engine can be repaired...it is not a throwaway at all.

Diagnose the leak and cooling system. Pressure check the system with a cooling sytem pressure tester to find and repair any leaks.

Pressure test the head gasket by introducing 120 PSI air pressure thru the spark plug ports and watch the cooling sytem for bubbling as each combustion chamber is done. This is a sure fire test that is relatively easy and simple to do that is fool proof in finding a head gasket leak or vindicating the head gasket as OK.

Check the water pump drive belt and water pump drive belt tensioner. Exercise the tensioner and lube the pivot point. Replace the water pump drive belt if it is the original. The water pump is at the rear of the engine and is driven off the rear of the inlet cam on the left side of the engine.

Service the cooling system with fresh coolant and add the GM coolant supplement. If there is an internal leak the supplement/sealer may seal it up to prevent the coolant intrusion at least partially. Search using "coolant supplement" and read my posts. Use the supplement and be sure to install it into one of the radiator hoses NOT the pressurized surge tank. Possibly there is a chronic leak from a porosity in a casting somewhere and the supplement will immeditately cure that problem.

Make sure that the vapor vent line from the water pump cavity is open and flowing and not restricted. Take the 3/8 hose off the pressurized surge tank when the sytem is cold and start the engine momentarily. Coolant should pee from the hose flowing toward the surge tank in a vigorous stream. If not, the vapor vent circuit is plugged somewhere and needs to be serviced.

The 94 Northstar came with the green conventional silicated coolant that needed replacement every 2-3 years/24-32K miles to keep the corrosion inhibitors in the coolant from becoming depleted. IF the corrosion inhibitors were depleted due to inadequate cooling system service then the engine and cooling system will incur damage from internal corrosion...i.e...radiator leaks, heater core leaks, head gaskets, etc......

[RGibbs]

Thanks for the responses. I don't believe it came with the Dexcool. I think I read on here someplace that Dexcool started in 95 or 96. When I bought it it had the green stuff and that is what I have always used.

Yeah, I am looking forward to what Bbobinksy has to say as well.

[BeelzeBob]

Originally Posted by danbuc

I think that car originaly came with Dexcool from the factory. When it started leaking, did you flush it first, or just keep dumping in new coolant. Was the coolant the green stuff? If it was, that might be your problem. Dexcool does not mix verywell with regular green coolant. It can be flushed and replaced with it, but I think you still have to use the coolant suppliment tablets to help prevent corrosion. It sounds to me like the coolant was slowly eating away at the engine, causing leaks to occure. At this point, you are probably better off buying a new car. From the way you described it, it sounds like your mechanic thinks the heads are now warped. In the future, if you have a car with Dexcool, make sure you top it off with Dexcool, or drain it first before filling it with the green stuff. This will prevent major problems like the ones you had. Good Luck.

uh.....93/94/95 Northstars had the conventional green silicated coolant in them from the factory. DexCool was introduced for the first time in the 1996 model year. That car came with the green silicated coolant which is the correct stuff for it.

I have personally never seen a Northstar with a "warped head"....even on ones that have been run dry for extended periods of time and severely overheated. Just does'nt happen. The head gasket may be damaged due to corrosion from lack of cooling system service but likely the head and block is fine.

Even if someone was refilling the car with DexCool instead of the correct green coolant it is highly unlikely that is what caused any problems. The two will mix fine without turning to jello, especially given the rate the thing seemed to be needing coolant added.

[danbuc]

Thanks for the info Bbob, I was just trying to remember what I've heard in the past about mixing the two. I didn't realize that the 93/94/95 N*'s came with the green stuff. Thanks for the clarification. About that wraped head thing, I was only reffering to the way his mechanic described it. He said that it would heat up casuing the headbolts to "stretch" which would mean some sort of movement. I realize it would take a tremendous amount of heat and pressure to warp a cylinder head, and that the gasket would fail long before the metal did. Only responding to what was mentioned.

[zonie77]

From my limited experience the engine may still be good. The first one we did had a history of overheating and still just needed gaskets. No Head milling or anything!
It is a major job but when you are done you know what you have. A used engine is a "pig in a poke".

THe mechanic is not impressing us with his lack of knowledge...