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GM Vehicle Leaking Intake Manifolds-Anyone?

ricschricsch Posts: 540
edited March 2014 in Chevrolet
Former or current GM owners, post here if you have experienced a problem with your GM auto or truck with an external or internal coolant or oil leak related to the intake manifold/gaskets/mating surfaces. Also, state year,vehicle type, mileage. Curious as this seams to be a common problem with GM. I have had a few early '90's GM trucks that had exteranl leakage, my sister just had to replace the engine in a '97 S-Blazer with only 46K miles due to an internal leak.


  • rick0068rick0068 Posts: 2
    I had a 97 lumina that leak coolant externally
    and probaly internally with the oil. I cleaned
    the overflow reservior real good put sealer in
    the radiator and eventually traded the car. The
    engine had about 66,000 on it.

    I also presently haave a 96 cutless with the same
    engine and same problem. This cars problem poped
    up with 95000 miles on it. I put a sealer in it
    also and plan on trading it also.

    Both cars were very well cared for. I was guessing it could be the Dex cool coolant.
  • ricschricsch Posts: 540
    Thanks for the reply. I have heard that it could possibly be the Dexcool, seems that as the coolant deteriorates, it becomes acidic, and starts to break down the gasket material, also have been told that mating surfaces of the engine don't always allow for a good seal. GM recommends 5 years/100K on the coolant life, from what I have seen, I wouldn't go past 3 years/50K personally. I've been told that a person can test the ph value with litmus paper, probably worthwhile. What make of vehicle will you trade your current vehicle in on?
  • adc100adc100 Posts: 1,521
    92 3.1- 125 K when leak occurred
    94 3.1- 76K when leak occurred

    I have heard the DexCool theory but I don't believe its the whole answer. Dealer told me in 2001 that it was still occurring even with DexCool. I assume it is a problem with Aluminum heads/cast iron block.
    Great engines otherwise but fatally flawed.

    Does anyone know if the 3.4 engine is prone to this? My understanding is -yes.
  • jack937jack937 Posts: 2
    97 Tahoe 4dr 4wd 350V8 75000 miles. Replaced leaking intake manifold.
  • rs_pettyrs_petty Posts: 423
    If anyone with this problem has done the repair I'd like to hear any tips. My 99 Lumina just diagnosed with this problem. How hard can it be?
  • chuckm6chuckm6 Posts: 1
    My wife drives a '95 Silverado, which she bought new with the 5 liter V8. She changes oil and filter at 3,500 miles. The truck now has 71,000 easy miles on it. One day she said the oil pressure gauge was doing funny things and then stabilized. I checked her oil and found it to be down almost two quarts in about 2,500 miles. There are no external leaks, and no smoking, even at start up. The tail pipe has no oil residue in it. After the last oil change I added a quart at 1,700 miles. I just changed the spark plugs and the PVC valve. There was a little oil on the air cleaner cover. The Dexcool (late 95 trucks) is past due to be changed, which I will do very soon.---Might this problem have something to do with the leaky intake manifold you described?
  • wtdwtd Posts: 96
    I had the intake manifold gaskets replaced on my 98 ext-cab Z-71 with the 5.7L V-8 at 24,000 miles. Luckily the truck was still under warrenty. Mine was leaking at the front and rear of the engine.

    This is a widely know problem with the Vortec V-8 engines. The mechanic that worked on mine said that the intake was torqued down too tight from the factory, eventually causing the gaskets to crack and leak. This might be the reason the intakes on the above mentioned cars are also leaking.

  • jc1973jc1973 Posts: 63
    well i have a 1994 sunbird with the 3.1 engine which was very poorly maintained for the first 80000 miles have a 150000 on it now and still havnt had a problem how can you actually tell when the gasket is going
  • rs_pettyrs_petty Posts: 423
    The gasket is plastic with the seals imbedded to just seal the runners. Mine had cracked causing the leak. The symptom is coolant loss. My wrench said it cracked from the heating/cooling cycle and he'll probably see more - probably exacerbated with 2 different metals (aluminum and cast iron). Confirmed the same on the Vortec engine and the lack of chevy putting enough bolts on the manifold - said there were only about 2-3. The repair is very difficult (8 hour shop time). Intake disassembled, fuel rails/injectors removed, rocker arms and pushrods removed, engine tilted forward, and then all put back together. The stinker is that GM part was all that was available - no better aftermarket design. Stupid GM engineers - my last chevy.
  • alcanalcan Posts: 2,550
    Here's the book time for V6 Sunbird intake manifold replacement:

    1984-2000 Models
    Four... 3.9 hrs
    V6.... 5.4 hrs
    Includes: R&I plenum, runners, fuel rail, and injectors
  • davy1davy1 Posts: 3
    Intake manifold leak at 59k. Kicker is that the dealer says manifold gasket is back-ordered with no anticipated delivery date. Mentioned he has 2 others on the lot also needing the same repair.

    Same problem killed my 84 S-10 2.8Litre 4WD when it had 104k.
  • mcpdjohnmcpdjohn Posts: 44
    I just recently had that problem with my '96 Sierra 5.7 liter Vortec. I had 79K on the truck, but the coolant change interval is "100K miles or 5 years, whichever occurs first". I was two years beyond the time limit, and I believe my Dexcool went acidic as a result, costing me a new gasket. I did the job with a friend. It was a big job (IMHO). We had to pull the distributor too. I wouldn't recommend this job to just anyone. You need to be pretty competent under the hood to get this one done. I bought a Fel-Pro gasket set from Auto Zone and it worked fine. My lesson learned is, change coolant in accordance with the maintenance schedule. I don't blame this one on GMC. I blame myself.
  • wtdwtd Posts: 96
    I doubt it was caused by your antifreeze even though it was in longer than it called for. The intake leak is a well documented problem for this engine and is caused by inproperly torqued intake bolts. I've read many topics and information on this where this leak occured at your milage or less. Mine leaked at 24,000 miles and 3 years on the coolant. I personally blame GM as it was a mistake on their part.
  • corlt1corlt1 Posts: 29
    My 92 LT1 Corvette with the 5.7L (350) V8 has had the intake manifold removed and replaced twice by the dealer. Each time the fix lasted about 3 years. It's leaking again, but alas, it's now my weekend only car that sits in the garage most of the time. Mine appears to leak only oil. Chevy uses a gasket only where the intake and water ports meet the head. They use RTV silicon sealer at the back and front of the manilfold and this is my problem. I wish someone made a gasket with the manifold end seals, like the older Chevys.
  • msm4msm4 Posts: 1
    I just had my 1999 Tahoe intake manifold coolant leak repaired. It has 44,000 miles on it. The dealer where I purchased it quoted over $500 for the repair. I complained that this was a known problem and should be covered by an extended warrantee. They would not pay for the entire repair but they did split the bill 50 50. The repair cost me $275. So, complain to the dealer and GM and hopefully you'll get a brake on the repair cost. Then complain to the FTC. Enough complaints and maybe GM will be forced to cover this repair.
  • corsicachevycorsicachevy Posts: 316
    There is an archieved forum regarding intake manifold leaks on GM's 2.8/3.1/3.4 V6 engines. If anyone is interested, I believe there are about 100 posts relating to this issue. It may be worth a look.

    A coolant leak on my 1996 Chevrolet Corsica is what actually got me interested in Edmunds Townhall - so something good did come from it. :-)

    I had my Corsica's leak repaired at about 70,000 miles (I think) and the car now has over 100,000 miles. Has anybody had this problem re-occur? One more $650 repair bill and my Corsica will be ready for the glue factory.
  • ddonohueddonohue Posts: 1
    My olds cutlass has been leaking coolant. First the mechanic thought it was just a gasget now it's the whole damn engine. Unfortunately Oldsmobile won't do a damn thing for me. Isn't that typical. I don't even have 60000miles on this car and it needs a new engine. What a joke. If I don't get some kind of satisfaction from them this for sure will be my last GM car.
  • leadfoot4leadfoot4 Posts: 593
    "the whole damn engine" doesn't leak coolant or oil. The valve covers, intake manifold gaskets, timimg cover seals, crankshaft seals, oil pan gaskets, and thermostat housings leak. That's only six major places to check.
    It sounds like your mechanic is setting you up for a big repair bill, or doesn't want to be bothered with the job, and trying to scare you off. I think you should find another mechanic.
    Or, find yourself a couple cans of spray engine degreaser and give the engine a good bath. That way, you can find the source of the leak and repair just that. The airstream that is generated by driving the car has a tendency to blow fluids all over, making a small leak look really big. A clean engine is easier to diagnose.
  • i am working on one of these again, just doing a 3000 mi service oil change, check fluids on this one with 97,000. noticed that coolant level low and none in resivior .so i suggested a cooling system sevice. next thing i did was pressure test the cooling syst and sit and wait. sure enough ,there she blows! no other leaks. now, what i really came in to this forum is to find out what the labor manual says for time to do this job. does anybody know . i am a ASE cert. tec. but i think my service writer is nuts. how about this 32.00 parts and 250.00 LABOR? YOU HAVE TO BE KIDDING ME. the last time i did one was a 92 5.7 SURBURBAN and i charged 500.00 labor and i new that was a deal . the one before that a 97K1500 5.7 started at 800.00 plus parts .whats going on ? can anyone tell me what alldata says for time?
  • alcanalcan Posts: 2,550
    Check my reply in "It's gonna cost HOW much???" topic. Those times are Mitchell. Btw, you should be getting to where you can do those in your sleep by now. LOL.
  • alerowneralerowner Posts: 1
    I have a 2000 Alero with 25k on it. Serviced religiously for scheduled mainenance. So far I have had two sets of breaks, rotors etc.(all under 10k when done) Now I am told that the light keeps coming on because I have two leaks, the manifold is one and the water pump. They also claim they need two weeks for parts and the car is safe to drive....any feedback?
  • wainwain Posts: 479
    5 japanese cars I owned -up to 130K miles on some never leaked one drop.

    All GM cars I have owned, most purchased new, ALWAYS leaked. Some coolant, some oil.

    The answer is simple.
  • corsicachevycorsicachevy Posts: 316
    alerowner - Safe to drive? That depends.

    Has your oil started to get greyish and slimey? If that is the case, then your leak has compromised your lubrication system and could cause some internal damage. Do you know how long your engine has been leaking coolant? Two weeks likely won't harm you engine severely (or at all), but I would keep my driving to a minimum just to be safe. They will (or should) change your oil when they do your manifold/water pump work.
  • There is an online petition for this problem located:

    If you have had this problem please visit and sign

  • jaybo4jaybo4 Posts: 8
    The intake failed on my motor too.
    The tube that connected the heater hose to
    the engine cracked off the manifold.
    The manifold needed to be replaced for $600.
    I was later told by another tech that they can
    drill and tap that hole and screw in a plumbing
    type of fitting. Too late now...

  • Anyone fix the leak on a 3.8L? What is involved? Anything to watch out for? does the intake have to be replaced or just the gasket? What comes off? I have a 91 w/throttle body.

  • pernaperna Posts: 533
    I had the 3.4 that started leaking oil around 22k miles. Lower intake replaced under warranty, dumped the car soon afterward.
  • dirkdaddydirkdaddy Posts: 313
    As someone said earlier, to repair the 3.4 intake seal, you have ot do a lot of work. Disc. alternator, fuel injector rail, throttle body, upper intake, valve covers, lower intake, rockerarms loosen and pushrod removal. typically that means disconnecting the exhaust and motor mounts and tipping the motor forward. Pretty big job, but not bad if you have time and tools.

    I'm contemplating it myself as I have a well equipped shop, but my leak is exernal so far and very small. And its a Van, so its 2x harder.

This discussion has been closed.