GM Vehicle Leaking Intake Manifolds-Anyone? - READ ONLY

29 messages, Last post on Aug 08, 2002 at 8:53 AM

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#1 of 29 GM leaking intake manifiolds-anyone had this problem by ricsch May 09, 2002 (5:24 pm)
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.
#2 of 29 3.1 engine, intake manifold leak by rick0068 May 09, 2002 (6:45 pm)
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.
#3 of 29 rick0068- by ricsch May 10, 2002 (3:20 am)
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?
#4 of 29 2 Corsicas by adc100 May 10, 2002 (3:49 am)
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.
#5 of 29 leaking intake manifold 97 tahoe by jack937 May 11, 2002 (6:00 pm)
97 Tahoe 4dr 4wd 350V8 75000 miles. Replaced leaking intake manifold.
#6 of 29 DIY Repair or Not by rs_petty May 13, 2002 (9:38 am)
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?
#7 of 29 95 Silverado Pick Up by chuckm6 May 13, 2002 (10:22 am)
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?
#8 of 29 98 silverado by wtd May 14, 2002 (2:17 pm)
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. Wayne
#9 of 29 by jc1973 May 14, 2002 (10:11 pm)
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
#10 of 29 3.1 Repair by rs_petty May 17, 2002 (6:54 am)
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.