Chevy/GMC 4.3L V6 Intake gasket replacement

[Land Yacht]

Here's a couple of sites that cover the job. The 4.3L in my S-10 started using coolant 4-5 years ago, and the lifters started to rattle. I knew the intake gaskets were a weak point in this motor, so I took it to an independent shop to replace them. Cost was $600-$700. I am hearing a little lifter noise again, I think if I need to do it again I will do it myself. When the gaskets leak, coolant runs down into the lifter valley and washes the oil off of the lifters, and if it gets bad enough contaminates the oil to the point that the main bearings will fail. Catching it early is the key here. Notes on Dexcool: It is crap. If you have the opportunity to change to a universal coolant like NAPA all type compatible or equivelent I highly recommend it. Dexcool works OK until you get air into the system, then it forms solids that will plug up heater core, radiator. Some believe that changing the coolant type will hasten intake gasket failure, I guess it might be best to wait to do it when the intake gaskets need replacement. Another note, NEVER use an abrasive disc to clean up the heads/intake surfaces. Abrasive particulate from the disk end up in the oil and bearing failure follows. There might even be a GM data bulletin about this because the problem is so common. Use a bristle disk, or like me, just use a razor blade scraper. Another note, there should be no need to seperate the upper and lower intake if the problem is coolant leakage from the lower intake gaskets. Keeping the upper and lower bolted together should save some time.

http://d-tips.com/General/Articles/article.aspx?id=/free/How%20to/GM%204.3L%20Intake%20Manifold%20repair/43intakearticle.art


Can't find the other site right now... Will add it next monday. Covers some details not mentioned in the link above.



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[Crosley.In.AZ]

I wonder if that tomslik fellow has seen many of this failure at PepBoys where he works

[model a vette]

I'm guessing that this leak is common on the later 4.3 engines with less bolts in the intake due to the redesign of the heads. Don't you just love it when they change something that IS working for something that cost less but doesn't do it's job?

[wayne petty]

the gaskets were designed to look great on paper..   use minimal materials..

there just was not enough material around the water passages to support the molded silicone seal...

the thermal cycling and water pump pressure on the coolant passages break the plastic that holds the silicone seal in place...

the new gaskets are much better in structural design..  might use a few cents more in plastic..


why do i think this is a cause... there is significant pressure behind the thermostat...  i have had to change too many of these...   mostly on astro vans...   be sure to order the kit with the valve cover gaskets...   pick up spark plugs and wires...  cap and rotor.. and a new coil...   and an egr gasket.. they don't come in the intake kit..

the spark plugs and wires are easier to change when the intake and valve covers are off..   at least in the astro vans..

i also stuff the intake valley with towels... to prevent dirt from falling in..

[enjenjo]

It isn;t just the 4.3 with a problem. 3.1, 3.4, and 3.8 all have problems too. I think it;s the gasket material breaking down. Local shop owner showed me some he is trying, the plastic is replaced with dead soft aluminum, with the silicone O ring gaskets. I have had the gaskets on my 3.8 replaced once so far at 65,000 miles, and the plastic elbows on the water pump replaced twice.

[Crosley.In.AZ]

I did an R&R  on intake gaskets in a 3.4 chevy V6  for my brother 2 years ago.  His Lumina is low mileage vehicle given to him by his elderly  mom n law.

I had not seen the problem  of these gaskets , although I heard about it.

[tomslik]

I wonder if that tomslik fellow has seen many of this failure at PepBoys where he works

1 or 2;)

anything with that type of gasket is gonna leak eventually.
s-10's are really good about plugging heater cores too.
dexcool sucks but i like it (think about it)


how's things at aamco?

[model a vette]

I had heard about the intake gasket issues with the 60 degree V6s but had not heard of them on 90 degree engines. Live and learn.

I can almost hear the discussion about Dexcool around the conference table:

"We have come up with a new coolant that doesn't have to be changed for 50,000 miles. We can eliminate the radiator cap because the customer won't have to check the radiator fluid. Think of the cost savings!"

"Any downside?"

"Only a minor one. If the fluid DOES go low and air gets in with the fluid, the fluid becomes semi-fluid and clogs any slow moving parts of the system. But really, how often does that happen in real life?"

[Crosley.In.AZ]

regarding DexCool..  I run the stuff about 2 yrs , then remove it on my new vehicles from GM.    I want to get some use of the stuff.

I then flush the cooling system with the hose water.  Then flush that with a couple gallons of distilled water , then add the long life -  extended life coolant , Usually Prestone .

From what I see and hear  the gaskets are a poor design - materials for any real world use and life span.

[GMRodder]

Replace with Felpro gaskets they seem to last the longest.  Use silicone sealer around the water jackets on the intake too.  Replace your antifreeze every two to three years.  The new engines seem to get more acidic than in the old days.  Thus the heads and intake surface pits quicker now.

[Land Yacht]

Here's a couple of sites that cover the job. The 4.3L in my S-10 started using coolant 4-5 years ago, and the lifters started to rattle. I knew the intake gaskets were a weak point in this motor, so I took it to an independent shop to replace them. Cost was $600-$700. I am hearing a little lifter noise again, I think if I need to do it again I will do it myself. When the gaskets leak, coolant runs down into the lifter valley and washes the oil off of the lifters, and if it gets bad enough contaminates the oil to the point that the main bearings will fail. Catching it early is the key here. Notes on Dexcool: It is crap. If you have the opportunity to change to a universal coolant like NAPA all type compatible or equivelent I highly recommend it. Dexcool works OK until you get air into the system, then it forms solids that will plug up heater core, radiator. Some believe that changing the coolant type will hasten intake gasket failure, I guess it might be best to wait to do it when the intake gaskets need replacement. Another note, NEVER use an abrasive disc to clean up the heads/intake surfaces. Abrasive particulate from the disk end up in the oil and bearing failure follows. There might even be a GM data bulletin about this because the problem is so common. Use a bristle disk, or like me, just use a razor blade scraper. Another note, there should be no need to seperate the upper and lower intake if the problem is coolant leakage from the lower intake gaskets. Keeping the upper and lower bolted together should save some time.

http://d-tips.com/General/Articles/article.aspx?id=/free/How%20to/GM%204.3L%20Intake%20Manifold%20repair/43intakearticle.art

Added the link below. Pretty good detail. Looks like he uses the abrasive disk = bad.

http://www.handymanlyness.com/archives/auto/repair/engine_mech/intake_manifold/GM_truck/gasket_replace_99_Jimmy.html