4.3 Intake Manifold

John R · May 30, 2003

Has anyone had problems with the plastic intake manifold on the newer 4.3's warping and start leaking antifreeze either in the oil or just out on the ground?

I have A friend that's A mechanic and he tells me there have been

problems with this. From what I have been told the antifreeze leaks into the oil and we all know what that does.

slickracer · May 30, 2003

Mine had to be replaced at 33,000 miles. Antifreeze was leaking on to the ground. The real problem is a crappy gasket design.

bowtie_pasta · May 30, 2003

Yikes! What year did they start using this design?

Truckman031 · June 1, 2003

Has anyone had problems with the plastic intake manifold on the newer 4.3's warping and start leaking antifreeze either in the oil or just out on the ground?
I have A friend that's A mechanic and he tells me there have been

problems with this. From what I have been told the antifreeze leaks into the oil and we all know what that does.

My cousin is a mechanic at a Chevy dealership and he has said the 4.3s have bad intake manifolds. Some leak, some don't.

l4x4113 · January 2, 2006

Has anyone had problems with the plastic intake manifold on the newer 4.3's warping and start leaking antifreeze either in the oil or just out on the ground?
I have A friend that's A mechanic and he tells me there have been

problems with this. From what I have been told the antifreeze leaks into the oil and we all know what that does.

My cousin is a mechanic at a Chevy dealership and he has said the 4.3s have bad intake manifolds. Some leak, some don't.

<{POST_SNAPBACK}>

Hey does your cousin know if there was a recall on them because i know a lot of people with that problem including me???

Crew Cab Sonoma · January 9, 2006

the 96-up 4.3 intake manifolds are 2 piece. plastic upper, and aluminum lower.

no coolant flows through the upper plastic part, only the lower part.

the problem is with the intake to cylinder head gasket. its fairly common on these engines for coolant to start seeping around the coolant crossover ports at each corner of the manifold, at around 50-70K miles.

you do not have to remove the plastic upper part of the manifold, or even the throttle body, to remove the manifold.

Truckman031 · January 9, 2006

I had to have my intake gasket replaced 1000 miles ago(60700 miles). There is no recall, as I had to pay $800 in repairs. Normally, my cousin fixes the truck (I pay him on the side), but he no longer works at a Chevy dealer.

SilveradoBlues03 · February 11, 2006

Does this leakage happen with 4.3's up to '03? I have an '03 Silverado with the 4.3 and getting close to the end of my new car warranty.

Anyway this can be checked BEFORE damage is done to the engine?

Thanks

Truckman031 · February 12, 2006

I'm not sure if the new 4.3s have that problem. I don't think they changed anything, so I'd have to guess that you might have that prob. down the road. Unfortunatly, the intake gasket usually doesn't go out until 50,000 miles or more.

As far as damaging the engine, I don't think it does. You will know when it happens, as your truck will start leaking coolant out of the blue.

gmpartsguy · February 14, 2006

All 4.3 with vin code W or X (eighth digit of the vin#) will leak. It is a fairly easy job if you have better than average mechanical ability. Buy the GM gaskets as they have been redesigned and are fairly inexpensive compared to aftermarket. Aftermarket wants to sell you uppers and lowers. You only need lowers. Make sure that you perform an oil and filter change before you start the motor. I know a guy that didn't. His truck is now at my house waiting to get a motor put in it. Coolant is not a good lubricant.

bowtie_pasta · February 15, 2006

It's somewhat ironic to see this topic bumped up from the past. I see my post in '03 and the intake manifold event happened to me not too much later. Mine lasted until ~110k. I paid $490 for the dealer to do it.

rdnkcpa · February 17, 2006

I'm doing the same thing to my 1999 Chevy Astro with the 4.3L. I took off the dog house and I can see the leak on the backside of the mainfold right behind the distributor. My water pump has also developed a leak as well. It looks like tons of fun to get this thing apart. All of sudden my van has started leaking coolant, oil, and the power window motors both died with in a couple of months. Right now the van is parked in my garage, my wife is driving my Silverado and I'm driving my old beater.

So i don't have to remove the throttle body, what about the distributor?

The water pump job looks to be real fun. The A/C compressor, P/S pump are on a big bracket that seems to have to be removed to get at the water pump.

And according to this thread GM has redesigned the gasket? Am I safer with GM parts or aftermarket?

bowtie_pasta · February 17, 2006

I'm doing the same thing to my 1999 Chevy Astro with the 4.3L. I took off the dog house and I can see the leak on the backside of the mainfold right behind the distributor. My water pump has also developed a leak as well. It looks like tons of fun to get this thing apart. All of sudden my van has started leaking coolant, oil, and the power window motors both died with in a couple of months. Right now the van is parked in my garage, my wife is driving my Silverado and I'm driving my old beater.

So i don't have to remove the throttle body, what about the distributor?

The water pump job looks to be real fun. The A/C compressor, P/S pump are on a big bracket that seems to have to be removed to get at the water pump.

And according to this thread GM has redesigned the gasket? Am I safer with GM parts or aftermarket?

<{POST_SNAPBACK}>

I would make sure you get the redesigned gasket for sure. If you get and it's done right you shouldn't have to worry about the intake manifold for the life of the engine. There is also a special sealant/adhesive that is required, GM can supply this too.

After far as the water pump, you should not have to remove the AC/Power Steering bracket. At least my Haynes manual does not specify that. You should be able to do it just remove the fan shroud and fan. I've also heard it's easier to reach the left bolts it you remove the belt tensioner too.

Good luck.

rdnkcpa · February 19, 2006

I'm doing the same thing to my 1999 Chevy Astro with the 4.3L. I took off the dog house and I can see the leak on the backside of the mainfold right behind the distributor. My water pump has also developed a leak as well. It looks like tons of fun to get this thing apart. All of sudden my van has started leaking coolant, oil, and the power window motors both died with in a couple of months. Right now the van is parked in my garage, my wife is driving my Silverado and I'm driving my old beater.

So i don't have to remove the throttle body, what about the distributor?

The water pump job looks to be real fun. The A/C compressor, P/S pump are on a big bracket that seems to have to be removed to get at the water pump.

And according to this thread GM has redesigned the gasket? Am I safer with GM parts or aftermarket?

<{POST_SNAPBACK}>

I would make sure you get the redesigned gasket for sure. If you get and it's done right you shouldn't have to worry about the intake manifold for the life of the engine. There is also a special sealant/adhesive that is required, GM can supply this too.

After far as the water pump, you should not have to remove the AC/Power Steering bracket. At least my Haynes manual does not specify that. You should be able to do it just remove the fan shroud and fan. I've also heard it's easier to reach the left bolts it you remove the belt tensioner too.

Good luck.

<{POST_SNAPBACK}>

I was looking at it again today. I agree the brackets don't have to come off for the water pump, but I'm not sure about the intake manifold. I'll keep picking at it. Thanks for the information.

pm26 · February 19, 2006

I hate plastic intake manifolds. I think that the only reason the manufacturers use them is that they are cheaper to make than aluminum cast manifolds. Of course, to justify using cheap plastic, they will tell you how plastic maniflods keep the air cool and make the vehicle run better. And then they given you the weight saving benefit story. You know, the similar crap they used to justify donut spare tires in cars.

It is not just US manufacturers that have switched to plastic intake manifolds. Even BMW uses them. I have not had my truck long enough to have problems with the plastic manifold, but I have never had any problems with aluminum cast intake manifolds on any vehicle, driven well in excess of 100k miles. And I certainly did not notice any negative performance impact.