Intake Manifold Leak

[AstroManiac]

I tried searching but didn't come up with anything, so...

I have a 97 Astro AWD...
How common is it for the intake manifold gasket to leak antifreeze/water on the 4.3, at the front driver side???

Yesterday morning, temp low 30s, driving along at 65-70 mph on the freeway, I noticed that the water temp gauge had climbed a bit from where it normally runs.
Then we noticed that the heater stopped putting out warm/hot air!

We pulled off the freeway & into a gas station & when I raised the hood, didn't see any steam or water leaking!
I put $.75 into the water/air machine & removed the cap on the radiator overflow tank & it was empty, though I had filled it 2 days before!
I then, cautiously, removed the radiator cap & it didn't seem to be hot, until I started putting water in & it filled up!
My wife was standing a little ways from the the van & told me the water was running out as fast as I was putting it in!
It appeared to be leaking at the back of the engine!

We called AAA & a rollback carried us 37 miles home!

Once at home, I pulled the engine cover & started slowly running water into the radiator! The Astro was sitting in the driveway, so it was a bit higher in the front!
It wasn't long before the water was pouring out again!
It was coming out of from between the intake manifold & the head & then running back along the manifold & down the back of the engine!
It was very difficult to see exactly where it was leaking, but with a couple different small mechanic's mirrors & a bright flashlight, I finally figured it out!

This Astro has 200,000 miles on it & the engine has never been taken apart! The first 140,000 miles it ran on CNG "compressed natural gas" & now after 60,000 miles on gasoline, the inside of the engine is fairly clean!

We run whatever gas is the cheapest & the inside of the intake manifold shows this! I am just amazed at the buildup of "yuck" under the top cover of the intake manifold & in the manifold itself!
Looking into the intake port on the heads though, show the backside of the valves to be fairly clean!

I'm going to order all of the gaskets & other parts I need & I'm sure it will take a full day just to clean everything up!!!

While I have it down this far, is there anything else I need to check???

Thanks... Have FUN FUN FUN... AstroManiac

[mikedamech]

Yes there is a high rate of failure and not only the 4.3. Get a Felpro gasket set and a Multi port injection kit from Linder Technology and enjoy another 100,000 Miles.

[91AWDAstro]

Good luck on your work. Might want to have that intake hot tanked and checked for leaks.

[AstroManiac]

I had the intake manifold "hot tanked" & it was run thru the cleaning cycle 3 times! It cleaned it real well & only needed attention to a couple areas. They did a pressure test & it passed.
I bought a FelPro Intake Gasket Set & was very impressed with the quality!
I was right, it took a whole day to clean everything!
I didn't find any evidence of the "spider" leaking & the poppets were very clean.
The fuel system had not been holding pressure for almost a year. This made it hard to start first thing in the morning & after it had sit for 20 minutes or so. When it wouldn't start, I'd give it a quick shot of starting fluid & it would fire right up.
So... I replaced the fuel pressure regulator & hopefully it will start OK now.
The original intake manifold bolts were at the point of no return, so they were replaced too!
Since this Astro has 200,000 miles & still had all of the original radiator, bypass & heater hoses, of course they're going to also be replaced.
During disassembly, a hose bib on the heater valve broke & it looked as if it had been cracked for quite some time. A new one was fairly inexpensive, only costing $19.99.
I figured while everything was apart, I might as well do a tuneup too, so I picked up a cap & rotor, as I already had new uninstalled plugs & wires I bought a couple years ago.
I replace the serpentine belt about every 50,000 miles & it was time again.
I installed the partially completed intake manifold this afternoon & will complete everything else tomorrow morning.
I will post a report as to how everything works!

Note... About 50,000 miles ago, the distributor's gear completely wore out & let the engine jump time! Since the shaft was a bit loose too, I went ahead & bought a rebuilt distributor that came with a new cam sensor. When I pulled it during disassembly, there wasn't any noticeable wear on the gear at all!

Have FUN FUN FUN... the 'Maniac

[AstroManiac]

OK... test drive... before the intake manifold started leaking, the Astro ran great!
I get it all back together, fire it up & fill it with water (for now) & warm it up!
Sitting at idle, if you "hit" the gas pedal, it dies out! If you push it easy, the rpms come up OK.
Took it for a drive around the neighborhood & it ran, if I was easy on the throttle & it worked best if I manually shifted it.
I hooked up the fuel pressure gauge & it read 56 psi at idle & would raise to 60 psi at a higher rpm.

Everything was cleaned... maybe I got some spray cleaner in the throttle position sensor???

Took it for some more cruising around & let it idle for 20 minutes while unloading some stuff in the back of the van at our storage unit & then drove several miles to have dinner!
After we left the restaurant, it seemed to run better & the hesitation didn't seem as bad.
Stopped for an ice cream cone & let it sit & idle & when we left it seemed to work even better!
Maybe something (throttle position sensor) is drying out???

I still haven't changed the fuel filter or the engine oil & filter!!!

ALSO... are the 2 fittings that screw into each end of the fuel filter suppose to have "o-rings" on them???
They've never had any since I bought the van & I've never installed any & it has never leaked.

[peppy]

Can someone post complete instructions on changing intake manifold gaskets on '91 Astro AWD?

Thanks!

[mikedamech]

Sorry about your problems with your 97. I do these all the time, there is a TSB on the tightening of the intake bolts, it says that improper sequence and torque are critical to main bearing failure, so I personally would leave this job to a professional. And not to get you more down but you can't see a poppet valve going bad, for 300 bucks and get rid of a component with a high failure rate, fix it while it's open not put a bandage on. Fuel pumps on this vehicle are very expensive, a new filter every 30,000. 52 lbs pressure is not always going to start this van because of the POPPET valves.

[AstroManiac]

Hey Mike, I am a retired profession mechanic & over the last 40+ years, I have owned & operated 3 different auto repair shops.
I do all of the maintenance & repair on my own vehicles, as I do not trust 90% of the "so-called" mechanics in my area.
I'm not sure where you got the 52 psi number at, but as I stated in my post, the psi ranged from 55 psi to 62 psi.
A friend made a custom test unit to check/test the spiders/injectors/poppets etc. & everything worked great when tested on it. Also, the poppets on this system fired at a low of 46-49 psi.
The fuel pump was replaced after the original pump died at 163,000 miles.
I finally changed the fuel filter & replaced the "ignition control module" as it was not allowing the injectors to fire upon startup & now everything is back to normal & it is running great.
Also, I replace the fuel filter every 15,000 miles or after 1 year, whichever comes first!
In reference to the TSB, a friend came up with the better "bolt tightening sequence" a long time before GM ever issued their TSB.
On this van, the intake gasket "blew out" to the outside of the engine, so the water/coolant did not go inside the engine & into the oil pan.
So... water/coolant being sucked up first by the oil pump & delivered to the main bearings ahead of the oil was not a problem.

[LaGrasta]

This post scares me. My hope is to attain 300,000 on my '98 2WD. I'm at 140,000.

I had a small coolant leak a the intake manifold and added some stop leak and it's been fine ever since (over a year ago). A dealer actually discovered the leak during my complaint of a possible bad spider (it wasn't) and said it's not worth fixing the leak and to consider an engine replacement. I wrote him off as crazy.

I'm "scared" because I'm trying to stay on top of everything, careful not to neglect anything. All this poppet talk and bolt sequence makes me think even if I fix it, it isn't going to be correct. I question my fuel filter, belt, etc service intervals too. As the miles are getting higher, I know it's going to be more critical.

Radiator and tranny has been flushed twice.
Two fuel pump assemblies and three fuel filters

Any advice on PREVENTATIVE maintence?

[mikedamech]

Hey Mike, I am a retired profession mechanic & over the last 40+ years, I have owned & operated 3 different auto repair shops.
I do all of the maintenance & repair on my own vehicles, as I do not trust 90% of the "so-called" mechanics in my area.
I'm not sure where you got the 52 psi number at, but as I stated in my post, the psi ranged from 55 psi to 62 psi.
A friend made a custom test unit to check/test the spiders/injectors/poppets etc. & everything worked great when tested on it. Also, the poppets on this system fired at a low of 46-49 psi.
The fuel pump was replaced after the original pump died at 163,000 miles.
I finally changed the fuel filter & replaced the "ignition control module" as it was not allowing the injectors to fire upon start up & now everything is back to normal & it is running great.
Also, I replace the fuel filter every 15,000 miles or after 1 year, whichever comes first!
In reference to the TSB, a friend came up with the better "bolt tightening sequence" a long time before GM ever issued their TSB.
On this van, the intake gasket "blew out" to the outside of the engine, so the water/coolant did not go inside the engine & into the oil pan.
So... water/coolant being sucked up first by the oil pump & delivered to the main bearings ahead of the oil was not a problem.

Hey Maniac, I wasn't directing my post to you only but to everyone who has a vehicle with these types of engines. and typically the coolant leaks both at the left front of the engine and into the inside, and water won't hurt the engine it's the grit from dextron that has been in the system too long that eats the bearings.
I've seen bad fuel pumps that, if the ign, switch is cycled will start the engine but not until the pressure on MY gauge gets to 59 or so lbs.

[AstroManiac]

While the antifreeze/coolant/water combo is corrosive, the real problem is that when the oil pan has that combo in it due to a intake leak, it's on the bottom under the oil & when you start the engine, the "combo" is what is sucked up first & then the oil.
That makes for "basically" a dry start & it pounds the rod bearings out.
Then the flakes of rod bearing material, eventually scar the main bearings.

The GM 2.8 V6's intake manifold leak was way more common than the 4.3's leak.

[1996astro]

Exactly what happened to my 97. The guy I bought it from had the intake gaskets replaced but apparently not soon enough. If he had I wouldn't have it today.

[ParkPit]

I tried searching but didn't come up with anything, so...

I have a 97 Astro AWD...
How common is it for the intake manifold gasket to leak antifreeze/water on the 4.3, at the front driver side???

Yesterday morning, temp low 30s, driving along at 65-70 mph on the freeway, I noticed that the water temp gauge had climbed a bit from where it normally runs.
Then we noticed that the heater stopped putting out warm/hot air!

We pulled off the freeway & into a gas station & when I raised the hood, didn't see any steam or water leaking!
I put $.75 into the water/air machine & removed the cap on the radiator overflow tank & it was empty, though I had filled it 2 days before!
I then, cautiously, removed the radiator cap & it didn't seem to be hot, until I started putting water in & it filled up!
My wife was standing a little ways from the the van & told me the water was running out as fast as I was putting it in!
It appeared to be leaking at the back of the engine!

We called AAA & a rollback carried us 37 miles home!

Once at home, I pulled the engine cover & started slowly running water into the radiator! The Astro was sitting in the driveway, so it was a bit higher in the front!
It wasn't long before the water was pouring out again!
It was coming out of from between the intake manifold & the head & then running back along the manifold & down the back of the engine!
It was very difficult to see exactly where it was leaking, but with a couple different small mechanic's mirrors & a bright flashlight, I finally figured it out!

This Astro has 200,000 miles on it & the engine has never been taken apart! The first 140,000 miles it ran on CNG "compressed natural gas" & now after 60,000 miles on gasoline, the inside of the engine is fairly clean!

We run whatever gas is the cheapest & the inside of the intake manifold shows this! I am just amazed at the buildup of "yuck" under the top cover of the intake manifold & in the manifold itself!
Looking into the intake port on the heads though, show the backside of the valves to be fairly clean!

I'm going to order all of the gaskets & other parts I need & I'm sure it will take a full day just to clean everything up!!!

While I have it down this far, is there anything else I need to check???

Thanks... Have FUN FUN FUN... AstroManiac

_________________
Have FUN FUN FUN... AstroManiac

Once you'd figure out the main problem you should must fix your problem for sure.
I hope you'll solve your problem soon :-)