Dreaded GM 3800 intake manifold gasket problem?

[saberz]

Originally Posted By: sciphi
If you do need to change the IM gaskets, here's an excellent reference: http://www.pontiacbonnevilleclub.com/forum/viewtopic.php?f=53&t=3591

Read that, then get a pressure test done. That'll tell you if the leak is internal, external, or if it's a radiator cap.

The cost is about $250 in parts for the DIY. At a shop it will be that plus 4-6 hours of labor. I did my intake gaskets myself, and it cost me about $250 after everything.


Listen to the man. My brother had to get the gaskets done because of a coolant leak and it was in excess of 1200 with a few side jobs done on the car as well. He got 01 Impala from in in late 08 and has roughly 100k on it now.

 

[sciphi]

My friend's Bonneville puked the black coolant elbow in the picture. It left a nice mess on the ground.

From my picture, I'm guessing you saw the little bow in of the gasket at the coolant passage. That's where it would have shortly failed.

Larry, the upper intake manifold gets cooked by the EGR since there's not enough of an air gap between the EGR stovepipe and the upper intake. Recent redesigns tweaked the stovepipe diameter to increase the air gap, and put a steel insert into the upper intake mani so it cannot scorch the plastic as badly.

 

[The Critic]

Honestly, although there has been good advice given in this thread on how to perform the repair, some fluctuation in the coolant level does not necessarily indicate a problem.

There may be nothing wrong at all, and the pressure test may confirm that. I would instead, sample the used oil to check for coolant contamination instead of paying your mechanic to test the cooling system.

 

[sciphi]

Critic, if the coolant level is consistently dropping on these engines, that's an ominous sign. It could be the radiator cap, it could be you're about to have a major problem on your hands.

And, the pressure test can be done by any garage in an hour. The oil analysis takes a bit longer. By the time the oil analysis comes back, the lower intake manifold gaskets could have already failed.

On this engine, in this case, I believe the best way forward right now is with a pressure test. The used oil analysis can be used to follow up either the fix or to find a leak that is starting.

 

[swalve]

I did this last summer with my 97 Grand Prix. It is a long job for the DIYer, but not impossible.

When I got it apart, I found the gaskets to be in pretty bad shape. They were a plastic frame with orange silicone molded double lipped oring sorts of things between the passages. It looked to me that the plastic frame either shrunk, or the oring things went through a swelling and shrinking process. In some spots, they were broken, and in other spots they were smushed together.

I don't remember what kind of gaskets I used for the replacement.

What I did notice was that the aluminum had gotten pitted where the gaskets had leaked. I cleaned it up as best I could, and then worked in some silicone sealer in the hope that it would get into the pits and seal them. SO far, so good.

Pitfalls which turned it into a much longer job than I expected:

- the coolant elbows looked fine, so I didn't get any replacements. They fell apart and it took a while to find some in the local stores.

- Mine is the supercharged version, I don't know if it is the same on the NA version- the fuel rail has to come out, and the orings seemed to be in OK shape. But I somehow nicked a couple and when I fired it up, gas went everywhere. Again, had to go looking for orings and replace them after the fact. I would suggest changing them out while you are in there just for good measure.

- Probably a good time to change the spark plugs and wires since you have half the engine off anyway. Same for rocker cover gaskets. (Wish I had...)

There are a lot of steps and fiddly little parts. I find that the best way to do a job like this is to set up a space to store the parts as I take them off. A side wall in a garage works well, or if you are inclined, a series of rubbermaid containers. Take something off, put it in the storage area. As you take off each piece, put it in the area next to the last piece in chronological order.

(I have a good memory for these things, but for vacuum lines and wiring harnesses, they almost always will "show you" where they go once you put them back together- the length of the connector and the shape of the connector almost always means that it ends up back right where it goes. Vacuum lines are a little trickier, especially if they are replacement ones that aren't molded. Since they all usually go to and from the manifold, you can tape or zip tie them onto the bracket for the part they go into, or use dabs of paint for ones that are ambiguous. Different colors, or put the same number of dots on either end.)

Once its all apart, go through the removed parts and clean them up and do any minor repairs on them as necessary.

Now, when you are putting everything back together, all your parts and fasteners are in the right order so you don't have to remember everything.

Using this process, you can tackle almost any sized project. A real anxiety reducer- if you know you did it right in the disassembly process, you know you will reassemble it in the right order.

 

[Benzadmiral]

Update, all,

He did the pressure test this morning, and it held pressure perfectly. It turns out he has done these gasket replacements before, has seen what we're talking about. His advice to me was to put some of the GM sealing tabs in the coolant -- he gave me a packet of 'em; how many should I put in? -- and keep a careful eye on the level in the tank. He tells me the tabs should reduce the acidity in the Dex-Cool somewhat, "like Alka-Seltzer." And I'll have another UOA done after this oil change.

Bullet, it appears, dodged, for now.

Since the dealer has already sold me the car and they won't be risking blowing a sale, I could ask them to see if the work was already done at some point. If they did it, warranty or not, they should have the record of it. Or I could ask the previous owner, whom I see now and then at the barber, if he had any internal engine work done. Not likely, I guess, that the car would have needed the gaskets done at less than 44K miles, which is when I bought it . . . but if the work's been done, that would be a big load off my mind, hey?

 

[Stu_Rock]

Have you replaced the radiator cap on this car?

My Park Avenue stopped losing coolant after I replaced the cap with a Stant cap.

 

[10bears]

Originally Posted By: Benzadmiral
Update, all,

He did the pressure test this morning, and it held pressure perfectly. It turns out he has done these gasket replacements before, has seen what we're talking about. His advice to me was to put some of the GM sealing tabs in the coolant -- he gave me a packet of 'em; how many should I put in? -- and keep a careful eye on the level in the tank. He tells me the tabs should reduce the acidity in the Dex-Cool somewhat, "like Alka-Seltzer." And I'll have another UOA done after this oil change.

Bullet, it appears, dodged, for now.

Since the dealer has already sold me the car and they won't be risking blowing a sale, I could ask them to see if the work was already done at some point. If they did it, warranty or not, they should have the record of it. Or I could ask the previous owner, whom I see now and then at the barber, if he had any internal engine work done. Not likely, I guess, that the car would have needed the gaskets done at less than 44K miles, which is when I bought it . . . but if the work's been done, that would be a big load off my mind, hey?


Benzadmiral,

That's good news! If the coolant sealing tabs are the GM part number like I bought, info is to use the entire package of 6 added to the radiator when cold. That should be 40 grams and is appropriate for our car's size of cooling systems.

The GM type are kind of brown grainy "dog vitamin" looking things. If you have something other than this, or even if not, suggest you get your mechanic's advise.

You can expect the tabs to make your coolant look a bit murky and this will slowly cycle 'til it's visible in your coolant recovery reservoir, too. This is normal.

Regarding UOA: Please remember that these cars "hold back" about 1/2 quart of oil after draining in the bottom of the oil pan. And any previous contamination will stay right at the bottom of the pan. So if you continue getting pesking minerals "suggesting" coolant, you may want to use an oil extractor or whatever to vacuum out the last quart in the bottom of the pan.

It's your call of course. Just a suggestion if you keep getting mineral readings a bit off and want to rule this out.

Once you get things where you want them, I suggest putting a line on your coolant recovery reservoir wherever the exact cold coolant line is. This way, if it ever starts to drop, you know it right away.

Again, when my car was getting ready to suicide, it was dropping about 1/2" in about 1 hour of operation for whatever that baseline is worth. My Dad's car was about the same right before the hydraulique.

Your mechanic is the guy "hanging his hat" regarding the issue, so please DO allow his advice to take precedence over my own. Above are suggestions only and YMMV - especially on this UIM/LIM issue.

Congrats again on the good news!

Kind regards,

Larry S.
10*B
ASE Cert MM - Retired

 

[10bears]

Originally Posted By: Benzadmiral
Update, all,

He did the pressure test this morning, and it held pressure perfectly. It turns out he has done these gasket replacements before, has seen what we're talking about. His advice to me was to put some of the GM sealing tabs in the coolant -- he gave me a packet of 'em; how many should I put in? -- and keep a careful eye on the level in the tank. He tells me the tabs should reduce the acidity in the Dex-Cool somewhat, "like Alka-Seltzer." And I'll have another UOA done after this oil change.

Bullet, it appears, dodged, for now.

Since the dealer has already sold me the car and they won't be risking blowing a sale, I could ask them to see if the work was already done at some point. If they did it, warranty or not, they should have the record of it. Or I could ask the previous owner, whom I see now and then at the barber, if he had any internal engine work done. Not likely, I guess, that the car would have needed the gaskets done at less than 44K miles, which is when I bought it . . . but if the work's been done, that would be a big load off my mind, hey?


The DexCool is controversial according to what I've read online. I don't know that the sealing tabs will help solve the DexCool's proclivity to cause degradation of the plastic framed and other gaskets. Please keep in mind that the gaskets are also blamed for their premature failures, so that sword has more than one edge as usual.

I haven't heard that the sealing tabs "correct" the DexCool's problems anywhere else, but I don't have sufficient proof to argue the point, either. Whether deserved or not, there seems to be a lot of animosity going around about DexCool. Very charged topic.

But again, I'm not an expert on this UIM/LIM topic and your mechanic is the guy taking a position regarding your car so his advice should take precedence IMO.

Whatever you decide on that, I would suggest refraining from any cooling system flushing caustic chemicals now or in the future since I've heard that they can cause a borderline system to breach. And, it would likely remove any of the sealer tabs material that may have migrated to microscopic slow leaks - as they are intended to do.

In my mind, the coolant sealing tabs might stave off a "hit or miss" EGR passage leak for awhile now or future. And, if your mechanic says the pressure test showed no pressure drop for a good long while, that's definitely a good sign.

fyi

Larry S.

 

[10bears]

Originally Posted By: Stu_Rock
Have you replaced the radiator cap on this car?

My Park Avenue stopped losing coolant after I replaced the cap with a Stant cap.


I think that's a good idea to check, too. My old Stant cap was not leaking but the rubber seals looked really used up. So I replaced it with another Stant. Cheap insurance, IMO.

L

 

[wtd]

A pressure test will not always show a bad intake gasket depending on how bad the leak is. On my 98 chevy truck with the 5.7L, I was slowly loosing coolant in the overflow tank and oil analysis showed slightly elevated levels of coolant. No external leaking. I took it to the chevy dealer for them to pressure test the system and they told me everything was normal and that the system held pressure.

I also put in the GM coolant tabs. I didn't really feel comfortable with doing this so I had the intake gaskets replaced and you could see where the gaskets were coming apart and causing a leak.

On many GM V-6 and V-8 engines its just a matter of when and not if the intake gaskets are going to fail if the engine is using the original gaskets or original type replacement gaskets.

I expect that I will have to have the ones in my truck replaced again at some point since I have the second version of gasket in it now that has the metal around the bolt holes but is not made of aluminum like the final version.

I personally would have yours fixed because I can almost bet that the gaskets are starting to fail and you don't want to ruin your bearings by waiting.

 

[mrsilv04]

Can someone please share the part number for the GM coolant tabs that can be used with the 3800?

Is it 3634621?

Thanks.

***************

3634621 - GM Cooling System Seal Tabs- For Cadillac Aluminum Engines & Other GM Iron & Aluminum Engines 3634621

Pace Price
$3.83


Detailed Description
Organic formula designed for use in cooling system to seal leaks and prevent leaks due to porosity in engine castings.

Compatable with Dex-Cool

For use in :
1999-Current Cadillac Northstar V8- 3 Tablets
1982-1994 Cadillac 4.1L,4.5L,4.9L - 3 Tablets

Small Block Chevy- 3 Tablets
Big Block Chevy- 4 Tablets
4 & 6 Cyl. - 2 Tablets.

Note. Tablets should be thoroughly
crushed and mixed with coolant or water and added to cooling system radiator.

Car should be run and mixture allowed to thoroughly circulate. Failure to crush tablets may result in a clogged radiator or heater core.

 

[10bears]

Originally Posted By: mrsilv04
Can someone please share the part number for the GM coolant tabs that can be used with the 3800?

Is it 3634621?

Thanks.

***************

3634621 - GM Cooling System Seal Tabs- For Cadillac Aluminum Engines & Other GM Iron & Aluminum Engines 3634621

Pace Price
$3.83


Detailed Description
Organic formula designed for use in cooling system to seal leaks and prevent leaks due to porosity in engine castings.

Compatable with Dex-Cool

For use in :
1999-Current Cadillac Northstar V8- 3 Tablets
1982-1994 Cadillac 4.1L,4.5L,4.9L - 3 Tablets

Small Block Chevy- 3 Tablets
Big Block Chevy- 4 Tablets
4 & 6 Cyl. - 2 Tablets.

Note. Tablets should be thoroughly
crushed and mixed with coolant or water and added to cooling system radiator.

Car should be run and mixture allowed to thoroughly circulate. Failure to crush tablets may result in a clogged radiator or heater core.


Here is the part number info I found/used in ordering them from Pace Performance dot com.

Again, I don't recommend them as a fix. I used them after the UIM/LIM refit just for my superstition because so many things were leaking before.

Larry

12378254 - GM Cooling System Seal Tablets Contains Five 4 Gram Tablets

Part#: 12378254

Manufacturer Part#: 12378254

(Qty: 2 x $3.93)

 

[10bears]

Looks like I was wrong on the grams per dose. The entire package is supposed to be used for the Gen II size water jacket, but that is 20 grams, not 40 as I'd previously stated. LS

 

[10bears]

Well, I see your post says: "2 tablets". So maybe the other forum I read on this was wrong. Suggest people gather info and arrive at their own decision on that. 5 in my car hasn't clogged anything up or wrecked anything... YET!

 

[Benzadmiral]

Thanks, all,

I'll put two crushed-up tablets in this afternoon or tomorrow, and go from there. My plan was to change the oil next weekend, and I'll take an oil sample. Sure, I'd love to vacuum out the last 1/2 quart of old oil, but my Topsider -- which worked beautifully on my Benzes -- won't draw oil out of the dipstick on this car. Are there more powerful units that can do this?

 

[10bears]

Originally Posted By: Benzadmiral
Thanks, all,

I'll put two crushed-up tablets in this afternoon or tomorrow, and go from there. My plan was to change the oil next weekend, and I'll take an oil sample. Sure, I'd love to vacuum out the last 1/2 quart of old oil, but my Topsider -- which worked beautifully on my Benzes -- won't draw oil out of the dipstick on this car. Are there more powerful units that can do this?


Benzadmiral,

Perhaps make a J shaped copper tubing hook for your Topsider and try applying it thru the drain plug hole instead of down the dipstick tube?

I'm suggesting that the Topsider's suction may be able to draw the oil out without the vertical drop from the top of the car.

I used 5/16" copper tubing and bent it with a tubing bender.

In actual use, as long as the tubing is hot, the hot oil is being drawn out. The copper tubing cools to luke warm quickly when the oil is exhausted.

I don't how a Topsider works... so if this is a manual pump the above may make it a 2 person job.

It sure makes a drooling mess out of a shop vacuum, so I really don't recommend that!

This may not work if there is much sludge in the oil pan. The smallish copper tubing could plug up?

Larry

 

[Benzadmiral]

Larry,

A Topsider is partly manual. It's essentially a big gas can with a bicycle pump attached to one opening, and plastic tubing to the other. You clip the tubing shut, work the bike pump about 40 times (I think) to create a vacuum, slide the tubing where you want it, and unclip. The vacuum in the can pulls the fluid up the tube -- so you don't have to pump the oil manually. Mother Nature abhors a vacuum; she'll do the rest.

It's occurred to me that I could set the Topsider up alongside the car, shut the clip, and feed the tube underneath to where I'll be working with the drain plug. Once the oil has slowed to a drip, I could slide the tube into the oil pan and unclip it to suck out whatever oil is left down there.

 

[EmilJSteindal]

Who makes the best manifold gaskets? I need to replace both the upper (last one lasted about 70,0000mi after being changed at a shop, including the plenum), and now it looks like the lower is leaking as well. I would like to use the best one thats out there to increase my chances it will last. Also, have seen some negative effects of using Dexcool anti-freaze as it may eat away of gasket materials. Any thoughts?
Thanks for any feedback.

Emil

 

[ArrestMeRedZ]

The factory has improved their gaskets, but the Felpro Problem Solver series is one of the best, plus it's readily available.

Since I replaced my gaskets in my '97 5.7 Vortec with a standard GM set (before the problem was widely known), I've switched to Zerex G-05 coolant to try and extend their life. Knowing what I know now, even if I had used the newer gaskets, I'd never use Dexcool again with a wet intake.