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Jeremy airjer W

When GM 3.8 intake plenums go BAD!

24 posts in this topic

Its been a while since I have done one of these and as luck would have it I had the camera with me. This one came in last night. The customer stated that it started running ruff and she noticed a lot of white smoke behind her as she drove down the freeway.

These plenums are notorious for breaching the cooling passages around the EGR inlet tube.

38EGRtube.jpg

In this photo you can see the hole in the coolant passage.

38intakehole.jpg

When this happens it literally dumps hot coolant under pressure into the intake of the motor. This photo shows all the coolant filling up the the lower intake. There was at least half a gallon sitting there.

38intakewater.jpg

This shows the lower intake with all the water removed.

38intakeclear.jpg

Part of the update is to install a new EGR tube that has a smaller diameter so that there is a gap between the passage and the plastic plenum.

38newintake.jpg

These usually start leaking with the vehicle shut off. Its not unusual for the vehicles to be towed in because they are hydro-locked. It is also not uncommon for the starter nose cones to break of when the customers try to start them. After getting a new plenum, updated EGR passage, injector o-rings, PCV valve, plugs, oil change and a coolant flush it was good as new.

Here's the underside of the plenum if you curious.

38wholeintake.jpg

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Hey airjer, I have a 3.1 and had the intake done once already. It must have been before they started making a better gasket (or something) as I think it is now doing it again. A puff of smoke upon startup and slow draw down of coolant, and slight "Wetness" when parking.

Is what I am seeing basically the same thing as your pics? Is a 3.1 intake still about $500 ballpark?

Thanks, great pics.

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Great pics and explanation airjer. Thanks for posting.

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Is what I am seeing basically the same thing as your pics? Is a 3.1 intake still about $500 ballpark?

No they are not the same. The 3.1 has issues with the lower intake manifold gaskets. The upper plenum on a 3.1 is dry, meaning there is no coolant running through it. There is no permanent fix for the lower intake gaskets leaking. I've seen them fail as soon as 30,000 miles and I have had some that had gone over the 100,000 mile mark before they started leaking. You can expect the repair to last between 30k-100k as well. A couple of the cars we service are on there third set!!!

The felpro metal/rubber gasket seem to be the ticket on the 3.1's. We have been installing them for a little over a year so it is still to soon to know how well they will perform but I like the concept of the gasket a lot better than the original design.

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Airjer do you have a ball park price what that job would of cost? I have a 94 bonneville that I think is in need of that same job. It kind of sputters every so often and puts out some white smoke.

Thanks

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Labor rates will vary depending on where you are but you can expect anywhere from $600 to a tad over $1000.

Keep in mind that when these fail it is catastophic. There is no question what has happened and the vehicles are barely opperable. The symptom you are describing may not be related!!

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Ya those fel-pro problem solver sets for the 3.1/3.4 are the way to go. They have been around for a few years and all the problem solvers I have sold (it has to be in the hundreds!) never had a come back. Cant say the same for the standard/oem set. For an extra 25 bucks the problem solver set is the way to go.

Dorman sells a updated plenum for the 3.8 that is pretty sweet. It comes with everything to do the job too. (looks like thats what you used airjer). I really like those 3.8's when you get the problems taken care of. They seem to last forever when its all updated.

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It was a dorman. They include the PCV valve, spring, both PCV seals, New vacuum tube for the brake book and o-ring, All the gaskets for install of the plenum and throttle body and the updated EGR tubes. You don't need anything else when you get these!

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My wife has a 2000 Malibu, 3.1. Car has approximately 80,000 miles. She is losing antifreeze and it seems to be leaking from the lower intake manifold gasket, as there is a small puddle on top of the engine and staining around the gasket. I don't think it is getting into the engine as I don't notice white smoke and the car runs great. Oil is not milky. But when I top off her expansion tank it is filthy and appears to have an oil sheen. Is it possible to get oil into the coolant if the lower intake gasket fails or do I have a head gasket issue too?

Several years ago I did flush and drain the DexCool and refilled with green stuff. I've done this to all my GM's since I had a bad experience with a 97 Blazer w/ V6 Vortec and gumming issues. I understand the issue of keeping the coolant topped off and system leak free to prevent air ingress but it just seemed much easier to go the old fashion way to prevent the possible issues.

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as there is a small puddle on top of the engine and staining around the gasket.

If the puddle is forming under the throttle body than you have a lower intake gasket leaking.

If you did a drain and fill with green coolant than all kinds of weird looking stuff can fund its way into the overflow. If it was actually flushed with green coolant than it is less likely to see what you are seeing. The last possibility is that it is residual "stop leak" that has made its way in there. If it looks like a strawberry milkshake than its possible for the trans cooler to be leaking. Not that I have ever seen a GM do that before. whistleshocked

It is not very common for a 3.1 to have a head gasket failure. Its cousin the 3.4 entirely more possible!

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airjer-

After two attempts to get my dealer to explain what has happened to my 3.8 and failing, you have done an excellent job of it. Mine failed at 30K and again at 60k. I'm just wondering if they did not use the update at 30 and I am sure hoping they used it at 60. It now has 80 some and am waiting for it to go again. If this is such a known fault, why has it not got a recall? The local GM dealer in Duluth just can't seem to get this repair correct.

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GM has a TSB on this (01-06-07-001 i think). GM's fix is to replace the lower intake as well as the upper intake. I have not seen the lower intake so I can only assume they have made the egr port smaller.

The Dorman/NAPA kit gives you new EGR ports that seat into the lower intake manifold. Basically you remove the old one with a pair of pliers then install the new one that comes with the kit (2 different sizes are included) The old tube makes a great install tool. Insert it over the new one, it sticks up a little higher and takes the brunt of the hammering to seat the new one into the bore.

The Dorman kit has to be a lot cheaper than replacing the lower and upper intakes!

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Did you not suggest lower gaskets/serp tensioner connectors while it was 1/2 apart? It looks pretty juicy.

Big AL-

Recalls are only for safety issues. I doubt anyone has died because of these gaskets or upper intake failures, except maybe when they get the bill. Tsb's on the other hand, they admit some fault, maybe improve a part and you pay for it! If I were you I would also find a competent independant to fix your car, unless you want your dealer to get three strikes first. You've got about 10k to think about that....

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Did you not suggest lower gaskets/serp tensioner connectors while it was 1/2 apart? It looks pretty juicy.

To old for the serp belt tension/coolant passage assembly, Coolant nipple was already replaced, they just about fell over when they got the estimate for the plenum and they where from out of town. The lower was not an issue at this point.

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Where can I get the updated intake tube? Im working on a 97 Grand prix with a stuck lifter and noticed the intake is about melted through! Not leaking coolant yet but its very close. Are any off brand intakes any better than any others? (Dorman or Delphi) Dorman claims there intake will solve the problem without the updated tube?

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Where can I get the updated intake tube? Im working on a 97 Grand prix with a stuck lifter and noticed the intake is about melted through! Not leaking coolant yet but its very close. Are any off brand intakes any better than any others? (Dorman or Delphi) Dorman claims there intake will solve the problem without the updated tube?

Most of the aftermarket parts stores will have the updated tube in the kit. Car Quest/ O-Reilly auto parts/ Bumper to Bumper.

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Yup, the dorman kit comes with everything you need. If its off replace it!

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Thanks guys! It amazes me every day the amount of car info on this "fishing" site!

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So my girlfriend just bought a 2004 Grand Prix with a series III 3800. Is she going to have this same issue, or did they get it figured out by this point?!

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I don't remember which year they switch to aluminum but if you look under the plastic cover and see shiny metal your fine. If you see black plastic you may also be fine. Seems like the late 90's where the worst for this to happen.

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Thanks guys! It amazes me every day the amount of car info on this "fishing" site!

Think of Hot Spot Outdoors as the Fleet Farm of the Web. If you can't find here you don't need it! grin

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Originally Posted By: Dozer
Thanks guys! It amazes me every day the amount of car info on this "fishing" site!

Think of Hot Spot Outdoors as the Fleet Farm of the Web. If you can't find here you don't need it! grin

Thats pretty good! And suprisingly true!

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