PING: shiden_kai (Re: 3800 intake)

Ian (and others),
I value your opinion and expertise and would sincerely appreciate some advice. "I never thought it would happen to me, but..." Last night upon a
cold start, I noticed a miss in my well-maintained '99 Regal LS with 86,400 miles. The miss disappeared after several seconds and was fine the remainder of the evening. This morning, the miss returned accompanied by a flashing, then steady SES light. After returning home from my short trip, my scan tool revealed a P0306 (cyl. 6 misfire). I installed new OEM plugs at 50,000 miles, but am still on my original wires. Upon inspection, I noticed my coolant reservoir was almost completely empty. I monitor it religiously due to the known problems with 3800 intakes. To conclude, I think my upper intake and/or gasket finally bit the dust and is dumping coolant into the no. 6 cylinder causing the misfire. Local dealer wants $700 for the repair or I can perform the repair for the cost of parts. My question is, based on this information is it likely that my plastic intake has failed? If I choose to perform the repairs myself, do you recommend any parts other than a new intake and gasket set? Would you recommend removing and inspecting the intake before I order the parts? Or, should I simply order a new upper intake and gasket set based on my symptoms and the history of this type of failure?
Thanks in advance, Roger
zroger73 at yahoo dot com
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zroger73 wrote:

It certainly sounds like you have the upper intake manifold problem. I guess I'd be more inclined to either pull the upper intake off and have a look, or at least pull the throttle body off and take a look inside for any signs of antifreeze. Have you looked around the outside edge of the seam between the upper and lower intake? If you see any new or old dexcool leaking there....you can be certain that the intake is toast.
As far as replacing/repairing the lower intake...how long do you plan to keep the car? You could replace the upper intake and be fine for a long time even with the older style lower intake in place. Or you could find one of those kits where you simply extract the EGR pipe from the lower manifold and install an updated smaller EGR pipe. I think that in your situation, I'd go that route....save yourself some money and it should work fine. No matter what...you will be replacing the upper intake.
Ian
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shiden_kai wrote:

Ian,
Thanks for your suggestions and advice. I removed the upper intake last night and discovered the area on the intake that surrounds the EGR pipe had corroded through - it appears to be a textbook failure. Someone suggested that I use a Dorman aftermarket intake rather than a new OEM intake, since these supposedly are reinforced in the weak areas. Personally, I prefer to use all OEM parts. For the cost of a new intake plus the relative ease of the job, I think I'd be satisfied to replace just the intake and gasket for now and plan on doing it again in the future (chances are I'll still own the car as a spare vehicle since depreciation was so bad, even though the car literally appears brand new inside and out and has no other problems). I noticed a TSB issued last year that seems to indicate that GM updated the design of the upper intake and gasket, but my heart tells me that won't truly fix the problem in the long-run. A dealer that sells GM parts online prices the intake at $154USD and the gasket at $27, but will take a few days to ship. I imagine my local dealer will be at or above list ($224), but I should be able to get it same or next day. I'll do a bit of price comparison tomorrow. I threw together a quick web page on my experience this afternoon at the link below. It's a "final" rough draft, so the text might contain some factual errors that I'll eventually correct.
http://home.cablelynx.com/~zroger73/intake/intake.html
Thanks again for your help, Roger
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UPDATE: The repair is now complete. I replaced the upper intake plenum and gasket with new OEM parts. Total took a little under four hours. So far, no codes and no vacuum, coolant, or fuel leaks. I'll keep an even closer eye on things for a few days, but I think the repair was successful. I updated the info on the link I posted earlier. Thanks again for your help, Ian.
Roger
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zroger73 wrote:

Hey, no problem! Good work!
Ian
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