98 Buick LeSabre 3.8L V6 - lower intake manifold
01-26-2018, 12:53 PM
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98 Buick LeSabre 3.8L V6 - lower intake manifold
Was losing coolant internally and started to break down the motor to replace the lower gasket. As soon as I got the upper manifold off I saw the lower manifold full to the rim with a milky mix of oil and coolant and soaked it up. Once I got the manifold off, I saw two (1 on each head) of the four coolant ports plugged up with some gritty, sandy, sticky funk. The matching locations on the manifold also had this stuff on them. As I was cleaning this stuff off the manifold I saw that, underneath the layer of grit, the port had been previously filled in with what appears to be JB weld. I dug out the gritty funk from the ports on the head but am now at a loss of what to do next. If those ports aren’t sealed, the coolant will certainly blow the gasket once it hits the solid port on the manifold. Has anyone else had this happen? Any advice will certainly be appreciated. The local GM service department of course “has to see it before they can answer questions”.
01-26-2018, 01:10 PM
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Usually, when you see crud like that, this has been losing coolant for awhile, and the customer has just been adding to the system when it gets low, instead of fixing the source of the leak.....
99 out of 100 times when you see the top of the lower intake filled like that, it'* because the coolant passage in the upper plenum has degraded(this is the area of the upper plenum where the EGR stovepipe passes up through)......you can almost bet on it, that there is a hole there....
And if the oil is milky down in the pan, be prepared for future bearing problems....We had a situation where the customer was just adding coolant to his car whenever the low coolant light came on......then the car wouldn't start.....it was hydrolocked...he kept trying to start it, and broke the nose cone of his starter......the oil was milky and over filled(from the coolant)......we told him his best bet was a junkyard motor....he took a chance with a new lower intake gasket and new upper plenum and gasket.....we flushed his coolant and we changed his oil twice before giving it back to him......one month later, a rod went through his block.....
99 out of 100 times when you see the top of the lower intake filled like that, it'* because the coolant passage in the upper plenum has degraded(this is the area of the upper plenum where the EGR stovepipe passes up through)......you can almost bet on it, that there is a hole there....
And if the oil is milky down in the pan, be prepared for future bearing problems....We had a situation where the customer was just adding coolant to his car whenever the low coolant light came on......then the car wouldn't start.....it was hydrolocked...he kept trying to start it, and broke the nose cone of his starter......the oil was milky and over filled(from the coolant)......we told him his best bet was a junkyard motor....he took a chance with a new lower intake gasket and new upper plenum and gasket.....we flushed his coolant and we changed his oil twice before giving it back to him......one month later, a rod went through his block.....
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01-26-2018, 01:26 PM
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Thanks, Tech II for the quick response. The oil in the pan looks ok so I plan to replace the upper plenum with the upgrade. I still wonder about the coolant ports...if coolant flows through the system then hits that filled in port, the gasket will surely fail, again. It would make sense, to me, to seal off the port on the head that matches the sealed port on the manifold. I’m thinking that someone, in the past, may have done just that using some sort of foam crack sealer. Have you ever heard of someone sealing off the coolant ports on the heads?
I’ll ponder for a while before doing anything else th the old Buick. Thanks again.
I’ll ponder for a while before doing anything else th the old Buick. Thanks again.
01-28-2018, 07:31 PM
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Progress update
I cleaned up the mating surfaces and realized that what first looked like JB weld filling a port on the manifold was actually 20 years worth of stain and build-up. I don’t understand the engineering here, the head has an open coolant port that leads to a solid spot on the manifold; where is the coolant going to go? It seems to me that the new and upgraded gasket is doomed to fail. I went ahead and picked up a new upper manifold (with the upgrade) and hope to start reassembling in the morning.
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Soft Ride (01-29-2018)
01-28-2018, 09:00 PM
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This link may help with great information for you. https://www.gmforum.com/mechanical-1...ts-l36-297702/
For the LIM gaskets I used these.
Did you buy the Dorman Upper intake with gaskets as well #615-180?
Considering the plastic elbows break/leak easily, now would also be a good time to find & install all aluminum.
For the LIM gaskets I used these.
Did you buy the Dorman Upper intake with gaskets as well #615-180?
Considering the plastic elbows break/leak easily, now would also be a good time to find & install all aluminum.
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Tmille28 (01-28-2018)
01-28-2018, 09:38 PM
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@Softride, thanks for the response. Yes, I got the Fel Pro gasket set for the lower as well as the Dorman upper manifold/gasket. I just need to pick up the aluminum elbows.
I’m concerned about the torque settings for the lower manifold to block bolts; One source (Haynes manual) says 132 inch pounds but another source (Auto Zone on line manual) says 12 inch pounds. Your thoughts?
I’m concerned about the torque settings for the lower manifold to block bolts; One source (Haynes manual) says 132 inch pounds but another source (Auto Zone on line manual) says 12 inch pounds. Your thoughts?
01-29-2018, 01:43 AM
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Please read/reference the link I posted from post #5 above.
There is also torque sequence++ etc, shown in that thread.
Dan states 132 inch lbs which would convert to about 11 foot lbs.
I used a good inch lb torque wrench @ LIM bolts are 132 inch pounds- UIM bolts are 89 inch pounds.
Hope this helps, and good luck with the re-installation.
There is also torque sequence++ etc, shown in that thread.
Dan states 132 inch lbs which would convert to about 11 foot lbs.
I used a good inch lb torque wrench @ LIM bolts are 132 inch pounds- UIM bolts are 89 inch pounds.
Hope this helps, and good luck with the re-installation.
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Tmille28 (01-29-2018)
01-29-2018, 10:59 AM
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The Haynes manual says to apply sealant to both mating surfaces and to add some RTV to each corner of the end seals. The new gaskets are steel and rubber, do i still need a layer of sealant on both surfaces? the instruction sheet with the FelPro gasket only addresses the small dab of RTV on the corners of the end seals.
01-29-2018, 02:44 PM
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No extra RTV on new gaskets needed, except in the 4 corners.
As in Dan'* post with the photos, I RTV'd only the 4 corners before installing the new LIM gaskets.
Also RTV in prep for the rubber end runner gaskets though, also shown in Dan'* pics.
I also cleaned up each bolt & applied a bit of thread sealant to each of the LIM bolts.
As in Dan'* post with the photos, I RTV'd only the 4 corners before installing the new LIM gaskets.
Also RTV in prep for the rubber end runner gaskets though, also shown in Dan'* pics.
I also cleaned up each bolt & applied a bit of thread sealant to each of the LIM bolts.
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Tmille28 (01-29-2018)
01-30-2018, 03:07 PM
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Progress update and a question.
getting ready now to install the new upper intake manifold; do I need to apply gasket sealer to the mating surface of the lower manifold? Thanks in advance.
getting ready now to install the new upper intake manifold; do I need to apply gasket sealer to the mating surface of the lower manifold? Thanks in advance.