A fix for the Series 2/3800 V6 upper intake?

[GMCSonoma]

I was told by a wholesale account about this kit, and over @ the BonnevileClub.com they seem to swear by it as well...
Check it out!
http://www.autopn.com/store/pc/viewP...229112#details

[68w46]

At 140K miles on my 96 Bonne I'm replacing my upper intake gasket and TB gasket for the first time. I don't see where my upper plenum is cracked. There was water in all cylinders and my plenum was soaked on the inside so I'm assuming my problem is coming from the upper gasket and not the lower ones next to the heads. The TB was sticking so when I removed it to investigate I saw where coolant had been slowly leaking for a while, it was very gummed.

I guess where I'm going with all this is I wonder since I got it down this far should I change the lower gasket also. I really don't THINK they're leaking.

[lght1]

Hi

There are several better solutions to the uim leak ( egr chimney and /or warpage at the tb).

One is to do as i did, and use the L26 aluminum UIM..which guarantees that these two problems are gone for good. It requires a tb adapter.

The other, is a UIM with a steel lined egr chimney port which should, especially with a 2000 and up LIM, ( reduced LIM egr chimney diameter) fix that problem. I am not certain about how effective that UIM would be to the warpage problem but would give it a shot.

For the LIM leaks, the aluminum framed GM lower gaskets are the only ones that should be considered.

With both of these repairs, flush the cooling system, making sure to remove every trace of OAT coolant and replace with a HOAT such as G-05.

BTW, when doing a UIM repair on these engines, esp with high miles, do the LIM gaskets as well. Its not much more work, and you will be very glad you did.

Also, replace the oem radiator cap with a good quality aftermarket.

My L36 has gone 100,000 miles in 2 yrs with the L26 upper and the Felpro lowers. G-05 coolant and a stant is also being used.

UOA shows 0.0% coolant in each lab analysis.

[GMCSonoma]

Which aluminum upper plenum???

For what engine?? The L26?

Do you have a part#???

What mods did you have to do for this???

Thanks!

[lght1]

Hi
The L26 UIM is aluminum and fits perfectly to the L36 LIM. The problem is the tb mounting. Since the L26 uses a drive-by-wire tb, its mounting is different from the L36 and an adapter is needed.

This is the L26 upper intake mounted with adapter to the L36 LIM. Notice that this installation requires a valve cover breather as the OEM PCV system is now inoperable. BTW, my used oil analysis are very good with this setup.

I would have to say, that i think that the composite UIM i linked to above, combined with the alum LIM gaskets is the best way to repair these engines.

Here is a comparison of the LIM gaskets from a friend's 1999 LeSabre I repaired last May. He had thought his lowers were "ok"...



Notice the distortions. This is why we needed the aluminum framed LIM gaskets that GM now offers. FelPro offers similar LIM gaskets for the 60 degree crowd now. Its the ONLY way to go.


Although I have used mine with the L26 Aluminum upper these past 2 years, I would use the steel lined composite now.

[GMCSonoma]

Steel lined composite upper intake manifold or gaskets???

The 3800 (L36) intake gaskets have been metal for a while...

[lght1]

Hi

Severasl posts ago, I gave a link. That is the UIM I would use.

As for the LIMs, the GMs have been metal framed for about a year. I have a set waiting for the right L36 to come along in my garage.

[GMCSonoma]

Originally Posted by lght1

Hi

Severasl posts ago, I gave a link. That is the UIM I would use.

As for the LIMs, the GMs have been metal framed for about a year. I have a set waiting for the right L36 to come along in my garage.

OK, I see you have the link hidden in the word "other"...

Same thing as what I posted originally...only installed already...

The 2007 GP uses a PCV on the "L26", upr manifold OE#89017732...
What about an adapter...where did you procure that???

[lght1]

the kit was first about about 2 yrs ago. its quite a process and a lot can go wrong..including warpage of the orig delphi so i prefer aftermarket.

also, one should consider resizing the pre mid year '99 LIM chimney as there will likely be fitment issues.

If this isnt practical, than swap LIMs for a 2000 and up as they are already reduced diameter chimneys.

With my L26 UIM, it wouldnt matter.

[GMCSonoma]

What about the TBI adapter???????????

Where can I get one of those? I spent a little while last night doing a Google search to no avail...

[lght1]

Hi

Here is the link for the adapter. It will be best to use a L67 TB and tune the car for proper fuel trims.

Mine was custom made at a machine shop and I use a '99 TB and MAF with the '97 PCM. My trims are nearly right on with out needing any tuning.

Since the L36 and L67 TBs are of different diameter and shape which affects flow characteristics, tuning is most likely necessary to avoid running an excessively lean fuel trim.

This is why I suggest that people use the above linked UIM and newer (2000 and up) LIM. You gain the reduced diameter EGR chimney which aids in keeping the composite UIM EGR pasage from degrading.

[GMCSonoma]

Originally Posted by lght1

Hi

Here is the link for the adapter. It will be best to use a L67 TB and tune the car for proper fuel trims.

Mine was custom made at a machine shop and I use a '99 TB and MAF with the '97 PCM. My trims are nearly right on with out needing any tuning.

Since the L36 and L67 TBs are of different diameter and shape which affects flow characteristics, tuning is most likely necessary to avoid running an excessively lean fuel trim.

This is why I suggest that people use the above linked UIM and newer (2000 and up) LIM. You gain the reduced diameter EGR chimney which aids in keeping the composite UIM EGR pasage from degrading.

Thanks!!! You ARE the 3800 guru!!!!!

[lght1]

Hi

Thanks, but this is all stuff I learned from other people and my own work car, an Olds LSS with 246,000 miles on the clock.

BTW, even the 4t60E, not to mention ball joints, tie rods, and steering rack are orig to the car.

Maintenance is the answer.

Also, did you notice the high velocity TB for the L36 in conjunction with the HV insert for the UIM on that same site ?

Solid performance gains on the relative cheap. If you add rockers and port out the front exhaust manifold.... good times.

BTW, what ever you do, remember to always...ALWAYS replace the plastic coolant elbows found at the belt tensioner. They are brittle and often break.

[Opusnbill7]

So after reading this, I have a question...are the 2000 and up Series II's immune from this problem? It sounds like they have the "newer" metal-lined intakes that shouldn't have the problem, but is that true?

[big swede]

Just make sure you use the manufacturers specs for torque specs on the bolts. I don't remember them off hand but they are very light and a lot of people actually crack the upper manifold while putting it back on leading to more leaks.