For my 60k 99 Lesabre L63 engine, I want to cool the egr where it enters the plastic manifold. By point i ask a few Qs:
*Could I cut the little pipe and lengthen it a few feet and get it to cool the gases? Think that will work?
*Some say that blocking egr can hurt the catalyst in 2 weeks Seems farfetched. Opinion?
*I do not want to see the CEL light. Is it reasonable to run reduced egr and thereby keep the plastic cool
*I drive like old man. Does that keep my egr temp low? How about colder thermostat?

I just want to protect the L36 engine from harm that is caused by hot egr gasses to the plastic manifold. Any experiences are appreciated.
Cats and muffler are related, thats why using this post. Thanks.
And yes, its hard to beat the OEM.

Now moved into a new thread. Rickie, do you have the OEM intake or the Doman plastic intake manifold?

Its the OEM with 65k easy miles. Have no troubles but have read all about the composite manifold. Has anybody dramatically extended the EGR feed tube to like 3 feet so that the gasses arrive alot cooler?

What about the possibility of restricting the amount of egr to just below the ck engine light activate?

I hear blocking EGR can encourage ping and slightly detune other parameters. Somebody actually said that bypass will fry the cat in 2 weeks.I should think not by a long shot. My goal is to save the gasket and manifold labor. It aint broke so why wrench on this showroom preserved car that I will wait till April to drive. (92 year old Mother in law car)

So; Finally, My goal is to operate within parameters and just take extended measures to feed extra cool EGR vapors to the manifold. I have to suppose that if economics were possible, then GM would have done it. I have heard much of the feed tube spacer trick that seems marginal to me. If the isolated spacer is really a perfect solution I would be surprised. Heh, I do not want to take things apart if I can make the manifold happy without wrenching. Are there any wonder stories of the isolated sleeve being a really good fix that you have heard? I appreciate your position of knowledge from others feedback. Many thanks.

Best regards, Rickie

Logically, I should just drive it as is. I just hate to leave the bit of weakness of this engine/car unserved.

My series 2 with a 140k miles runs great, even on long hot summer highway trips. I did upgrade to the Dorman intake manifold, & the Dorman metal coolant elbow as the plastic elbow blew up.
I also have had to replace the upper & lower intake manifold gaskets now twice due to coolant leaks.
Replace the coolant every 5 years & check for contamination or oil getting into the overflow tank. If there are no leaks, the over flow should remain at the correct level.
Check to make sure the electric cooling fan also operates correctly.
Other than that, it still runs fairly cool, & using the A/C reduces temperature if stopped in summer traffic.
I also run with the Series II plastic cover removed year round to reduce heat.

Every once in a while check the fuel pressure regulator by removing and plugging the vacuum line to the FPR & then leave car running for 5 minutes looking for fuel coming put of the FPR.
You don't want the intake manifold to go ker boom and the video below explains it well
Go to 1 Min 45 onward to see the leaking FPR.
Replacing the FPR is not a bad idea on these cars, as they are older cars now.

In this case it is BEST to correct the OEM. I have used ATP UIMs on ALL of my 3800 equipped cars and have never had an issue. I also make sure that I'm NOT using Dex-Cool and just regular green anti-freeze. It'* cheap insurance against hydro-locking your engine or at worst damaging your crankshaft bearings due to coolant mixing with the engine oil.
The ATP manifold is inexpensive and has a metal sleeve at the EGR stove pipe passage. Just do it and have peace of mind going forward.

I had never thought of this. It might help, but it would take more than a few feet. Maybe 50 feet?

The point of EGR is to return some exhaust gases to the combustion process to cool the combustion process by reducing the amount of oxygen available in the combustion chamber during the intake stroke. I don't think cooling EGR gases a bunch would harm this process, but I've never heard of this being done.

In order to cool any significant amount of EGR gases, the solution would have to dissapate a lot of heat continuously. In order to do this it would need either a lot of tube length under the hood where it is hot, or less tube length in front of the radiator where it is cooler . . . plus a bunch to get there and back.

All of this extra tube distance might present an additional opportunity for carbon build-up inside, but I think the chance of this would be low on a properly-running engine.

I don't think this would be far fetched. The necessary time interval would depend on how the vehicle is used. With no EGR where the maps are adjusted for EGR, you would likely end up in a lean-burn situation that would make everything a bit hotter in the applicable conditions as well as change the mixture of what comes out of the engine toward the catalytic converter.

Reduced EGR temperature? Answered above. Reduced EGR flow, also answered above. Check engine light? I think you'd see it unless mixture mapping was changed to compensate.

Slow driving? Yes, that will keep temps lower.

Colder thermostat? No, I don't think that will help at all, and might decrease your fuel economy in the process. It will also reduce your heater'* performance when in cold environments.

The only way to have no problems with this manifold is to either (1) not ever let the exhaust get warm (unlikely at distances greater than a half-mile per heat cycle) or (2) replace the manifold with an improved unit with a metal sleeve.

I suggest (2). While you're there taking care of (2), I also suggest replacing the plastic coolant elbows with metal units, and also replacing the fuel pressure regulator.​

Answered with authority and best of knowledge! Thanks,
I think I should get into the digital tune hobby.. After all the system is designed to circumvent external changes unless we go to the heart of the system.
Finally, When trouble for this car is least detected I will do the manifold and gaskets and fpr. I will watch that coolant. And will try to find a emissions monitor so I can interrogate the system.
Appreciate your answer! Rick.