My name is Rob and I’m new to this forum. I recently purchased a 1996 Olds 88 LS with 86K miles on it. It has the 3.8 liter normally aspirated engine. I’ve been reading on here about the upper intake manifold failures that these engines are prone to, and would like to take preemptive action to prevent a failure and subsequent major engine damage. There is no sign of coolant in the oil, or oil in the coolant, and the coolant level doesn’t change. After looking at my engine’* UIM, the date on it is June 2003. The guy I purchased the car from kept meticulous records (I have records from every oil change and inspection etc.), but there is no record of the UIM being replaced. I’m wondering if it was replaced by GM under a “secret” recall. There is a service record around that time when the car had 69K miles on it where it mentions hard starting and they replaced the battery. I’m wondering if that’* when it was done. If so, there’* less than 20k miles on the new UIM. I’m also wondering if they would have replaced the lower intake manifold as well. How long can I expect this UIM to last if my assumptions are correct? Should I modify the existing UIM with the heat shield or just replace the whole thing with the mentioned APN kit? Thanks in advance. You guys are a God send!

Recalls are generally for safety items. I'm not aware of a recall for any L36 manifolds, that does not mean it does not exist, just that I've never heard of one.

The usual opinion from forum members here is that modifying the plenum with a smaller EGR stovepipe will prevent the failure. An APN/Dorman manifold will work fine as well, I have not read about any failures with those.

For sure keep an eye on the coolant level. If you would like to prevent the failure ahead of time and you had some money to throw around go ahead and put either a APN/dorman and/or modifiy your existing manifold with the dilion design.

You may also want to change your lower intake manifold gaskets while you have the manifold off as it is much easier to get to them, plus if there is Dexcool I'd swap it out with the green stuff...I personally use the DEX approved stuff (prestone).I have not had any problems. On the other hand a lot of people with GM cars with dexcool swap to the green stuff without any problems.

Also if you do the lower intake gaskets, I'd go with the aluminum framed design that was recently put out from GM.

As far as HOW LONG yours is going to last, it may last a few more weeks it may last 10 more years, the failures are random and I dont think there is any pattern.

Some here will say why throw parts at it if its not broke, some will say replace it as preventive maintanence to insure the car is reliable..I'm stuck in the middle of that argument.

Finally APN vs Dorman, APN should be cheaper, they are just under $100 vs around $130-$150 for the Dorman at your local autoparts store..The dormans may be cheaper online I'm not sure I've never shopped for them. When I did a UIM replacement a couple weeks ago we went with the dorman without the stovepipe modification, again on this car it did not have a failure, it was purely preventative

Are there any issues with going to the green coolant - do you have to be careful not to mix them? Is there anything wrong with sticking with the Dex compatible Prestone stuff? Where can I get a hold of the part to modify the existing UIM (the “Dilion” design)? Would I be able to see the condition of my existing UIM by removing the throttle body?

A smaller(5/8") stovepipe was GMs approach in 1999, But without a heat shield to protect the plastic EGR bore in the UIM, these fail, too.

These are NOT the same. Dorman uses an even smaller (1/2"+) stovepipe to increase the insulating gap between the hot pipe and the plastic, but still no heat shield. APN is the only commercially availabe UIM kit to provide a smaller (1/2") stovepipe and a metal heat shield to protect the UIM.

Here are my recommendations for UIM/LIM repairs for the 95-05 L36.

Please note that if you cannot wait for parts in the mail, you will not get the best fix.

The best fix for the LIM - GM aluminum frame gaskets......$59
The best fix for the coolant elbow(*) Dorman Help.........$6
The best fix for the UIM - APN upper intake manifold kit......$115 including shipping

In addition, I recommend the following steps to keep engine operating temperatures down, to ensure that coolant flows around the hot stovepipe area in the plastic UIM, and to eliminate any possible harm from the use of Dex-cool - all factors that protect and extend the life of the UIM and LIM gaskets.

Flush coolant and re-fill with "mixes with any color"
Drill a 1/16" hole in a 180F thermostat flange and refill according to: http://www.bonnevilleclub.com/forum/...=article&k=100
Install an after-market transmission cooler.

I use only a scraper and degreaser to clean gasket surfaces on the cylinder heads to avoid introducing abrasives into the engine.

Regarding the UIM, the longest-lasting fix will come from an upper intake manifold protected by a heat shield and the use of a reduced diameter stovepipe to provide an insulating gap between the hot stovepipe and the metal heat shield. The only commercially available kit that provides those features is from APN. Dorman UIMs have NO heat shield protection for the plastic EGR bore, but rely solely on the insulating gap provided by a reduced diameter stovepipe.

UIMs can be sleeved, plugged, and otherwise repaired for re-use, and these repairs can be made at low cost. But, unless the UIM is fairly new, most will typically exhibit warpage at the throttle body sealing surface and at the coolant passage sealing surfaces around the EGR bore. When considering repair of a UIM, don't forget to add the costs of a new UIM-LIM gasket and throttle body gasket, typically about $45.

From Sears, a smaller 3/8" drive deflecting beam type torque wrench does just fine for UIM/LIM work. It costs $25. http://www.sears.com/sr/javasr/produ...id=00944690000

You will have no problems if you switch to the "mixes with any type or color coolant". Some here think the orange Dex compatible coolant can be used like Dex but does not have the harmful characteristics of Dex. Others think it just Prestone Dex. No one thinks the "mixes with any type or color" coolant will cause problems like Dex does.

You can contact Bob Dillon by PM. There is a link to do this in a Techinfo article that you need to read to bring you up to speed on these L36 issues. http://www.bonnevilleclub.com/forum/...e=article&k=38

To evaluate the condition of your UIM, it must come off the LIM. Probe the EGR bore with a dental pick, a large sharp needle, or similar tool, and compare how it feels when you probe the outside top surface of the UIM. If the EGR bore is still sound, you can install a reduced diameter stovepipe and perhaps extend the life of the UIM somewhat. But a better plan would be to install a heat shield and a smaller stovepipe. You also want to make sure that the old UIM has not warped badly where the coolant passages meet those on the LIM and where the UIM mates to the throttle body.

There are several repair/upgrade options you can consider for the UIM if it is serviceable. If the EGR bore has softened, but the sealing surfaces are still good, you can install a sleeve as a heat shield, or send the UIM to Bob Dillon who will exchange it for one he has sleeved. Bob can also sell you a 5/8" stovepipe so that you will have about a .090" gap between the hot pipe and shield.

If the EGR bore is in good shape, you could install a shielded stovepipe that will give you a .100" gap and a heat shield for the EGR passage without cutting the plastic to install a sleeve. These are described here: http://www.bonnevilleclub.com/forum/...ic.php?t=70553

You can purchase a sleeve and reduced diameter stovepipe and install it yourself for about $20 using the method described here: http://www.bonnevilleclub.com/forum/...ic.php?t=33565 (PM me if interested in this option.)

Remember, when considering any UIM repair work to include the cost of a new UIM-LIM gasket and throttle body gasket (about $45).

That'* great advice. Thanks a lot. Looks like it'* time to start ordering parts and keep a close watch on the coolant level. This way I can do the work at an opportune time. I think I'll go with the APN upper intake. It'* very reasonably priced and by the time you add in the cost of buying the gaskets etc., it doesn't make any sense to mess around. Also, I may be able to save a little money by ordering the lower intake gaskets from www.gmparstdirect.com. Are there any special tools I'll need besides the torque wrench? I'm not sure I understand about drilling the hole in the thermostat - isn't the bleeder screw sufficient? About how far from the edge of the thermostat on the flange should the hole be? Does anyone have a picture of a modified one? Do you have a recommendation on an aftermarket trans cooler? About how much do they cost? Are they hard to install?

No.
No.
Put the rubber gasket on it and drill close to the gasket in the flat part of the flange.
Bulkpart low pressure drop cooler; about $65, easy install. 4490 is a good pick. http://www.bulkpart.com/Merchant2/me...e=tru-cool-lpd

Rob.. to answer you question from the original post, there isn't any secret recall we know of. However you can check the production date on your UIM to know if it'* ever been changed.

Where do I buy an APN UIM?