Hmmm.... "Intercooled" EGR gases..... interesting thought. Theoretically it should work, because it'* the chemical makeup of the gases that provide functionality, not temperature. Might be a possible solution!

Bill and all,

I was fooling around with my spare LIM yesterday and thinking about this thread.

First of all, the coolant passages from the LIM to the UIM are .375. 1/8" pipe plug tap size is .348, so, that'* a little bit, but I ran an 1/8" pipe tap through anyway. As we know, pipe threads are tapered to seal against water flow.

Some threads went into the lower, but the pipe plug won't tighten down because of the larger size. Rats.

So, I got out my drill and opened the coolant passages to .500. Now a Dorman core plug (555-074 steel, or 565-005 brass) fits perfectly.

Now let'* think about this. The coolant passage in the LIM plugs easily with hand tools everyone has at hand. The core plug is .500, .125 larger than the OD of the coolant passages in the upper. If the core plugs are epoxied in place, that means that when the upper is in place, it effective clamps the core plugs as well as them being held with epoxy. My assessment is, therefore, they ain't going anywhere, and they're only holding maybe 15 PSI and coolant temps around 250 tops. These plugs are designed for oil galleries, and that means they're designed for right around the same temp, and probably are least four times the pressure. So, I'd say they'll work with no problems.

My thinking is this: with a plugged LIM, the .020 sleeve Bill is working with, as well as the smaller stovepipe, a kit can be compiled that doesn't require much work, can be assembled with hand tools everyone has, is cheap to ship,and will work.
No returning cores for sleeving, no problems with availability of cores.

The sole negative, if it is, is lack of throttle body heat. I talked to Boosty on the phone yesterday, and it seems our brothers over on the Grand Prix site are routinely blocking off throttle body heat and seeing no problems. Some of these folks live in upper NY state and Minnesota, so it appears that even those in cold climates are seeing no problems.

I also talked to a pilot buddy (He'* a retired airline pilot and a CFI with over 20,000 hours) about carburetor icing and our situation, and he essentially said not to worry, that the size of the single bore in a throttle body would preclude icing at any altitude an auto will obtain, especially in view of the proxiimity of the EGR pipe and the exhaust loop under the throttle body.

Bill, I'm just not concerned about the stovepipe heating the UIM on shutdown, espeically with the .020 sleeve in place.It seems very unlikely at best with the air gap we're talking arout.

So, as the weather here clears and it warms up, I think my '99 is gonna be the test mule for this. If this works, and I don't see any reason it won't, I think we'll finally be at the point where solving this problem quickly and without a lot of bother is upon us.

Remembering a Regal person that mentioned a kit he picked up, I quickly took a peek at ZZP'* site. Found this TB spacer that blocks off coolant. They are using it for gains due to lower TB temps..however it serves as an example that people are doing it w/o problems. However this info is addressing gains on SC'*.

http://www.zzperformance.com/grand_p...ts1.php?id=225

Wow! Just got around to this thread. This is some really good stuff and I will be following the results as you post them Bob. Seems like the Bills and Bob have really taken this issue to another level.

I am impressed (Mom always said I was easily impressed, lol) and appreciate what you are doing!

OK, guys, I think this problem is solved. Better yet, it'* quite a bit simpler than the sleeved upper, what with the core problem, shipping costs, and turnaround time.

To accept this repair as the final and easier solution, however, we need to accept as an article of faith that the throttle body heating in the Series II is superflous. After doing some thinking, some netsurfing with our brethren over at the GP site, and thinking about some anecdotes provided by members here who live in cold climates like northern NY state and Minnesota, I think the thinking is valid.

When I got the spare LIM from Mark (Vital49), I degreased it and ran it over to my buddy with a shotblasting cabinet, and it came back looking like a new one. As you know from my previous posts in this thread, I discovered that the two coolant passages in the LIM were just a bit too large to tap for 1/8" pipe thread, which would have been perfect. Pipe threads just do not leak.

However, no go, I tried the tap and 1/8" pipe plugs, and they wouldn't tighten down enough. So, I came in and surfed the Motormite/Dorman site, and ordered some 1/2" core plugs from my NAPA guy. I drilled the coolant passages out in the LIM out to .500 from their as-cast .375. Next, I mixed up some JB weld, buttered up the plugs well, and drove them into place with a brass hammer and a 1/4" socket extension. Next, in an abundance of caution, I filled up the cups with JB weld to the LIM surface. Pix below of the manifold drilled, and then with plugs inserted.





As I was talking about this problem with Boosty and afterward mowing my grass, an idea came to me. OK, we can plug the LIM easily, but the UIM is plastic ; that'* the whole problem, and plastic is easy to drill. Hmmmm. I inspected the UIM core I have and sure enough, the holes in the coolant passage are .375 as well, and there'* a lot of meat around them. Yup, you guessed it, they drill to .500 easily. The picture below is the upper with coolant passages drilled to .500 and the same Dorman core plugs inserted. They could easily be epoxied into place.



So, it occurs to me we have two solutions that will work. We need to keep in mind that GM very nearly got this problem right. Most upper failures occurred around 60,000 miles or better, and some (post 99) haven't failed yet.

Best of all, these two are what might be called "driveway solutions." You can tear the car down and the UIM problem can be fixed overnight with tools everyone has and parts everyone can get easily. No shipping, no core problem, just a simple fix and button 'er up and go, no more worries.

The stovepipe solution? An easy one, and it'* Bill'* .750/510 one. On older cars with the .750 bore, one simply removes the .750 stovepipe carefully and JB welds it to the EGR bore. We don't have to worry about coolant leaks; either plugging the UIM or LIM (or both for our more cautious mechanics) negates the coolant leak problem, and the .120 gap in place with the .750/.510 stovepipe ensures the new sleeve/former stovepipe isn't toasted.

Bill, I know you're concerned about stovepipe cooling and the temperature in the now-empty coolant passages in the UIM after shutdown. I thought about that and what the solution might be, and you're going to laugh your *** off about this, because here it is:

http://tinyurl.com/lltbx


I wondered how we could check that, and it occurred to me that if the UIM coolant passages now had no coolant; they were dry. So, I searched thermometers on the net, and this one popped up! Note that it has a 4-foot cord. This means I can drill a hole into the dry coolant passage and insert the probe and know for sure, and I can even duct tape it to the windshield base and know the temp under driving conditions, as well as shutdown, which is your concern, Is that cool, or what?!

So, we may have simplified this process quite a bit. As I did with the original sleeved upper, my car is going to be the test mule. I've ordered gaskets, and since I have to change the heater core soon, I figure I might as well ruin a whole weekend, and will do so as soon as the weather breaks.

A few things in closing: thanks to Mark (vital49) for shipping me this LIM for a few bucks plus freight.

Secondly, if these ideas sing to you and you haven't done anything about your upper yet, I'd do two things: Run down to the auto store and get 4 Dorman (or Motormite) PN 555-005 plugs and toss them in your toolbox.

Last, I happen to know Bill Buttermore is reluctant to pitch his .750/510 stovepipe here because he'* a fancy-schmancy,highly ethical, big-whoop moderator here now.

I'm not. So, I think all those with unrepaired UIMs should order one of his stovepipes when he'* got them done and have it on hand for when the inevitable happens. Bill, please send me one along when you're up to speed.

Comments and/or thoughts, guys?

Again BOB, you've blown me away with the time, thought, and effort you've put into this. The LIM plug job is primo. I'm interested in the temp data from the dry coolant passages if you do that.

All very good stuff, IMO.

While I want to stay on topic with the Dorman fix and this new approach. There are a couple of SC'd people working on blocking off the lower intake coolant holes like you did to keep temps lower.

Nice piece of work Bob! Looks like your fix will definitely solve the leaking coolant issue. Plus, it is cheap, and relatively easy to do.

Call me overcautious, but TB icing will happen sometime, somewhere, to someone. May only be one guy in a thousand, but with my luck, it would be me! I'm gonna keep working to find the cheapest and best way to keep the coolant flowing and the heat off the plastic.

The old stovepipe is pretty thick with a wall about .045. That will give a gap with a new Dorman .510 pipe of about .075. A thin-wall .750 tube would give a gap of .100. If the old pipe is used, you might want to cut it down a bit from 1.420 to about an inch.

And for the newer 99+ cars, we will also want to install a .750 sleeve to keep the upper cool. I hope our tests show we will be able to use hi-temperature silicone as an adhesive for the heat shield/sleeve. It is good for 650F, and may be a little more forgiving than JB weld.

That is cool. I hope that with a sleeve or shield, you will find the temperatures are much less than without. If not, no reason to bother with a shield. I think you will want to install the probe so that it is in contact with the plastic wall next to the EGR bore, so you don't pick up any insulating effect from air. Makes me wonder how important the coolant is for preserving the plastic?

But, without coolant to leak - what is the worst that can happen to the EGR bore? I would guess distortion and possible loss of a sealing surface creating a vacuum leak. Not nice, but a whole lot better than coolant in the combustion chamber.

You have definitely increased the number of options for fixing this nasty little problem.

Just a lowly gearhead, Bob. And a lot of the time, not up to the job description! To clarify, I can cold press a .750 x .500 from a stainless tube and two rings, and just add a .750 ring to the new Dorman .625 x .510 so that it can be used in the older .750 LIMs.

Will do.

Great work! I think what we are developing here is a range of options that are practical, relatively easy to do, and relatively inexpensive. Whichever method you choose, I agree with Bob, that it is a good idea to get hold of the few little pieces you will need to do these mods ahead of time, so they are in your tool box when you need them. Bottom line, if you are willing to give up the TB heat, this should be a bulletproof fix!