OK, somebody help me out here.

I just got a Delphi UIM from Vital (thanks, buddy!) and gave it a good look-see this morning. I note that even a casual glance at the EGR passage reveals to a car guy that this thing is bound to fail, much less the automtoive engineers at The General.

I looked at the Ken-Co kit online, and not only do they not sell to individuals, but it strikes me as pretty expensive for a minor machining job. I have a hobbyist lathe and could turn this out of aluminum bar stock in a few minutes.

So, my question is this: Is the passage from the LIM to the UIM just a "transit tube," if you will? Or is there an EGR valve inside it?

Does anyone have an old one laying around they can send me so I can mike it and maybe start making chips? I'll be happy to pay at once with PayPal for your trouble.

Oh, and one more question: Are plastic UIMs OK for the parts washer? Someone tell me how you clean this freakin' mess up!

And some words of advice to The General: Keep saving maybe $1.38 on each car so your customers can eat a $1400 repair. This is the type of thing Toyota greatly fears.

There is not an EGR valve inside, just a tube from the LIM through the UIM and protruding up about 1/4" into the flow path. I had a friend machine a new reduced diameter EGR stovepipe for my '95 and a sleeve for the UIM. He used stainless. I was afraid to use aluminum because the original pipe seemed to be made of stainless. By the time my buddy was done, he had more $ in time than the $80 KenCo charges for their kit. Now, I don't know if the KenCo kit uses stainless but I do know they will sell direct to you.



Here you can see that the route of the EGR gas appears to contact the aluminum of the LIM anyway, so maybe aluminum would be OK?

Ranger made one for his car and helped me with my dimensions. If I remember correctly, the bottom O.D. was 0.0750" and the shoulder was about 0.0250" high. I am not sure that a sleeve is necessary if you have a new manifold, but I believe that 57Chevythunder used the sleeve with his new UIM when installing the KenCo kit. I used one on mine because I re-used my old UIM, and the plastic surrounding the tube had degraded. I reamed mine out 'til I ran into good plastic, then JB welded in the sleeve my buddy made for me. My sleeve really should have been a little taller than it came out.

e-mail address where you can purchase the KenCo kit if you decide to is:
gagparts@maine.rr.com

The cost is $80. You get the reduced dia pipe, a sleeve, some high temp epoxy and it ships to you for free. If you have to pay a machinist, $80 isn't bad. But if you have your own lathe, heck, go for it.

Thanks, Bill! My e-mail address is in my profile if you want to e-mail it to me directly.

I had saved this information, thought it might come in handy. The numbers given below include an increase in the height of the sleeve that I think would have worked better. Remember, these numbers were for a reamed and sleeved UIM. The old UIM had an I.D. around the pipe of about 0.0790-0.0800" Kinda hard to tell with all the carbon built up on it. I do remember when I took it off that there was about 0.015" clearance between the original pipe and the carbon coated plastic of the UIM.
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Old EGR pipe specifications 95 Bonneville SLE

Material: appears to be stainless steel

Height:.........................1.420
Outside diameter:.......0.750
Inside diameter:..........0.680* (hard to get this measurement)
Wall thickness:............0.035 (approx)

New EGR Pipe Specifications:

Pipe

Material: 306 stainless steel

Height:......................1.420
Base diameter:........0.750 ( may want to add a little for a tighter press fit)
Shoulder height:.......0.250
Inside diameter:.......0.525
Outside diameter:....0.588
Wall thickness:.........0.032

Sleeve

Material: 306 stainless steel

Height:.........................0.800 (not sure on this, measure your own for fit)
Inside diameter:..........0.760
Outside diameter:.......0.830
Wall thickness:............0.035

Composite plenum bore hand reamed to 0.829

Air gap produced: 0.086

JB weld used to set sleeve in upper intake manifold
Blue (medium) threadlock used to set pipe in lower intake manifold

Machining and material cost $59.29* February,2005
* Machinist friend reduced labor rate
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I want to repeat, for those without access to a lathe, the KenCo kit seems to be a reasonable deal. If you were knockin' these out all day long, you could easily beat KenCo'* price. But if you have to pay $50/hr at a machine shop where they have never done one before, you will be lucky to get out for less than $80.

Also, I have only put a few hundred miles on my '95 since this installation. I have no idea how long it will hold up. It just seems to make sense, though, that keeping the heat away from the plastic can only lengthen its life - especially if you do a new UIM with the reduced diameter EGR pipe.

I originally bought the Ken-Co kit too. For whatever reason, it wouldn't fit. So, I just reassembled without it. I am interested in a sleeve...

Are you saying your KenCo sleeve wouldn't fit? 57Chevythunder said the KenCo sleeve was way too tight in his new UIM. My friend machined my sleeve to fit the ID that we had reamed on the old UIM, so my fit was not a problem. If the UIM is sound, I wonder if a sleeve is needed anyway. In KenCo'* blurb, they say the sleeve can be used to restore a UIM that has eroded all the way through to the coolant passage by epoxying in a new sleeve. GM doesn't use a sleeve. In my case, my engine made 127,000 miles with that tiny 0.015" air space between the tube and the plastic. The heat had started to crystallize the plastic, though. I would think that the air space alone is what makes the difference. [edit: Wrong!...read on] If your UIM is new or good, I wonder what benefit the sleeve would provide, with a reduced diameter pipe. Maybe conducting heat quickly away from a hot spot? Maybe no benefit at all.

I miked the ID of the EGR hole in the manifold that Vital shipped to me. It'* .755 and is not eroded at all.

I was wondering why ANY space if left between the EGR pipe and the plastic of the UIM, but I think I just had a lucid moment: Bet this very small air gap, which obviously leaks a small amount of vacuum, is to draw air past the EGR pipe and cool it.

If the EGR pipe is .750 OD and the ID of an uneroded UIM is .755, obviously, it'* designed in for some reason, and cooling makes sense.

Your thoughts, gentlemen?

(edit) Dolp! Major brain fart in the thinking above. Expansion due to heating?

Big duh!

There should be no vacuum leak. The space around the pipe dead ends at the lower intake manifold. And, the gasket has a ring around the pipe as well. I'll bet that original .0025 gap grows to something more as the plastic disintegrates around the hot pipe. That may explain why my gap was more like .015. Anyway, it seems that a larger gap around the pipe can only help in terms of insulating the plastic from heat damage. It may also help to keep the wall thickness of the pipe pretty thin so the pipe does not hold heat. I would think that the air rushing past the top 1/4" of the pipe through the TB is a significant source of cooling, and the passing stream may create some flow around the pipe for some distance down in the hole. I think the coolant passages protect the plastic too, taking heat away from the plastic and into the coolant. That'* why I would not do the plugs unless I was gonna plug the EGR too. But I would not want to do plug EGR for fear of burning valves.

OK, think of this. The plastic uppers that do fail must erode out quite a distance from the standard EGR pipe to break into a cooling passage. Quite a ways farther even than the 0.086 gap I have made in mine. So maybe that sleeve is pretty important after all. Perhaps what it does is quickly conduct heat away from any one spot on the plastic, slowing or preventing deterioration by heat. It is hard to know what the air flow might look like around the pipe, but if there is a spot with little or no turbulence, that might be where the heat builds up and the plastic is most vulnerable. Hence the need for the sleeve. Yeah, I think I'm glad I put the sleeve in.

[edit: If the pipe is not perfectly sealed in the LIM, what the vacuum will suck up between the pipe and the plastic UIM is hot exhaust gas when the EGR valve is open. So when you set that pipe in the LIM, you might want to make sure you have a really good press fit. I put blue threadlock on mine, but I don't know if it will hold up to the heat. I am hoping the coolant in the LIM will preserve it.]

OK, just one more thought then I'm goin to bed. I think the sleeve should extend up into the airstream to provide air cooling to the plastic it is in contact with. I am not sure whether it should be as high as the center pipe. Maybe not, we want that center pipe to be cooled too, not insulated. My sleeve is too short - slightly less than flush with the bottom surface of the hole. This wants a sophisticated heat transfer analysis by some smart person.