UIM swap L36 plastic to L26 alloy questions

**GT in Kennesaw** · 12-24-2012

Has anyone successfully swapped the UIM on their L36 to a alloy L26 UIM? I have a 01 GT with 175,000 miles and the upper and lower manifolds are leaking. I already had to replace the elbows some time back, now this. I'm done with plastic engine parts. I'm getting the aluminum elbows from ZZP and have a alloy UIM coming. There are several differences between the parts other than the material used. I've seen several posts (none here) suggesting all kind of solutions. I'm looking for someone who has actually made the swap and solved some of the issues. I'm also considering swapping the L67 TB for the oval one that's on there now. That may be more trouble than it's worth though. Has anyone successfully done that? Any help would be appreciated.
Thanks.

**blueguy** · 12-24-2012

Swapping to the L67 TB will require a tune.

The L26 UIM can use the L36 gasket (I think I trimmed a smidge off of it to get it to clip in)

You have to tap and seal off the EVAP (I think on the front, right side of the L26 UIM looking at it from the intake opening)

You also need a GenV to GenIII adapter plate (4 bolt to 3 bolt) and slap that thing on there...I sealed mine with RTV just because.

I had to extend the vacuum lines a tad as well, and remove the EVAP canister bracket...at this time I also did new fuel injector o-rings, etc.

It's pretty straight forward.

**GT in Kennesaw** · 12-25-2012

Thanks for the information. A couple of questions; did you notice any change in drivability or gas mileage as a result of the mod? What did you do about the coolant passage to the TB? Regarding the EVAP, I've seen 2 methods posted elsewhere, one drilled/tapped a hole in the side of the TB into the existing EVAP port and used a fitting to connect to the UIM EVAP port. The other drilled through the outsise of the UIM into the throat of the UIM, and plugged the EVAP port and the hole drilled on the outside. What method did you use, if either?

**Bio248** · 12-26-2012

the EGR tubes are different size.

there is also zero gain in doing this, so i dont see a point in switching. yes, i did have an L26 UIM on my L36 setup. would i do it again? no. the newer dorman parts are updated and they'll be fine for as long as you have your car.

**txslow6** · 12-26-2012

Most just do it cause it looks nice if polished.

**GT in Kennesaw** · 12-26-2012

I didn't think about the look so much, I'm just concerned about the leaking. The car had a factory recall mod for the "stove pipe" issue. Not really sure what they did, but it obviously didn't prevent the problem. I also have had an issue with the EGRV on this car. I'm on the 4th one. It's actually the only problem I've really had with this car. Until now. I've removed the EGRV several times whenever I got the "Check Engine" light and code for it. Sometimes a little cleaning did the trick, but I'm on number 4 (aftermarket). I've also read and heard that the Dorman part will still fail. I've had people tell me it's not as good as the redesigned GM part. My conclusion is that GM switched to alloy for a reason. It might be a waste of time, but I bought a new AC Delco L26 UIM kit for $78, cheaper than the plastic. Hard to pass up.

**GT in Kennesaw** · 01-01-2013

I'm still waiting for the new UIM, but since there's plenty to do before it arrives, I've started. I took a few photos and will post them. This shows what everything looked like. So far only the intake filter cover and hose removed and a few of the connectors off the throttle body.

**GT in Kennesaw** · 01-01-2013

From the front of the engine, obvious signs of leaking.

**GT in Kennesaw** · 01-01-2013

With the UIM off.

A bit of oil puddled in the LIM

**GT in Kennesaw** · 01-01-2013

The good news, no water/oil "milk shake".

**GT in Kennesaw** · 01-01-2013

Here, you can see the evidence of the gasket failure. The space between the EGR pipe and the water port is destroyed.

Confirmed here. The gasket on the UIM

**GT in Kennesaw** · 01-01-2013

I question if this is a "distorted" or "warped" plastic UIM failure. It might just be a simple failure of the gasket. Opinions?

**Scottydoggs** · 01-01-2013

mod your lim, never worry about it again. http://www.grandprixforums.net/how-mod-lim-46931.html

**GT in Kennesaw** · 01-01-2013

This is with the LIM removed.

**GT in Kennesaw** · 01-01-2013

Originally Posted by scottydoggs

mod your lim, never worry about it again. http://www.grandprixforums.net/how-mod-lim-46931.html

I saw that post. Have it bookmarked. I'm still undecided about closing off the ports.

**BillBoost37** · 01-02-2013

Since you are going wtih the L26 UIM, your ports will be blocked by the adapter plate. You might as well plug them and ensure the gasket can never have an issue. Because the gasket on the L26 is nearly the same as the L36. Being a gasket, they can and may leak.

The stovepipe recall was to make the size of it smaller inside the EGR hole of the UIM. They figured more air around it may keep the manifolds from cracking and filling the motor with coolant.

The oil you found puddled is very normal and not bad at all. It comes from the PCV. Due to the low areas in the manifold it will collect.

**GT in Kennesaw** · 01-21-2013

Since my last post I have completed the project. Three times. Here's some details.

First order of business was to clean up everything. Sounds like a great excuse to get that parts washer I've always wanted.

The new UIM.

The 1/4" NPT plug and tapped EVAP hole on the UIM

If you look below the tapped EVAP hole, you'll see it the small opening in the throat where it leads. I thought this would be a great place to get vacuum for the PCV air inlet (now at the top of the UIM instead of through the throttle body mounting area). Turns out, I was wrong. More on that later.

So I decided to put a 1/4" fitting there and connect the vacuum port to the air inlet. UIM and LIM and adapter and TB test fit.

**GT in Kennesaw** · 01-21-2013

The decision was made to plug the water ports. Thanks for advise.

And to open up the area under the end cap per the 5/19/2011 post by BillBoost37.

A little cleanup time

I replaced all the "safety" bolts with standard hex bolts (4 x 0.7mm)

These are the parts I had to buy. Two items not shown are the water pump (more later) and the PCV valve assembly. And yes, those are aluminum elbows.

Looking down the throat of the UIM, the top of the stove pipe is well below the throat area. I did not cut the pipe. Either I misunderstood the need to or the recall fix is shorter than the original. Or, do I need to take the UIM off and cut it?

LIM in place. Valve covers were removed and cleaned up too.

And the UIM in place.

The throttle body is a good 2 inches more to the left now. There will be problems.

Such as the wiring harness has to be tugged a little.

The air box has to be moved over and it's still a struggle to get the hose in place.

Then there's the throttle cables.

Next, I had to find a way to connect the combo tube from the EVAP solenoid and FPR to the throttle body. The solution. Two of these.

To make this.

In place.

**GT in Kennesaw** · 01-21-2013

So I got everything together, changed the oil/filter, added fresh antifreeze and connected up the charged battery. Things were going to be great. Or so I thought. I was loosing coolant all over the ground. It was coming from the front of the engine and it wasn't shy about it. I thought it was the elbows. Wait, they're aluminum now. The only place I could find water was along the bottom of the water pump. I should have known. I went ahead and tried to start the engine and on the third crank, it was running (I should note that I pulled the fuel rails out of the car to replace both "O" rings on the injectors. There was no gas in the rails). By then water was spraying everywhere so I shut it down. Back to Amazon to order a water pump. I got the pump (this Friday) and Saturday I pulled off the old one and this is what I saw.

A little more cleanup and...

So I put it all back together for the second time, refilled the coolant again. and fired it up.
It started, idled, ran. For awhile. No leaks, water or air. It was hunting a bit but otherwise was running smoothly. The curious thing was that at idle, it now had a V8 burble at the exhaust. But why was it smoking? I waited for the temp to come up and stabilize, but before it could, it started to howl under the hood. It sounded like a slipping belt, only worse. Wait, I replaced the belt, so that can't be it. I pulled the belt off to make sure all the pulleys turned freely (they did) and decided to fire it up with the belt off. Sure enough, there was the squealing without the belt on. Now what? Back to Google for the answer. Found it on (you guessed it) The Grand Prix Forums. The PCV valve? Really? So I got the whole PCV valve assembly (I had broken off one of the ears that hold the connector on top when I was was tearing down the top of the engine, so no big deal). Put it on and fired it up, and no change.

Time to think. So, the original L36 and the L26 setup both draw vacuum for the PCV inlet after the MAF sensor, but before the throttle plate. My clever setup was drawing vacuum after the MAF sensor, but not before the throttle plate. It was on the engine side of the plate. It was creating such a strong vacuum in the crankcase that it was hard to pull the oil cap off (which also made the noise stop). Back to work. The EVAP hole in the new UIM had to be plugged (as originally planned) and I needed another source for the vacuum. In my defense, I saw a post on the Bonneville Pro Forum that actually drilled a new hole through the UIM to create a port that was already there. At least I didn't do that. I did see a post somewhere (can't find it now) where someone drilled out the plug in the bottom of the throttle body to tap for a fitting, but I don't think he posted the final results. But that seemed to make the most sense. Off with the throttle body and down to the drill press. I drilled out the plug (brass—you can see what's left of it in the photo) and tapped it for a 1/8 NPT elbow to 3/8 pipe barb fitting.

I had to remove some excess aluminum from the throttle body to make room for the elbow (at bottom right).

With the elbow installed. Note that I point it away from the crossover pipe.

Here's the throttle body back on the car.

The elbow at the top of the UIM has a short section of plastic tube connecting to a 3/8" ID hose, then to a longer piece of plastic tube that I bent to turn under the throttle body. They're both left over from the "emission hose" Help parts I bought to make the adapter for the purge solenoid/FPR connector. I used one of the rubber sleeves to connect the elbow on the bottom of the throttle body to the plastic tube.

So, for the third time, I put it all back together and it started up perfectly, idles smoothly, runs nice and no squealing noise. That fixed it. I don't have the V8 burble anymore, but It's all good.

The only negative thing I've noticed so far, is a slight bogging down during shifts. It seems to happen under light throttle only. That will have to be the next post. I'm going to drive the car a bit to see if there's anything else to report.