97-03 NA L36 UIM Failure

[BillBoost37]

As many know, the weak spot on the L36 is not actually the LIM gaskets, but the UIM itself. Correct, not even the UIM gasket. Got a chance to document this issue recently and wanted to share so that L36 owners realized why it is suggested that they change the UIM or plug the coolant ports leading out of the LIM.

Typical L36 , UIM is black plastic/nylon material


The failure is evident if the car suddenly loses about a half to full gallon of coolant and the motor hydrolocks or appears to be burning coolant.
Reason behind the half to full gallon is the LIM fills when the UIM fails


Here's the UIM upside down. The large hole is where the EGR tube passes hot gasses through the manifold. A passage that is flanked on both sides by coolant passages to the throttle body. (the two smaller holes)


Looking at the EGR area with a pick...we can usually find a crack or hole





In the early model 97-99 L36's the EGR stovepipe was much larger. When buying a new Dorman etc UIM kit, you usually will get different diameter pipes. This is to put a smaller pipe into the place of the large old pipe. No matter what you put in though..the pipe usually doesn't have enough air gap to the UIM to keep it from expanding and contracting with the heat cycles, which cracks and degrades it.


Often if you catch the issue early enough and don't beat up the bearings trying to start a hydrolocked engine too many times, you can fix the issue and save the motor.

The different sized stovepipes that you get when you buy a new UIM kit.

Easy

[MoarkatsINmuhtrailer]

Good job bill. I'd also like to add that in the tunnel for the egr pipe, you may not find a hole cuz it will be extremely small. Or in some cases it will be a very noticeable hole. When mine went out, I wasn't so sure it was the uim even though I replaced the lim gaskets then the engine hydrolocked.

The hole in my uim is so tiny it takes all you've got to find it. So even if you think there is no hole... It's there.

[matt5112]

L26 UIM time?

[MoarkatsINmuhtrailer]

Fbody l36 uim and lim?? I think so

[TheOtherNick]

That requires a lot of work.

[MoarkatsINmuhtrailer]

Extension of the throttle cables, plug some ports. So far from setting it in my engine bay it doesn't look like too much work.

And for the upper radiator hose just use one from a 95 aurora 4.0

[BillBoost37]

It's a 5 minute thing if you have two 1/4" pipe plugs and a 1/4" NPT tap and 7/16" drill for it. Drill, tap and plug the LIM. Then there is no more issue with the UIM possible. No need to buy a new one, no need to worry about hydrolocking or any other issues.

L26'ing requires a TB adapter, different intake and a pcv hose where you likely drill/tap the TB. Not horrible, but more than some want to do.

[BillBoost37]

Added the stovepipe picture.

[Rico]

I went with the Dorman and it came with the smaller pipe (actually 2). Removing the old pipe was biatch...And I had to beat the hell out of the new one to get it in.

50K on it now with no problems...'knocking on wood'.

[Dtrick22]

Is that the motor from my Intrigue?

[BillBoost37]

Yup, it was filled to the gills

[apierce1289]

As many know, the weak spot on the L36 is not actually the LIM gaskets, but the UIM itself. Correct, not even the UIM gasket. Got a chance to document this issue recently and wanted to share so that L36 owners realized why it is suggested that they change the UIM or plug the coolant ports leading out of the LIM.

Typical L36 , UIM is black plastic/nylon material


The failure is evident if the car suddenly loses about a half to full gallon of coolant and the motor hydrolocks or appears to be burning coolant.
Reason behind the half to full gallon is the LIM fills when the UIM fails


Here's the UIM upside down. The large hole is where the EGR tube passes hot gasses through the manifold. A passage that is flanked on both sides by coolant passages to the throttle body. (the two smaller holes)


Looking at the EGR area with a pick...we can usually find a crack or hole





In the early model 97-99 L36's the EGR stovepipe was much larger. When buying a new Dorman etc UIM kit, you usually will get different diameter pipes. This is to put a smaller pipe into the place of the large old pipe. No matter what you put in though..the pipe usually doesn't have enough air gap to the UIM to keep it from expanding and contracting with the heat cycles, which cracks and degrades it.


Often if you catch the issue early enough and don't beat up the bearings trying to start a hydrolocked engine too many times, you can fix the issue and save the motor.

The different sized stovepipes that you get when you buy a new UIM kit.

So this is what we going to do to mine Bill? Only with l26 :-D Hope we can plug my coolant holes up or something (if we even need to since you got my l26 uim at your place). Can't wait!

Sent from my XT912 using Tapatalk 2

[bloaty57]

Bill.....I have the 00' L36 and I replaced the uim without the stovepipe because I read where that year was of a smaller diameter......but from what you mentioned, replacing the stock one with the stovepipe doesn't make a hell of a lot of difference anyway. I also read what Rico said about it being a pain to pull or change out the stock tube. I'd almost think that you'd have to cross drill the tube and use a puller of some sort so you didn't have to kill yourself getting it out. The only other option I thought of was putting the narrow stovepipe in then wrapping it with a thin layer of that white heat fiber wrap they use in high heat applications. It will take direct heat from a torch and not even discolor.
Regardless....I have hex type (drive) aluminum threaded plugs in the shop and I think they'd fit flush, but unless I missed something, would there be any issues with the throttle body and/or it throwing codes ?

[Rico]

Bill.....I have the 00' L36 and I replaced the uim without the stovepipe because I read where that year was of a smaller diameter......but from what you mentioned, replacing the stock one with the stovepipe doesn't make a hell of a lot of difference anyway. I also read what Rico said about it being a pain to pull or change out the stock tube. I'd almost think that you'd have to cross drill the tube and use a puller of some sort so you didn't have to kill yourself getting it out. The only other option I thought of was putting the narrow stovepipe in then wrapping it with a thin layer of that white heat fiber wrap they use in high heat applications. It will take direct heat from a torch and not even discolor.
Regardless....I have hex type (drive) aluminum threaded plugs in the shop and I think they'd fit flush, but unless I missed something, would there be any issues with the throttle body and/or it throwing codes ?

To remove the old tap from side to side with a dead-blow hammer and it will loosen. Grab it with a good pair of channel locks and twist. I also put a piece of wood on the LIM to pry upwards. I was worried about ruining the hole in the LIM.

I don't think you'll have to worry about it if you use the new thin style. This creates some distance between the pipe and the UIM.

Could you please elaborate on your last question about the TB and codes?

[bloaty57]

Rico.....
If I understood Bill's post correctly, he mentioned totally plugging off the port, and I assumed he meant the tube or riser that you're suppose to replace with the narrow one from the kit..........thought it was something new, or a work around to avoid problems in the future. I just wondered if he meant totally deleting it and plugging it off and if there were possible problems with codes popping up or anything like that..........?

I omitted installing the narrower stovepipe when I did mine a couple of weeks ago. I had just read where the 00' L36 had a narrower tube and the other wasn't necessary, but it still is thinner than the one I had in the manifold, so......back to surgery . It'd also be nice if Dorman had more detailed instructions with the new plenum. Their instructions were like......."take old one off, clean....put new one on"......duh!........not a thing about the upgrade/mod.

[Rico]

Bill was referring to the coolant ports that go up through the UIM and into the flange on the throttle body. He plugs them because they are a known point of failure.

"As many know, the weak spot on the L36 is not actually the LIM gaskets, but the UIM itself. Correct, not even the UIM gasket. Got a chance to document this issue recently and wanted to share so that L36 owners realized why it is suggested that they change the UIM or plug the coolant ports leading out of the LIM."

[BillBoost37]

If you plug the coolant ports, there's no worry about changing the stovepipe. Because then the coolant that would be in the manifold on the sides of the EGR port/stovepipe area isn't there and there will be no worries about the area rupturing and filling the LIM with coolant.

I've had good success with simply grabbing the old pipe with channel locks and twisting/pulling. I hear Rico has a few years on me, maybe his strength isn't what it used to be? (I kid) Also ..I found to put the new pipe in.. finding a deep socket that fits over the small diamter of the pipe and catches the edge that sits into the LIM works well as a driving tool.

I would not suggest that non-coloring material as it likely still transfers the heat.

[bloaty57]

Thanks Bill.......
Dumb a$$ question.........I'm sure some college kid/engineer had a reason for running the coolant up in the uim, but obviously with your work around, it's not all that important apparently ?.......correct ?
The cloth or heat weave I was referring to protects the plastic coating on wires in kilns and lead pots, which I use to melt alloys for bullets and such. The heat in the bottom of those crucibles gets 800+ degrees. It's very similar to the foam blocks they use under the shuttle as far as anti heat transfer is concerned, but in cloth form. They make gloves out of it and I've literally held a torch to my hand with them on and it barely felt warm inside the glove......very cool stuff....literally

I don't know about Rico...... I'm at the "double nickel" mark (55) and good sized, but I still might need the aid of one of my burly sons :P
Btw.....the socket idea sounds like a good one......I do the same installing bearings........I'll give er' a try......tks...

[BillBoost37]

The only purpose of those ports is to deliver coolant to the TB. And if you've ever pulled the TB...it's literally a groove that turns the coolant around to the other port. It's a joke, supposedly it is designed to keep the TB from icing. I know many people with blocked coolant ports in Canada etc that never have any icing issues. Here on the CT/MA border I've run all my 3800's this way for about the last 7 years w/o issues.

Cool on that cloth.

[bloaty57]

Thanks Bill.....makes a ton of sense based on your explanation. Initially, I thought the coolant was piped in there to cool the EGR port or something........huh, go figure on the icing thing. You'd think from my past life in the AF and the time I spent with aircraft de-icing I would've figured that one out. I've heard of TB's icing before though. Can't quite remember the model or years of the cars when that came up, but I think it was the late 80's early 90's..........icing would cover the whole air valve.

Good tips all........thank you