Community Member Credit: ATTappman
Recently I had to remove my UIM to tighten the hose clamps on the coolant hoses connected to the backside of the UIM. Here’s a description of the job with some photos. The car is a 1997 GLE Fed spec.
First, you have to remove the air intake. Start by popping off the four clips that secure the top of the air filter box:
Disconnect the MAF sensor electrical connector:
Disconnect the two large vacuum hoses and one small hose from the resonator:
Note that I unhooked the IACV end of the second large hose, to keep the hose attached to the resonator.
Loosen the hose clamp on the throttle body, wiggle the air duct off of the throttle body, and lift the whole air intake assembly out of the engine bay:
Disconnect the two electrical connectors from the throttle position sensor:
Disconnect the four electrical connectors from the IACV/fast idle solenoids/EGR temp sensor:
Unhook the cruise control and accelerator cables from the throttle lever. Note that the accelerator cable runs underneath the little tab on top of the throttle lever:
Remove the three 10mm bolts that secure the cable brackets to the UIM. Move the whole assembly to the back of the engine bay:
Disconnect the electrical connector on the EVAP purge volume control valve:
Disconnect the electrical connectors to the ignition coils and the front O2 sensor:
Unhook the wiring harness. It’s secured by plastic clips. With a pair of needle-nose pliers, compress the two “wings” on the bottom of the clip while simultaneously lifting up from the top. Move the wiring harness to the passenger side of the engine bay:
Remove the two 10mm and two 12mm bolts/nuts securing the EVAP purge control valve and the EVAP purge volume control valve to the UIM:
Remove the 10mm bolt holding the EGR temperature sensor bracket onto the IACV. This bolt is hard to see – you can locate it by feel. You’ll need a 3″ extension or a deep socket. The EGR temp sensor wire is in the way – make sure to move it aside to keep from pinching it with the socket. (No pics for this – it’s too hard to see).
Remove the three 12mm bolts holding the IACV to the throttle body. You need an extension for the bottom bolt (my camera battery went dead here and I switched to my cell phone camera – the pics are blurry, sorry):
Lift off the IACV, being careful not to lose the gasket in the engine bay:
Move the EVAP valves back toward the driver’s side of the engine bay. Most of the hoses will still be attached:
Remove the clamps on both ends of the PCV hose assembly, remove the 10mm bolts holding it to the UIM, and remove it:
Unscrew the two screws holding each ignition coil, and pull out the ignition coils. (No pics).
Unhook the vacuum hose from the UIM to the brake booster:
Now comes the hard part. The UIM is bolted onto the rear cylinder head with two support brackets. The EGR guide tube is also bolted to the UIM with two bolts. All of these are 12mm. The best way to locate the support bracket bolts is to feel with your hand along the firewall side of the UIM. Here’s what it looks like with a socket and ratchet on one of the bracket bolts:
You can see one of the EGR tube bolts, but you have to locate the other one by feel. It’s difficult to get a socket on the right UIM bracket bolt. You need a pretty shallow socket and a low-profile flex head ratchet (this is one job where Snap-on tools pay off). If you can’t use a ratchet, try a 12mm offset wrench. Once you loosen the bolts, use a socket to spin them off. Be careful not to drop them.
Taking off the left EGR tube bolt:
At this point, I was soaked with sweat and had a backache, so I stopped taking pictures.
The only remaining bolts are the four 12mm bolts on the front of the UIM. There’s a pattern for tightening these bolts, so I loosened them in the opposite order. If you’re looking down at the UIM from the front of the engine bay, the tightening order is 4-1-2-3 from left to right, so take them off in the reverse order.
Now the only thing holding the UIM on is two coolant hoses in the very back. If the UIM won’t separate from the lower intake manifold, take a thin putty knife and gently pry between the UIM and the gasket, being careful not to gouge the UIM.
Next, get an assistant (I used my wife – she’s a good scout) to hold the UIM as far up in the air as they can. This will reveal the two coolant hoses on the back of the UIM. It’s an extreme PITA to loosen the hose clamps and pull off these hoses. When you pull on them, you just pull the UIM and your assistant toward you. It took me a lot of patience and a lot of swearing to get them off. Getting them back on is no fun either. Maybe somebody can share a trick for this.
With the coolant hoses off, you can lift the UIM out of the engine bay. Here’s what it looks like with the UIM removed:
You can see the two support brackets and the top of the EGR guide tube. Here’s what my EGR guide tube looked like the first time I took the UIM off:
Reinstallation, as they say, is simply the reverse of removal.
Be careful not to knock the EGR tube gasket off into the engine bay. If you put in a new EGR tube gasket before reinstalling the UIM, it helps to tie two loops of fine dental floss through the EGR tube bolt holes and the gasket. This will secure the gasket to the EGR tube and keep it from falling off when you’re putting the UIM back on.
When reinstalling the UIM bracket bolts, get your assistant to move the UIM up and down slightly so that you can align the bolt holes on the UIM with the bolt holes on the cylinder head.
As you may have noticed, I rethreaded most of the bolts into their holes to keep from losing them. The ones you can’t do this with are the IACV/EGR temp sensor bracket bolts, the UIM support bracket bolts, EGR tube bolts, and UIM bolts themselves. I made post-its for each set and put the bolts on the post-its.
I used Permatex gasket adhesive to hold the UIM gasket and the IACV gasket in place during reinstallation. It was mildly successful.
That’s about it. Hope this helps somebody.