Try those O-rings out. But don't go to the dealer...instead get the o-rings from Advance/Autozone. In the "help" section, there should be an assortment of O-rings in a blister pack. Clean both your metal pipes (one going to the water pump, other goes into the intake manifold...and this is NOT the metal pipe fitting mentioned earlier (that goes to the top of the water pump). Slip on the best fitting o-ring you can find, and lightly coat with blue RTV. Reassemble (make sure all the coolant ports are dry first) and let sit for a an hour or so. Refill, start, let it come up to operating temp.

Another thing...did you properly torque the intake mani down?

Good idea, but my leak is definitely originating on the driver side. Appears to be just under the throttle body. The accesory side with the water pump is dry as a bone.

Yeah, I torqued mani bolts in sequence working from center outward. Don't own an inch/lb TW so I used judgement on torque. Definitely did not overtorque, just snugged then a lil' more.

Under the TB eh? Could be the TB gasket itself, or maybe the temp. sender since it is on that side of the manifold.

Did you think to clean the threads off the intake bolts, chase the threads on the heads, and loctite? There are a few places where if the manifold isn't tight enough, it will seap coolant out (when I first did mine, I neglected to clean, loctite, and torque properly. After running for a few minutes, coolant started steadily dripping from the front driver side, near the thermostat housing. Those bolts backed out and would not hold their torque at all unless cleaned and loctite coated)

OK, I just came from the garage...this is getting weird. I removed the throttle body to better observe where leak was coming from. There is a sensor right below the TB in the manifold...not the temp sensor right beside the mani bolt on firewall side, but right above the TB bracket bolt...dont' know which sensor it is but when I was blowing some air to dry off around it, I noticed that when air entered the plastic plenum in a small round opening just below the main plenum throat, (now exposed w/ the TB removed) coolant dripped out the a similar opening just under the throat on the other side, the firewall side. When I blew air directly in this opening - coolant flowed out of the opposing hole. Is this normal? I didn't think any coolant was supposed to be present in the L27 upper plenum???
BTW - yes, cleaned all bolt threads and whatnot...this appears to be where my leak is originating.

Looks like the dripping coolant is coming from the bottom side of the throttle body. I took the TB off, smeared RTV sealant on both UIM and TB mating surfaces and reassembled. There was no gasket present here when I first disassembled, just the silicone bead on the UIM. Let sit for a few hours and started it up after idling for a couple of minutes, the drip started again in the same spot. After searching this great site, found some info explaining that the TB has a "chin" that gets coolant thru the UIM...precisely where mine seems to be leaking. Is it possible that the UIM is cracked? When I visually inspected it, it looks fine. The one stud on the UIM is a bear to tighten. It goes thru a TB brkt bolted to LIM. I may not be getting a good seat on that? I'm ready to curl up in corner and have a good cry. Has any body dealt with this before? I kinda think its something to do with that nasty 3rd UIM/TB bolt?

Sorry I didn't get here before. The silicone bead in the UIM is the gasket for the TB. Pull it out and clean it off.

If the leak is coming from the TB/UIM you probably need to clean the gasket. Reinstall with a bead of RTV Blue on both sides. This gasket is dealer only and expensive. The sleeve the TB stud goes into has flat portion on the backside. Hold it with a combination wrench. The lowest bolt on the TB can be easily done with a 13mm socket, a 3/8 U-joint, a 12" wobble extention and a 3/8" rachet.

If the leak is coming from the UIM/LIM you need to pull the UIM and fix the leak at the O-ring surrounding the TB Coolant ports.


My TB leak pissed me off so I tapped the holes in the LIM and installed 1/2-13 plugs in the ports. Look at the UIM TB mounting face for cracked plastic allowing the gasket to twist.

Thanks Dame. I've obtained the gasket for the TB...I stupidly did not realize that this was a replaceable gasket. I'll remove the TB and pull that gasket and replace w/ the new one. The only leak visible is a steady drip from bottom of TB, I can see it dripping on a sensor directly underneath. I'm hopeful that this will cure my problem. I understand your directions for getting at the lower rear TB stud, but does the stud just go thru the TB bracket (longer end 1st) then just thread into the UIM? Seems like the bracket prevents the TB from fully seating against the UIM? I'll make sure that I prevent the sleeve from turning per your advice. Might just be my own ignorance but I wanted to be sure that I'm installing this the correct way.
Thanks!

That's how mine leaked and it was a degraded UIM allowing the gasket to twist.


The lowest bolt on the TB is somewhat tricky. The TB attaches straight to the UIM, but the three holed bracket goes over that stud, then a nut to retain it. Should be the long end of the stud into the UIM.

Well, I think I finally have got the leak sealed. I had to loosen the nut on the bracket located just below the TB where the stud passes thru. This allowed the bracket to draw in just enough to allow the TB and UIM to seal. Now all is dry and life is good.
This site is a great resource and I appreciate all the help. Thanks! :)