I've been smelling coolant for a while now, no leaking obvious but can always smell it after my car is turned off. I started looking around the water pump and found what looks to be a timing cover bolt hole that looks wet. Does anybody know what this bolt hole is here for? Sorry for the blurry pic.

 

I just replaced the intake manifold on my 91 RS 3.1L and the heater hose quickconnect that is screwed into the front of the IM was completely corroded and falling apart. You can actually see it in your picture and it looks like there are some chunks of something right below it. It was producing a small steady leak of coolant that ended up on the top of my water pump. GM made the connector out of cast aluminum and it's prone to failure.

I tried to remove mine with the IM out of the car and the connector just snapped completely off, leaving the threads in the hole. I got the remaining half of the connector out of the hole with some "precision chiselling" and then replaced the connector with a 1/2" threaded fitting with a 5/8" hose nipple on it. This allowed me to bypass the throttle body coolant lines and replace the factory metal coolant line that clicks into the problem connector. Next I just ran a 90 degree 5/8" heater hose directly from the new fitting to the heater valve on the passenger side of the engine bay. Easy peezy lemon squeezy!

A lot of other members have had the same problem so I'd bet you're in the same boat as the rest of us. Good news is that it's an easy fix. At the most, you would just have to remove the intake hose, throttle body, thermostat housing and upper rad. hose to gain easy access to it. Hopefully yours won't snap off like mine did!

Anyways, let me know if you found the leak. I almost forgot.. I really have no idea what that hole you pictured is for, but next time I'm under the hood of my car I'll take a look and see if it's being used for anything.
Good luck. -Darren.

 

I could be wrong, but isnt that hole used to keep from breaking the seal on the timing chain cover when you replace the water pump? (see Haynes manual)

 

The Haynes manual also states that the 3.1 no longer needed to hold the timing cover on, unlike the 2.8's.

 

ooo you lucky 3.1 people!! lol anyway, its not used for anything then right?

 

I always firgured that if I'm doing the work to pull the water pump, I might as well do the timing cover and inspect the chain, it's like an extra 5 bolts and 15 minutes.