Here's a stumper for the gurus --

Occasionally after driving my 2004 (like the 45 min. commute to/from the office), as I walk around the right front fender, I catch a *very* light whiff of coolant.

Here are the clues:

-- This has become noticeable only in the last 3-4 months.

-- I *think* the level in the reservoir has *slowly* begun to decrease, but I'm not sure if my observations are accurate, as I haven't yet begun to check in a systematic way (the car is driven regularly (about 8K miles/yr), but between my C6 and sharing the car with my wife, I'm in it at irregular intervals). I did add a bit of coolant to top off the reservoir several months ago, but didn't think much of it at the time because the coolant is about to be changed (i.e., I didn't think it unusual to be a bit lower than new, given that it was 4+ years old).

-- I have been over every square inch of the car that I can access (I have a 4-post lift), including as much of the reservoir as possible without removing it, and have not been able to find even a *suggestion* of a coolant leak anywhere -- water pump weep hole, throttle body lines, hoses, etc..

-- No coolant smell in the exhaust.

Any ideas? The only thought that immediately comes to mind is the possibility that the reservoir cap has gone bad. Would these symptoms fit a bad cap?

Thanks for any suggestions!
Mark

 

The coolant tanks on C5's have a tendency to develop small pin hole leaks that can be hard to find. The leaks are small enough that they evaporate almost instantly with the high under the hood temps but will produce the anti freeze smell. it takes about six weeks on my daily driver to lose enough to set off the low coolant light.

 

Thanks for the info -- are there any places on the reservoir which are particularly prone to developing leaks?

 

Check around the TEE were the two hoses connect to the tank. Run a clean rag under the tank. If the tank is leaking there is usually an accumulation of anti freeze on the bottom of the tank.

 

Have you looked at the oil after driving it to check for coolant? Does it get worse when you turn the heater/defrost on?

 

I bet its coming from the water pump gasket on the back side. Very hard to spot. It usually drips down onto the front spring area or sprays front of oil pan. Mine did it for 4 years with the slight anti freeze smell once in a while then all the sudden stopped a few weeks ago after I flushed the system out.

 

Yep -- dipstick oil is exactly as I would expect after ~3K since last change -- no color change or other evidence such as foaming or water.

Nope -- no heater hose or heater core-related issues.

Thanks for the thoughts,
Mark

 

Thanks again, Doug -- I will do a the rag test this evening when I get home.

 

Interesting. If Doug's rag test doesn't show anything this evening, I'll put the car up on the lift and look harder in this area.

 

That was my problem

 

My 02 Reservoir leak was from cracked fitting on the top, aft of tank, near the Pressure Cap. The plastic cracked where the Tube comes out of the tank. Very small leak - Kept getting coolant on the heater hoses right below it. New tank about $50 from GM Parts House.

Phil

 

I recently replaced my coolant reservoir because of a leaking tubing fitting on the underside of the tank. I was smelling coolant when I parked it before I replaced the tank and I still smell it after I replaced the reservoir. I see no leakage as I did before the replacement, but I still smell coolant when I kill the engine and get out of the car. Could it be residual coolant in the area?4

 

Had the same problem...it is the water pump. Even though there was no dripping, I reached around and got the wet finger under the pump just above the belt. Another dead giveaway is the belt squeal on cold startup. The coolant seeps onto the belt and you get a squeal for about 15 seconds upon startup the next morning. The leak is verrrryy slow, that is why there is no puddling....it is most noticeable (smells strong) when parking back in the garage after car has been at full temperature. I had the dealer install an Autozone pump ($138.00)...this is a hard install because the old gasket material has to be scraped off and is hard to get to without laying on the engine, unless you are very tall.