hello all. i have a strange problem with the impala. it seems to be loosing coolant , but not in the usual ways. i first noticed this about a month or so ago when lauren told me the coolant light was on. i added water, and all was well. over the past month or so, it used about 1/2 gallon of coolant. i chalked this up to either a very slow leak or a bad lim gasket.

about a week ago, i added some straight dex cool to top it off. all was well. yesterday night, i pulled into the gas station lauren went in to buy some cigs, and i noticed a fair amount of what i thought was steam coming out the grille. i popped the hood, smelled the coolant, but didnt see any steam at all. i looked in the coolant bottle, and the coolant was down to half. closed the hood back, no more steam. we proceeded the 50 miles home with no issue, and no coolant loss. she actually took the car to work over 40 miles away today with absolutely no coolant loss.

2 things that may or may not be worth noting: i believe her thermostat is stuck open. ( car only warms up to about 150*F in 35 degree temps)

also, when i noticed this steam, the temp outside was right on the threshold of freezing at about 34*f and the car was not hot and did not smell hot (i squeezed the rad hose to confirm the coolant was indeed flowing and it was not too hot to hold) so i am suspecting it was just warm water, like a hot coffee. the problem is, i could not find any water.

for the time being, since the car is running well and there are no codes and does not overheat i left a jug of water in the trunk till i can get some more light on this intermittent issue.


thanks alot for any and all enlightenment!

i would replace the thermostat and make sure you bleed the air because air bubbles can give you funky readings and variable reading like that

Time to do a pressure test. I would be looking at a failing LIM gasket or a water pump. I have seen a water pump failing on a 4.3 look like a failing LIM gasket. Also, a remote chance is a hairline crack in the top of the radiator, being that it is on top will only leak under pressure (not gravity), and since you are not heating up so much, your pressure is also lower than normal. A alternate way to check is to go for a long cruise at night, then check under the hood with the engine running with a strong pinpoint flashlight.

Get that pressure tester on and you will likely find the source of the problem.

x3 on the pressure tester. I have had similar symptoms when the leak was on the bypass side of the system (hose, inlet, etc), and that was tricky because it would only leak when the car was warming up and the thermostat wasn't open yet.

thanks for the help guys. i did notice a fair bit of gray gunk in the rad cap today. im suspecting a failing pump. which is just phenomenal considering i have no garage and it is currently 18*F outside. looks like ill either be freezing or shelling out alot of cash in the near future.

When was your LIM Gasket replaced?
I ask because you mention you thought it could be the problem, but did not mention if you had replaced the gasket or not.

Gunk in the radiator cap is not what you want to see, I'd give it a good coolant flush and fill in the future, once you find the issue.

i believe that is sealant put in by gm. i havent seen any car from early 2000'* that didnt have the gunk. even the 03 monte i bought 6 months old. i flush it a couple times and put prestone extended life in but even doing that it will normally come back in a year or two

Ahh, hopefully that is all it is then, I have never really had any gunk under my cap, but I have always flushed and filled a little sooner than necessary, I do have a new cap now though, of course the old never had any gunk on it that I can recall.

i never have seen that gunk on any trucks or anything before 99 anyway. neither my bonnie or yukon did it. and the yukon was very neglected all its life i believe

well, turned out to be a very easy fix. it was the thermostat, and a bad thermostat seal. replaced the thermostat expecting to see lots and lots of steam, but replacing the thermostat also fixed the leak. the thermostat was stuck wiiide open. car barley got to 140. now it goes right up to 190. with no leaks. some things turn out easier than expected after all!

now ive just got to do the flush and figure out the abs issue.