I recently changed the thermostat in my girlfriends 96 Maxima (140k) about a week ago.
It was obvious it was sticking...usually sticking while open...so you'd see the temp drop while driving on the highway. After replacing it, all seemed fine...

But now it seems that the coolant level is dropping. No signs of leak from the Tstat housing.
I'm thinking possibly it's her water pump leaking, as my sister has this same problem...although hers reaks of coolant all the time. Neither Maxima has any signs of external leaks though. My father replaced her thermostat with one from AutoZone less than a month ago, and the temp is starting to raise and fall again. Is it common for non dealer thermostats to fail early>? I havent had him check the temp sensor yet.

Is this a common problem? When a maxima has a failing coolant pump, does it usually keep the leak contained? Also, is there a easy way to confirm its leaking without a major teardown?

 

Water pump leaking will appear as if it's coming from the lower oil pan or the AC compressor. When it gets bad, it'll pour on the ground by the RF wheel when at a stop or when you turn the engine off.

 

so when theres no coolant leaking on the ground, but it wreaks and shows signs of coolant loss, where is it leaking to?

 

Any white or sweet smoke from the exhaust?

 

first off, did you make sure to bleed any air pockets from the system after replacing the t-stat?? they do have bleeder valves built (or should) but if you have huge air pockets they won't be much use. I know a few people that have overheated their cars from not bleeding the system properly. All depends on the location of the t-stat, i don't know where it is on the maxima(i dont have one yet) but if you had any coolant leak out in the process then an air bubble will have been introduced into the system.

 

I only drained enough out of the radiator to be below the thermostat level.
I doubt its air...but I suppose its possible. I didnt bleed it at all. I just ran it a while and topped it off after it dropped.

 

not that I've noticed from the girlfriends. I havent looked at my sisters closely yet, I just know hers stinks of coolant over by where the pump is. But according to her, and my father..no coolant ever hits the ground. So its gotta be leaking internally...and probably burning off inside.

 

yea after reading through the manual they don't mention a proper bleeding process so its probably not an issue, kinda hard to pinpoint where its leaking to, does it just smell outside the car or inside to, the only other place i can think of is that its leaking into the cabin. i know this sounds stupid but was the t-stat oriented properly with the "jiggle valve" facing upwards? trying to think of what this could be...

 

my girlfriends doesnt smell at all. my sisters smells out by the engine.
no sign or smell from my girlfriends.

 

I just had my system flushed and I smelled coolant so I got my car up to temp and took it to a car wash and hit the radiator with water and all the places that coolant may or could have hit when it was being changed. Of course bing careful not to hit any electrical parts in the process. This eliminated the smell.

Incidentally, if you just changed the themostat and there were no leaks, I have seen instances where once you open the system and the fluid level drops the water pump starts to leak from the weep hole, indicating a bad pump. That may be the problem.