Thread: Sloshing sound only after car has sat and cooled down.

Hello everyone I have a 2006 Pontiac Grand prix Special edition with the series 3 3.8L. and 137xxx Miles
Im pretty DIYer and would like to solve this problem myself.
After the car has sat overnight or 5 hours (probably just long enough to cool down.) and I start it up if I move the car or just rev the engine in park it will make a sloshing water sound, almost as if there was standing water that is being moved now. after driving for a 1/4 mile It doesnt make the noise anymore until it sits.
I checked my coolant today and the overflow jug was a little low, it was fine at the radiator, I topped it off and The noise persists. I had someone else inside the car rev it in park and I was looking at the engine bay and had them rev it, I couldnt hear the noise over the motor but they said they heard it inside.
Transmission fluid and level is good. The plastic Elbows have been replaced with metal. I thought maybe it was a leaking heater core but my passenger side floorboard is dry and I dont get a sweet smell. Would a LIM Gasket failure cause this noise only at startup? Wasnt the LIM gasket material changed in the series 3 revision and wasnt nearly as big as a problem?

Please please please any insight would be wonderful, I know that this is the best resource for this and im suprised we still have active members on this forum . Really dont want to be neglectful to my car and have a larger issue later.

heater core trapped air. I get the same thing every now and then. flush it if it bothers you

I find it relaxing like those serenity sound discs

It doesn't, assuming no I'll issues from this.

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Actually reading up on it. Seems like this makes the antifreeze corrosive and wears through the heatercore. I'll try to bleed it with my Lisle funnel

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Originally Posted by timothylockhart

It doesn't, assuming no I'll issues from this.

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Well back in 2015 you had a thread called wimpy heat, did you ever resolve it?

If you have excessive air in the core you will have substandard heat during the cold months
With air in the system period you will have erratic coolant temps.

Crack the bleeder bolt on the thermostat next time you get it home before you shut it down. Crank the heat first

For crying out loud, now you got me paranoid.
I better get that last little bubble outta there. I already changed the heater core once.

My 2000 GT has this "water flow noise" that I can hear the water flowing through the dash/heater core after start-up and through warm-up sometimes....and I, too, have changed the water pump, thermostat, coolant, hoses, and bled the system well. As long the heater core is not leaking, and you get good heat (I get GREAT heat) I would not worry about it to be honest with you. I have no leaks on my LIM gaskets that I can tell, and I also replaced me leaking coolant elbows with metal/aluminum ones. My car has 125k on it and runs like a champ after I bought it and "fixed it up" after serious lack of maintenance from the previous owners. Just my two cents.

Originally Posted by spazzz

Well back in 2015 you had a thread called wimpy heat, did you ever resolve it?

If you have excessive air in the core you will have substandard heat during the cold months
With air in the system period you will have erratic coolant temps.

Crack the bleeder bolt on the thermostat next time you get it home before you shut it down. Crank the heat first

Will do, the heats whatever honestly this car is only driven for 4 months out of the year and stored throughout winter.

I get paranoid easily too but I don't want to rip the whole dash apart. Probably would squeak like hell when I got it back together.

Didn't know the 3.8 has any bleeders. I've honestly never had to work on this car since i became a DIY'er and haven't popped the cover off and looked at the motor

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Also temps are actually really solid. Something I like since the 3.1 I owned had a blown head gasket and overheated on me until I fixed it.

Now sadly that car will overheat or damn near it if I sit idle long enough thinking plugged radiator or maybe one of the fans arent Working as they should.

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Originally Posted by timothylockhart

Also temps are actually really solid. Something I like since the 3.1 I owned had a blown head gasket and overheated on me until I fixed it.

Now sadly that car will overheat or damn near it if I sit idle long enough thinking plugged radiator or maybe one of the fans arent Working as they should.

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The 3.8L are a little more resilient I believe from what I have experienced and read (if anyone can argue that, please do, my 2000 GT is the ONLY GM so far I have ever owned so I'm new at this, I have only worked in the Auto Parts industry for about 20 years and just heard about what is good and what is not.) I can tell you, however, that last week, we have a slight heat wave, not real bad, but like near 80 and humid, here in PA, and I had to climb a mountain at about a 35% grade for 1-2 miles....and I ran my Prix, with the A/C on....cruise on...at 60mph...in Drive....letting it struggle...kicking in/out of O/D and shifting gears on its own.....and she didnt reach near 210. It faired very well. I was impressed. Now, granted, I re-did almost the entire cooling system last year, but still, I was impressed for a car that has been abused its whole life until I got it, with 125k on it, and stress testing it like that. The 3800's are great engines and will last forever IF taken care of AND maintained.

The engines might be the transmissions are a whole nother story.

Starting to get weird TCC lockup I think I'll be having the transmission rebuilt by 175.

Had to do it in the 3.1 01 gp @160k miles. What a *****

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Originally Posted by timothylockhart

The engines might be the transmissions are a whole nother story.

Starting to get weird TCC lockup I think I'll be having the transmission rebuilt by 175.

Had to do it in the 3.1 01 gp @160k miles. What a *****









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I'm praying mine holds up...at least for awhile yet. I have 125k on mine....and my car was abused its whole life until I got it. It was a quart low when I got it...but once I topped it off, she's been fine since. Goes right into gear, and shifts as smooth as a babys bottom every time. I've been tempted to change the fluid and filter, but I'm kinda scared to....b/c...."if it aint broke, don't fix it"....right?? lol

Originally Posted by mr2000gt

I'm praying mine holds up...at least for awhile yet. I have 125k on mine....and my car was abused its whole life until I got it. It was a quart low when I got it...but once I topped it off, she's been fine since. Goes right into gear, and shifts as smooth as a babys bottom every time. I've been tempted to change the fluid and filter, but I'm kinda scared to....b/c...."if it aint broke, don't fix it"....right?? lol

Should use that logic next time you're tires are almost bald

I kid. I had it done on mine because fluid was not pretty pink.


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Originally Posted by timothylockhart

Should use that logic next time you're tires are almost bald

I kid. I had it done on mine because fluid was not pretty pink.


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Mine is not either, but its not burned either. So I'm on the fence....b/c the tranny is working perfectly. I can do it myself, and put Mercon III back in it, or....I work at a Ford dealer (yes, make fun guys)....and have it completely flushed out, and upgrade it to Mercon V (which I read in a GM TSB that they recommend)....but it will cost a lot more. So, I don't know. I might eventually just swap out the filter and put III back in....its just an extra "beater" car for me, so I'm not looking to spend a ton of $$$$ on this car......I got it REALLY cheap b/c it didnt run when I bought it AND it was a Police Impounded car they wanted off the lot.

I thought GM wanted updated to the Dex VI?

I know Ford updated all the earlier 4R's to the Merc V to try and stop the TCC shudder issue. Not sure if Mercon V meets the Dex VI specs, but then again I don't use my Ford trans fluid in the GM's, never really thought to look. Last thing I want to do is have to rebuild the 4R in my Vic right now. The trans in the 00 GPGT is getting bad enough.

Originally Posted by FordMan77

I thought GM wanted updated to the Dex VI?

I know Ford updated all the earlier 4R's to the Merc V to try and stop the TCC shudder issue. Not sure if Mercon V meets the Dex VI specs, but then again I don't use my Ford trans fluid in the GM's, never really thought to look. Last thing I want to do is have to rebuild the 4R in my Vic right now. The trans in the 00 GPGT is getting bad enough.

I don't think Dex VI can be mixed with V.....its more like LV fluid....they are not compatible. I would have to double check that though. However, I'm almost positive when I was going through the GM TSB's on AllData, GM said something about replacing the Original III with Merc V.

Well. I bled it yesterday. Got some air out. Didn't slosh this morning so I think I'm in the clear.

Time will tell though.

Thanks everyone for the help. Time to start checking why the other car overheats

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Hope that did it for ya!! Good luck!

It did fix my sloshing on this car! Other cars being a ***** tho

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