Help diagnosing overheating issue in 2004 V8

[Sexsymbolx]

Hi everyone -

Can anyone give me their thoughts on this:

Over the last few days my 2004 V8 has been acting up. Normally the temperature gauge sits perfectly at the halfway point. A couple days ago a few minutes after I started driving in the morning the fan came on. Engine didn't get hotter. About 30 seconds later the fan shut off. Everything was fine from there on - idling at stops, in traffic, under load, up hill, higher speeds all no issue.

Yesterday was insanely hot in LA. This time the temperature gauge did climb a little as the fan came on. Then the fan shut off and just fine for the rest of the trip. Again, this happens only after the car has sat for a bit.

It seems to me like a sticking thermostat. Only happens when starting the car from a cold start and once it drops down it doesn't go back up.

I picked up the incredibly overpriced thermostat and equally overpriced o ring today.

Does this sound like I'm on the right track? Any other suggestions? Anything I should check?

And just how horrible is it to replace the thermostat. It looks like it sucks.

Thanks everyone!

Tim

 

[1LoudLS]

well to be honest, while there is a small chance that there might be a thermostat problem, chances are your car is not a special snowflake, and you are now starting to have the same plastic cooling system parts failure as (almost) every other LS out there has had.

with even the littlest amount of searching, you would have found that there is literally a sh!t ton of threads like this one. long story short, the plastic parts in the cooling system (every single one of them including the radiator is subject to this) get extremely brittle with age and use, then they start to develop tiny cracks, usually when it first starts, these cracks are so small that liquid coolant will not leak out, but as the engine cools off air leaks in to the system and causes overheating problems. eventually coolant will start to leak/pour out (sometimes at an alarming rate due to a parts basically exploding.

also I just throw this out there, if in some magical way your problem is not directly due to a part failing, chances are good that while you start taking it apart, one/some/all of the parts may just start to fall apart in your hands.


also with a little searching, you will most likely find that a lot of people are inclined (often against recommendation) to only replace the one part that they can see/tell is broke/leaking while assuming that the rest of the parts are fine. you would also most likely see that when they only replace one or two parts, the car may work fine for a day, week, or month but then starts overheating again until they replace another parts... and so on... and so on... well since all of the plastic cooling parts are subject to the same environment and are built with the same kind of plastic, all of the parts have the same life expectancy and tend to all fail around the same time. its always strongly recommended that somebody replaces all of the plastic parts at once as to not have to keep doing this every few weeks.

 

[1LoudLS]

oh and while not crazy hard to replace the T-stat, there a little more to it than most cars, and as mentioned above, there is also the added degree of difficulty of having to replace a lot more stuff when parts start breaking as you remove them.

 

[Sexsymbolx]

Yes, I considered that, but my symptoms are completely different from what the posters in those threads have had.

If it is indeed possible that the issue is air in the system then perhaps someone can explain to me why it exists only when starting the car and then after roughly the time it takes for a thermostat to open it goes away and doesn't resurface no matter what conditions the car faces.

Also, the majority of the plastic cooling parts have been replaced with dealer parts within the last 4 years.

Again, not saying that's not what's happening, but I've not seen a post with this exact symptom.

 

[joegr]

Yes, I considered that, but my symptoms are completely different from what the posters in those threads have had....

No, they really aren't.
You can't tell by the gauge when it is marginally overheating. That gauge is still dead center when the engine is at 240 degrees.

Go ahead with your theory and replace just the thermostat. Maybe you will be lucky. If not, maybe the worst of it will be that you wasted a little coolant when you have to go back and replace more parts. Worst case is that the front and/or back housing cracks apart when you go to replace the thermostat and your car is down until you can get those parts.

Also, the majority of the plastic cooling parts have been replaced with dealer parts within the last 4 years.

Majority is not all. All is very important. They probably left the 45 degree outlet pipe as that one is the most labor intensive to replace. Unfortunately, it is also a big failure point.

Lastly, do note that having it run hot has greatly aged the plastic parts.

 

[Diplomat 1]

Having been in this situation multiple times (coolant leaks) I would start there. Try and look for a leak by eye and if not do a pressure test (rent one). I would listen to joegr and Loudls they know what they are talking about. Good luck