Intermittent overheating in Venture 2004 minivan.

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ColonelKlink

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Hi,
This is a 2004 Venture with 3.4l engine with 170,000 miles on it. I was on a 400 mile trip, the outside temperature was 25F, and 350 miles into the trip, the temperature gauge shot up into the red zone. I stopped the vehicle, shut it off, for 15 minutes. I restarted the engine, and I finished the trip alright, temperature stayed slightly hotter than usual, but not in the red zone. The next day, I drove back 400 miles with no issues.
I am really worried why the temperature would get into the red zone travelling at 70mph with 25F outside and not doing anything unusual driving-wise. Could this be a symptom of something serious brewing, such as head gasket etc. or what?
thanks for the help!!!
 
head gasket AND there's a bubble that forms under your thermostat keeping the thermostat pellet from "seeing" the heat so it stays closed making it worse.

A temporary kludge would be to drill a 1/8" hole in the t-stat so it burps the exhaust air that forms behind it.

Also take note of both air bleeds on this van and get them purged properly. Could just have an air-lock along with low coolant.
 
Check engine oil for signs of antifreeze and vice versa. Check for signs of external leaks where the lower intake mounts. Pressure test cooling system and radiator cap.
If there are no signs of improper pressure, no leaks, no intermix, etc., then replace radiator cap, thermostat, and flush the cooling system.
 
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You need to tell us if you lost, or are loosing, any coolant or not.
You say you shut it off 15 minutes and then finished your trip with no problem. It could be a simple sticking thermostat or faulty gauge.
 
Originally Posted By: salv
Check engine oil for signs of antifreeze and vice versa. Check for signs of external leaks where the lower intake mounts. Pressure test cooling system and radiator cap.
If there are no signs of improper pressure, no leaks, no intermix, etc., then replace radiator cap, thermostat, and flush the cooling system.


This is solid advice
 
Originally Posted By: Chris142
Got coolant? Have you removed the cap and looked? If that's ok I'm going with a bad thermostat. Have fun with that! They hid it in a real bad place.


Cripes I forgot about that!

The awful bolt, I'd like to say it's the bottom, doesn't have to come out all the way though. The gooseneck has a slit so you remove the top bolt, loosen the bottom, and slide the whole shebang up and out.

This will dump a pleasurable amount of coolant on your transmission and wiring harness.
 
Since then, I made a 450 mile trip with no issues. The condition of the oil seems normal, with no sludge in it, and in the morning I will check the coolant level. I have a hunch this might have something to do with thermostat, but I'll have them check all those items you mentioned.

Best regards - Captain Klink.
 
Originally Posted By: salv
Check engine oil for signs of antifreeze and vice versa. Check for signs of external leaks where the lower intake mounts. Pressure test cooling system and radiator cap.
If there are no signs of improper pressure, no leaks, no intermix, etc., then replace radiator cap, thermostat, and flush the cooling system.


+2
 
If you haven't ever replaced the LIM gasket, you need to do that immedialtely. Google the GM 3.4L V6 and you will see the Lower Intake Manifold gaskets fail starting around 60k or so. Same with the 3.1L V6. This has been a serious problem with the GM V6's and GM stands behind them 1000% ---way behind! If you get the intake manifold repair, be sure they use the upgraded,improved design IM gaskets. Fel Pro makes a good one.
 
Originally Posted By: ColonelKlink
Since then, I made a 450 mile trip with no issues. The condition of the oil seems normal, with no sludge in it, and in the morning I will check the coolant level. I have a hunch this might have something to do with thermostat, but I'll have them check all those items you mentioned.

Best regards - Captain Klink.


Wait - thought you were Colonel Klink. What happened? Did you get a demotion?
wink.gif
 
Run it 'till it blows, then have a junkyard tow it away.

I fixed my Grandparent's 2001 Montana (same thing). I found coolant via a used oil analysis so I did the LIM. After I did that it would stutter as if it was dropping a cylinder right after start-up for about 5 seconds. Sometimes, it would stall, or would be hard to start.
I checked the air coming out of the radiator for HC, which was positive. I pulled it back down and the HG on the rear bank was eaten away around the coolant passage all the way to the fire ring around the back right cylinder.
 
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I also find that HG failures are common on 3.1 and 3.4 engines.

If you go to your automotive machinist, they might have a set of rebuilt 3.1 or 3.4 heads just waiting for you, because of such high failure rates.
 
I did one of these a couple of years ago with the same issue.
2 rebuilt heads and top end gasket set from Fel-Pro fixed it right up. $700 and a weekends messing around is a lot cheaper than a used engine or another car.
 
Originally Posted By: Jim Spahr
If you haven't ever replaced the LIM gasket, you need to do that immedialtely. Google the GM 3.4L V6 and you will see the Lower Intake Manifold gaskets fail starting around 60k or so. Same with the 3.1L V6. This has been a serious problem with the GM V6's and GM stands behind them 1000% ---way behind! If you get the intake manifold repair, be sure they use the upgraded,improved design IM gaskets. Fel Pro makes a good one.


Venture vans in model year 2004 had the upgraded LIM gasket from the factory (I also own one). That being said, 170k miles is a lot so there is always the chance it has failed despite the improved design.

It could be as simple as low coolant. The factory fill was DexCool, and if it hasn't been serviced in a long time and is now low that could be a big problem. DexCool and air in the cooling system don't play well together.
 
Originally Posted By: babyivan
In general, iron blocks with aluminum heads are a bad combo.


Boy, that there is some real BALONEY!

What universe do you live in, man? It's not like aluminum heads are something new.
 
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Originally Posted By: babyivan
In general, iron blocks with aluminum heads are a bad combo.

Many auto makers made perfectly good engines with aluminum blocks and iron heads for decades.

During the 80s, every Nissan gasoline engine was an iron block with aluminum heads, and none of those engines were ever trouble prone. They were some of the toughest engines in their price range.

The most common iron block plus aluminum heads combo I can think of is the Ford Modular, and those are rarely a problem.
 
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