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Tractor Nut
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Discussion Starter · #1 ·
My wife called me while I was at work and said she was driving our van and it was severely overheating. Of course, she doesn't watch gauges and didn't notice until it started lacking power was stating "HIGH COOLANT TEMP" on it's message display. I'm assuming that in attempt to not kill itself completely, it put itself into some sort of limp mode.

I'm sure some of you already know, but GM's 3.4L engine is known for it's issues with the intake gasket and head gaskets. In fact, nearly a year ago, I had both the intake gasket and head gaskets replaced on this van because it was overheating. There are no numbers on the temperature gauge on this van, so I don't know what actual temperatures it was reading, but last time we had an issue, while idling, the gauge indicator would go into the red, but not while driving (when it was getting air flow). This time, it goes into the red regardless of if you're driving or not.

This van works well for our family as we have 4 kids, it's comfortable to ride in, and I've always been happy with it in terms of power. At this point though I'm concerned this is going to be a frequently reoccurring issue. I haven't diagnosed the problem yet because I'm still at work, but I plan on checking it out first thing in the morning. It wouldn't surprise me if I'm dealing with the same problem I had last time since these engines are notorious for this, but I'd be relieved to find out it's something else. I wouldn't mind hearing it needs a new radiator, water pump, even just a radiator cap! Those would be great!

What are some tips for diagnosing my problem? I'm not a mechanic by any means, but I tinker with tractors and small engines. I don't have any experience with cooling systems other than knowing where to put coolant and replacing hoses! What's the first step? Visual inspection to look for leaking coolant while running? Pressure test?
 

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i hate them *** 3.4s did many head gaskets and intakes on them ...Sometimes it will eat a hole in the intake as well where the water flows threw it ...I would look for a leak first off.. check the intake gasket first ..usely it will go right above the trany ..If its puffing white smoke the head gasket is cooked ...Also check to see if the fan is coming on..you can check the rad by watching the flow with the rad cap off but make sure its cool before you remove cap dont want you to get burned ...check to see if the belt is turing the water pump also ..let us know what you find
 

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Resident Man Of Many Hats
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I'd do a pressure test to make sure the system doesnt have any leaks, you can also buy a test kit that will detect exhaust in the coolant (which is a dead giveaway that your head gasket is toast). Typically when the pumps on those motors go out they start spewing coolant out the weap hole on the water pump. I've seen a few that just tank though with no signs and no warnings. I hate to say it but with those motors I would almost put my money on the intake gaskets. I like to plane the surfaces on the intake manifold and cylinder heads and use an upgraded gasket (factory replacements are junk just like ones they replace). It may cost a little more but it's worth the cash to not have to worry about it. With it overheating though, if it got to hot its almost worth it to pull everything apart just make sure nothing warped. Nothing is worse then replacing everything and not checking the heads only to find out that one or both need machine work. I'll hope and pray for your sake it's only a thermostat.
 

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Tractor Nut
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Discussion Starter · #4 ·
Since I don't have experience with this, I just want to confirm some of these troubleshooting methods...

If I remove the radiator cap, and look into the radiator with the engine running, and I can't see coolant moving, is that a sign that the water pump isn't working (aside from it leaking - which I will look for too)? Could it also be a sign of a clogged radiator? I ask because I know my overflow tank looks nasty, it has chunks of rust and all kinds of crap. I've had the coolant flushed twice over the last 3 years, but it is immediately "rusty". If all of the hoses on the radiator are get hot, does that mean that the radiator isn't clogged?
 

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Tractor Nut
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Discussion Starter · #5 ·
After getting home tonight, I took a quick look at the van.

Coolant isn't leaking from the van onto the ground that I can see. There are no wet spots. I did however see some coolant on the engine below the throttle body. I checked the oil before and after starting the engine and it didn't look obviously milky to me. I do think that the coolant level has dropped however because the last time I looked at the van, there was coolant in the overflow tank, but tonight there wasn't (on the flip side, tonight it's very cool here 60 degrees, versus last time I checked it was probably 95 degrees). I removed the radiator cap and saw that the coolant level was just over the fins. I started the engine and the coolant level very slowly crept up to the point where I had to put the cap back on to stop coolant from running out, but there wasn't an obvious current to the coolant within the radiator (even while revving the engine), just a very gradual increase in it's level. I let the van run for about 10 minutes and during that time the temperature crept up to 3/4 on the temperature gauge (it normally stays at about 1/3). While the engine was running, I didn't see any obvious leaks. I did notice that the hose on the right side of the engine was hot, but the hose on the left side was cold. Even with the engine temperature up, I couldn't get any heat inside the van.

I do feel like I'm losing coolant but can't prove it at this point. I thought that both radiator hoses should be hot, but they weren't. Could that be a clogged radiator? The thermostat is roughly 1 year old in this van, so I am assuming it's OK (but we know what happens when you assume!).

Based on this information, can you guys make any assumptions?
 

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sounds to me like it isn't circulating coolant if one rad hose is cold. Maybe thermostat?
My 3.1 did that. T stat worked one minute, parked about 15 minutes, and on restart, over heated, t stat was so stuck shut, you couldnt pry it open it with a screwdriver.
I would try thermostat first.

I used Felpro severe duty head gaskets, Felpro intake gaskets and head bolts on mine 2 yrs ago, 30k later its still good. But i have saw people do this head/intake repair and it not last half that length. Or leak soon after repair. Sometimes i think its lack of being spotless and perfectly clean, and not using something to get the embedded oil off the parts, like spray brake cleaner. Most the engines i have worked on, if someone had used silicone sealer someplace on it, you could lift off the silicone in one piece like a rubber gasket, and its usually coated with oil on one side or the other, if you clean with brake parts cleaner real well, you have a hard time cutting the bond between metal and sealer with a sharp knife. Makes a lot of difference in sealing.
 

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The thermostat that is causing overheating won't stop you from getting heat from the heater, either the coolant level is low in the engine or the water pump isn't circulating coolant. Coolant on the engine under the throttlebody is usually an intake gasket leak.
 

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Or you have a combustion leak into the cooling system that is displacing the coolant. This is a typical situation we have today in using a complicated engine in a mundane application where a simple cast iron pushrod V6 would have done the job just fine. One of my ex employees had a mid nineties Buick Century with the 3-litre V6 that ran to 200K with almost no maintenance. He even ran a bad water pump so far that the ball bearings fell out on the ground. Still ran fine after that, in fact he even drove it to the crusher after a fender bender, it was uninsured and it wasn't worth the repair and the NY state fines.
 

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There's so many 0% financing deals out there right now, I'd say give it the bullet and move along if you can afford to.
 

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Tractor Nut
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Discussion Starter · #10 ·
Well, I've decided I'm going to try an easier, possibly short term fix first. I am going to try and flush out the radiator myself and also try some Bar's Head Gasket Repair first. And of course, change the oil after all of that.

If I can get things back to normal after that, maybe it'll buy me some time to find a deal on another used van, or give me the opportunity to trade it in with a little more value towards a new one.

The more and more reading I do regarding this problem with this engine makes me think it's a lost cause for me. I don't have the money to keep dealing with this problem over and over.

All of my vehicles are GM and I've been happy with them other than this. I won't own another vehicle with this engine in it for sure. I hear the newer Uplander has the 3.8L which isn't as prone to this problem. I'll take a look at some Freestars and Caravans too - both are nice.

As far as new vehicles, it looks like a lot of companies are transitioning to Crossover vehicles and I'm not sure how I feel about those for a family of 6. I kind of like the layout of a van.

Anyway, I'll update this thread after I've attempted my "quick fix" on my days off.
 

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well if it makes you feel any better about the crossover vehicles my aunt and her husband have 6 kids and they all fit in their chrysler aspen it of course has the 3rd row seating but all 8 of them fit comfortably so you may want to take a look at one of those as well
 

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I would NOT use Bar's Leaks in it...or any other "stop leak" ,the worst is "Porter-Seal",it'll clog up everything in the system..

if any sealer is required I would reccomend "Aluma-Seal" or a similar powdered metal product..there is a fairly new product gaining popularity among the used car dealers called "Blue Devil",that supposedly seals bad head gaskets and cracked blocks and heads--all the coolant must be drained and flushed out good first,then you add the Blue Devil to water and let it run with the thermostat removed,and it coats all the surfaces with a glass like coating..personally I'd never trust it to last,but many guys who have used it swear by it..(I suspect it is soduim silicate or "water glass" you used to be able to buy at drugstores decades ago,that old timers used to seal leaky radiators & blocks,myself)..

These engine can be a bear to purge all the air out of the cooling system,even if they have bleeders..my friend does many engine swaps on these types of cars and repairs,and many times I have seen him spend more time trying to bleed the air from one,than it did to put the new water pump & thermostat on!..

Some water pumps on many cars now use PLASTIC impellers,that can lose their press fit on the splines on the water pump shaft,especially after being overheated..this can cause intermittent overheating and can be difficult to diagnose,as sometimes the impeller will pump sufficient coolant and then NOT,usually shows up more at highway speeds ..(My Ford Countour's V6 had a service bulletin warning of this,it supposedly "could" have a plastic impeller on the water pump!)..
 

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After getting home tonight, I took a quick look at the van.

I did however see some coolant on the engine below the throttle body.

Based on this information, can you guys make any assumptions?
Yes. Your LIM gasket needs redone again, unfortunately.

I have a 2000 Venture and the coolant under the trottle body is the tell-all indicator. Since we don't have all the details about your Olds' history, I can only assume the previous LIM gasket job was done improperly or with pre-redesign parts.

The concern now is the shape of the cylinder head gasket. Have that evaluated before replacing the LIM gasket.
 

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i am sure it your intake gasket again ...buy the fel-pro one they make a better on and it has a thicker and stronger gasket ...I wish you where closer i have one in stock that is brand new ..I ordered for a customer that deiced to junk the van ...I have the new spark plugs to
 

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first thoughts: water pump, then check a thermostat, then check the OIL. if it's frothy, or pale brown, or foamy, or looks like melted choc icecream--you know it's a gasket or head.

2nd thoughts: compression test in each cyl. will tell ya if it's a head / or gasket as well. this will show troubles even if the Oil looks good. so plan on this step just to be safe

3rd: start testing electric components, fans, relays, temp sensors etc

4rth: flow-test the radiator if all the above check out. but by this point, something should have shown up

happy hunting!:trink39:
 
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