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Unread 02-23-2014, 05:54 PM   #1
sevenscrew
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gm 3.1 overheating problems

Okay heres the story, i got a 2000 chevy malibu 3100 series.

the car was diagnosed with a bad lower intake gasket.

Not sure if this is related or not, but its heat would be hot for the first 10 minutes of running at operating temp.. then out of no where it decided to go cold and temp of car starts to spike to touching the red

i did the gasket job and replaced the T stat with it. now the same thing is happening but it appears worst. Heat blows very hot then 5-10 mins driving around the block heat goes to real cold and the temp spikes up to red(have to shut off and let it cool down just to go home).

to my knowledge the fans arent turning on either. Not sure if they are even related to the issue though.

I felt some parts and the upper rad hose is hot, lower is warm(only checked it once was hard to reach next to the exhaust manifold).

i drained the coolant and filled with new coolant. started it with the cap off and squeezed the upper with the heater on full blast. lots of bubbles came out. also cracked open the bleeder screw til full coolant was shooting out with no air noise.

still no go... I am not sure what to do/test next. I appreciate any help thanks!

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Unread 02-23-2014, 07:06 PM   #2
Rebel442
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Sounds like Head gaskets, Why was the lower intake gasket bad? leaking? or because of this issue?
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Unread 02-23-2014, 07:25 PM   #3
sevenscrew
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Leaking. How can I check the head gasket
At no point have I ever seen coolant on the dipstick or bubbles.

There was oil caked on the inside of the reservoir for coolant though I cleaned it out before I put coolant in.


Is it possible the heater core is intermittently clogging? Thermostat intermittently getting stuck? How come the efans didn't kick on even past 7/8 temp guage
image-1673639224.jpg

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Unread 02-23-2014, 07:43 PM   #4
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I forgot to mention an important step. When it spikes (the temp) the heat gets cold but then usually a moment after it drops fast back down to normal operating temp and I regain heat
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Unread 02-24-2014, 09:40 AM   #5
number40Fan
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Sounds like a head gasket/cracked head to me.
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Unread 02-24-2014, 10:32 AM   #6
Balvar24
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Quote:
Originally Posted by sevenscrew View Post
Not sure if this is related or not, but its heat would be hot for the first 10 minutes of running at operating temp.. then out of no where it decided to go cold and temp of car starts to spike to touching the red
Sounds like a loss of coolant flow issue.

Waterpump?
Bad T-stat?
Bad head gasket?
Air in system?

Are you losing any coolant/oil?
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Unread 02-24-2014, 11:02 AM   #7
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I will monitor fluid some more but doesn't appear to be burning oil or losing coolant. There is no white or bubbles on the dip stick.

I am thinking maybe the thermostat randomly closes and gets stuck?



Now why aren't the fans turning on when it peaks to the red .
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Unread 02-24-2014, 11:57 AM   #8
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What tells the fans to come on?
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Unread 02-24-2014, 03:09 PM   #9
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Thermostats won't randomly do anything. They're controlled by a temperature spring, as they heat they open as they cool they close. If they get stuck, it's in 1 position not after x minutes it decides to do something different than at x=1 minutes. Same with a plugged anything, it either is or it isn't. A bad head gasket/head will what you're saying is happening. When the engine isn't running depending on where your heater core is, you have fluid throughout. As the engine runs you get exhaust gas being pushed into the coolant and after a few minutes it causes an air lock in the heater core. No coolant=no heat. Air lock + exhaust into the cooling system means low/no cooolant flow=overheating. Engine cools down, air finds its way out, and you're back to normal for a few minutes.

If it is a bad gasket there might not be any white smoke, depends on where the break is. The easiest way to tell is to take the radiator cap off and start the engine. If you see bubbles or turbulence, it's probably exhaust gas. There's no way to look at the gasket without pulling the head, and once you pull the head you're replacing the gasket anyways. If it's a cracked or warped head, you have bigger issues.

Or, it's possible when you changed the intake gasket you didn't align it right and you've blocked coolant passages. But if you're seeing oil in the coolant reservoir, I'd say ^^^^ again.

Your fans should come on once the engine is up to temp, if they're not, it's another issue. It will cause heating issues when parked or slow but your fans don't come on much when you're driving. The air flow while moving does the job and they're only needed when there's no air.


Not knowing how long you have had the car, assuming it's fairly recent here's my guess.

PO had the fan/relays go bad and didn't fix it. He drove/idled for quite a while and the engine overheated. The overheating warped your head and/or trashed the gasket along with the intake gasket and or warped your intake. He sold it to you saying it just needed a new gasket. You've now got a $3000 problem for a new head/intake and labor.
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Unread 02-25-2014, 06:26 AM   #10
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Quote:
Originally Posted by Balvar24 View Post

Sounds like a loss of coolant flow issue.

Air in system?
This is what it sounds like, you need to bleed the cooling system.
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Unread 02-25-2014, 11:58 AM   #11
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I tried bleeding it several times. Started with cap off and no bubbles occurred so I squeezed upper hose to get all air out and cracked open the bleeder.

After temp got almost. 3/8 the fluid started rising and falling while bubbling a lot. Tailpipe has a lot of water coming out
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Unread 02-25-2014, 12:15 PM   #12
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Water is the result of combustion. If it was steam then it would be a different deal.

I replaced heads on a 3.4 (same engine design) that didn't smoke, only got hot. Found cracks in both heads between the valves. I used a http://www.ebay.com/itm/Lisle-Coolan...c44496&vxp=mtr while it was running, with just a little water in the funnel, and the bubbles never stopped.
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Unread 02-25-2014, 01:09 PM   #13
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Quote:
Originally Posted by sevenscrew View Post
I tried bleeding it several times. Started with cap off and no bubbles occurred so I squeezed upper hose to get all air out and cracked open the bleeder.

After temp got almost. 3/8 the fluid started rising and falling while bubbling a lot. Tailpipe has a lot of water coming out
That's the important part.
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Unread 02-25-2014, 06:23 PM   #14
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I had a 99 Monte Carlo with a 3.1, we did the intake gasket and thought we would never get all the air out of the system. I finally caved and took it to a pro, he used something like what was posted above.
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