Overheating randomly

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mrashley

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My daughter has a 2003 Alero, 3.4L that randomly overheats. she has been out of town for the last few weeks so I've been driving it trying to figure out whats going on. About 2 years ago I had the thermostat and water pump replaced and it has not run properly since then. Example:

The other day I was driving home from work around midnight, temp outside is about zero. I started the car and let it run for about 5 minutes before leaving work. The temp indicator was still clear at the bottom of the gauge and the heater was blowing cold air. As I was driving on the interstate, the temp gauge slowly rose to just over 3/4 then dropped down to just under half and blew warm air inside. Within the next mile, the temp rose to the red and the red indicator light came on. I pulled over, shut the engine off and rested for about 2 minutes. Started back up and the temp then never rose above the 1/2 mark and blew warm air. The next day, the same thing happened however after I shut it off and restarted it never cooled down.

I have replaced the thermostat again, and bled the system (not sure if it was bled properly) but the car overheats within a couple miles of driving.

I'm at a loss. I'm going to put another water pump on it tomorrow. How do I test temp sensors, sending units? What is the proper bleeding procedure? Any other ideas??
 
additional information

I should also note that the 'service engine' light is on. I have pulled codes in the past and they all indicate misfires. It runs a little rough when I first pull out of the driveway, as the engine warms up it smooths out a little. In the last month, I've replaced the O2 sensors, spark plugs and wires.
 
A few things. On the fitting right above the water pump, where the crossover pipe attaches, there's a bleeder fitting. There MAY be one on the water outlet (thermostat outlet) also. That's where you bleed.

Do you see any bubbling or symptoms of exhaust gas in the cooling system? It almost sounds like an exhaust leak into the cooling system, an intermittent one. I'd do a leakdown test (well, a compression test THEN a leakdown test) on all six cylinders.

RwP
 
I agree that it sounds like one or both head gaskets are bad. The overheating and the misfires on multiple cylinders are very good indicators. Just air in the coolant wouldn't cause misfires.

To double check: Clear the error codes. Start with a cold engine. Keep checking for misfire capture errors as the engine warms up. You'll very likely see misfires before the engine ever gets too hot. That's another indication that there is at least one problem somewhere else other than the cooling system.


There are a few things you can do:

1) Check for exhaust gases in the coolant. There are kits, use google.

2) Do a compression check.

3) Do a leak down test.

A leak down test is best. Since I have a leak-down tester and compressor, *I* would do a compression and leak-down test first on the front three cylinders. The back cylinders can be a huge pain to get to.


It should be cheap and easy to do #1 and #2 (maybe $25 each for the stuff).
#3 requires a real air-compressor, and a decent leak-down tester is ~$80 (last I checked).

Good Luck!
 
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FYI:
41kgygOIsYL._SL500_AA300_.jpg

Lisle 75500 Combustion Leak Detector
Price: $30.57
http://www.amazon.com/Lisle-75500-Combustion-Leak-Detector/dp/B0007ZDRUI/



Better, what I suggest:
0062860400246_P321146_300X300.jpg

http://www.amazon.com/UVIEW-560000-Combustion-Leak-Tester/dp/B000NPDL76/
UVIEW 560000 Combustion Leak Tester
Price: $54.73


Update 05/17/2017
The video that I originally posted a link for was removed.
WTF!?!?

So, screw **#&*^## people removing videos. :)
Below is a link for videos on youtube for combustion leak detectors. :)

https://www.youtube.com/results?search_query=combustion+leak+detector



.
 
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