Buddy's car overheated, now it wont start - LS1TECH



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Buddy's car overheated, now it wont start

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Old 08-02-2011, 12:18 PM   #1
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Default Buddy's car overheated, now it wont start

My buddy blew a headgasket in his '95 LT1 Z28. He let the motor cool down and then drove it home about 15 miles. It ran hot the whole way home, but never got into the red on the temp gauge. About 3 blocks from home, the car died, but then started up again while coasting and then died in the driveway.

The serp belt and everything spins so I dont think the motor is locked up or anything like that. but what else could it be? I was thinking maybe the ICM?

thanks for any input.
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Old 08-02-2011, 12:23 PM   #2
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Why is it overheating? If the water pump is leaking it is possible the opti got wet, and that can cause what you are describing.
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Old 08-02-2011, 12:24 PM   #3
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Is he sure it's a blown gasket???
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Old 08-02-2011, 12:44 PM   #4
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How do you go from a blown headgasket and then assume the ICM is the issue because the car wont start? i dont get it. Does the oil look milky?
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Old 08-02-2011, 01:17 PM   #5
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Pretty positive its a headgasket. It smoked like crazy out of the exhaust before it was parked (before the cool down) and exhaust was bubbling out of the radiator when the cap was off.

ICM's go bad due to heat many times, hence why people do the ICM cooling mod. Its still got the oem ICM with 100k+ miles.

Oil doesn't look milky, but pretty positive there is exhaust in the coolant.
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Old 08-02-2011, 01:19 PM   #6
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I've seen a number of instances where a severe overheating has caused failure of some electronic component within the vicinity of heat, namely the ICM, coil, and opti.
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Old 08-02-2011, 01:27 PM   #7
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^so im not crazy for thinking this. Good
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Old 08-02-2011, 09:43 PM   #8
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ok fair enough. makes sense. haha
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Old 08-02-2011, 10:07 PM   #9
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As you were suspecting the ICM from your opening post, did you check for spark with a test spark plug directly from the coil during cranking? This would be the first test on the list.

How many miles on this car? Any coolant in the oil? You can check this by looking at it's level.
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Old 08-02-2011, 11:34 PM   #10
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It boiled some of the coolant out of the overflow-so it is low. No coolant in the oil, however.

Havent tested a plug yet. Never done that before, assuming you just pull the plug with a wire on it and put it on something metal and crank the motor?
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Old 08-03-2011, 12:50 AM   #11
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You get a spare spark plug and spark plug wire. One end to the plug, the other directly to the ignition coil. Lay the spark plug on any metal body or engine component. have a buddy crank the engine while you watch the spark plug.
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Old 08-03-2011, 10:29 AM   #12
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I just had a similar thing happen to me and it ended up needing a new opti, the harness was melted!! I also had to replace the coil wire thingy...I hope you guys figure it out soon....
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Old 08-03-2011, 01:47 PM   #13
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Im thinking the motor is going to get pulled sooner or later here. Probably replace the ICM and opti while we're doing the headgaskets.
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Old 08-03-2011, 01:53 PM   #14
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http://www.arrowheadradiator.com/hea..._leak_test.htm

the link above is a tool we use at the shop to test head gaskets, works very well and is worth the money when owning these cars.
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Old 08-24-2011, 02:19 AM   #15
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Back up top, I have a general question that pertains to this project.

When you blow a head gasket, obviously it can get exhaust in to the coolant, coolant in to the exhaust, oil into the coolant, and coolant in to the oil...

The motor has been sitting for a few months now and plugs have not been pulled. We drained the oil tonight and it came out at exactly 5 quarts, normal looking oil (not chocolate milk style)

Is there still a chance there is still coolant in the cylinders if there is no coolant in the oil that was in the oilpan?

Kind of a newbie question but I wasn't 100%

Thanks guys
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Old 08-24-2011, 12:16 PM   #16
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Could be leaking into the cylinder itself, the head could be cracked or warped as well. You said it was smoking, but the oil is not molly and oil not in coolant. That tells me it might be leakig into the cylinder directly. Your going to need to diag more before anything. Have the heads checked
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Old 08-24-2011, 01:16 PM   #17
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Sounds like what happened to mine. Head gasket blew and was dumping my rad fluid into the cylinder, no change in oil level etc. etc.

Hook up a radiator pressure tester (rent them from vato zone)
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