LT1-LT4 Modifications 1993-97 Gen II Small Block V8

Possible Head Gasket

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Old Dec 12, 2010 | 10:44 PM
  #1  
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Default Possible Head Gasket

My 1997 TA has been running good, but I can notice something is off. I could never put my finger on what it is until a few days ago. First my symptoms are a rough idle, but when I go wot it seems fine; no white smoke, no oil in water or water in oil. So the other day after a 100mi drive I got out to look at my new tail lights and I noticed stuff all over my back bumper, all the way up to the tail lights. When I took a closer look I noticed the stuff looked orange/red ; so I thought the only thing in the car that is orange/red looking is the antifreeze. I don't see any leaks up front so I figure it has to be from the exhaust. I pulled the plugs and all but cylinders 7 and 8 looked bad; less than 2,000mi on them. I am not sure if it is the gaskets yet, it is not losing water from the radiator yet maybe the overflow; its a slow leak if it is. Can a head gasket just slightly leak and cause a low rpm miss but go away at wot and have no smoke or water in the oil? It has a electric water pump so the water being pumped into the motor should not increase with higher rpms.
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Old Dec 13, 2010 | 12:06 AM
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Make sure that it is really coolant on the bumper, if it is check for leaks under the car first, check your plugs and get a coolant pressure tester on it
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Old Dec 13, 2010 | 03:31 AM
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If its got a head gasket out and has coolant going through combustion chamber and exhaust system its not going to still be red when it comes out the tailpipe. Yes you can have a little leak that seems to come and go but its not going clear up when you rev it up then come right back when you go back to idle then go away agian when you rev it up again. My shop truck has had a minor headgasket leak for several years now and on a real cold moring like now it will blow smoke for a min or 2 when we first start it then goes away untill it sets for a week or it gets real cold(freezing or below). Its a 88 with 375K on the original engine so its not getting fixed LOL when it goes its taking a ride to the grave yard. If its burning coolant in the cylinder it will have a white powdery ash type substance on the ground strap that will eventually foul the plug causing a dead cylinder. Post some pictures of the plugs if you can both the good ones and the bad. Another thing you can try is warm the engine up and then put a pressure tester on the cooling system and let it set over night. The next morning crank the engine over without the spark plugs in it and see if it blows any liquid out. I think you have something else going on as you have 6 bad cylinders and 2 good cylinders according to what you are reporting on your plugs and your not loosing any antifreeze. If this car has a automatic in it your coolant is not the only fluid in this car that should look red are you sure its not transmisson fluid on the rear bumper cover? If you are sure the plugs, wires and opti are good start the car up in the dark and stare at the coil. I have seen many GM external HEI coils over the years that idle bad or seem to miss at idle that end up being the coil starting to go bad. If you stare at it in the dark you will see a arc when it misses. try this stuff and get back to me with your results and I will try and help you out.
Take care
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Old Dec 13, 2010 | 07:35 AM
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Originally Posted by Doughboy692
If its got a head gasket out and has coolant going through combustion chamber and exhaust system its not going to still be red when it comes out the tailpipe. Yes you can have a little leak that seems to come and go but its not going clear up when you rev it up then come right back when you go back to idle then go away agian when you rev it up again. My shop truck has had a minor headgasket leak for several years now and on a real cold moring like now it will blow smoke for a min or 2 when we first start it then goes away untill it sets for a week or it gets real cold(freezing or below). Its a 88 with 375K on the original engine so its not getting fixed LOL when it goes its taking a ride to the grave yard. If its burning coolant in the cylinder it will have a white powdery ash type substance on the ground strap that will eventually foul the plug causing a dead cylinder. Post some pictures of the plugs if you can both the good ones and the bad. Another thing you can try is warm the engine up and then put a pressure tester on the cooling system and let it set over night. The next morning crank the engine over without the spark plugs in it and see if it blows any liquid out. I think you have something else going on as you have 6 bad cylinders and 2 good cylinders according to what you are reporting on your plugs and your not loosing any antifreeze. If this car has a automatic in it your coolant is not the only fluid in this car that should look red are you sure its not transmisson fluid on the rear bumper cover? If you are sure the plugs, wires and opti are good start the car up in the dark and stare at the coil. I have seen many GM external HEI coils over the years that idle bad or seem to miss at idle that end up being the coil starting to go bad. If you stare at it in the dark you will see a arc when it misses. try this stuff and get back to me with your results and I will try and help you out.
Take care
good info.......it could very well be a head gasket the lt1's are kinda popular for doing this.......try a coolant pressure test and see if the system is loosing pressure this is a good starting point as well........and also as for coolant out the exhaust it can happen....happened to me.....when i first bought my car with the stock motor it was snowing. I had the car sitting outside my garage in the snow ready to come in to start the teardown and when i went outside i had to little spots of green in the snow behind the car...so if the leak is bad enough you will see color possibly.....
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Old Dec 13, 2010 | 01:19 PM
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Originally Posted by Doughboy692
If its got a head gasket out and has coolant going through combustion chamber and exhaust system its not going to still be red when it comes out the tailpipe. Yes you can have a little leak that seems to come and go but its not going clear up when you rev it up then come right back when you go back to idle then go away agian when you rev it up again. My shop truck has had a minor headgasket leak for several years now and on a real cold moring like now it will blow smoke for a min or 2 when we first start it then goes away untill it sets for a week or it gets real cold(freezing or below). Its a 88 with 375K on the original engine so its not getting fixed LOL when it goes its taking a ride to the grave yard. If its burning coolant in the cylinder it will have a white powdery ash type substance on the ground strap that will eventually foul the plug causing a dead cylinder. Post some pictures of the plugs if you can both the good ones and the bad. Another thing you can try is warm the engine up and then put a pressure tester on the cooling system and let it set over night. The next morning crank the engine over without the spark plugs in it and see if it blows any liquid out. I think you have something else going on as you have 6 bad cylinders and 2 good cylinders according to what you are reporting on your plugs and your not loosing any antifreeze. If this car has a automatic in it your coolant is not the only fluid in this car that should look red are you sure its not transmisson fluid on the rear bumper cover? If you are sure the plugs, wires and opti are good start the car up in the dark and stare at the coil. I have seen many GM external HEI coils over the years that idle bad or seem to miss at idle that end up being the coil starting to go bad. If you stare at it in the dark you will see a arc when it misses. try this stuff and get back to me with your results and I will try and help you out.
Take care
Yes I need to go out and buy one of those pressure testers. I have 6 good cylinders and 2 bad; I have replaced all the ignition parts about 2,000 mi ago. It looks black, but if you really closely look it is red/orange looking. I don't want to pull the heads until I know for sure. I think the pressure test and pulling the plugs out will be the best way to know for sure, or wait and see If coolant goes down; it should go down or at least drain the overflow tank sooner or later.
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