Head gasket vs. Intake Man. Gasket?
#1
Head gasket vs. Intake Man. Gasket?
I rebuilt my 460 back in August and things went relatively well. I was driving it yesterday and noticed a small amount of white smoke coming from the tailpipe. I checked the oil and, sure enough, it was milky. My first reaction is that I have a blown head gasket. After doing a little reading, it seems that a leaking intake manifold gasket would produce similar symptoms. My coolant looks clean, but was slightly low.
1) I've seen the chemical test for a blown head gasket where you test for combustion vapors coming from the top of the radiator. Would a leaking intake manifold gasket also test positive? i.e. can I use this test to differentiate between head and intake manifold gasket failure?
2) Is there a different test to determine which gasket is leaking?
Obviously if I just bite the bullet and replace the head gasket, the intake manifold gasket gets replaced and there is nothing to think about. I'm trying to avoid replacing the head gasket if there is a way to positively determine if it is only the intake manifold gasket that is leaking. It was 14 degrees out this morning. I don't want to do unnecessary work on a newly built engine.
1) I've seen the chemical test for a blown head gasket where you test for combustion vapors coming from the top of the radiator. Would a leaking intake manifold gasket also test positive? i.e. can I use this test to differentiate between head and intake manifold gasket failure?
2) Is there a different test to determine which gasket is leaking?
Obviously if I just bite the bullet and replace the head gasket, the intake manifold gasket gets replaced and there is nothing to think about. I'm trying to avoid replacing the head gasket if there is a way to positively determine if it is only the intake manifold gasket that is leaking. It was 14 degrees out this morning. I don't want to do unnecessary work on a newly built engine.
#2
Update: the reason I am leaning towards intake manifold gasket is that I have true dual exhaust pipes and the amount of white smoke coming out of each of them is equal. That means either both head gaskets failed at the same time with similar severity, or the intake manifold is leaking coolant into the galley. Am I thinking about it wrong? I forgot to mention the engine did briefly get up to 230 degrees during my first attempt at cam break-in. It was shut off as soon as it got to 230.
Any insight is appreciated.
Any insight is appreciated.
#3
Before i would tear into anything, you may want to rent a cooling system tester and see if it holds psi.
Also, try using a clean, clear Mason jar at the end of the exhaust and collect some the white smoke. See if it smells sweet.
14°F temperature can give odd readings of white smoke from exhaust and milky appearance in the crankcase.
Also, try using a clean, clear Mason jar at the end of the exhaust and collect some the white smoke. See if it smells sweet.
14°F temperature can give odd readings of white smoke from exhaust and milky appearance in the crankcase.
#4
Thanks Timbersteel - we seem to be on the same page. I definitely want to do a proper diagnosis before tearing anything apart. As much fun as rebuilding the engine was, I am not in the mood to do any serious engine work this time of year.
I've noticed the slight white smoke a few times before, but always chalked it up to the fact that it's winter. Any vehicle is going to give white smoke in the cold - at least until the system is completely warmed up (right?). My concern is that the oil was milky and smoke was present even after driving from work back home (40 miles). Please correct me if I'm wrong.
If the intake manifold gasket is blown, will the cooling system hold pressure? I know it won't with a blown head gasket.
I've noticed the slight white smoke a few times before, but always chalked it up to the fact that it's winter. Any vehicle is going to give white smoke in the cold - at least until the system is completely warmed up (right?). My concern is that the oil was milky and smoke was present even after driving from work back home (40 miles). Please correct me if I'm wrong.
If the intake manifold gasket is blown, will the cooling system hold pressure? I know it won't with a blown head gasket.
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Out of curiosity, what Temp does it run at down the road?
I had an 83 Cutlass that I put a 160 stat in because oy was the only thing in stock at the time. And in the dead of winter it would barely run 160. The oil wasn't milky milky, but cloudy milky because it wouldnt get hot enough to boil the condensation out and it would build up. Put a 195 in it a month later and Voilà no more cloudy oil. Just a thought.
I had an 83 Cutlass that I put a 160 stat in because oy was the only thing in stock at the time. And in the dead of winter it would barely run 160. The oil wasn't milky milky, but cloudy milky because it wouldnt get hot enough to boil the condensation out and it would build up. Put a 195 in it a month later and Voilà no more cloudy oil. Just a thought.
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Went to re-torque the intake manifold and sure enough, almost all of the bolts were loose! I was surprised when I changed the oil that there was no initial coolant coming out of the plug. Oil looked black coming out (engine had not been started).
What did strike me as odd is that there was a small drop of oil hanging from the pan plug, and a small drop of green antifreeze hanging from the oil drop. I saw a few more spots like that - like a combined oil/coolant leak. The loose intake bolts explain that, so I'll monitor things closely over the next few days.
What was disheartening was that when I started the truck, there was initially no smoke. Then after about a minute of running, there was so much white smoke that the whole truck was enveloped. I let the truck run for about 10 minutes until it reached operating temperature with no improvement to the amount of smoke. Seems like things got worse after torqueing the intake manifold down....
Might be time to buy a combustion leak tester.....
What did strike me as odd is that there was a small drop of oil hanging from the pan plug, and a small drop of green antifreeze hanging from the oil drop. I saw a few more spots like that - like a combined oil/coolant leak. The loose intake bolts explain that, so I'll monitor things closely over the next few days.
What was disheartening was that when I started the truck, there was initially no smoke. Then after about a minute of running, there was so much white smoke that the whole truck was enveloped. I let the truck run for about 10 minutes until it reached operating temperature with no improvement to the amount of smoke. Seems like things got worse after torqueing the intake manifold down....
Might be time to buy a combustion leak tester.....