Blown head gasket.. i think

[81_Chevy]

well after my whole ordeal with trying to figure out why my truck was smoking out the exhaust my dad told me to open up the radiator. opened it up and it was about 3/4 or a little less full, so originally it WAS the trans fluid coming from the vac mod but i fixed that and it still smokes so im thinking that ive got a blown head gasket, or even worse possibly a cracked head/block.

the engine only has about 45,000 miles on it so im hoping it would just be a head gasket.

me and my dad dont really want to take my truck to a shop to get this done (since we have our own shop and tools/knowledge to do it) but we just dont really have the time right now. what can i check to see that it might be a blown head gasket without taking the heads and everything off? pull the plugs or headers? im pretty clueless right now on what to do. any help would be nice! 

-Nic

[mehunter1]

Well what color smoke is it?  Trust me you will know that you have a blown head gasket.  It will be a really heavy WHITE smoke.

[bd]

A blown head gasket when there's white smoke out the exhaust is passing coolant into the cylinder(s).  Pull all the spark plugs and inspect them for moisture.  When you crank the engine over with the plugs removed a cylinder blowing coolant out the spark plug hole is a sure sign.  Otherwise, run a compression check on all cylinders.  They should be within 5 - 10 PSI of one another and, if stock, around 150 - 160 PSI, per cylinder.  If you have an infrared gun, check exhaust temperatures from all cylinders a couple of inches out of the heads; a cold one isn't firing properly.

[bd]

If you determine a blown head gasket, you should also check for coolant in the oil.  Since oil floats on water, momentarily remove the oil drain plug to see if any water gushes out of the oil pan.  If there's water in the oil, don't delay your repairs, because the longer the delay the greater the potential for corroded bearing journals, etc.

[81_Chevy]

it is white smoke, and thanks bd ill definatly do all of those things! thanks alot!! 

[bigchevyc30]

if im right there is a tool you can rent from like autozone that will basically sniff for exhaust in your radiator that will give you a for sure if its that

[81_Chevy]

A blown head gasket when there's white smoke out the exhaust is passing coolant into the cylinder(s).  Pull all the spark plugs and inspect them for moisture.  When you crank the engine over with the plugs removed a cylinder blowing coolant out the spark plug hole is a sure sign.  Otherwise, run a compression check on all cylinders.  They should be within 5 - 10 PSI of one another and, if stock, around 150 - 160 PSI, per cylinder.  If you have an infrared gun, check exhaust temperatures from all cylinders a couple of inches out of the heads; a cold one isn't firing properly.

Alright bd time to rack your brain,
     i pulled all the spark plugs and the number 8 cylinder plug was the only one bad. it was black and very wet, but not fouled out with water or coolant. it looked more like oil to my dad. i did the radiaotor check and there was no bubbles coming up through it. after about 1 min of running the smoke started coming out the pass tailpipe (duals), and since my timing is off my dad thinks it might be the valve not seating correctly letting some oil in. i checked the oil level and it was a little down, also on the upper end of the dipstick there was bubbles?    not entirely sure what that means. were gunna mess with it on Saturday and see what else we can find. we will probably run a compression test to see if losing pressure. that will tell us for sure. i also ran the engine with out the plug in and some fluid did come out but im pretty sure it was gas, but i could be wrong. any help is greatly appreciated.

im trying to talk him into some votex heads to go with my new carb and intake 

-Nic


also its not heavy white smoke. its the light smoke with a little bluish tint you get from burning oil. but that still doesnt explain why my coolant was so low. hmmmm...

[bd]

...i pulled all the spark plugs and the number 8 cylinder plug was the only one bad. it was black and very wet, but not fouled out with water or coolant. it looked more like oil to my dad. i did the radiator check and there was no bubbles coming up through it. after about 1 min of running the smoke started coming out the pass tailpipe (duals), and since my timing is off my dad thinks it might be the valve not seating correctly letting some oil in. i checked the oil level and it was a little down, also on the upper end of the dipstick there was bubbles?    not entirely sure what that means. were gunna mess with it on Saturday and see what else we can find. we will probably run a compression test to see if losing pressure. that will tell us for sure. i also ran the engine with out the plug in and some fluid did come out but im pretty sure it was gas, but i could be wrong. any help is greatly appreciated.

im trying to talk him into some votex heads to go with my new carb and intake 

-Nic


also its not heavy white smoke. its the light smoke with a little bluish tint you get from burning oil. but that still doesnt explain why my coolant was so low. hmmmm...

Important question:  Does your 350 have an EGR valve?  How do the #4 & 6 plugs look?  Any "fluffy" dry coke deposits?  Do you see a "puff of bluish smoke" out the exhaust on initial start-up in the morning?

Whitish smoke with a bluish cast is oil burning.  Coolant "smoke" (actually water vapor) is quite white.  When it results from a blown head gasket it's also typically profuse, but only after the engine runs for 30 - 90 seconds, depending on severity of the compression leak.

To see compression bubbles in the radiator would require quite an aggressive leak and the engine would probably overheat rather quickly.  Of all the methods readily available to you, I think you will be best served using the compression test to check for a blown head gasket. 

Or, if you want to experiment and have a radiator pressure tester, with the engine stone cold, remove the cap and install the tester on the radiator.  Start the engine and watch the tester as it builds pressure.  Pressure should increase gradually as the engine warms and the thermostat opens.  If pressure builds very rapidly (say, 10+ PSI in 30 - 40 seconds), it's an indication of compression leaking into the cooling system.  However, don't let the pressure build beyond ~15 PSI! 

Bubbles on the dipstick don't necessarily mean anything, unless they're milky.  If you see moisture or coffee colored "cream" building under the oil fill cap or on the dipstick, you've got water in the oil.  A rusty dipstick may also be an indication of water in the oil. 

Remain open to the idea that low coolant level could be just an external leak.  Use a pressure tester to pressurize the cooling system in the morning BEFORE you start the engine.  Many coolant leaks are temperature sensitive and at their worst with the engine cold, or nearly so while in the process of heating/cooling.  See if the cooling system holds pressure for 20 minutes or so. 

Avoid the pitfalls of jumping to any conclusions if you don't have probable cause (supporting evidence collected from tests or observations).

[81_Chevy]

my truck does not have an ERG valve that im aware of. the 4 and 6 plugs looked normal, no fluffy coke deposits or anything.

there was no smoke on initial start up, only after about 30 sec of running the smoke started coming out.

i will do a compression test today after work or tommorow and report back. and i will also check for water in the oil.


-Nic

[bobcooter]

So you replaced the bad vacuum modulator initially?

[81_Chevy]

So you replaced the bad vacuum modulator initially?

  correct sir.

okay, well after some playing i think we've determined a blown head gasket. we tried to put some stop leak head gasket sealer in it. it DID work. but for a very short time. i was able to driving into town and back with no problems! but after i got on it a little the problem started again. the white smoke coming out the exhaust. while driving its pretty heavy only under a load, but at a idle in park the smoke slowly starts to disappear. i did check the oil and there was no water in it what so ever. i also drained the radiator (black fluid) and put new anti freeze in it before i took the drive into town and the level went back down again.

on other news, i FINALLY got the timing right. after messing with this whole ordeal: http://forum.73-87chevytrucks.com/smforum/index.php/topic,25292.msg210797.html#msg210797

i had finally realized what was wrong, even after all the years my dad has worked on cars and our style trucks (35+ years) we had put the timing light plug on the #2 cylinder and not the #1 cylinder because we had not bothered to look on what cylinders were what! man after i told him and hooked it up we both felt REALLY stupid. and the worst part is that we have been messing with this timing for over 4 months trying to get it right!    but now we finally got it right and it runs awesome! except the possible blown head gasket problem.

so there is no oil in the water, after i drive it and let it run the coolant level in the radiator is low, and the oil level stays the same. all the plugs are good except #8. ill be having my dad do a compression check after school today since i have to go to work. im sure it will show low compression since we dont know what else it would be.

any help is nice! 

-Nic

[81_Chevy]

okay, compression check showed that the bad cylinder (#8) has about 135-140 PSI and then after about 1 min you can notice that the pressure goes down about 10ish psi and continues to go down VERY slowly.

-Nic

[bd]

Nic,

Post the compression readings for all cylinders and elaborate on what you mean by this...

...then after about 1 min you can notice that the pressure goes down about 10ish psi and continues to go down VERY slowly.

                             Are you watching the compression gauge bleed down between tests? 

----------------

Do you have a cooling system pressure tester?

And, ...this question keeps coming up, so let's settle it.  If you unplug the steel vacuum modulator line from the intake manifold fitting and cap off the vacuum port on the fitting, does the "smoke" clear up?

[81_Chevy]

ya im watching the tester bleed down in between test.

unfortantally i dont have a cooling system tester :/

and i will get all the compression readings and i will unhook the vacuum line and plug it. im assuming that its not safe to drive with no vacuum to the trans?

[bd]

The compression gauge bleeding down between compression tests means the check valve in the gauge is leaking.  It has no bearing on the engine's compression, so ignore it unless it bleeds down quickly - in which case, use a different gauge or replace the check valve.

To run a dry/wet compression test:

• make sure the battery is fully charged
  
  
• remove all the spark plugs
  
  
• attach the compression gauge to a cylinder and crank the engine through five complete compression strokes
  
  
• watch the gauge - by the second 'pump' pressure should reach about 70+% of maximum
  
  
• record the reading then go to the next cylinder and repeat the process
  
  
• after checking all the cylinders, in turn, start over with 2-3 squirts of motor oil in each cylinder just before running the second compression check.  Record the readings and post them.

Don't drive the vehicle with the modulator disconnected.  Just run it stationary and watch the exhaust smoke.  You should be able to tell if there's any improvement.  And, be sure to cap the vacuum port into the manifold.