Just curious.

[Laqota]

I just did a head gasket tester on my coolant, came back negative. This kind of sweet and potent smell, accompanied with white smoke, has been blowing out my exhaust.

It turned out that one of my spark plug wires didn't click all the way and wasn't firing. Can a spark plug not sparking cause a cylinder to flood, then gas goes in to the manifold, heats up and dissipates in to white smoke? Thanks.

I'm wondering because it stopped right as I clicked it in. I also noticed it's running better.

 

[ali_c20]

Sweet smell that sticks on the back of your throat is unburned fuel. Coolant smells sweet too but different. The unburned charge is pushed out of the cylinder at the exhaust stroke and leaves thru the exhaust pipe as smoke. It's good that your engine is running better with all cylinders firing.

 

[fast 99]

Depending on how bad the gasket leaked an exhaust system can hold quite a bit of coolant. Sometimes it takes a while to burn all of it out.

 

[Laqota]

Sweet smell that sticks on the back of your throat is unburned fuel. Coolant smells sweet too but different. The unburned charge is pushed out of the cylinder at the exhaust stroke and leaves thru the exhaust pipe as smoke. It's good that your engine is running better with all cylinders firing.

Yeah, it's like a really sweet smell and is still there but the smoke isn't as thick as it was. It's probably not a gasket problem, but I have some spare intake gaskets because I did a head gasket test that came back negative (if those are accurate) so I might just do it anyways. I have a lot of time on my hands.

 

[YakkoWarner]

A valve seal could also be allowing trace amounts of something into the combustion chamber as well - probably on the intake side since it is being pulled into the chamber and then pushed out on the exhaust. That probably wouldn't be revealed on a compression or head gasket test. I know I get some oil and smoke out of my passenger side exhaust is I am really ripping down the highway (70+ which on some roads is legal here). I suspect it to be valve seals allowing oil in, and at high enough RPMs enough oil is pooled up in the rocker arm area to seep in, whereas at lower RPMs it drains back down to the pan without pooling up top.

 

[Laqota]

A valve seal could also be allowing trace amounts of something into the combustion chamber as well - probably on the intake side since it is being pulled into the chamber and then pushed out on the exhaust. That probably wouldn't be revealed on a compression or head gasket test. I know I get some oil and smoke out of my passenger side exhaust is I am really ripping down the highway (70+ which on some roads is legal here). I suspect it to be valve seals allowing oil in, and at high enough RPMs enough oil is pooled up in the rocker arm area to seep in, whereas at lower RPMs it drains back down to the pan without pooling up top.

I was loosing oil in the past (quickly) but it was my Valve Cover gaskets. It doesn't lose any oil now, haven't had to fill it up in a bit. It's just my coolant I have to keep filling up every 100 miles.

 

[pnwnvrdn]

Losing coolant, white smoke, sweet smell....all point to a bad head gasket, warped head, or cracked head.

 

[YakkoWarner]

Losing coolant, white smoke, sweet smell....all point to a bad head gasket, warped head, or cracked head.

Could also possibly be a failed intake gasket. Since removing the intake is one of the first steps in pulling a head anyway, its a logical place to start before breaking off all exhaust manifold/header bolts to get the head off. If the problem is there, you don't have to go deeper.

 

[Ricko1966]

If it's loosing coolant with no external leaks and white smoke in the exhaust #7 is right on, as for an intake leak,on some cars that would be logical,but not SBC the coolant passages are a mile away from the intake ports. I've seen the radiator block test pass more than once and still have a blownnhead gasket.Make sure !!!! you dont have an external leak. Pull your plugs,look at them, they can tell you a lot. No external leaks, funny looking plugs, face it ,you are pulling heads.

 

[Grit dog]

I was loosing oil in the past (quickly) but it was my Valve Cover gaskets. It doesn't lose any oil now, haven't had to fill it up in a bit. It's just my coolant I have to keep filling up every 100 miles.

If it ain’t dripping coolant it’s eating it.
Nothing to do with a spark plug wire oil leak or unburnt fuel. That’s coincidental.
Unfortunately it sounds like a head gasket?

 

[Laqota]

If it's loosing coolant with no external leaks and white smoke in the exhaust #7 is right on, as for an intake leak,on some cars that would be logical,but not SBC the coolant passages are a mile away from the intake ports. I've seen the radiator block test pass more than once and still have a blownnhead gasket.Make sure !!!! you dont have an external leak. Pull your plugs,look at them, they can tell you a lot. No external leaks, funny looking plugs, face it ,you are pulling heads.

I'm not really afraid pulling my heads. I live on a street of mechanics and they have recommended me to pull my heads, even if it was an intake just because of how old it is.

Just ripped my intake off and drained my coolant, ready to take out my rocker arms n stuff. My intake gasket is bowed and rock solid so It was probably my intake but I'm gonna do my heads anyways.

 

[Laqota]

If it ain’t dripping coolant it’s eating it.
Nothing to do with a spark plug wire oil leak or unburnt fuel. That’s coincidental.
Unfortunately it sounds like a head gasket?

I got my heads off, and a bit disappointed but it's going to be a personnel vehicle so I'm not too worried. Pistons got some clearance for the walls a bit, you can see about a cm of the compression rings. There is rust on my head and block where it's leaking in but the mechanics I live near said giving it a go with 50 grit should do the trick. So far, I'm not sure if anythings warped but the head gasket is rusty so I'd believe it's that.

I'm gonna get the other head off soon.
Head gasket (Side facing down)

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Head Gasket (Side Facing Up)

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Cylinder Head

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Pistons and Block

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[Rickf]

Is it me or does one of the combustion chambers look different than the others?

 

[Albrigap]

How many miles on the engine?

New head and intake gaskets won't hurt a thing.
Have a machine shop check out the heads too before you put them back on.
They do crack.

 

[Grit dog]

@Laqota, bummer dude. I’m not an expert at reading engines, but it certainly appears to be eating coolant on #5 and possibly others.
If it was a smooth running engine save for the coolant leak and you have more time than money, I’d consider cleaning up the head and block, straight edge it and check carefully for cracks. Get new top end gaskets and go for it.
Hard to say what’s best, based on your budget, time and how you plan on using the truck, but an old crusty 305 is not a motor to stick any real money into.