Headgasket blown and blowby... related ?

[purvisgs]

I am looking at a 1.6L na engine that has pretty severe "blowby" (looks like blowby at least... when you pull the oil filler cap- steady stream of puffing white smoke...)  but engine starts easy on first crank right away.

After running for about 15+ minutes, the coolant system starts to get pressurized and classic blown headgasket symptoms (stiff radiator hose, overflowing/bubbling coolant).

I don't have any prior info or history on this engine.  I'm wondering if there is ANY chance that the blown headgasket is causing the the smoke or pressure that I am observing in the crankcase...

Any input appreciated.

I don't currently have a way to test compression or do a leakdown test.

[Gizmoman]

Hmmm,
Not sure what you need help with. If the HG is blown, that's your biggest issue and needs solving first.

[burn_your_money]

Is the vacuum system properly hooked up with no leaks?

I don't think a compression or leak down test will really help you out because the head gasket issue would give the same results as blowby.

[theman53]

Does the smoke go away if you rev it up past idle? If so I find it normal on the ones I have seen.

On the cooling end do you have a steady stream going into the expansion tank in the little hose? Water pump could be part of your issue too if you don't.

[libbydiesel]

The system is supposed to pressurize in in the first 15 minutes.  Coolant shouldn't boil over, tho, unless you're running without the cap on.  Blowby like you describe is probably not related. 

[8v-of-fury]

If she is a good price, do the HG/bolts/oil/coolant for $150 and see what happens. Likely the issue, but you won't know til you pull the head.

[TylerDurden]

If you can get a compression tester, it would be good to see the numbers before the engine gets hot... At least you will know if you're also looking at a ring-job.

[burn_your_money]

Wow 15 minutes, I read that as 15 seconds. That's completely normal for the hoses to go hard after that long. I think the cooling system holds 15psi usually. Maybe 18, it's been a while since I checked.

My thoughts on the vacuum system still stand though.

[purvisgs]

OK I guess I wasn't very clear...

This car definitely looks to me like exact same symptoms I have seen before with a blown head gasket. Slightly brown sludge in water, heavily boiling over when cap is on, and rock hard coolant hoses.  I would estimate more than 20psi.  Water pump is pumping water.  Vacuum system seems OK although I haven't gone over it very thoroughly...  It's a little hard to tell as it has a bit of an exhaust leak also right now.

I am just trying to decide if I should spend the time and $ on a headgasket vs dropping in another engine.  I don't have the time or proper tools to do rings right now...  And I would rather put in another engine if the one that's in there now will be burning quite a bit (any substantial amount) of oil..

I'm wondering if there is any scenario where replacing the headgasket would improve the amount of "blowby" I am seeing out the oil filler cap when removed.  It's hard to describe the amount of smoke I'm seeing, but to me this much would normally indicate worn rings and  burning "quite a bit" of oil.

Is there any possible way that you could see water or exhaust gasses getting into the crank-case via the blown headgasket and causing the blowby I'm seeing?

Thanks for all the input!

[8v-of-fury]

Is there any possible way that you could see water or exhaust gasses getting into the crank-case and causing the blowby I'm seeing?

Yeah, if the rings are shot However if they were that bad would it run?

[TylerDurden]

These engines are known for a bit of blowby... also known for needing rings at ~250K miles.

Rings can be pretty bad before it will fail to start. (<300psi in the holes)

If the car will be in a cold climate, an engine heater will help starting.

[libbydiesel]

If the coolant is being pressurized by combustion gases then the head gasket is the likely suspect.  In that particular failure mode, the head gasket would have a breach between a coolant channel and one of the cylinders/combustion chambers.  It is also possible that the head gasket can fail in another mode so that there is a leak between one of the cylinders and one of the oil drains that return the oil from the valve area in the cylinder head.  In that failure mode, combustion gases are pushed into the crankcase and massive blowby occurs.  It is rare that the head gasket will fail in more than one mode at a given time unless there is some extreme issue like overheating or running enough boost to blow a section of head gasket out.  It is possible but not overly likely that the coolant issue and blowby are related. 

[JoeCanuck]

Guessing blowby from the gasses from the oil filler cap is tough.  There is always blowby, which is why the crankcase needs ventilation in the first place.  The quality and quantity of the blowby is very subjective, and as libbydiesel mentioned, head gaskets tend to pick one failure mode at a time.

The vw system is a bit different than the average system I'm familiar with.  If I'm seeing things correctly under the hood of my, (new to me), Jetta, it looks like the overflow/reservoir bottle is pressurized.  I'm used to having the cooling system pressurized but the overflow at ambient pressure.

Regardless, the sludge in the coolant is a very good indication of a coolant leak, besides the bubbles.  Also check the oil...the level, (is it rising), and the colour, (water turns it ugly).   Blown head gaskets can also lead to water getting into the cylinder, which gives off a white smoke...and you can often smell the coolant in the exhaust.

Oil use is a good indication of blowby....if the gasses are getting past the rings, oil is probably going the other way, and it would probably have been happening for a while.  Are you getting blue smoke under power on situations?  (Blue smoke at startup or when backing off the throttle is very often valve guides...with N/A engines).  If you're not seeing blue smoke, you're not burning oil and your rings are probably fine...though a compression check would verify that...but maybe not since a blown head gasket could also show as weak rings.

My guess is head gasket.  You can verify that with a pressure check of the coolant system.  Any bleed down means a leak and if it's not leaking externally, the most likely culprit is the head gasket.  If it is leaking into the cooling system, it will definitely not hold pressure.  You can probably rent the kit for a few bucks if you don't have one, but the test should be cheap in any case....though I'd be reluctant to drive the car right now.

[Gizmoman]

If you have another "known good" engine, I'd drop that in. Get to the other one when you have the time and proper tools.

[theman53]

Again, does the smoke go away if you rev it up? I find that normal if it is just at idle.