It happened

:
Mazda P5
Blew my head gasket some how.
I took a trip up a mountain to stay in a cabin, there was no overheating or loss of power. I heard a rattling from the exhaust so I turned the car off looked around and didn't see anything. Then I started the car back up, no rattling. Coming down it was smoking profusely.
I'm going to go back and look at it since I'm home, waiting for it to cool off.
Also I haven't seen smoke since coming down the mountain. Drove it for an hour no smoke, just checked the oil it doesn't seem to have coolant in it.
 
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This...

Wouldn't going down a mountain create increased vacuum ??


"The compression rings are a whole different story, and they are doing their job pretty good.

To make things worse, oil rings have sooooo weak initial tension, compared to the compression rings, that it is almost natural to have such a result.

take a look in this picture. Look at the gap between ends of the compression rings, and compare to the gap between oil rings... You will get the idea...
https://www.horsepowerparts.com/imag...WSC/8550xx.jpg

Ok, so why does it only smoke on cold starts...

well, here's why:

Once you start up the cold engine, there is increased idle rpm, creating a huge vaccum in the intake manifold, as well as in the cylinders, as the pistons are trying to suck the gases in, but the throttle fully closed prevent thet from happening..."

https://www.mazdas247.com/forum/showthread.php?123770462-Smoke-on-cold-start/page2
 
You could have been sucking in enough oil for a smoke show but not enough to use up all your oil.

Some guys burn a quart every 500 miles.


I say just drive it for a bit and see how it behaves if the smoking stops put in some seafoam (or equivalent) and stay off the mountains.
 
I drove it off the mountain stopped got lunch, then drove it again nothing. Then stopped for a bit (2 hours ish) and seen just the slightest bit when I slowed down and sped back up.
 
I don't think a blown head gasket kinda comes and goes (but it can if you've got a cracked head that only leaks when hot or cold)

You need to find out if that's oil or coolant coming out your exhaust.

The tester will test for coolant in the exhaust. (I don't know about oil)
 
OK, so I tried this with the car warmed up, tested from the radiator cap location and the overflow hose location. Tested while the car was on, was pumping for about a minute at each location.
https://photos.app.goo.gl/Ah4hSmC7QGX4Ao8U9
This is the outcome. I did not change the fluid to make sure it was getting a better reading on whether it was a head gasket.
 
I've never used that tester before. Does the blue color mean there's exhaust in the coolant ??

A compression test or a leak down test might be your next step.
You'd hate to replace your head gasket then find out it was your oil rings.
Does your car burn any oil ?? Do you ever need to add oil ??
 
Me either so I watched video's of it last night to see. Haha. The tester actually is blue, you put it in your radiator and if it turns yellow/green it means bad head gasket. My car does burn oil but not enough to be noticeable like it was the other day.
 
Smoke after deceleration can also be oil getting sucked in through worn/dried valve stem seals.

It takes very little oil to create a major show of smoke. little goes a long way...

Let your car sit overnight. Have someone else start it first thing in the morning and maybe rev it up a little bit a few times. If it smokes during first start of the day but not while you're driving under throttle, it is more likely to be valve seals than oil rings. Oil rings will create smoke all the time, particularly under throttle.
 
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