Blow by into valve cover, white/light grey smoke.

[Robalan]

Title says it all. Runs fine, more smoke coming out of exhaust when accelerating. It has 270000km on the clock and Just completed a 3300km road trip in the old girl. Mazda b3 carb.
I've checked intake and there is no oil being blown into intake. No excessive oil loss anywhere, no bubbles/excessive pressure in cooling system.
I don't have a pressure tester so I can't check cylinder pressures. But any help on what it could be would be much appreciated.
One thing on the road I noticed was that at high speed under load(5th gear/110kmh) the engine was bogging down like it was still warming up. Which incidentally disappeared once the air outside warmed up.


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[Sid_RallyX_82]

•Check coolant level
•Inspect oil condition
•Inspect spark plug condition (dark crusty, light crusty, oily, SUPER clean, worn, etc...)
•Do compression test
•Report all results

[ryanprins13]

What do you mean by blow by into valve cover?
The pcv system allows air from the intake tube into the one side of the valve cover and sucks it out the other side past the pcv valve into the intake manifold. All blow by is supposed to go through the valve cover and be sucked back into the intake manifold. When it gets bad enough to overpower the pcv system (which is easy) it blows out the inlet into the intake tubing which you say is not happening.
So with no oil loss is the only symptom the smoke coming out the tailpipe?
Compression testers are loaned for free at some parts stores.

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[Robalan]

So if I take the filler cap off the valve cover there is air being pushed out of the hole, what I think is too much, or is that completely normal?
Coolant level is fine, oil condition is fine, 4000km ago I did oil filter and oil, little bit black but doesn't look too bad.
But yeah mostly it's just been smoking out of the exhaust, I have only started it up to temp since I've noticed and haven't driven it. I didn't notice any smoke coming out when I got home from the trip.


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[WmWatt]

Excessive pressure under valve cover could be leaks around the exhaust valves. I had that from carbon buildup on one exhaust port keeping the valve from fully closing. It showed up as reduced reading on compression test and also as black exhaust stain on underside of valve cover. I cured it by by additive in oil to remove carbon. Not likely to cause smoke out exhaust though. "Smoke" could be unburned carbon or moisture. I think oil tends to produce dark smoke and water light smoke but not sure about that.

[Dragonhealer]

Sounds like minor blowby, these engines can run forever just getting more and more worn. Black in the oil is carbon, that is from blowby.
light blue smoke is oil, white smoke is water (rarely combusted brake fluid).
keep the oil and filter fresh, and drive on!

[ryanprins13]

It would be hard for someone else to tell how bad it is unless they could feel it but you can google dodge trucks that can levitate their oil cap by like an inch at idle and blow it way into the air with a throttle snap, lol.

How long have you owned this car? There could be a lot of buildup in the cat converter causing the smoke. I blew mine out once and was amazed. 120psi air and 20 minutes later i was still blowing grey junk out. It was unreal.
If the carb has been adjusted badly and is running rich there could be a lot of buildup in the exhaust?
I had a festiva with bad valve stem seals that would consume 1 litre of oil every 600km. With a cold start in the winter it would shoot oil 5ft out the tailpipe

With whats blowing out the oil cap- do you think it can be all sucked though the pcv system or is it too much?

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[Robalan]

Looks like it's a head gasket, foaming of the coolant ☹️


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[Rick the Quick]

If the head gasket is leaking into the coolant jackets you should experience overheating. It will overheat quite quickly from my experience. If you pull the head make sure to check for warpage. A machine shop can mill it flat. You should get a leak down gauge to confirm the leaking head gasket theory. A leak down test will tell you where the compression pressure is escaping. If the head gasket is leaking you should see bubbles in your coolant. Air coming out exhaust indicates exhaust valve leakage. Air coming out the intake indicates intake valves leaking. Air coming out of the crankcase indicates piston ring leakage. You can take the oil filler cap and listen. Some sniffers will detect carbon monoxide in the coolant. If carbon monoxide is present in the coolant you can be sure the head gasket is leaking. You may want to look to upgrade to a B6 engine. From my experience putting a head gasket on an engine with a lot of miles is like opening a can of worms.....The machine shop may find other problems, like valve guides, exhaust valves in need of replacement, etc. I wouldn't put too much money in a worn B3. I would find a newer replacement. Just my 2 cents worth. Good LucK!

[Robalan]

If the head gasket is leaking into the coolant jackets you should experience overheating. It will overheat quite quickly from my experience. If you pull the head make sure to check for warpage. A machine shop can mill it flat. You should get a leak down gauge to confirm the leaking head gasket theory. A leak down test will tell you where the compression pressure is escaping. If the head gasket is leaking you should see bubbles in your coolant. Air coming out exhaust indicates exhaust valve leakage. Air coming out the intake indicates intake valves leaking. Air coming out of the crankcase indicates piston ring leakage. You can take the oil filler cap and listen. Some sniffers will detect carbon monoxide in the coolant. If carbon monoxide is present in the coolant you can be sure the head gasket is leaking. You may want to look to upgrade to a B6 engine. From my experience putting a head gasket on an engine with a lot of miles is like opening a can of worms.....The machine shop may find other problems, like valve guides, exhaust valves in need of replacement, etc. I wouldn't put too much money in a worn B3. I would find a newer replacement. Just my 2 cents worth. Good LucK!

2 cents worth? That was priceless info. Thanks heaps. Gonna do compression tests and get back to everyone.
Looking at finding a donor car with either a b5 or b6 carb engine if it's no good, like you say it's probably got lots of other stuff I need to fix.


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[Robalan]

I just bought this for 400 aud so now I have something to drive while I fix the other. Or do an engine swap [emoji857]


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