White smoke on first startup

Post Wed Aug 04, 2021 9:04 am

Hi zone.

Wondering if anyone has any suggestions for what could be causing my issues. Recently done a bit of work to my M40, installed a new head gasket and cat mainly. I gave it a start this morning to bleed the system and break the cam in and had loads of white smoke coming out of the exhaust. It was relatively thick and hung in the air, but when it was coming out of the exhaust it seemed to be slowly drifting out, rather than shooting out as it was before I replaced the head gasket. Had a look around and couldn't see anything weeping from the gasket externally nor could I see any smoke coming out of oil filler, or emulsion on the cap as there was before.

Any suggestions appreciated.

Post Wed Aug 04, 2021 5:25 pm

Possibly just water in the exhaust/condensation .
If the water and oil are clean then that is a good sign.
The last three e46`s I have had looked terrible for this, is was like electing a new pope each start up but they were/are fine.

Mart.

Post Wed Aug 04, 2021 7:21 pm

Initially I hoped it was just the exhaust clearing from being sat for a month or so, but it quickly built up to the point where it was basically like a cloud from a smoke machine. I don't mind going back to do the head gasket again but I'm not sure what would've caused it to fail in the first place. Would a sniff test still detect anything if the coolant hasn't even circulated?

Post Thu Aug 05, 2021 6:55 am

I blew my head gasket on my M20...water into cylinder 5....after the rebuild it took about a week of driving to clear the crap and water out of the exhaust...it stank like hell and was pretty embarrassing really...but it cleared up after a long hard drive...remember your system outputs litres of water during combustion and it readily condenses in the exhaust unless its really hot. And yes it was like a smoke machine...billowing clouds of smelly vapour! Check your water level doesn't change at all once bled to rule out the head gasket.

Paul

Post Thu Aug 05, 2021 8:13 am

Cheers Paul. Do you reckon it's worth carrying on with bleeding it? Anything I should do in the meantime to figure out whether the gasket is good or not?

Post Thu Aug 05, 2021 9:03 am

I'm not familiar with the M40 but a quick compression test...and check when its running that there's no crazy back pressure in the expansion tank...is it running ok? I mean normaly apart from the steam?

Paul

Post Thu Aug 05, 2021 9:29 am

Yeah seemed to be fine, no missing or anything like that. Suppose a compression test will be the next step and then back to running it. Appreciate the encouragement.

Post Tue Aug 10, 2021 10:27 am

Thought I'd update this thread instead of starting a new one. Had my first go at running the engine properly today. Was keeping it at about 2.5 and it seemed alright, there was also much less smoke coming from the exhaust this time.

About 6 minutes in I had a pop come from the exhaust accompanied by a 500ish drop in rpm, the rpm climbed back easily. While I was having a look around the same thing happened again. I shut the engine off and did a quick compression test, all cylinders came back just under 150psi.

Wondering if anyone has any idea what this was? The engine seems fine but I'm not eager to run it again for the time being.

Post Wed Aug 11, 2021 3:21 pm

You could always get or see if you can borrow a block tester to check the headgasket to detect if any combustion gasses are making there way in to the coolant circuit.

https://www.amazon.co.uk/Block-Tester-B ... th=1&psc=1

Also worth checking if head is porous around cyl five inlet side under the rocker cover, pressure tester and look for beads of water, usually get very emulsified oil as a sign though.

Post Wed Aug 18, 2021 7:45 pm

Seems alright now, not getting any exhaust smoke and the compression tests looked alright. Only getting a bit of white on the filler cap, presumably from the old head gasket going bad. Now I'm hunting idle issues where it's either almost dying at 600/700rpm or climbing to 1500, as well as power steering issues.

Assuming it's to do with the way I put the manifold back together, time to double check the hoses.

Post Thu Aug 19, 2021 12:15 pm

I know this is obvious, but I remember doing three oil changes over a period of a week, including filters to get rid of the " mayo" in the system - I bought the cheapest oil for this then finally replaced with good oil and clean filter after all the residue was washed out - if water got into a cylinder then the oil is contaminated badly.

Paul

Post Thu Aug 19, 2021 5:06 pm

paultv wrote: ↑
Thu Aug 19, 2021 12:15 pm
I know this is obvious, but I remember doing three oil changes over a period of a week, including filters to get rid of the " mayo" in the system - I bought the cheapest oil for this then finally replaced with good oil and clean filter after all the residue was washed out - if water got into a cylinder then the oil is contaminated badly.

Paul

Now then, a contentious issue here, would you recommend an oil flush if they are still around?
I would rather buy some cheap oil (25 litres are very cheap) and some cheap filters but a "flush" may the way to go ?

Mart.

Post Thu Aug 19, 2021 8:15 pm

Goal at the moment is probably to sort out the idle and then drive it and see if the mayo hangs around. Not getting any going up the dipstick anymore so it seems to be decreasing.

Also the steering felt really heavy, might be because I'm not used to it anymore but more likely that the power steering has somehow given up. Need to give that a closer look as well.

Post Fri Aug 20, 2021 7:04 am

Don't flush...the risk of blocking oilways with dislodged crap is high.... just run some cheap oil and flters...and make sure the engine gets up to running temp...if you have an oil cooler there may be sludge in it too.

All the water should gass off over time.

Paul

Post Fri Aug 20, 2021 2:01 pm

paultv wrote: ↑
Fri Aug 20, 2021 7:04 am
Don't flush...the risk of blocking oilways with dislodged crap is high.... just run some cheap oil and flters...and make sure the engine gets up to running temp...if you have an oil cooler there may be sludge in it too.

All the water should gass off over time.

Paul

My way of thinking too Paul unless you are down to the block alone.

Mart.

Post Fri Aug 20, 2021 10:19 pm

I think the important thing here is if you trust your own work - simply do oil & filter changes when the engine is warm as the guys have suggested.
If everything is sound a good drive with the engine at temp will flush out any residual moisture in the oil from the original issue.

A smoke test will also confirm if everything has been put back together and is air tight.

Also make sure there is no residual oil in the cooling system - as cooling system hoses and plastics don’t age well with oil.