magic stuff for diesel engines

[Jinxed]

I think I have blow by probably on one cylinder out of six. When the engine is cold there is none but when its warm at idle it puffs, I can feel the pressure at the rocker cover outlet and some whitish mist is emitted. The engine runs well though, and starts from cold instantly. Instead of tearing it apart is there an additive I can err add to free up possible stuck piston rings? Engine is a sabre 180c

 

[rafiki_]

Start with a compression test, to determine exactly how poorly the cylinder is. You could also try a bore scope to see how much damage is visible on the bores. The problem might be valve seating? Cylinder head refurb?

 

[Freebee]

if its blow by its coming past the rings /bores not cylinder head/valves.

 

[Jinxed]

Yes gents, should have mentioned the background i know! Just done the head gasket, cant see any fault with the head, its perfect, valves all good, compression test all good (cold). Starts in a second or so... hence my question about some ring unsticker. But why it only happens when hot i dont know. Must be something expanding when hot... And before you ask, no i couldn't tear apart the bottom end at the time i did the head... unfortunately

 

[BruceK]

I've just woken up and still cant remember my name yet but if a compression test was good when all cylinders were cold then I can see how this is blow by in the traditional sense. When pistons etc warm up tolerance gaps tighten dont they? Crank cases naturally pressurise are you not possibly being over sensitive?

 

[Jinxed]

Glad you slept well Bruce K. Yes possibly too curious, its runs fine just cannot understand why such a simple engine is confusing me. The answer to that is i must be stupid. But will see how it runs Brighton to Guernsey and back, preferably on two engines.

 

[rotrax]

I had a BMW motorbike once - an R50S - wish I still had it, they are worth 30K!!!!!

It had a timed breather which 'pulsed' out through a 8mm bore breather pipe in the outside of the engine.

Being a flat twin the breather valve opened as the pistons came together, reducing the internal pressure.

It closed as they separated, giving a partial vaccum inside the engine. This contributed to its astounding oil tightness. Apart from the top end it used no gaskets, metal to metal joints.

Triumph motorcycles used a timed breather too.

Compared to the BMW type it was a joke, tiny by comparison.

Could you have a breather issue? Blockage or dirty perhaps?

Worth a check.

 

[Portofino]

I had a BMW motorbike once - an R50S - wish I still had it, they are worth 30K!!!!!

It had a timed breather which 'pulsed' out through a 8mm bore breather pipe in the outside of the engine.

Being a flat twin the breather valve opened as the pistons came together, reducing the internal pressure.

It closed as they separated, giving a partial vaccum inside the engine. This contributed to its astounding oil tightness. Apart from the top end it used no gaskets, metal to metal joints.

Triumph motorcycles used a timed breather too.

Compared to the BMW type it was a joke, tiny by comparison.

Could you have a breather issue? Blockage or dirty perhaps?

Worth a check.

Old air cooled 911 s were metal to metal but remember there’s no circulation of cooling fluid being air cooled like your old BMW bike .

@ the op , you say it occurs when hot .If so it’s your HG sorry you must have ballsed up something .

HG issues not necessarily a breach of gas to water , they can in this case be just gas to oil spillways hence the blow by when hot , and smoke later .
Or a cracked block , bore porosity maybe hard to see .

Why did you strip it and do the HG n the first place you have not said ,start at the beginning ps .

 

[BruceK]

Is the engine at an angle for shaft drive and the dipstick not calibrated? i.e. rear crank foaming up the sump?

 

[Jinxed]

Yes good point, its installed flat though. However as we're making way then cylinder 6 is lower down, its a known issue with fords. I kept the oil level at minimum too. But that is the end that the head gasket failed which might be a coincidence, may be not . I'm getting the venting from the breather at idle though, so I thought that cant be responsible for it..... This may stay a mystery, cannot see any cracks or damage to the block or head, doesn't mean there isn't any.

The head gasket had been leaking for a little while, needed a top up of coolant now an then and it was gurgling a bit in the header tank, sure sign of a gas to coolant leak somewhere, and the breather was venting a lot on one cylinder. No oil consumption, then I had a catastrophe and all the coolant shot out of the header tank and was everywhere in the rocker cover and coming out of the vent - which was vented to outside the boat so luckily I saw it, shut down the engine quickly and the temperature didn't go up much at all, the head wasn't warped and all looks fine. The bores look fine, the pistons aren't cracked as far as I can see

I have read somewhere that the turbo might oil drain might be pressurised but that wouldn't explain what I think is only venting due to one cylinder. I think I'm going to rag it and see what changes

What I think is happening to make me think it could be a stuck piston ring? Possible corrosion from the coolant loss. And I only get a bit of puffing from the breather when the oil has warmed up and the viscosity has reduced around a piston allowing a gap... the hypothesis fits what's happening

 

[QBhoy]

I’d start with looking at the injectors.

 

[limecc]

My theory is that it doesn't blow by when the oil is cold and thick, but when it thins out you lose the seal. Sounds like the rings are terminally worn and you might buy a bit of time using a thicker oil. What grade are you using? Unlikely to be gumming with today's oils.

Edit: I see you thought the same in an earlier post I didn't read.

 

[Portofino]

My theory is that it doesn't blow by when the oil is cold and thick, but when it thins out you lose the seal. Sounds like the rings are terminally worn and you might buy a bit of time using a thicker oil. What grade are you using? Unlikely to be gumming with today's oils.

Edit: I see you thought the same in an earlier post I didn't read.

They usually do the opposite, smoke when cold as the rings don’t seal until they heat up .
Smoke stops when warmth and expansion occurs .
See it every winter in every marina with just about every diesel and with DD s also in the summer .
The whole dim thing of diesels ( not so much petrols ) relies on massive expansion and sealing up of the rings with the huge increase in cylinder temps .
Thats why the oil turns black very quickly because combustion gets past the cold rings at start up normally.

This is an old school engine built for longevity using traditional methods / tech btw so should fit this pattern .

You might find a few of the latest “ throw away “ block only ( no wet liners ) toy engines with CR , stuffed with ECU s with rings / pistons , and block made of new fangled metallography which happens not to smoke on a cold morning .But will it last decades of use / abuse ?? .

Trad engines have the rings , pistons, liners and block all changing dimensions aiming for optimal while running , working .
Should be as tight as tolerances permit running nicely loaded .

Loose when cold .

Thats why you can bar a cold diesel easily ……the rings are so loose as not to cause too much resistance.
A cold petrol you are often better removing plugs to let the gas out , overcome the resistance of the compression ratio which is nearly 1/2 that of the diesel .

But the diesel compression ratio in terms of baring resistance is meaningless as the rings when cold leak .

 

[BruceK]

and you might buy a bit of time using a thicker oil

Be wary, you cant chop and change. If you go thicker oil you need to stay on it for life. Wear patterns alter.

 

[Jinxed]

I'm using 10w -40 truck oil recommended by Opie

Thing is, I am seeing this crankcase pressure release on only one cylinder, hence me thinking its a one piston problem - broken or stuck ring. As for the expansion I am going to test it and get it hot, if there's less blowby being released then all good, if its an idle problem (moderate heat, thinner oil, less expansion of metal creating the biggest gap hence the blow.)

anyway Im probably going to do nothing about it for a year or two until i take the bottom end off....

 

[Jinxed]

I had a BMW motorbike once - an R50S - wish I still had it, they are worth 30K!!!!!

It had a timed breather which 'pulsed' out through a 8mm bore breather pipe in the outside of the engine.

Being a flat twin the breather valve opened as the pistons came together, reducing the internal pressure.

It closed as they separated, giving a partial vaccum inside the engine. This contributed to its astounding oil tightness. Apart from the top end it used no gaskets, metal to metal joints.

Triumph motorcycles used a timed breather too.

Compared to the BMW type it was a joke, tiny by comparison.

Could you have a breather issue? Blockage or dirty perhaps?

Worth a check.

I have had r1100s for 12 years plus...... played with the motor, hoses, fuel pump, coils... keeps running no issues its just so simple