Blow-by assessment - opinions needed!

[cattlerepairman]

Did some PMCS on the truck today.
It always had noticeable blow-by from the slobber tube. I am about to rip the valve covers off and adjust the valves and I thought I post a little video here to get opinions as to whether this is normal, questionable or downright bad.

Engine is a LD-465 with a D-turbo. Runs fine, plenty of power. I do not hear strange noises or valve train clatter - but I really cannot compare it to another truck.

http://youtu.be/MbfPXLk04dQ

 

[JasonS]

A fair bit more than my brother's truck; a lot more than my truck. Don't really know what is normal. Typically, you would check crankcase pressure with a manometer; if excessive, followup with a compression test.

 

[doghead]

If it does not "use" or loose oil, don't worry about it.

 

[m-35tom]

i would saw that is way excessive, but i have seen worse. mine is a 1974 engine that was run hot several times, has scored cylinder walls, piston noise, and for some reason has almost no blow-by.

 

[PowerstrokeNC]

Nice and tidy engine bay, clean too!

 

[RAYZER]

Worn out compressor can cause exsessive blow by.

 

[cattlerepairman]

If it does not "use" or loose oil, don't worry about it.

Nope, no noticeable oil consumption. It oozes a little oil that the fan blows around and I am still not sure where it comes from. I suspect the air compressor gasket. I cleaned everything but cannot find it on idle or running the engine up without load. Oils when under load but I have not yet found a way to climb into the engine bay while driving up a hill.

rayzer, thanks for the tip with the compressor. I just cleaned the air filter on it but did not check the compressor. It produces pressure, that is all I know. I should also check turbo shaft play. A loose turbo can cause blowby, too.

 

[Ford Mechanic]

Worn out compressor can cause exsessive blow by.

Excellent point hadn't thought of that!

 

[JasonS]

Wouldn't that stop once the compressor stops?

 

[welldigger]

That is considerable blow by. My truck has almost zero. Even on a cold morning nothing comes out of my slobber tube.

Since its running good and not using oil I wouldn't worry about it much since the fix would be to re-ring the pistons.

 

[Coffey1]

I don't if it's good or bad but that's one clean looking engine bay nice job.

 

[Djstorm100]

How is the compressor tied in to creating blow by? I've seen the mount the compressor mounts to and looks as if it is almost part of the block?

 

[welldigger]

How is the compressor tied in to creating blow by? I've seen the mount the compressor mounts to and looks as if it is almost part of the block?

The engine oil that lubricates the compressor drains through the bottom directly into the crank case. When the rings in the compressor wear out the blowby from the compressor is vented into the crankcase.

 

[Djstorm100]

The engine oil that lubricates the compressor drains through the bottom directly into the crank case. When the rings in the compressor wear out the blowby from the compressor is vented into the crankcase.

Thanks for the explanation makes perfect sense.

 

[todds112]

So, remove the compresser belt and run it and see the difference? Is there a rebuild kit/procedure for the compressor? I have alot of blowby. My compressor is a bit loud.

 

[welldigger]

So, remove the compresser belt and run it and see the difference? Is there a rebuild kit/procedure for the compressor? I have alot of blowby. My compressor is a bit loud.

That would be a sure fire way to tell. But if your compressor still builds pressure and you have excessive blow by I honestly don't think it will be the air compressor. More likely your engine piston rings are worn.

If by chance it is your air compressor just replace it. If you look around n.o.s ones are available for a couple hundred bucks.

 

[cattlerepairman]

Loosened the compressor belt all the way and ran engine. No difference in the blowby. Thanks for the differential diagnosis.
When I hold the (gloved) hand half an inch about the oil filler opening I can feel the pulsating of the gases coming out. Piston ring/valve issue?

I am planning to service the injectors, adjust the valves and do a compression test. Perhaps I will have more facts after that.

 

[Flyingvan911]

My engine just has a little "smoke" drift out of the slobber and oil cap (if removed) when the engine is hot in the winter. Nothing when cold.

 

[topo]

I had blowby like that and found a hole in a piston in my m52a2 .

 

[cattlerepairman]

I had blowby like that and found a hole in a piston in my m52a2 .

I feel better already!