3B Over-pressure relief tube????

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Cruiser D

Cruiser D

10 Year 15 Year
Joined
Aug 10, 2006
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16
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55
Location
Toronto
Diesel-rookie here....trying to get familiar with my new 87 BJ71 (3B, 24V, 250000km, totally stock).

When at idle, I've noticed exhaust and/or smoke coming out from under the hood, there is a tube coming out from under the exhaust manifold, about 1" in diameter, about 8" long. The amount of smoke puffs coming out seem to vary.

What is this pipe and is the smoke any concern?

Cheers
D
 
Cruiser D said:
Diesel-rookie here....trying to get familiar with my new 87 BJ71 (3B, 24V, 250000km, totally stock).

When at idle, I've noticed exhaust and/or smoke coming out from under the hood, there is a tube coming out from under the exhaust manifold, about 1" in diameter, about 8" long. The amount of smoke puffs coming out seem to vary.

What is this pipe and is the smoke any concern?

Cheers
D
Click to expand...

Where are you, and where did you buy your vehicle? Is it a Cdn truck?

That tube is commonly called the blowby tube. It is for crankcase ventilation. Instead of routing the PVC tube into the intake air stream to be reburned, some diesels simply vent to atmosphere.

How much smoke is an indication of wear. There will always be some; quantity is the key. Some people have routed the blowby tube into the air intake, between the air filter and the intake manifold.

hth's

gb
 
Yes its a Cdn truck....I'm in Toronto.

The amount of smoke definetly seems to be worse now that I have run some injector cleaner through. Does that mean my rings may be getting worn?

Right now the tube just vents down on top of my front drive shaft....is there any mileage gains from recycling this?
 
I had an '84 that vented so bad on some days that folks would ask if the engine was maybe on fire and I'd be turned away from the smog station without being let in!! On it's good days I could still get the smog check done and pass easily!!

In my opinion it's a big hassle to repipe it to the intake and there would be little gained in doing that. You may even cause problems if you pipe it in such a way that oil vapour that comes out of that tube condenses and pools somewhere in your piping and doesn't allow it to vent the pressure any longer.
 
or in an extreme case the engine could becoem a run away if there is enough oil getting by the rings...
being that low km it shouldn't be blowing that much oil, do a compression test and see the condition of the rest of the motor, could be time for an overhaul...
 
humm, repipe along side the exhaust...
how come i have the idea of "burnt oil smell" coming to mind?
 
Come on folks...I really do not think running away would be in issue. Many diesels have the blowby plumbed into the intake stream between the valve cover and the intake manifold. Make sure your bends are smooth, and any residue can drain back into the side cover.

Do not plumb it into the framerail. The oil is acidic.

Plumb it into the intake air.

If the engine has not been serviced regularly there could be a build up of crud not letting the rings seat, or oil create a layer. Do a few quick oil changes or consider something like this: http://www.auto-rx.com/index.html Read about others experiences here: http://theoildrop.server101.com/cgi/ultimatebb.cgi in the cleaners section.

If it really is that bad that it is a 5th cylinder, and nothing you do service wise makes it better...then as Crushers says look to a rebuild.

Do a valveset, then take the compression numbers when the engine is at operating temp.

hth's

gb
 
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