Crankcase Breather & Dipstick Blowout?

[supplyguy]

Took my car to John Erskine's Fiat mechanic (G&S) in Maryland Friday to explore the massive oil leak problem (1971 1608). In addition to the distributor seal leak, the gentleman showed me that crankcase breather hose is larger than the inlet for the aftermarket 4x6 air filter, and the back pressure is causing oil to push the dipstick up and leak. He disconnected the hose, added two quarts of oil, I've driven about 100 miles since, and for the first time my car still reads full on oil. I am hoping this is a good news story and my oil leak will be drastically reduced.

Three questions: I thought the carb created some sort of vacuum drawing the crankcase emission up to the filter rather than the engine pushing the gasses north. Wondering how there could be so much pressure that the restricted flow into the filter causes the dipstick to push out and leak so much. So much pressure to blow other seals?

Second, I see from this forum many others have this big hose/little inlet problem and many leave the crankcase hose disconnected. I hate the fumes and unfinished look. If routed out of sight and low enough to pull the emissions under the car, is that what this filter would do? http://www.amazon.com/MAGNUM-WASHABLE-C ... B007YZJOSI

Last, is there an aftermarket filter that has the proper sized inlet so the original crankcase filter tube ill fit?

Many thanks in advance.

[So Cal Mark]

I've seen this on a few cars, usually if they have some blow-by. Those filters are universal and most cars use a pcv valve so that the breather hose to the filter is used to draw fresh air into the crankcase. Using a small filter on the breather hose cures the problem as long as the inlet size is correct for the hose

[AZ79]

I wonder, could this be the problem with my engine? I, too, have a much smaller outlet piece on my vent hose... When I get oil on top of my engine, there's always a drip on top of the dipstick... This might be the answer to MY problem, too. Thank you!

[AZ79]

...and it's not. I zip-tied a sock onto the crankcase vent tube, my dipstick AND my oil cap... Then took it out on the freeway, got back and if anything, it put MORE oil on top of the engine.
Freeing that hose up didn't seem to matter one bit.

[mgbgtn]

The hose from the air filter to the motor is to let filtered air in. The pcvalve is to pull the crankcase pressure and fumes into the intake manifold. If the pc vale is plugged it will cause the crankcase to pressurize and blow oil out the breather hose and dipstick tube. To check the pc valve, pull it out and give it a shake and it should rattle, if not then it is plugged and should be replaced. Disconecting the breather hose from the air filter will allow it to pull in dirty air and increase wear in the motor!

[AZ79]

What if I have no PVC valve?

[mgbgtn]

There has to be a way for the motor to relieve the crankcase pressure. Some have a vapour/oil seperator on the left side of the motor just behind the oil filter. Look for a line going from the intake manifold to a fitting on the motor.

[maytag]

PCV = Positive Crankcase Ventilation
The PCV valve (when present) is there to allow the pressure in the motor to vent, without drawing any outside air into the crankcase. it's a one-way valve. Over-pressure is vented through the valve before it blows seals, rings, and slows-down the piston traveling down the bore.
the PCV valve is connected to the air cleaner for two reasons: to scrub those crankcase emissions back through the motor. the 2nd reason is that theoretically, the vacuum present in the air cleaner will not only scavenge those fumes, but can also create a vacuum in the crankcase. When a vacuum occurs in the crankcase, it is a good thing, as it helps the rings seal, and reduces windage.

Now, having said that, I'm not sure I've ever seen a PCV valve on a Fiat TC. But I've never had one that hadn't been "modified" by the previous owners, so maybe there should be one? Still: there should be no circumstance where the motor is drawing air into the crankcase.

So why is your dipstick blowing oil? because you are NOT venting the crankcase, and that overpressure needs to go somewhere. check the flame-trap in the vent under the intake manifold. see if it is creating a blockage. Really, there shouldn't be much pressure in the crankcase unless you've got new rings which haven't sealed yet, or you have a problem (broken ring, blown headgasket, holed-piston, etc etc)

[So Cal Mark]

no pcv valve on the Fiat TC. The breather hose allows air to go both ways, in and out of the motor. Zip tieing a sock over the hose is not the best way to go

[AZ79]

no pcv valve on the Fiat TC. The breather hose allows air to go both ways, in and out of the motor. Zip tieing a sock over the hose is not the best way to go

lol, I just did that as a temp test.

[bagodonuts]

could you post a picture of the pc valve and all that. I too am getting oil on top of the engine shortly after a rebuild (high compression pistons, performance intake cam, lightened flywheel--nice).

much appreciated

[So Cal Mark]

there is no pcv valve on your engine

[seabeelt]

If you have oil on top of your engine, most probable causes are leaking cam box gasket, leaking valve cover gasket or leaking oil filler cap gasket. If your air filter is very oily, I would suspect some other type of problem

[majicwrench]

Engine has to vent both pressure which gets past rings and pumping pressure/vacuum created with pistons pushing up and down. Hence big hose from crankcase to air filter. Air does indeed flow both ways, but generally out of crankcase due to some blowby. No PCV on our engines. If pressue in crankcase gets too high from either excess blowby or restriction, will do things like blow oil all over the place or push out dipstick. Not sure how much smaller your tube on your air cleaner was than the hose, but it should be pretty close. If it works well now, eureka, but I would suspect you likely have a bit more blowby then you should. Such is life. Factory air cleaner has proper sized tube.
Keith

[SLOSpider]

On the couple of engine I have seen the beather can get pretty clogged up with oil particles that have broken down and restrict the holes into and out of the system. Last engine someone had put what looked like a cam seal in there! Its a good Idea to remove that round breather unit, clean out the passages, change the oil cause junk will get in the pan, replace the gasket and hoses and see how she does. Its a routine thing to do but over looked.