Hi all,

First post
Working on my XJ6 late series 1, i am about to replace the breather housing cap on the front of the engine, since the rubber is obviously and completely torn. The whole breathing cap system is open into the air
Since the handbook recommends to clean/replace the flametrap / gauze filter, i will also unbolt the breather and replace gauze and gaskets.

questions:
How important is it to make the breather cap and hoses air-tight ?
The hoses eventually end up in the carburators, where i assume the crackcase fumes are "recycled" and added to the gas/air mixture?

Thanks for any advice on this
Jan

 

this breather design started with the early XK engines and kept going until at least 1987 in the 6 cylinder 4.2 liter.
I don't think it has to be 100% air tight, just tight enough for fumes to travel to either air filter or carbs. The 3.4 and 3.8 liter engines travel to the air filter housing which connects to the carbs.
Tighten the clamps enough but not overly tight.
Clean the mesh gauze in gasoline, reinstall with new gasket and tighten the 4 nuts with new copper washers, but not so tight the aluminium or the copper washers get deformed. In my two XK engines I use two gaskets.

 

After seeing how gunked up my intake valves and ports were, I elected to route my breather into an OIL CATCH CAN ( Oil Catch Can Kit Reservoir Tank Engine Black Polish Baffled Universal Aluminum | eBay ) then to the carbs. I empty the can every month or so. I used heavier hose than what came with the kit.


OIL CATCH CAN on the left of pic

 

Thanks for the relevant feedback guys. In the mean time I have got everything back in place.

just wondering:
how do these exhaust gasses end up in front on the engine ? Is this a result of leakage along the exhaust valves guides or something ?
and…
Why are these gasses returned to the carbs anyway?? Is emission control the only or main motive?
Otherwise why not lead these gasses to the exhaust? Or straight into the air?

 

Good question - As a result of "blow-by" which is the explosion gases (on the power stroke) sneaking past the rings there is positive pressure going into the sump. This oily, misty air is then vented at the front of the engine, past the timing chain cover passageways up to the "breather". Emission restrictions dictated that oily air NOT go out into the open atmosphere, so it got a path back through the intake to be burned (or re-burned), and output on the exhaust stroke. I do suppose there is a way it could be vented instead into the exhaust manifold, but I'm sure there is some legislative answer for that, which is above my pay grade.

 

to reduce air pollution. Combustion engines have been polluting the air since 1900. 120 years of polluting the air. Something had to be done and Emission Controls were born.

 

When I had my first XJ6 Series 3 back in the late '90s ( pre forums, google, etc so no info resources ) my car had issues with the crankcase breather not removing the fumes but pressurizing the crankcase instead ( making every cam nut etc leak oil ). I'm not sure what the problem was, possibly mis-plumbed at the throttle body. I blocked off the throttle body hose connection and ran a straight hose from the crankcase elbow down beside the side of the engine with a piece of screen to keep out bugs = vented to straight to atmosphere. It would still pass emissions tail pipe test if I changed the oil right before the inspection ( the shop didn't check to see if all the emission parts were there, only checked if all the lights worked and sniffed good ). The only problem was the oil would start turning milky from moisture being sucked into the engine when it cooled possibly. I just changed the oil more often, as a result.
Don't think I would do that now, the possibility of the contaminated oil causing engine damage would keep me up at night.
I'm a much better mechanic now too, so I would get the system to function correctly !

Cheers,
Brian

 

Brian that is exactly why I have left the systems in my XJ as they came from the factory, first because I am not a mechanic and second because I am not a mechanic. Trying to outsmart the factory never works for most owners though I am sure there are people who know what the heck they are doing, I don't care to compete.