BMW K1600 Forum banner
  • Hey Everyone! Enter your bike HERE to be a part of this months Bike of the Month Challenge!
21 - 40 of 54 Posts

Registered
Joined
41 Posts
Discussion Starter · #23 ·
1004ron : All the hoses attached to the intake-air silencer (air intake/filter box, crankcase ventilation system) looked like new on the inside and I could blow through all of them quite easily. The line from the crankcase (vent line) could not be blown into (because of one way valve) , but air came out of it when I blew into the crankcase return line. The oil coming out of the crankcase vent goes into the intake-air silencer, and what is not returned to the engine ether accumulates there or is sucked into the engine and burned.

Gunnert : The plug in the drain line of the intake-air silencer was in place, but seeped oil after the oil level had risen in it. Over time, I guess the rubber line lost some of it's elasticity, so I put a wire tie on it very loosely so the plug could still be pulled out and no more leaks.
 

Registered
Joined
41 Posts
Discussion Starter · #24 ·
Where I currently stand, I still get oil in the intake-air silencer and no smoke from the exhaust. I ran the same 55 mile course on multiple days. The course is about half twisties and slab. The max rpm of each test was only done when accelerating, not the entire trip.

  • Max rpm 4K, moderate throttle, only few drops of oil.
  • Repeat number one, only few drops of oil.
  • Max rpm 6K, 70% throttle, small stream of oil.
  • Max rpm 7K, full throttle, 0.5 oz. of oil.

Two weeks ago I did two repeats going through gears 2,3 and 4 up to about red line. About two oz. of oil came out of the intake-air silencer.

It is hard to separate the effects of rpm and throttle, it is just more natural to give it more throttle going to higher rpm. Currently, I would not go far from home without taking oil with me and a way to drain the intake-air silencer.

I am going to take the intake-air silencer out again and re-inspect it, all the hoses and valves again. If the oil issue is being caused by a cracked piston, why isn鈥檛 there more oil in the air box at low rpm? There would still be blow-by from the compression/ignition cycle? Is the blow-by at low rpm low enough the oil separator can handle the extra mass flow and do it鈥檚 job?
 

Registered
Joined
1,440 Posts
Can鈥檛 help you on the last question, but I鈥檓 just curious about something, not insinuating anything but my question is-
Do you run premium 91 fuel, or regular 87?
 

Registered
Joined
41 Posts
Discussion Starter · #28 ·
I took the intake-air silencer (air box) apart again. All hoses are still clear of blockages. The PVC valve still works as a check valve. The control valve to the secondary air system is still closed when there is no power to it.

I know the basics of how the secondary air system works on motor cycles, but not enough to trouble shoot it (like it鈥檚 parts locations). There is one thing I noticed when looking the air box over that puzzles me. The two hoses that go to the oil separator part of the air box did not seem to have any fresh oil in them. However the hose for the secondary air system did have fresh oil in it. Was that oil migrating from the air box to that hose or was the oil coming from the engine head through the secondary air system to the air box? Does any part of the secondary air system come in contact with any part of the oil system where a leak could occur?

Oil should only get in the part of the air box that the secondary air system valve is in (that is also where the overflow drain hose connects) when the oil separator overflows into it enough to fill it about 2 inches.

Can anyone think of a way oil can get into the air box from the secondary air system?

I disconnected the hose from the air box to the secondary air and plugged it. I will ride it for a while and see if that changes the amount of oil that collects in the air box.
 

Registered
Joined
41 Posts
Discussion Starter · #30 ·
Well, I knew it was a shot in the dark and I tried it only out of last resort desperation, but disconnecting the secondary air line from the intake-air silencer had no effect on the oil accumulation in the intake-air silencer box. Thus I reconnected it.

It is looking like a cracked piston(s) may be the only possible cause left. The fact that the engine does not smoke yet, may be because it is not forcing enough oil vapor into the intake-air silencer for that to occur yet.

Next move??
 

Mr.Fix It
Joined
9,329 Posts
@williagw , pull the plugs. If one cylinder has a cracked piston land groove then that will be the cylinder blowing oil. I'd "think" the spark plug would have to show evidence of that oil...

Duane
 

Registered
2013 GTL
Joined
1,878 Posts
A piston issue will result in excessive blow-by and crankcase pressure, and it will also allow oil into the combustion chamber - I haven't come across a case where the pistons had that type of damage and there was no exhaust smoke.
 

Registered
Joined
41 Posts
Discussion Starter · #33 ·
Gunnert :
You said your engine was replaced at 45,000 miles. You also said that tear down revealed nothing definitive. Were the individual pistons inspected?

All :
I have questions about what I call the PCV, the check valve between the crankcase and the oil separator in the air box. Mine does function as a check valve, but does anyone know what pressure differential it should open at? I have not tried to take it out yet; does it screw out or just pull out? My thought is that if it opens at to high a pressure, oil from the oil tank can backup into the oil separator through the oil return hose.

Although I can blow through the oil return line and hear air bubbling out through the oil in the oil tank, I am going to take out the dip tube in the oil tank in order to make sure it is 100% open so that oil return rate is not reduced.

Any thoughts?
 

Registered
Joined
1,183 Posts
The more I see of this thread, the more I tend to discount the piston issue - these things blow smoke when the ringlands crack. You would see it, smell it & have witness on the exhaust cans, as well as the airbox. The OP has tried the forum recommended test & failed to lay a smoke screen, so we need to look elsewhere IMHO.

Having checked out the breather system & secondary air, this really only leaves the oil separator in the sump, creating a sumping or oil foaming problem, which is explored in this old thread ......... Condensate drain tube questions.

It's an issue any classic bike owner will be aware of, but a rarity with modern dry sump bikes ....... well, maybe with the exception of a few early Harley M8s allegedly.

Surely a simple oil change will reveal whether there is excess oil in the crankcase area (sumping). A sample of the oil itself could be sent for analysis & ultimately the sump cover could be dropped down to check/examine the separator if necessary.
 

Registered
Joined
41 Posts
Discussion Starter · #37 ·
I just finished a test. After reaffirming that the breather hose from the crankcase to the oil separator and the oil breather/return hose from the oil separator to the oil tank were both open and clear, I did the following. I reassembled everything except the ends of these two hoses that connected to the oil separator in the air box. Added a temporary extension to them and started the engine. After the engine was warmed up, I varied the rpm up and down and gradually increased the max rpm until I got over 6K rpm鈥檚. Time at max rpm varied from a couple of seconds to eventually about 10 seconds. Oil (not oil vapor) finally came out of the hose (about a half oz.) that was connected to the oil tank return. No oil or oil vapor came out of the hose connected to the crankcase vent. Note, the hose connected to the oil tank, connects to a dip tube that goes down to near the bottom of the oil tank and its end is always in oil. Thus any pressure in the oil tank would push oil (not oil vapor) up the dip tube through the hose and into the oil separator, overflowing it and ultimately into the condensate drain area. Thus a lot of oil can inter the condensate drain area quickly.

How did the oil tank get pressurized if the crankcase vent hose had nothing come out of it (did PCV fail)? How many oil pumps are in the engine? Does one pump scavenge the dry sump and also pump from the oil tank to pressurize the lubrication system? Could the PCV work when the engine is cold, but fail when it is hot? Where is the oil pressure regulated, in the pump? Isn鈥檛 there a second oil separator in the oil tank and what does the inside of it consist of, can it fail?
 

Registered
Joined
41 Posts
Discussion Starter · #38 ·
As quickly as it started, my GTL seems to have quit blowing oil into the air box. Ten days ago, I road 275 mi. with the air temp. between 40 & 55 F. Then a week after that I road 80 mi with air temp at 45 F. Best I could tell zero oil was lost & no oil was in the air box drain ether time. Now there is no way I can see air temp in that range could affect oil getting into the air box or not.

So, what else was different? At least three times I had checked the two hose between the engine and air box. Both looked clean and air would go through them with no apparent restriction. The last time I had it apart, I blew air through them with a little higher CFM (being careful not to pressurize the oil tank). I do not know if blowing air into the oil return line that goes to the oil tank and out through the vent line passes through any other component such as the oil separator in the oil tank.

I had also added some engine coolant, it was a little low. That should not affect oil getting into the air box ether.

Obviously, more ridding is required to see what the future holds.
 

Premium Member
Joined
2,893 Posts
As quickly as it started, my GTL seems to have quit blowing oil into the air box. Ten days ago, I road 275 mi. with the air temp. between 40 & 55 F. Then a week after that I road 80 mi with air temp at 45 F. Best I could tell zero oil was lost & no oil was in the air box drain ether time. Now there is no way I can see air temp in that range could affect oil getting into the air box or not.

So, what else was different? At least three times I had checked the two hose between the engine and air box. Both looked clean and air would go through them with no apparent restriction. The last time I had it apart, I blew air through them with a little higher CFM (being careful not to pressurize the oil tank). I do not know if blowing air into the oil return line that goes to the oil tank and out through the vent line passes through any other component such as the oil separator in the oil tank.

I had also added some engine coolant, it was a little low. That should not affect oil getting into the air box ether.

Obviously, more ridding is required to see what the future holds.
Any update on this...I'm not experiencing what sees to be a very similar problem. I'm getting a lot of oil out of condensate drain. I get smoke out of the pipes, more on the left than the right but some out of both.

I've the the run-up through the gears and sometimes I get smoke and sometimes I don't. When I do, it continues for quite a while, even at gentle throttle usage. If it were the pistons, would the effects of the blow-by continue for 5+ miles, only to eventually stop? Or is that more likely something else?

I've not taken anything apart aside from opening the air box to clean it out. If I wanted to check the hose being referred to that may be plugged, how much effort is it to get to it?

Perhaps just a coincidence, but i thought it interesting that this seemed to start showing symptoms after changed the oil with a brand I've never used before. I've historically uses AmsOil but used Castrol for the first time (@50,000 miles). And, no, I didn't overfill it. After doing a proper warm-up and wait a minute, the dipstick came out completely dry. I've drained about 600-700cc from the drain hose (about 300-400 one time and 200-300 another. It took just a bit more than what I drained out to bring the level back up to max. So, I'm losing most of it through the drain and not through actual burning.
 

Registered
2013 GTL
Joined
1,878 Posts
Here's a post referring to oil in the air box caused by the positive crankcase ventilation system and its seperator - there's a few more on the forum.

 
21 - 40 of 54 Posts
Top